Escherichia coli strain in which RecBCD has been genetically replaced by the bacteriophage λ Red system engages in efficient recombination between its chromosome and linear double-stranded DNA species sharing sequences with the chromosome. Previous studies of this experimental system have focused on a gene replacement-type event, in which a 3.5 kbp dsDNA consisting of the cat gene and flanking lac operon sequences recombines with the E. coli chromosome to generate a chloramphenicol-resistant Lac- recombinant. The dsDNA was delivered into the cell as part of the chromosome of a non-replicating λ vector, from which it was released by the action of a restriction endonuclease in the infected cell. This study characterizes the genetic requirements and outcomes of a variety of additional Red-promoted homologous recombination events producing Lac+ recombinants.An cat was not frequently co-inherited with cat. (5) Recombination between phage sequences in the linear DNA and cryptic prophages in the chromosome was responsible for most of the observed Lac+ recombinants. In addition, observations were made concerning recombination events between the chromosome and circular DNAs: (6) Formation of recombinants depended upon both RecA and, to a lesser extent, Red. (7) The linked tetracycline-resistance marker was frequently co-inherited in this case.A number of observations concerning recombination events between the chromosome and linear DNAs were made: (1) Formation of Lac+ and Lac- recombinants depended upon the same recombination functions. (2) High multiplicity and high chromosome copy number favored Lac+ recombinant formation. (3) The Lac+ recombinants were unstable, segregating Lac- progeny. (4) A tetracycline-resistance marker in a site of the phage chromosome distant from lac and cryptic prophage sequences in the chromosome generates a partial duplication of the bacterial chromosome. When the incoming DNA species is circular rather than linear, cointegrates are the most frequent type of recombinant.The Lac+ recombinants arise from events in which homologous recombination between the incoming linear DNA and both  Escherichia coli strain in which RecBCD has been genetically replaced by Red exhibits greatly elevated levels of recombination between its chromosome and short linear double-stranded DNA species sharing sequences with the chromosome [The Red recombination system of bacteriophage λ promotes efficient double strand break repair/recombination. An romosome .cat gene and flanking lac operon sequences recombines with the E. coli chromosome to generate a chloramphenicol-resistant Lac- recombinant [red and the bacterial recombination genes recA, recF, recO, recR, recQ, ruvAB, and ruvC. Large numbers of chloramphenicol-resistant Lac+ recombinants were generated in these crosses as well. In this study, we characterize the Lac+ recombinants and the processes which generate them. Most appear to arise from events in which homologous recombination between the incoming DNA and the chromosome generates a partial duplication of the bacterial chromosome.In previous studies, we have characterized a recombination event, pictured in Figure ombinant -4. The drecA, recF, recO, recR, recQ, ruvAB, and ruvC. Deletion of recG increased the production of both Lac+ and Lac- recombinants. Lac+ recombinants accounted for 10–60% of the total chloramphenicol-resistant offspring of the crosses. These results strongly suggest that formation of the Lac+ recombinants takes place via homologous recombination, though they do not rule out the possibility that non-homologous end joining, or other varieties of "illegitimate" recombination, might be involved as well.Data presented in Table lac::cat sequences would be attached to phage sequences. Heitman et al. [in vivo are rapidly repaired by DNA ligase. The results of previous physical studies with other substituted λ phages cut in vivo by PaeR7 lead to the expectation that the λ lac::cat819 chromosome would be uncut, or only singly cut, much of the time in the infected cell [The reason for considering mechanisms other than homologous recombination in the formation of the Lac+ recombinants is because of the expectation that some of the phage-borne n et al.  showed tted cell ,6.lacZ (not shown). When the lac::cat dsDNA was delivered into the cell by a λ vector bearing a tetracycline resistance determinant (Δ nin::tet859 – described below) neither the Lac+ nor Lac- recombinants acquired tetracycline resistance. These findings suggest that the process which formed the recombinants did not involve the entire phage chromosome.Preliminary characterization of the Lac+ recombinants formed in cells which were wild-type for all the recombination functions revealed that most, possibly all, were unstable. When streaked on plates containing chloramphenicol and X-Gal, they segregated Lac- (colorless) progeny at variable frequencies. Southern gel analysis of chromosomal DNA from unstable Lac+ recombinants revealed that some of them were multiploid for lac locus, will produce a Lac+, chloramphenicol-resistant recombinant. Data presented below, in which simpler lac::cat recombining substrates generate Lac+ recombinants at a frequency approximately 1000-fold lower than Lac-, suggest the frequency of spontaneous lac duplications in Red+ but otherwise wild type E. coli is approximately 10-3, consistent with estimates of spontaneous duplication frequency in Salmonella made by Roth et al. [A baseline level of Lac+ recombinants was to be expected in these crosses. The recombination event pictured in Figure h et al. . The Laclac::cat segment were to recombine with more than one chromosome at a time. Further complicating interpretation of the experiment, the cells were infected at a multiplicity of 10 phages per cell.The crosses described above were done by infecting log phase host cells grown in rich medium. Such cells contain multiple copies of their chromosome. Complications might arise if the lac::cat segment and single copies of the bacterial chromosome. As shown in Table To reduce the complexity of the system, we switched to a cross procedure involving low multiplicity infection (0.1 phage per cell) of stationary phase cells. Presumably, under these conditions, most of the events producing chloramphenicol-resistant recombinants take place between single copies of the lac::cat, which are diagrammed in Figure lac::cat819, the progenitor of this series, has two PaeR7 sites. Upon infecting a host cell bearing the Δ recBCD::Ptac-gam-bet-exo-pae-cI substitution, it injects its chromosome, which circularizes. Expression of its lytic genes, including those necessary for phage DNA replication, is blocked by the action of cI repressor. Cutting of its chromosome by the PaeR7 restriction endonuclease in the infected cell releases a 3.5 kbp linear dsDNA, consisting of the cat gene and 1.3 kbp flanks of lac sequences on the right and left. . The ends of the flanking lac sequences match precisely their counterparts in the chromosome.To examine the dependence of Lac- and Lac+ recombinant formation on the structure of the DNA substrate, we constructed variants of λ lac::cat930 and λ lac::cat931 have only single PaeR7 sites, on the right and left, respectively. Cutting by PaeR7 in the infected cell should produce large linear dsDNAs related to the lac::cat819 fragment, but with long tails of non-homologous DNA extending from the left and right sides, respectively. Interestingly, both of these single-cut phages produce recombinants more efficiently than the double-cut λ lac::cat819, in both recG+ and Δ recG backgrounds  Some of the λ lac::cat929 chromosomes might be cut by the EcoK restriction endonuclease. The infected cells contained a functional EcoK restriction-modification system. λ lac::cat929 was grown in a similarly EcoK+ host, and therefore was presumably EcoK-modified. However, if the modification were not complete, there might be residual EcoK restriction activity, resulting in 10% of the phage chromosomes being cut. . (2) The production of the recombinants might not be Red-mediated. (3) The linear partner might be a broken bacterial chromosome.Approximately half of the strongly chloramphenicol-resistant recombinants generated by the uncuttable phage λ  partner . How, thhsdR, with a tetracycline resistance determinant. This replacement had little effect on the formation of recombinants by λ lac::cat929 . A fourth event, also not shown, involves recombination between λ genes and homologues in cryptic prophages in the E. coli chromosome (discussed below). As suggested in the figure, cointegrates formed by recombination in the right-side lac flank are phenotypically Lac-, while recombination in the left-side lac flank (or other loci) forms Lac+ recombinants. To test this idea, we constructed variants of λ lac::cat missing either or both lac flanks; they are diagrammed in Figure Cointegrates could in principle be formed by four different single reciprocal recombination events between the circular λ cat cassette with 1000 bp homologous flanks was only 10-fold more efficient than one with 40 bp flanks. Their experiments were done with cells which had been subjected to heat shock and electroporation. To test the efficiency of short-flank recombination under less extreme conditions, we constructed a short-flank λ lac::cat variant.The ability of the λ Red system to promote recombination events involving short sequence homologies makes it particularly useful for genetic engineering. Yu et al.  reportedlac::cat921 consists of the cat gene flanked by 40 bp sequences corresponding exactly to the terminal 40 bp at each end of the 1.3 kbp flanks of λ lac::cat819. As shown in Table lac::cat921 exhibits a several hundred-fold lower efficiency of recombinant formation than its long-flank counterpart, in both recG+ and Δ recG backgrounds. λ lac::cat921 was similarly inefficient in log phase cells (data not shown). These observations suggest that short-flank recombination may not be a significant activity of the Red system in nature. However, they do not speak to the question of whether long flanks work better because they provide a larger homology target for synapsis, or because they provide non sequence-specific protection, perhaps delaying exonucleolytic degradation of the recombining sequences long enough to permit recombination to take place.The fragment released by PaeR7 from the chromosome of λ lac::cat930, but not by the left side-cut λ lac::cat931  cloning the cat gene from the deletion mutant, along with flanking chromosomal sequences; (3) using the cloned, plasmid-borne flanking sequences, and Red-mediated gap repair, to clone the lac operon in a plasmid; (4) inverting the lac operon, relative to its flanking sequences, in the plasmid; (5) replacing the Δ lac::cat chromosomal allele with the plasmid-borne lac-inv allele.The strategy for inverting the chromosomal lac::cat930 and lac::cat931 alleles were constructed by replacing the left-side and right-side PaeR7 sites, respectively, of pTP819, with XbaI sites. To produce inverted derivatives of these two alleles, the plasmids pTP930 and pTP931 were digested with XbaI and XhoI (a PaeR7 isoschizomer); lac::cat inserts and bla-ori backbone fragments from the two plasmids were exchanged. The inverted alleles were then crossed into phage λ, as described in the Methods section.The single-cut E. coli K-12 [lac::cat930 and λ lac::cat931, and the efficiency of Lac+ recombinant formation by λ lac::cat930, were slightly elevated relative to those in the corresponding AB1157-derived strain.In constructing the chromosomal inversion, we switched genetic backgrounds, from the AB1157-derived strains with which most recombination studies have been done, to MG1655, the sequenced wild type oli K-12 . In the lac-inverted E. coli) were tested for Lac+ recombinant formation. The results are shown in Figure lac::cat930  in lac-wild type, and lac::cat1033  in lac-inv.The eight combinations of normal and inverted phages and bacteria  lacking its sequences derived from phage P22 was equally proficient at generating Lac+ recombinants. A derivative missing the left lac flank made Lac+ recombinants almost exclusively; the small number of Lac- recombinants in this case probably represent cointegrates made by uncut plasmid DNA in the fragment preparation.We constructed several other linear DNA substrates to test the generality of the model in Figure ion  and λ lac::cat930 (cut right) behave like their counterparts generated by electroporation of linear dsDNAs into Red+ cells: they segregate Lac- chloramphenicol-resistant clones at low frequency, and Lac+ chloramphenicol-sensitives at high frequency (data not shown). In addition, their formation also depends upon the presence of cryptic prophages in the chromosome: λ lac::cat819 was found to produce Lac+ chloramphenicol-resistant recombinants as only 0.13% (average of six measurements) of the total chloramphenicol-resistant progeny in crosses with TP750. These properties suggested both kinds of recombinant might have the same structures as well, but PCR tests of 50 of the phage-generated recombinants with the primers used to demonstrate type I, II, and III recombinants  when electroporated directly into cells .One aspect of Lac+ recombinant formation by λ ls Table . How doelac::cat-bearing λ phages and the bacterial chromosome, as well as the mechanism of their formation. Our studies uncovered a diversity of recombinant structures, including complex duplications and cointegrates. Recombination between λ and cryptic prophage sequences in the bacterial chromosome was found to be the most significant mechanism generating Lac+ recombinants. All of the Lac+ recombinants could be generated by homologous recombination events of types which have been previously described. In particular, there was no evidence for end-joining or other non-homologous recombination events. Perhaps the most surprising finding was the high frequency with which large duplications in the bacterial chromosome – up to 1 Mbp – could be generated by the Red system.The bacteriophage λ Red recombination system is of general interest for two main reasons. First, it is an intensively characterized and relatively simple system, which serves as a model for studies of homologous recombination -17. SecoE. coli strain DH5α (λ pir) [hsdR::tet allele in TP842 was constructed by using a Tn 10-containing E. coli strain as template in PCR with primers hsdRut (5'-TTGGACAGGCCCGCACAGCAATGGATTAATAACAATGATGCTCGACATCTTGGTTACCGT-3') and hsdRdt (5'-GCTGAATTTGCCCAGCAGGGTATCGAGATTATCGTCAAAGCGCGGAATAACATCATTTGG-3'). The Δ lac::cat allele in TP872 was constructed by using a Tn 9-containing E. coli strain as template in PCR with primers cat15 (5'-TCTGGTGGCCGGAAGGCGAAGCGGCATGCATTTACGTTGAATGAGACGTTGATCGGCACG-3') and cat16 (5'-AGAGTACATCTCGCCGTTTTTTCTCAATTCATGGTGTACAATTCAGGCGTAGCACCAGGC-3'). (λ pir)  was usedcI857 Sam7 containing the nin region genes was cloned into the EcoR1 site of pBR322. In the resulting plasmid, pnin, the nin genes are read clockwise in the conventional map of pBR322. pTP772 was constructed by deleting sequences between the two HindIII sites of pnin. pTP859 was constructed by cutting pTP772 with SacII and ClaI, blunting the ends with T4 DNA polymerase, ligating with NotI linkers (5'-AGCGGCCGCT-3'), cutting with NotI, and ligating with a NotI fragment of pTP857 [tetR and tetA genes of transposon Tn10.An EcoR1 fragment of λ f pTP857  containicat gene is flanked on both sides by lac sequences, PaeR7 sites, and λ sequences (for crossing into the phage), has been described [lac flank and PaeR7 site. pTP922 was constructed by deleting the lac and cat sequences between the two PaeR7 sites in pTP819. . pTP926, pTP927, and pTP928 were constructed by ligating the oligonucleotide 5'-TCGACAGTCTAGACTG-3' into the PaeR7 sites of pTP828, pTP829, and pTP922, respectively, eliminating the PaeR7 sites and replacing them with XbaI sites. pTP929 was constructed by ligating the XbaI-NcoI fragment of pTP926 containing the N-terminal coding sequences of cat and the NcoI-XbaI fragment of pTP927 containing the C-terminal coding sequence of cat into the XbaI site of pTP928. The orientation of the reconstructed cat gene is the same as in pTP819. pTP930 was constructed by ligating together the large ApaI-SacII fragment of pTP929 and the small ApaI-SacII fragment of pTP819. pTP931 was constructed by ligating together the small ApaI-SacII fragment of pTP929 and the large ApaI-SacII fragment of pTP819.pTP819, in which the escribed . pTP828 cat gene from a Tn9-containing E. coli strain with primers 5'-GACGCACTCGAGGCGTTAACCGTCACGAGCATCATCCTCTGCATGGTCAGGCCGGCCACTGGAGCACCTCAAAAACACCA-3' and 5'-GACGCACTCGAGGCACACAGCGCCCAGCCAACACAGCCAAACATCCGCGCGGGCCCGACCGGGTCGAATTTGCTTTCGAA-3'. The presence of the expected sequences from the synthetic oligonucleotides in pTP921 DNA was verified by automated sequencing (data not shown).pTP921 was constructed by ligating together two XhoI-digested DNAs: pTP922 and a PCR product made by amplifying the lac flank only) was constructed by replacing the XbaI-ApaI lacZY segment of pTP930 with a mixture of two oligonucleotides, 5'-CTAGTTGCAAGCTTGGGCC-3' and 5'-CAAGCTTGCAA-3'. pTP989 (right lac flank only) was constructed by replacing the NgoMI-XhoI lacZ segment of pTP930 with a mixture of two oligonucleotides, 5'-CCGGCAAGCTTGCTGGTGGGCAA-3' and 5'-TCGATTGCCACCAGCAAGCTTG-3'. pTP995 (no lac flank) was constructed by ligating together the small NcoI fragment of pTP988 and the large, ori-containing NcoI fragment of pTP989.pTP988 (left cat-containing fragment of pTP930 and the XbaI- and PaeR7-ended ori-containing fragment of pTP931. pTP1033 was constructed by ligating together the XbaI- and PaeR7-ended cat-containing fragment of pTP931 and the XbaI- and PaeR7-ended ori-containing fragment of pTP930.pTP1032 was constructed by ligating together the XbaI- and PaeR7-ended cat gene and flanking sequences from strain TP872 (Δ lac::cat) with primers 5'-CATCATCACGCGGCCGCGACGTTTGCCGCTTCTGAA-3' and 5'-ATCATCCACGCGGCCGCTGCGTTTTGCACCAGTACG-3'. In pTP1016, the cat gene is flanked closely by unique SphI and BsrGI sites. pTP1027 was constructed by electroporating SphI- and BsrGI-digested pTP1016 into strain TP829 (lac+); a plasmid formed by gap repair was isolated. pTP1028 was constructed by ligating SphI-digested pTP1027 with the oligonucleotide 5'-GTTGTACAACCATG-3', converting the SphI site into a BsrGI site. pTP1034 was constructed by cutting pTP1028 with BsrGI, ligating the two fragments back together, and screening for plasmids in which the lac genes were inverted relative to their flanking sequences.pTP1016 was constructed by ligating into the NotI site of pTP809  the NotIpir function, was constructed by ligating together two AatII- and Bam-digested DNA species: a PCR product made by amplifying a Tn10-containing E. coli strain with primers 5'-TCAACGTAAATGCATGGACGTCCTCGACATCTTGGTTACCGT-3' and 5'-TGTACACCATGAATTGGATCCCGCGGAATAACATCATTTGG-3'; and the ori-containing fragment of plasmid pLD54 [lac::cat-containing fragments of pTP819, 930, 931, 1032, and 1033, respectively, into the BamHI site of pTP1029.pTP1029, a tetracycline resistance bearing vector capable of replicating only in cells expressing R6K id pLD54 . pTP1018cat-containing fragment of pTP1051 into the BamHI site of pTP1029.pTP1047 was constructed by ligating the complementary oligonucleotides 5'-TCGTCTAGAGT-3' and 5'-CCGGACTCTAGACGAAGCT-3' between the SacI and NgoMIV sites of pTP1019. pTP1051 was constructed by ligating the complementary oligonucleotides 5'-CAGCATGCAT-3' and 5'-CTAGATGCATGCTGGTAC-3' between the KpnI and XbaI sites of pTP930. pTP1052 was constructed by ligating the complementary oligonucleotides 5'-CAGCATGCAGGGCC-3' and 5'-CTGCATGCTGGTAC-3' between the KpnI and ApaI sites of pTP1019. pTP1053 was constructed by ligating the complementary oligonucleotides 5'-GGCATGCAGGTTCTTTGAGTCCTTTGGGCGGCCGCGGGCC-3' and 5'-CGCGGCCGCCCAAAGGACTCAAAGAACCTGCATGCCGC-3' between the SacII and ApaI sites of pTP1019. pTP1054 was constructed by ligating the complementary oligonucleotides 5'-CCGGCGCGGCCGCAGGTTCTTTGAGTCCTTTGGTGTACAGAGCT-3' and 5'-CTGTACACCAAAGGACTCAAAGAACCTGCGGCCGCG-3' between the NgoMIV and SacI sites of pTP1020. pTP1055 was constructed by ligating the small SphI-NotI fragment of pTP1016 between the SphI and NotI sites of pTP1053. pTP1056 was constructed by ligating the small NotI-BsrGI fragment of pTP1016 between the NotI and BsrGI sites of pTP1054. pTP1057 was constructed by ligating the BamHI Ptac-gam-bet-exo-pae-cI operon flanked by sequences upstream from recC on one side and sequences internal to recD on the other, has been described [cI gene from E. coli strain TP507 with the same primers used in the construction of pTPP822. This construction has the effect of simply deleting the pae genes from pTP822. pTP996 was constructed by deleting the C-terminal coding sequences of bet and the N-terminal coding sequences of exo between the two HpaI sites of pTP978. pTP979 was constructed by ligating together two NcoI- and XbaI-digested DNAs: pTP822 and a PCR product made by amplifying the bla gene from pBR322 with primers 5'-CCACCAATCATCCATGGCGCGGAACCCCTATTTGTTT-3' and 5'-TTGTTGGACGATCTAGAGGTCTGACAGTTACCAATGC-3'. This construction has the effect of replacing pae and cI with bla.pTP822, which bears a synthetic lac::cat819 and λ lac::cat819 nin5 have been described [nin::tet859 was made by crossing λ wild type with plasmid pTP859, infecting a tetracycline-sensitive strain with the resulting lysate, and selecting a tetracycline-resistant lysogen. The Δ nin::tet859 substitution replaces λ bp 40388–43825 with the tetR and tetA genes of transposon Tn 10.λ escribed . λΔ nin:lac::cat921, 929, 930, 931, 988, 989, 995, 1032, and 1033 substitutions were crossed into λ wild type and/or λ Δ nin::tet859. The parent phages were crossed with the cat substitution-bearing plasmids. Phages which had acquired the substitution were either selected by plating on a strain lysogenic for phage P2 (Spi- phenotype), or identified by their clear-plaque morphologies . The structures of the substituted phages were all verified by their ability to generate specific products when used as templates in PCR (not shown).The 4), and shaken with chloroform. Two methods for crosses monitoring recombination between phage-injected DNA and the bacterial chromosome, both previously described, were employed: high-multiplicity infection of log phase cultures [Phages were crossed with plasmids by spotting enough phage to make a confluent zone of lysis on a lawn of a sensitive bacterial strain bearing the parent plasmid. After overnight incubation at 37°C, material from the zone was collected in TM  dimethylsulfoxide, 20 mM Tris-HCl pH 8.4, 50 mM KCl, and primers at 0.7 μM. Samples were heated to 95C for 5 min, then put through 30 cycles of 94C for 1 min, 55C for 1 min, 72C for 2–4 min, depending upon the length of the expected products. Primers for demonstrating the type I, II, and III tfa junctions were combined in a single mixture of 4 oligonucleotides: Jsp1 (GTTGAATGGGCGGATGCTAA), Jsp2 (TCTTCCACCAGAAAGCTACC), JncA (TGCCGTGTGAACGGTTTAC), and Jnc2 (TTCTAGCCCCATCATCTGTG). Primers for spanning the ACF-generated duplication  and Csj2 (CGAATAGTCGGCTCAACGTGGGTT).The structures of various Red-generated duplications in the PCR: polymerase chain reaction. X-Gal: 5-bromo-4-chloro-3-indolyl-β-D-galactopyranoside. IPTG: isopropyl β-D-thiogalactopyranoside. bp: base pairs.ACF carried out the experiments summarized in Table


Typically, randomization software should allow users to exert control over the different aspects of randomization including block design, provision of unique identifiers and control over the format and type of program output. While some of these characteristics have been addressed by available software, none of them have all of these capabilities integrated into one package. The main objective of the Random Allocation Software project was to enhance the user's control over different aspects of randomization in parallel group trials, including output type and format, structure and ordering of generated unique identifiers and enabling users to specify group names for more than two groups.The program has different settings for: simple and blocked randomizations; length, format and ordering of generated unique identifiers; type and format of program output; and saving sessions for future use. A formatted random list generated by this program can be used directly (without further formatting) by the coordinator of the research team to prepare and encode different drugs or instruments necessary for the parallel group trial.Random Allocation Software enables users to control different attributes of the random allocation sequence and produce qualified lists for parallel group trials. An important aspect of any trial that should be clearly stated in the final report is the method used to assign treatments (or other interventions) to participants . In the Without the use of computer software or Internet services the maintenance of the whole process of randomization and allocation is difficult. In addition, in the case of any necessary restrictions on the process of randomization (i.e. block randomization ) the com1. Independent running on a local computer without any need to access the Internet2. Different types of program output: to file (html or text files), window and system clipboard3. Provisions for different block design4. Capability to deal with a larger number of groups5. Specifying a name for each group6. Control over the format, length and ordering of the generated UIs7. Control over the format of generated sequence8. Saving or loading the randomization settings9. Viewing previously generated randomized sequencesRandom Allocation Software is a program created in Microsoft Visual Basic 6, and it installs in the same way as ordinary Windows software (i.e. running setup.exe and following on screen instructions). Once installed and run, there are some controls in the main window for specifying the number of groups (2 to 16), sample size and the name of each group. It also contains menu items to determine the program output and randomization settings. The default program output is saved into either html or text files, and it may also have output to a window or to the system clipboard. A variety of randomization options can be set in the options window. The length of generated UIs (named as Code in the program) can be between 3 to 10 characters and there are options for different alphanumeric structures. In addition, these UIs can appear in sequential or random order in the generated random list. The program can generate simple or block randomization in different types, including equal size blocks, multiple block lengths with random variation among the specified block sizes and complete randomized blocks (random number and size of blocks). The generated sequence will appear in a multiple columns format and the number of columns (1 to 10) can be changed in the options window. Output to html file will be formatted in the form of one block per table. Borders of the tables may be shown or hidden. By clicking the 'Generate' button in the main window the random sequence will be generated and opened by the default viewer for the output file (e.g. Internet Explorer for html files). Previously created output files can also be viewed from inside the program. Additional options include saving the current randomization settings, loading a previous setting and enabling the program to save the last setting upon program exit.During execution, the program produces a random sequence of allocation using the Rnd function that generates a floating point random number. The Rnd function uses the linear-congruent method for pseudo-random number generation as depicted by the following formula:x1 = (x0 * a + c) MOD (2^24) [12]where:x1 = new valuex0 = previous value a = 1140671485c = 12820163The seed of the Rnd will be the Timer function, which will return the number of seconds elapsed since midnight. Although this version of the program does not produce repeatable lists, it is possible to revise the program in subsequent versions to save the value of the seed to reproduce the same random list. The output consisted of shuffled allocations each of which is a UI, group name pair. The program checks for the uniqueness of the UIs and generates an error message if the specified UI length is insufficient to hold the entire sample size.Runs test was used to check randomness of the output list with sample sizes from 10 to 190  and from 200 to 3000 . Each runs test was carried out for the group number of 2, 3, 5 and 6. SPSS 10 software was used to perform the runs test.The program starts running with the default settings. Users may run the program with the default settings or set the number of groups, the name of each group and the sample size. Clicking the 'Generate' button figure  producesFigure In block randomization the final sample size is usually larger than the specified one.A total of 18 runs test were performed to check the randomness of the program output, which resulted in P values of 0.22 to 0.81.The main use of Random Allocation Software is to produce simple or block randomized sequences for parallel group trials. Its use is restricted to parallel group randomized trials. Compared with similar software, it enables the user to control the length, order and format of the UIs; and the type and format of the output. It allows specifying up to 16 groups for parallel trials.Random Allocation Software has been designed to produce random sequences consisting of UI, group name pairs with additional control over the output format and type. Available randomization software generally has limitations in the number of groups, naming each group, generating UIs and control over the output. Many of these problems have been addressed in the present software. As has been stated in previous sections, the main use of this software is for randomization in parallel group trials. The software can be revised to support crossover and other types of randomized trials. The experienced user may test the randomness of the program output by selecting numeric labels for group names and then exporting the generated list into a statistical software such as SPSS to execute a runs test on the exported data.Project name: Random Allocation SoftwarePublic use access: (Latest version)Operating systems: Windows 98, Me, 2000, XP. It should be noted that on some Windows operating systems  during installation of the program an error message like "Setup Cannot Continue... System Files Are Out of Date" may be displayed. If this happens, click OK and restart the system. Then run the setup.exe again. This is due to a known bug in the installation programs of Microsoft Visual Basic . This prProgramming Language: Visual Basic 6Other requirements: Internet Browser (Internet Explorer 5 or higher is recommended)License: Free for academic use.JIT = Just in TimeUI = Unique IdentifierThe author declares that he has no competing interests.The pre-publication history for this paper can be accessed here:


Wise et al. introduced a rank-based statistical technique for meta-analysis of genome scans, the Genome Scan Meta-Analysis (GSMA) method. Levinson et al. recently described two generalizations of the GSMA statistic: (i) a weighted version of the GSMA statistic, so that different studies could be ascribed different weights for analysis; and (ii) an order statistic approach, reflecting the fact that a GSMA statistic can be computed for each chromosomal region or bin width across the various genome scan studies.We provide an Edgeworth approximation to the null distribution of the weighted GSMA statistic, and, we examine the limiting distribution of the GSMA statistics under the order statistic formulation, and quantify the relevance of the pairwise correlations of the GSMA statistics across different bins on this limiting distribution. We also remark on aggregate criteria and multiple testing for determining significance of GSMA results.Theoretical considerations detailed herein can lead to clarification and simplification of testing criteria for generalizations of the GSMA statistic. Wise, Lanchbury and Lewis  introducn = 120 bins spanning the entire genome, and correspondingly 120 GSMA statistics. Wise  = 0, , andLevinson  proposedand Feng  to derivand Feng , we here.) = φ (z)[1 + c4H4 (z)], where φ(·) is the standard normal density function, , H4 (·) is the 4th degree Hermite-Chebyshev polynomial, H4 (z) = z4 - 6z2 + 3, and the constant c4 given by  (Stuart and Ord ; and, for the remaining order statistics T(110), T(109), ..., T(1), the criterion {PAvgRnk < 0.05 and Pord < 0.05} reduces to {PAvgRnk < 0.05}, equivalently, {Tj) , are less than 1.645 .Levinson  had propPAvgRnk < 0.000417} (0.05 corrected for 120 tests) for evidence that a bin is likely to contain a linked locus or loci. One can improve on this procedure by using Holm's  That is, in this particular instance, the unweighted GSMA statistics with either Bonferroni or Holm  As for the order statistic formulation and the aggregate criteria of Levinson [For practitioners utilizing GSMA statistics, the question arises as to whether the methods proposed here as well as in Koziol and Feng  are mereLevinson ), then tLevinson  or KozioLevinson , and shoLevinson  providesLevinson  and KoziLevinson  will typLevinson  can be bLevinson , we beliJAK conceived, designed and drafted the manuscript. ACF performed the statistical simulation.Both authors read and approved the final manuscript.


Framework for Program Evaluation in Public Health and community-based participatory research principles. Innovative approaches are required to address burgeoning chronic disease trends and risk factors. Worksites are an ideal setting in which to affect working adults and high-risk individuals. Using community-based participatory research methodology increases community capacity for evaluation, dissemination, and use of evaluation results.We describe the evaluation process and outcomes of Move & Improve, a worksite wellness program in Maine. The evaluation process was based on the Centers for Disease Control and Prevention's Move & Improve is an ongoing program that was implemented in 1996. Although evaluation data have been collected since the program's inception, a more systematic evaluation based on community-based participatory research principles was undertaken in 2003 and 2004 with the technical assistance of the Maine–Harvard Prevention Research Center and Colby College.The Maine–Harvard Prevention Research Center facilitated the development of a program logic model, evaluation questions, data collection instruments, an analysis plan, presentations, and reports. We used a cross-sectional study design with nonparticipant comparison groups.Data indicate possible program improvement strategies and substantial improvements in lifestyle factors among participants.Limitations of the evaluation include participant self-selection, cross-sectional study design, a lack of adequate resources for evaluation, and the challenges of using community-based participatory research methods. Despite these limitations, Move & Improve program staff consider the evaluation of the program a success and have learned ways to improve the program and future evaluation efforts. Overall satisfaction with the process has been nurtured through community-based participatory research methods. This approach also enabled us to meet key evaluation standards. Health statistics for both Maine and the United States  underscoFramework for Program Evaluation in Public Health  assisted with the evaluation design and implementation. The program evaluation is based on the Centers for Disease Control and Prevention's (CDC's) c Health  and commM-HPRC's approach to community-based program evaluation is rooted in the literature on community organization and community building -10. ThisEastern Maine Medical Center established the Move & Improve program in 1996 to motivate individuals to increase their physical activity and to make healthier lifestyle choices. Move & Improve became a program of Eastern Maine Healthcare Systems in 2004. Move & Improve is a free 12-week program beginning in March each year that is designed to improve health by reducing participants' risk of chronic diseases and obesity. Individuals become involved with the program primarily, though not exclusively, through affiliations with worksites. Other Move & Improve sites include schools and community organizations. Yearly recruitment efforts include reaching out to past and new participants through the mail, statewide newsletters, and collaborating partners statewide who promote the program locally. Under the guidance of volunteer site coordinators who are identified internally by worksites, participants are asked to engage voluntarily in at least 30 minutes of physical activity for at least 4 days per week for a minimum of 8 weeks of the 12-week program. Participants are asked to track their physical activity on a log (either on paper or through an interactive online activity log) and receive encouragement and tips for continued participation and physical activity throughout the program. In addition, the program offers participants community-based stretch breaks at the local mall, statewide monthly walking clinics or clubs, various exercise programs, physical fitness assessments, educational sessions, and other events.Bangor Daily News), the local CBS affiliate (WABI–TV 5), collaborating partners , various program sponsors, Move & Improve coalition members, the Move & Improve Web site, and the e-mail systems of some participating worksites.Various communication tools have been used over the past 8 years to convey helpful information to participants. These include a quarterly newspaper that features a tip of the week, good-for-you recipes, nutritional information, book reviews, and profiles of program participants and a weekly online newsletter. Move & Improve health promotion tips are shared communitywide and statewide through local newspapers . In both 2003 and 2004, a general forward movement through the stages of change was observed.Program participation and completion rates have continued to increase. In 1997, approximately 1000 participants registered for the program; in 2003, Move & Improve had more than 9000 participants, and in 2004 it had more than 11,000 participants. In 2003, almost half were first-time participants, and in 2004, approximately one third were first-time participants. In 2003, physical activity stage of change was measured using a five-stage algorithm  based on exercising 4 days per week for 30 minutes per day, adapted from previous stage-of-change research . In 2004Since the program's inception, participants have reported anecdotally positive effects, such as weight loss, reduced stress, and reduced absenteeism. A technical report compiled by the University of Maine in 2001  reportedIn early 2003, the Move & Improve program director approached the M-HPRC to help improve the evaluation design and process with the ultimate goal of contributing to general knowledge about worksite health promotion programs such as this one. The M-HPRC contributed some staff time and a small stipend to help with data analysis. A statistician from Colby College was engaged to help with data entry and analysis. M-HPRC and Colby College used principles of CBPR for carrying out this phase of the evaluation.The objectives of this phase of the evaluation were to 1) characterize Move & Improve participants and participation in the program; 2) learn which worksite and coordinator policies seemed to make a difference to participants; 3) explore whether physical activity and stage of change were affected; 4) learn whether participants experienced other lifestyle outcomes such as weight change, better nutrition, stress reduction, or reduced absenteeism; and 5) explore whether multiyear participation was more likely to sustain greater levels of physical activity.M-HPRC staff led discussions outlining Move & Improve evaluation questions and methodology and were available for technical assistance throughout the process. M-HPRC staff also facilitated the development of a program logic model outlining the program's major activities and desired outcomes. M-HPRC staff facilitated the articulation of the program evaluation questions and evaluation design through negotiation with the Move & Improve staff who would implement it with minimal time and resources. M-HPRC staff drafted the posttest participant and coordinator surveys, which were then discussed and revised with Move & Improve staff input. Initial results were drafted by M-HPRC and Colby staff and presented to program staff for interpretation and revision. Because this evaluation process was community driven, Move & Improve staff made all final decisions about evaluation methodology based on discussions with M-HPRC and Colby staff and available resources.The 2003 and 2004, evaluations used a cross-sectional study design. Both years' evaluation efforts included nonparticipant comparison groups. In 2003, the comparison site survey was conducted at a worksite in Maine among program participants and nonparticipants and at a nonparticipating corporate partner worksite in Vermont that had comparable demographics. Both comparison groups were suburban, and each had approximately 100 employees. However, the Move & Improve participant group was 63% female, whereas the combined nonparticipant comparison group was 86% female. The comparison groups were also slightly younger. The 2004 program identified a comparable comparison group (from a worksite employing more than 750 people) near the program office in Bangor, Me. Program staff decided to offer a pencil-and-paper format for the comparison group survey in 2004 rather than an online format, which the participants used.A posttest survey was developed to assess participant demographics, level of physical activity, physical activity stage of change before and after participation, change in other lifestyle factors, absenteeism, and years of participation. One thousand randomly selected participants were mailed surveys in 2003 within 1 week of program completion. In 2004, all participants were provided with an opportunity to fill out an online evaluation that followed participation in the program.In 2003, coordinator surveys were developed and mailed to all program coordinators. In 2004, coordinators were offered a survey online. The surveys assessed coordinator demographics, level of physical activity, and strategies coordinators used to motivate participants.decrease in physical activity, no change in physical activity, or an increase in physical activity. This three-level outcome was used in place of the stage of change because of the large number of sparse cell sizes resulting from small numbers reporting very large changes. As expected, few participants selected maintenance (which requires 6 months or more of consistent behavior) or precontemplation (which suggests not yet intending to take action). Contingency table analyses using the Fisher exact test were used to assess the strength of the association between this three-level measure of change in physical activity and the lifestyle factors about which information was obtained. We also explored where movement in stage of change tended to take place between preprogram and postprogram, stratifying by stage. Preprogram stage was determined by participants' recall at the end of the program.Because the information gathered from program participants was generally categorical, hypothesis testing to find associations between them was done using contingency table analyses. Healthy living indicators  were recorded as having increased, decreased, or not having changed — yielding three nominal categories for each indicator. Change in stage of change was calculated as being the final stage of physical activity (postprogram) minus the initial stage of physical activity (preprogram). Thus, a negative stage of change indicates a decrease in physical activity, and a positive stage of change indicates an increase in physical activity. A three-level categorical variable was used to indicate whether each participant had a Approximately 43% of participants in 2003 completed the program, and approximately 46% completed the program in 2004, the highest percentage thus far. Of the participants who completed the program in 2003, 317 (31%) responded to the evaluation; in addition, 177 (53%) of the site coordinators, 33 (83%) of the individuals from the in-state comparison site, and 40 (80%) from the out-of-state comparison site responded to the evaluation. In 2004, 902 (14%) of the 6291 participants who completed the program responded to the online evaluation; in addition, 139 (39%) of 355 site coordinators and 252 (34%) of the 750 eligible employee nonparticipants completed surveys in 2004. Participants from both years were predominantly female (87% in 2003 and 75% in 2004). The substantial decrease in the proportion of female participants in 2004 may be because of a significant program effort in that year to recruit more male participants. The most frequent participant age categories were 45 to 49 years and 50 to 54 years for both years, with approximately 20% of participants in those categories . Age andBoth years of data show that in the 3 months before participating in Move & Improve, more than half of all participants reported no regular exercise or only minimal exercise. As expected, the posttest data from both years show substantial increases in physical activity, with only about 5% of participants remaining inactive or minimally active both years, compared with 27% of comparison group nonparticipants in 2004. In 2004, 61% of all participants increased their physical activity stage of change by one stage or more, and 37% had an increase of two stages or more . In contP < .001) except for soft drink consumption (P = .08). These results are particularly impressive given that the ceiling effect would likely bias the results toward the null of no association.In both 2003 and 2004, a substantial proportion of program participants reported weight loss ; increased energy ; increased fruit and vegetable consumption ; decreased fat intake ; decreased television viewing ; decreased sugar-sweetened soft drink consumption ; decreased stress ; and increased water intake  . Each ofP = .02).Employee absenteeism seemed to be associated with improvement in stage of change. Employees with a forward movement of two or three stages averaged 1 sick day during the 3 months of the program, whereas employees who stayed the same or regressed in their stage of change averaged 1.5 sick days during the same 3 months in 2003. However, number of sick days reported was small, so we were not able to assess significance. Involvement with Move & Improve for 2 or more years was significantly associated with improvement in stage of change (Flextime, group activities, and incentives were the most common practices perceived by participants to make a difference. Coordinators cited group activities and incentives as worksite policies that came about most often as a result of the program. Yet, in contrast to what participants noted would be most helpful, coordinators tried to motivate participants most often using posters, office memos, wellness committees, bulletin boards, and e-mail tips and by registering employees for them.We evaluated Move & Improve's process and outcomes using CBPR methods. Limitations in our ability to draw conclusions about the program's success include limitations inherent in cross-sectional study design; the small size and location of the comparison groups; the lack of program resources, including staff and funds for long-term follow-up with participants; and challenges that arise from using CBPR methods and local decision making. Move & Improve participants are self-selected and therefore do not represent the general worksite population or any particular high-risk group. Because participants' stage at the start of the program was determined by recall at the end of the program, response bias may have slightly inflated the effects of the program as reported in 2003 and 2004.Move & Improve's challenge now is to increase participation and completion rates and to recruit worksites with higher-risk adult populations. The 2004 evaluation revealed that participants felt that incentives, group activities, and flextime at work made a difference in their participation. Coordinators, however, may not have been able to influence worksite policies to include these factors. Because evaluation data revealed that younger individuals and men tended not to participate at as great a rate as relatively older individuals and women, greater efforts should be made by the program to help coordinators recruit and retain these individuals and to understand barriers to their participation. Perhaps more coordinators should fit this profile to motivate individuals from these groups to participate. Our analyses also revealed that many participants who were already physically active did not change their stage of physical activity over the course of the program. Perhaps some formative data could help elucidate the types of program components that may motivate these individuals to stay active over time. To motivate and recruit individual worksites to participate, program staff could emphasize the data that indicate less absenteeism for participants. Objective record keeping of numbers of sick days taken by participants should be encouraged.Many final modifications to the evaluation design and instruments were made because of resource constraints by program staff after consultation with M-HPRC and Colby College. These circumstances may have compromised the scientific rigor of the study and our ability to draw objective conclusions from the data. One example is the decision to change the way physical activity stage of change, a key outcome, was measured in 2004. This decision was made by Move & Improve staff to align the outcome measure with the additional program goal of 5 days of physical activity per week for at least 45 minutes per day. Another example is the program's decision to offer paper-and-pencil surveys for the 2004 comparison site when all of the program participants had completed the same survey online. In this case, the employer preferred the pencil-and-paper format. Another modification involved the decision in 2003 to survey in-state nonparticipants for the comparison group from the same worksite as participants. This approach required fewer resources than going to another worksite. With a deeper understanding of the importance of consistency of measurement, Move & Improve program staff plan to use the original physical activity stage of change measure in the future and, because of staffing and funding constraints, discontinue the use of a comparison survey.utility was maximized by involving stakeholders so that identification of their needs and intent were not only addressed but were central to the process. Evaluator credibility was enhanced through the relationships that were nurtured. Any findings were first disseminated to key program stakeholders for their review and interpretation. The standard of feasibility was also positively affected through CBPR. Evaluation procedures had to be practical given the resources. Move & Improve staff made all final decisions on how to carry out the evaluation based on their assessment of whether they could get it done in a timely manner. Maximizing feasibility, however, may have also compromised scientific rigor.An advantage of using CBPR was that it increased our adherence to several core evaluation standards . The staMove & Improve program evaluation indicates that the program has been a success on many levels. Evaluation data indicate that Move & Improve has a significant impact on participants' lifestyle and risk behaviors and that longer participation in the program may also be associated with greater chronic disease risk reduction. Participants significantly increased their physical activity stage of change compared with nonparticipants during the same time period. Improved lifestyle factors were also significantly associated with forward movement in stage of change. Future evaluation efforts can minimize limitations by adding pretest data collection and keeping measures consistent over time. Longer-term follow-up of participants should also be attempted.The benefits of using CBPR methodology far outweighed limitations in scientific rigor. Move & Improve staff enthusiasm, at least in part because of its integral involvement with every aspect of the evaluation design, helped Move & Improve and M-HPRC staff overcome key barriers. Program staff gained appreciation for how to carry out successful program evaluation with minimal resources and how to improve their program. Several core standards of successful evaluation practice were also maximized. Relationships formed through the process of conducting CBPR-framed evaluation will help to sustain and improve future Move & Improve program evaluation efforts.


El camino saludable) is an obesity prevention program for low-income, predominantly Hispanic and African American families in an urban community in Tarrant County, Texas. Healthy Weigh Phase 1 was a successful community–campus partnership that took place in summer (June–August) and fall (September–November) 2003. The program met stated objectives and extensively engaged students from several health disciplines in service learning. This article describes what we learned about the evaluation of the program by examining the phase 1 evaluation process.Healthy Weigh (Family environments are important intervention settings for establishing life-long dietary practices. Available in English and Spanish, Healthy Weigh Phase 1 helped families that were at risk for overweight and obesity to adopt healthy eating, physical activity, and weight management patterns.Framework for Program Evaluation in Public Health standards were used to judge the overall quality of the phase 1 evaluation process.Analysis of a program logic model and formative evaluation data identified evaluation questions that could have improved the phase 1 evaluation process. Questions were categorized according to Donabedian's structure–process–outcome framework, and potential benefits of each question were identified. The Centers for Disease Control and Prevention's The phase 1 evaluation process successfully assessed the program's effects and generally met evaluation standards. Our critical examination also highlighted structure and process evaluation issues with potential for strengthening future interventions, community partnerships, and program outcomes.Lessons learned influenced the phase 2 grant activities. Most importantly, we learned that involvement of program participants as full partners in program design, evaluation, and implementation is essential. Our understanding and practice of program evaluation evolved as Healthy Weigh became a true community-based participatory research endeavor. El camino saludable) is a community-based obesity prevention program for low-income, predominantly Hispanic and African American families in an urban community in Tarrant County, Texas. Phase 2 has already been completed, and in spring 2005, Healthy Weigh implemented post-phase 2 activities  . Healthytivities . HealthyFramework for Program Evaluation in Public Health (referred to as framework in this article) standards , a faith-based community organization, provided the physical facility for Healthy Weigh, assisted with weekly reminder calls to participants, and was the primary source of participant referrals and community volunteers. CCC serves a community at high risk for overweight and obesity. Factors for overweight and obesity included the median household income , federal poverty level (44.6% below the poverty level), and people older than 25 years lacking high school diplomas (42%) . The popPhase 1 was offered twice in 2003  and consisted of 12 weekly sessions, prescreening, and postscreening. Participants chose to enroll in the English- or Spanish-language version of phase 1. Community focus groups provided input on program design, evaluation, and recruitment. Recruitment flyers were distributed door-to-door in target neighborhoods and through schools and CCC.Of 282 people screened for phase 1, most participants were female (72%) and Hispanic (82%) or African American (12%). Many of the participants were families; 46% of participants were younger than 19 years,  and 9% were older than 60 years. Many participants had limited proficiency in English or Spanish. Based on body mass index, 84% of adults were overweight or obese, and 50% of children and adolescents were overweight or at risk for overweight.Healthy People 2010  directed program implementation, which was carried out by registered nurses, a registered dietitian, paid staff, community volunteers, and supervised students from nursing, nutritional sciences, kinesiology, social work, and medicine programs. More than 160 undergraduate and graduate students from two universities served as educators, exercise leaders, meal preparation and service coordinators, table-talk leaders, child care workers, health screeners, and research assistants. Sixty percent of the students were volunteers, and most of the remaining students participated to meet course requirements. Many program participants also served as volunteers by helping with set up, clean up, and interpretation.structure, process, and outcome and determined how including these questions in the phase 1 evaluation might have strengthened program implementation and outcomes  and noninvasive methods for data collection fostered participant acceptance of measurements and made it easier for students to help conduct screenings. Concerted efforts to prevent phase 1 activities from interfering with CCC's daily operations and early negotiation for using equipment and space helped gain and sustain CCC's cooperation in evaluation procedures. Proactive communication with CCC's staff and university, funding agency, and community–partner organizations also contributed to political viability. Ongoing budget management based on financial requirements of the program, university, and funding partner helped ensure that resources were used effectively to achieve program processes and outcomes.Structure–process–outcome analysis highlighted ways the evaluation process could have better met the feasibility standards related to use of resources and political viability Tables –4. InvesTwo process variables also affected feasibility. Knowing more about why participants attended some sessions and not others could have promoted more cost-effective use of human and material resources needed for program physical activity and nutrition classes, family meals, and food-bag preparation. Systematically collecting data about participants who dropped out of the program might have helped improve retention and program design. Early clarification and monitoring of community partners' roles would have provided a framework for increased collaboration and communication among partners, making the evaluation process more politically viable.Eight framework propriety standards address legal and ethical characteristics and how the evaluation process affects all the participants involved. Although the lack of formal agreements among all key parties involved in the evaluation was a weakness, overall the evaluation process met propriety standards. Concern for participant welfare was evident in design of evaluation tools and procedures, the willingness to adapt the research design to meet participant needs, the commitment to building relationships with participants and CCC staff, and adherence to financial accounting standards.Informed consent and other screening tools were appropriate for participants with limited English proficiency. Documents were available in English and Spanish and were prepared at the fourth- to fifth-grade reading level in English, with reader-friendly formatting and adequate white space . BecauseParticipant privacy was maintained at levels consistent with community expectations. Staff members explained screening results and gave families copies of results in appropriate languages. Referrals for follow-up health care were based on prescreening findings. Efforts were made to obtain health care for participants who lacked regular sources of care.When formative evaluation showed that participants were unfamiliar with setting goals, we modified the screening protocol to include teaching participants about setting appropriate goals for healthy eating, physical activity, or weight management. Fifty summer participants asked to enroll in the fall program, so we revised the research design. Relationships with participants and their progress toward improved physical activity and healthy eating patterns were more important to overall program goals than strict adherence to the original research design.All financial reporting requirements of the university and United Way were met. Maintaining and properly cleaning the CCC facility, equipment, and supplies during and after each Healthy Weigh meeting also addressed fiscal responsibility standards.Twelve framework accuracy standards assess correctness of evaluation findings. The evaluation process for phase 1 grant objectives (see previous lists of outcome and process objectives) met these standards.Structure–process–outcome analysis revealed how the phase 1 evaluation process could have measured the findings more completely and accurately Tables –4. ColleProvided clear, complete understanding of effective participant recruitment and retention strategiesIncreased opportunities to build student–participant relationshipsPromoted investment of resources in staff building rather than managing staff turnover and shortages Produced more comprehensive assessments of service learning in this programWe undertook this critical examination of the Healthy Weigh Phase 1 evaluation to improve the evaluation design for future Healthy Weigh interventions. We learned that the phase 1 evaluation process successfully assessed program effects and generally met framework standards. Structure–process–outcome analysis highlighted additional evaluation factors related to structure and process that could strengthen subsequent Healthy Weigh interventions, community partnerships, and program outcomes.We have already applied lessons learned to improve the phase 2 evaluation plan and process. An English-speaking health action group formed during phase 1 helped design the phase 2 pilot. Although this particular health action group disbanded, participants and students who had been consistently active in Healthy Weigh formed a new health action group. This group of monolingual English speakers, monolingual Spanish speakers, bilingual speakers (English and Spanish), adults, and youths acted as a true partner in the design, implementation, and evaluation of phase 2.Another improvement was increased attention to monitoring the CCC–university partnership. Problems were avoided or addressed early in phase 2 by more frequent and intentional monitoring of the partnership. Contacting CCC after each Healthy Weigh meeting helped us be aware of and address actual or potential problems.This critical examination was valuable and challenging. As is frequently true of community health programs, the opportunity and resources to address a significant community health issue emerged rapidly. Faced with limited development time, we focused on creating a phase 1 evaluation plan that would assess effects of an evidence-based program and would be designed to be culturally and linguistically appropriate for the target community. Recognizing Healthy Weigh as a pilot intervention, we wanted to gain insights about factors and relationships that would optimize community partnerships, program design, service learning, and improvements in participant families' physical activity, healthy eating, and weight management behaviors. Formative evaluation data gathered during program implementation suggested that the investigators were frequently filling volunteer and paid staff roles and not obtaining all desired data.Critical examination of phase 1 evaluation enabled us to identify structure and process evaluation questions to include in future evaluation plans. These questions will enhance our insight and strengthen programs and their evaluation processes. Healthy Weigh has evolved into a community-based participatory research intervention as community partnerships have been established and nurtured. This retrospective examination made clear that we began Healthy Weigh Phase 1 without the community relationships necessary to involve all stakeholders in the evaluation process as we now envision and practice it.


Loads acting on scoliotic spines are thought to be asymmetric and involved in progression of the scoliotic deformity; abnormal loading patterns lead to changes in bone and disc cell activity and hence to vertebral body and disc wedging. At present however there are no direct measurements of intradiscal stresses or pressures in scoliotic spines. The aim of this study was to obtain quantitative measurements of the intradiscal stress environment in scoliotic intervertebral discs and to determine if loads acting across the scoliotic spine are asymmetric. We performed in vivo measurements of stresses across the intervertebral disc in patients with scoliosis, both parallel  and perpendicular  to the end plate, using a side mounted pressure transducer (stress profilometry)Stress profilometry was used to measure horizontal and vertical stresses at 5 mm intervals across 25 intervertebral discs of 7 scoliotic patients during anterior reconstructive surgery. A state of hydrostatic pressure was defined by identical horizontal and vertical stresses for at least two consecutive readings. Results were compared with similar stress profiles measured during surgery across 10 discs of 4 spines with no lateral curvature and with data from the literature.Profiles across scoliotic discs were very different from those of normal, young, healthy discs of equivalent age previously presented in the literature. Hydrostatic pressure regions were only seen in 14/25 discs, extended only over a short distance. Non-scoliotic discs of equivalent age would be expected to show large centrally placed hydrostatic nuclear regions in all discs. Mean pressures were significantly greater (0.25 MPa) than those measured in other anaesthetised patients (<0.07 MPa). A stress peak was seen in the concave annulus in 13/25 discs. Stresses in the concave annulus were greater than in the convex annulus indicating asymmetric loading in these anaesthetised, recumbent patients.Intradiscal pressures and stresses in scoliotic discs are abnormal, asymmetrical and high in magnitude even in the absence of significant applied muscle loading. The origin of these abnormal stresses is unclear. The aim of this study was to obtain measurements of pressures and stresses in the intervertebral discs of scoliotic patients in order to try to prove the hypothesis that asymmetrical loading was present in the scoliotic spine and hence could realistically be involved in curve progression. We were also very interested in the stress environment of the intervertebral disc in scoliosis in general. We considered that recording from discs prior to excision during anterior scoliosis reconstructive surgery involved minimal additional patient risk. However, in anaesthetised patients with additional muscle relaxation  no loading due to muscle activity is present. We therefore were unsure if our approach would show any meaningful results.Previous authors have theorised about the biomechanical role of asymmetrical loading in progression of the scoliotic deformity -3. Non-oThe cellular mechanisms by which abnormal loading may generate deformity has been shown previously in cell culture and in animal models. Cells of bone and disc are very responsive to mechanical stress,15, withMost of the information on loads acting on the scoliotic spine is derived from measurements of changes in spinal morphology and from modelling,24. TherPatients having anterior surgery for thoraco-lumbar scoliosis were considered for inclusion in this study. The control group was patients without scoliosis having anterior surgery involving total disc excision. These were patients undergoing kyphosis surgery or anterior lumbar surgery for back pain. They were chosen as a comparison group to the scoliotics because of the lack of lateral curvature at the disc levels operated on. Ethical approval was obtained from the Oxford Regional Ethics Committee. Written and verbal information about the study was given to patients 4–6 weeks before surgery. In those patients under the age of 16 years, the parents' consent was obtained as well. Details of the patients and controls tested are given in tables The pressure transducer used in the study was the same type as that used previously for pressure profile measurements -28. It hThe transducer was calibrated up to 1 MPa using a pressure vessel(a tube of circular cross section) with a known cross sectional area filled with water to which known loads were applied by a servocontrolled hydraulic materials testing machine . The rate of application of load during calibration was approximately 0.2 MPa/s. Over the range 0–1 MPa the voltage recorded was found to be linear with respect to pressure applied. Re-calibrations of the transducer showed that it was very stable and showed negligible drift over time. Before surgical use, the pressure transducer was sterilised using Perisafe  according to standard hospital protocols.In all the scoliosis and kyphosis cases the spine was exposed by a conventional transpleural and retroperitoneal approach, dividing the diaphragm close to its peripheral attachment. In the back pain patients, a retroperitoneal approach to the low lumbar spine was performed. Our normal practice is to insert spinal needles into exposed discs and to check the anatomical level by taking an x-ray. In these scoliosis and control patients, one of the needles was substituted by the pressure transducer. It was inserted through the convex annulus and the transducer pushed across the disc to the concave annulus Figure , the patThe initial position of the transducer/electrode tip and of the transducer membrane in each disc was assessed from the intra-operative X-ray film. These were scaled using the known diameter and length of the pressure transducer. The disc dimensions were obtained from the same X-ray. Results are given as the position of the transducer diaphragm relative to the concave border of the disc.Chart software  was used to convert the voltages obtained into stresses/pressures in accordance with the measured calibration coefficient. The data were then exported to Microsoft Excel for further analysis.Where appropriate, measurements are presented as means and standard deviations in n discs where n is the number of discs tested.In this study, pressure profiles were measured in 25 scoliotic and 10 non-scoliotic discs from 7 scoliotic and 4 non-scoliotic patients over a period of one year (July 2001 – July 2002). Details of the scoliotic patients in the study are given in Table The stress profiles generally showed asymmetries between the concave and convex sides of the curve for both the vertical and horizontal stresses.A peak in the vertical stress recorded in the concave annulus (far left side of the profile) was a common feature of the profiles in the scoliotic discs in this study, a typical example being shown in figure Previous pressure profiles measured in non-scoliotic, non-degenerate discs of similar age to the scoliotic patients show large hydrostatic central areas ,26 In maIn 5 cases, peaks in the convex annulus also occurred. On only 2 occasions was this higher than the maximum vertical stress in the concave annulus in the same disc.We analysed the pressures recorded in those scoliotic discs that showed hydrostatic regions. The hydrostatic pressure values varied between 0.1 and 0.43 MPa; the mean value was 0.25 ± 0.10 MPa (SD). The values for each patient in relation to the apical disc are shown in figure Hydrostatic disc pressures in the apical disc were not obviously higher overall or higher than at adjacent levels and the apical discs had more hydrostatic nuclei 6/7 (86%) compared with 10/18 non-apical discs (56%).We found a slight trend towards higher mean pressure progressing caudally for absolute disc level, shown in figure We analysed the maximum value of the stress in the concave annulus. No readings were obtained in the concave annulus of the T10/11 disc of patient 4 hence this disc is not represented. Stress levels were very variable, ranging from 0.1–1.15 MPa. For all discs where a recording was made in the concave annulus, the mean stress was 0.55 ± 0.28 MPa (SD), The magnitude of the peak vertical stresses recorded in the concave annulus for each of the scoliotic patients relative to apical disc level is shown in Figure The stress change across the disc was calculated from the first reading shown to be taken inside the anatomical disc minus the last reading taken before the transducer exited on the convex side. On some occasions, the last reading was probably out of the disc . In 18/24 discs, this value was positive indicating that higher stresses were found on the concave side of the curve. In only 2/7 patients was the stress positive and greater in the apical disc than adjacent discs. In 7/25 discs, stress was higher in the concave annulus than the convex without a concave stress peak being present.The stress change across each of the scoliotic study discs is shown in Figure Due to the low numbers of patients who both were having anterior surgery for non-scoliotic conditions and who consented to having pressure measurements performed during the time period of the study, we only have pressure profiles from 10 discs for comparison.Table Profiles showed significant variability in this group of patients.Patient P10 who was 26 years old showed a pressure profile with higher stresses towards the posterior annulus, a hydrostatic region and a trough of horizontal pressure in the anterior annulus. In both discs of patient 11, stresses were essentially zero throughout apart from an increase in vertical stress in both and a horizontal stress peak in the anterior annulus of the L5/S1 disc with no hydrostatic regions.In the kyphotic patients, patient 8 who had quite a flexible curve clinically showed profiles with pressure peaks mainly in the anterior annulus with an under pressurised central region. The T11/12 and L1/2 levels showed hydrostatic nuclei. Patient 9 who was a kyphotic with a curve that was noted to be very stiff intra-operatively had very narrow discs and made introduction of the pressure probe difficult. Only a few recordings per disc (mean of 2.75) were made and so profile shape could not be accurately determined.5/10 (50%) non-scoliotic discs showed no regions of hydrostatic pressure.For the patients with back pain, hydrostatic regions were seen in the L4/5 disc of patient 10 (0.214 MPa). The central regions of both discs in patient 11 showed negative pressures very close to zero level  and the horizontal and vertical pressures were very close in value over these regions. In the kyphotic patients, only the T11/12 and L1/2 discs of patient 8 showed hydrostatic regions with a mean of 0.030 ± 0.022 MPa. For patient 9, there were no hydrostatic regions however in order to indicate the general size of the stresses present, the mean vertical stress was 0.327 ± 0.33 MPa and horizontal was 0.627 ± 0.46 MPa over all 4 recorded discs.5/6 (83%) non-scoliotic discs showed stress peaks in either the anterior or posterior annulus (data from Patient 9 was disregarded due to too few data points per disc) with the T11/12 disc of patient 8 showing both anterior and posterior peaks. Of these stress peaks, 5/7 (71%) were anterior.All the non-scoliotic discs showed some stress difference across the disc. It was very variable in magnitude ranging from .057 to 1.33 MPa with a mean of 0.35 ± 0.39 MPa  we have also compared our results with intradiscal pressures measured in Japanese subjects with back pain prior to laser nucleotomy. In thisIn our study, the mean value of hydrostatic pressure for the scoliotic patients was 0.25 ± 0.10 MPa, > 3 fold higher than that measured in Yonezawa's patients.Figure We present new data on intra-disc pressure profiles of patients with thoraco-lumbar scoliosis. The overall hypothesis we were attempting to test in this study was that abnormal, asymmetrical loading was present in the scoliotic spine and contributed to the progression of the scoliotic deformity. However, due to the surgical positioning and anaesthetised state of the scoliotic subjects we were unsure whether any physiologically significant pressure readings would be obtained since the majority of loading across the motion segment is due to body weight and muscle activity -32. We wRather surprisingly, the readings obtained in the scoliotic discs were much higher in magnitude than we expected. The mean pressure reading in those discs with a hydrostatic nucleus (14/25) was 0.25 ± 0.10 MPa which was on average >3 fold greater than in the available control data Figure .Despite the lack of muscle activity, our results also showed evidence of asymmetrical loading in the scoliotic spine. Stresses were higher in the concave than in the convex annulus in 18/25 discs Figure . We did A number of scoliotic and non-scoliotic discs in this study had non-hydrostatic regions, 44% of scoliotic and 50% of non-scoliotic. For the nuclear matrix to behave in a non-hydrostatic manner it must be abnormal in composition or relatively dehydrated. This would be most likely due to glycosaminoglycan loss or potentially, mechanical loss of fluid due to chronic high loading. With regards to the non-scoliotic discs, the back pain patients would be expected to have degenerate discs with glycosaminoglycan loss. Patient 11 was known to have severe degeneration on MRI imaging and hence showed disc pressures close to zero and non-hydrostatic discs. Patient 10 was younger and had less severe degeneration consistent with higher pressures and a hydrostatic disc. For the kyphotic patients, patient 8 was a severely disabled, paraplegic from T4 distally due to invasion of the spinal cord by tumour. She had flexible kyphosis clinically and the T12/L1 level was non-hydrostatic presumably due to secondary degenerative change at that level. Patient 9 had a very stiff curve and almost complete loss of disc height at all levels and severely dehydrated discs. With regards to the scoliotic discs however, non-hydrostatic discs are less easily explainable. Glycosaminoglycan loss in not know to be severe in the scoliotic disc and althThe pressures we measured in discs with hydrostatic regions in the scoliotic patients were considerably higher than those measured in patients with kyphosis and with chronic low back pain, which were on average low and of similar magnitude to that reported by Yonezawa. In addiThe finding of high pressures and stresses in recumbent, anaesthetised scoliotic patients with minimal loading due to muscle activity was unexpected and its origins are unclear.The internal mechanical environment of the intervertebral disc is complex. The factors influencing disc pressure/stress at any point in the disc will arise from both intrinsic factors, viz. disc swelling pressure and matrix organisation and extriWith regard to externally imposed forces, body weight and muscle forces, though altered in scoliotic patients, should Ligamentous tethering or changes in annulus organisationcould be As well as differences in pressure levels, there were also profound qualitative differences between the pressure profiles measured in the study scoliotic discs during surgery Figure  and 5 anThe origin of disc stress peaks has been discussed previously in the literature,27 in noIn 18/24 discs, higher stresses were found on the concave side of the curve compared to the convex indicating asymmetrical loading. This is obviously not explainable by asymmetrical muscle loading since the spinal muscles were relaxed in these patients. The simple presence of concave annular stress peaks, due to the possible previously mentioned factors, could lead to a stress gradient across the disc. However, even in some discs without a defined stress peak, asymmetrical loading was present.c. 1.0 MPa, Figure This study has found that stresses in scoliotic discs are abnormal. Scoliotic discs in recumbent anaesthetised, muscle relaxed patients have higher nuclear hydrostatic pressures than those measured in non-scoliotic discs in this study and reported in the literature. In 18/24 discs from patients, a stress gradient from concave to convex sides of the disc was measured, with some very high differential stresses (Without the presence of muscle activity, these findings are very surprising and intriguing. Previous studies have implied that asymmetrical muscle loading is the origin of asymmetrical loading which via changes in cellular activity and hence asymmetrical growth causes a "vicous cycle" of progression in an otherwise physiologically normal spine,58. The AM carried out the pressure measurements in vivo, analysed the data and drafted the manuscript. DJ and MS were responsible for setting up and validating the pressure measurements in vitro and providing technical help. JF provided the clinical overview and expertise. JU and JF conceived the study, were involved in the study design and co-ordination and helped draft the manuscript. All authors read and approved the final manuscript.


There has been increasing interest in the ability of the internet to produce behaviour change. The focus of this study was to describe program exposure across three intervention groups from a randomised trial (RT) comparing traditional face-to-face, internet-mediated (combined internet plus face-to-face), and internet-only program delivery.Baseline and immediately post-intervention survey data, and exposure rates from participants that commenced the RT were included (n = 192). Exposure was defined as either face-to-face attendance, website usage, or a combination of both for the internet-mediated group. Characteristics of participants who were exposed to at least 75% of the program material were explored. Descriptive analysis and logistical regression were used to examine differences between groups for program exposure.2 = 10.37, p < 0.05), between intervention groups. The internet-mediated  and internet-only  groups were more likely to have been exposed to at least 75% of the program compared to the face-to-face group. Participants with high physical activity self-efficacy were 1.82 (95% CI 1.15–2.88) times more likely to have been exposed to 75% of the program, and those allocated to the face-to-face group were less likely to have attended 75% of the face-to-face sessions if they were classified as obese (OR = 0.21 95% CI 0.04–0.96).All groups showed decrease in program exposure over time. Differences were also observed (χThese results suggest that the internet groups were as effective as the face-to-face delivery mode in engaging participants in the program material. However, different delivery methods may be more useful to different sub-populations. It is important to explore which target groups that internet-based programs are best suited, in order to increase their impact. Current epidemiological evidence suggests that approximately 60% of the global population do not participate in sufficient physical activity for health benefit , definedGroup-based programs that offer face-to-face treatments are common and popular strategies in behaviour change research . UnfortuIn physical activity research only a small number of internet-based trials have been reported -19. A steSteps)  across the three delivery modes of the Health-outcomes  includinoutcomes .eSteps intervention /height [m]assessed . Eight qassessed .Self-report physical activity was assessed using the Active Australia survey. The Active Australia survey asks questions related to moderate- and-vigorous intensity activities performed for a period of at least 10-minutes . Test-rePhysical activity self-efficacy (PASE) was assessed using a five-point Likert-type scale questionnaire, which asked people to rate their confidence in performing physical activity in a range of conditions and situations from 'not confident at all' to 'very confident' . This questionnaire has been used in previous studies ,32. CronSocial support for physical activity (SSPA) was assessed using a five-point Likert-type scale questionnaire. Participants were asked four items related to how often ('never' to 'very often') over the last three months their family, friends and/or colleagues have supported them to be physically active . This questionnaire has previously been reported to have a Cronbach's alpha of 0.77 , and is web tracking was used to track exposure across the IM group. Exposure in the IO group was tracked using the same web tracking system used for the IO group. Specifically, web tracking for the IM and IO groups was collected using Advanced Web Statistics 5.9 (AWStats) [Exposure was tracked using weekly attendance rolls in the FACE group, which were collated by the facilitator. A combination of attendance rolls (collated by the same facilitator) and AWStats) . AWStatsprogram exposure was operationally defined as attending or being exposed to a minimum of 75% of the module/information sessions whether they were delivered face-to-face or via the internet. In this context, participants who achieved 75% program exposure, attended and/or logged onto the website a minimum of 7.5 times over the intervention period (excluding Weeks 1 and Week 12 as they involved face-to-face data collection). Dunn, Garcia et al. [program exposure for the intervention groups was based upon the assumption that participants that logged on to the Health-eSteps website actually read and interacted with the website material. This is similar to the assumption that those who attend face-to-face sessions actually listen and engage with the program facilitator/program material.Drop-outs were defined as not completing follow-up data in Week 12 or previously stating that they wanted to withdraw from the study. Seventy-five percent a et al.  report tDescriptive statistics of participant characteristics and weekly program exposure were analysed and reported using the mean (± SD), or numbers and percentages.at least 75% program exposure and change in the primary outcome measure , controlling for age, gender, BMI, as well as baseline ISE, PASE, SSPA, and group allocation. Physical activity was logarithmically transformed owing to its skewed distribution, and analysis conducted on the transformed variable.Seventy-five percent program exposure was dichotomised into yes (achieved 75% program exposure) and no (didn't achieve 75% program exposure). Chi-square analysis was first used to examine differences in 75% program exposure by intervention group. Analysis of Covariance (ANCOVA) was used to examine the effect of Logistic regression was used to examine participant characteristics and likelihood of achieving at least 75% program exposure. Seven variables  representing baseline characteristics were used. First, regression analysis was used to examine predictors of program exposure by demographic variables  for the entire cohort. Second, we included PASE and SSPA as psychosocial variables in the model, given their strong association with regular physical activity participation . AnalyseThe intervention attracted predominately women (83.3%) with an overall mean age of 38.4 years ± 11.2) and BMI of 32.2 (± 7.5) (Table 1.2 and BThe mean number of face-to-face sessions (exposure) attended by the FACE group was 6.1 . The mean number of logins (exposure) for the IM group was 11.5 and 11.8 for the IO group. However, internet access ranged from 2–102 times for the IM group, and 2–90 times for the IO group over the entire intervention period. Taking into account multiple logins each week for the internet-groups, overall average attendance for all three groups was 5.5 sessions (SD ± 2.3). A decline in weekly exposure was observed for each intervention group  of participants from the IM, and IO groups logged on to the website in Week 2, in which there were a number of incentives available. IM and IO groups received email notification of the incentives via the weekly email reminders, and the website homepage also highlighted the incentive opportunities. However, of the 91 participants who logged on to the site during Week 2, only 21 (20%) participants responded to the 'incentive opportunity'. Participants in the IM and IO groups were also given the chance to receive online advice and support from a Health-2 = 10.4, p < 0.05), with the FACE group showing the lowest with-in group program exposure rate of 28%, followed by 51% and 53% for the IM and IO groups respectively  = 9.85, p < 0.01, with a mean difference of approximately 124-minutes per week (p = 0.02), between participants with and without at least 75% program exposure.Overall, approximately 44% of participants demonstrated at least 75% program exposure, 61% achieved 60% program exposure, and 70% were exposed to at least half of the program material. Significant differences in program exposure was found for those exposed to at least 75% of the program material by intervention group (χThe IM group were 2.40 times more likely to reach 75% program exposure (95% CI 1.13–5.1), and participants in the IO group were 2.96 times more likely to reach 75% program exposure (95% CI 1.38–6.3) compared to the FACE group. Internet self-efficacy was not a significant predictor . Participants allocated to the IO group were 2.66 times more likely to be classified as having been exposed to 75% of the program material (95% CI 1.21–5.87) compared to the FACE group  and drop-out, to other physical activity interventions delivered via the same modality ,37. HoweeSteps website that may have assisted in user engagement similar to that observed in the FACE group, was the delivery of modules/information sessions on a weekly basis. In this respect, participants could not log on to the website and review the entire website in the one sitting. Further, the website material was built-upon on a week-by-week basis, possibly enticing participants to return to the site the following week. Strategies incorporated into the website such as a "What's New at Health-eSteps" section, weekly reminder emails and the numerous interactive features  may have also enhanced participant engagement in the website. However, this study did not examine specific strategies of engagement, therefore we can only speculate as to why participants returned back to the website.One of the strong points associated with the Health-eSteps program also used incentives to assist in enhancing program exposure across all three intervention groups, however without a comparison group (control with no incentives) this study can not conclude if the incentives had an effect upon program exposure or not. Although the limited observation of participant engagement with the incentive opportunities, suggests that new innovative incentives idea and engagement strategies are required. This may include the examination of different 'types' of incentives, combination of engagement strategies , addition of telephone counselling/support and/or the provision of more automated tailored feedback.The Health-Previous research has also highlighted that poor program outcomes are associated with poor program attendance ,39. TateeSteps website it was decided not to include a discussion board or online chat room based upon formative evaluation results [A potential avenue for future research is the examination of online chat rooms, support groups, and discussion boards for enhancing treatment effects and participant retention. For the Health- results , and the results ,36. Furt results ,42. Howe results . TherefoTo date, few studies have focused upon individual moderators of program effects ,45, suchParticipants who had higher PASE at baseline were more likely to have been exposed to at least 75% of the program material in the IM and IO groups. Physical activity self-efficacy is commonly reported in the literature as an important mediator  across aInterpretation of the findings presented in this study should be mindful of the following limitations. A methodological limitation to this study was that participants allocated to the IM and IO group still received face-to-face contact in Week 1 and Week 12 for data collection. Future studies should therefore, investigate the efficacy of changing behaviour with no face-to-face contact, and use internet-based data collection methods that may also increase the number and reach of the target population .eSteps RT was the first study of its kind to compare the efficacy of face-to-face with an internet-based behaviour change program, therefore examining program exposure across delivery modes, as presented here is of interest to researchers. The findings of this study were also based on self-report information and no objective measures of physical activity were used. The sample population were mainly female, living in a rural area of Queensland, Australia, therefore the results are not generaliseable to the population as a whole. Additionally, the study sample was self-selected and may be more motivated to change their behaviour than the general population.This study compared two types of 'exposure'; face-to-face program exposure (in-person sessions each week for an hour) with internet 'exposure' (logon frequency) in which the access time, day and location was not restricted. These two definitions are inherently different and plausibly reflect differences in the 'dose' of the intervention received. Examination of the amount of 'time' spent on the website (in comparison to a 1-hour session) was unable to be determined. However, the Health-The findings of this study support the growing body of evidence for the use of the internet in behaviour change research. Weekly exposure showed a similar decline over time, however the internet groups were more likely to have been exposed to at least 75% of the program material. Future research should investigate reasons for internet-based program drop-out and examine strategies for increasing participant exposure. It is also important to explore which target groups or populations that internet-based programs are best suited. Identifying factors that predict drop-out and program exposure is critical for the future development of physical activity internet-based interventions. In this context, we can increase the public health impact of internet-based programs, whilst providing effective alternate delivery modes for increasing physical activity in sedentary populations.The author(s) declare that they have no competing interests.RS participated in the design, development and evaluation of the intervention, performed the statistical analysis, and drafted the manuscript. KM participated in the design and evaluation of the intervention and helped to draft the manuscript. TD helped draft the manuscript. All authors read and approved the final manuscript.