PERCEPTION OF SELF-EFFICACY AND PROFESSIONAL BURNOUT IN GENERAL EDUCATION TEACHERS*

Purpose. The objective of the study was to determine to what degree general perception of self-efficacy protects general education teachers in Poland (educational stages II–IV) against professional burnout, and whether teachers of various subjects display any differences in this respect. Basic procedures. The study was carried out between April and June 2005 on a sample of 404 teachers (women n = 310, men n = 94). The diagnosis of the burnout syndrome was based on the Maslach Burnout Inventory (MBI). The perception of coping competences in teachers facing professional stress was measured with the General Self-Efficacy Scale (GSES) (Polish version) by R. Schwarzer, M. Jerusalem and Z. Juczyński. Main findings. Teachers are characterized by a high level of self-efficacy perception. Conclusions. As a factor preventing development of the three-dimensional burnout syndrome, perception of self-efficacy protects teachers against a loss of professional satisfaction, increasing emotional exhaustion and a tendency to depersonalize their pupils. Teachers of various subjects perceive the preventive role of self-efficacy differently.

Introduction
Teachers constitute a group classified as one of the so-called helping professions, which are risk groups particularly vulnerable to the professional burnout syndrome. The consequences of the syndrome have a negative effect on burned out teachers whose health deteriorates and who work less effectively. The resulting loss of social competences also disrupts teacherstudent relations crucial in the educational process. The decreasing involvement of burned out teachers due to the lack of professional satisfaction produces no new solutions and fails to improve the effectiveness of teachers' work.
In her analysis of pre-disposing and preventive factors in teachers, Sęk [1] confirmed the preventive role of perception of self-efficacy in the professional burnout syndrome in teachers. "The conviction of selfefficacy is confidence in possibilities of effective action in new, ambiguous, unpredictable or even stressful sit-uations" [2, p. 213]. Perception of self-efficacy must be discriminated from expectation of specific outcomes. It is a belief that we can cope with any unfavorable conditions. For example, a teacher can be convicted that he/she knows how to teach chemistry the best way, but he/she may be uncertain whether his/her students can learn it [2].
Perception of self-efficacy is a component of the cognitive system structure of each individual. According to Bandura [2] it plays a key role in human motivation. In intentional acts, the perceived self-efficacy affects one's aspirations, efforts, endurance, resistance to failures and the level of experiencing stress. A strong conviction of self-efficacy corresponds to good mood and higher immunity of the body [2]. Perception of selfefficacy consists of the specific part, i.e. perception of one's specific professional competences, and the general part, i.e. general perception of self-efficacy. The problem of perception of professional efficacy was thoroughly analyzed by Gaś [3].
Professional burnout occurs in conditions of chronic stress, the source of which is another individual. Stress depends on the actual context and conditions of performed work, so for different professions different stressors and loads can be distinguished [4,5]. Few re-search studies have been devoted to the scale and specificity of workloads of teachers of particular subjects. Tucholska [6] in her analysis of burnout causes in Polish teachers introduced the variable taught subject. Studies on professional burnout in PE teachers were also carried out by Brudnik [7,8] and Pec [9].
The aim of the present study was to determine to what degree general perception of self-efficacy protects general education teachers in Poland (educational stages II-IV) against professional burnout, and whether teachers of various subjects display any differences in this respect.

Material and methods
The study consisted of a diagnostic survey and was carried out between April and June 2005 on a sample of teachers of various subjects from state comprehensive schools from the Małopolska and Śląsk Provinces in Poland. In total 22 schools participated in the study (educational stages II-IV) from the provincial and district capitals as well as from smaller towns. The sample consisted of 404 teachers (310 women (76.7%) and 94 men (23.3%)).
The teachers' professional burnout syndrome was diagnosed using the Maslach Burnout Inventory (MBI) (Polish version by Noworol; unpublished) which allows assessment of the level of professional burnout due to chronic emotional stress. The MBI is a three-scale questionnaire consisting of 22 items: Emotional Exhaustion (EE) -9 items, Sense of Negative Personal Accomplishment (PA) -8 items, and Depersonalization (DP) -5 items. The subjects give their responses to each item on a seven-point scale: 0 = never, 1 = several times a year, 2 = once a month, 3 = several times a month, 4 = once a week, 5 = several times a week, 6 = every day. Subjects considered to be burned out were those with all three components of the syndrome present.
The teachers' perception of coping competences while managing professional stress was measured with the aid of the General Self-Efficacy Scale (GSES) (Schwarzer, Jerusalem, Juczyński; Polish version [10]). It is a 10-item scale measuring general perception of self-efficacy in coping with difficult situations and adversities. Subjects' responses are made on a four-point scale: 1 = not at all true, 2 = hardly true, 3 = moderately true, 4 = exactly true. The sum of responses to the 10 items yields the composite score, i.e. the Index of General Self-Efficacy.
The taught subjects were grouped into the following categories 1 : • humanities: Polish, history, civics, civil defense training, personal health and social education, religious instruction, pedagogy and history of education, arts; • sciences: mathematics, physics, chemistry, IT, technical education, music; • natural sciences: biology, natural science, geography, chemistry; • foreign languages: English, French, German, Russian, Italian, Latin; • physical education: PE, remedial exercises.
The collected data was statistically processed with the use of k-means clustering, Kruskal-Wallis one-way analysis of variance and the Pearson correlation coefficient [11]. All calculations were made by the Rutkowski Biuro Oprogramowania GEM using the SPSS/12 software package.
In the analysis of the teachers' professional burnout syndrome four homogenous clusters were distinguished, each grouping individuals with similar values of the burnout components: emotional exhaustion (EE), sense of negative personal accomplishment (PA), depersonalization (DP) (Tab. 1, 2).
Non-burned out teachers constituted one-third of the sample (Cluster II, n = 153, 37.9%). For them their work brought them real satisfaction, and with slight emotional exhaustion they related to their students very well (Tab. 2). Cluster IV (n = 51, 12.6%) included burned out teachers deeply frustrated with their work at school, with visible symptoms of emotional exhaustion and depersonalization. The teachers from Cluster I (n = 104, 25.74%) and Cluster III (n = 96, 23.76%) displayed different levels of the burnout syndrome (Tab. 2).
The progressive burnout noted among the teachers from Cluster I is indicative of the first crisis in profes- 1 As there were only 10 teachers of arts and 15 of religious instruction (clergymen and laymen) in the sample, religious instruction and arts were included in the humanities category and music in the sciences category. sional work (mean age = 36 years) (Tab. 2). With a low level of emotional exhaustion and average level of depersonalization, teachers who are disappointed with their work at school begin to lose the sense of value and usefulness of their work. Cluster III encompasses teachers who react to professional stress with emotional tension (Tab. 2). A high level of emotional exhaustion along with an average level of the sense of personal accomplishments at work yields a high level of depersonalization.
The male teachers under study, constituting a minority in the highly feminized school teaching community, experience professional burnout more often than their female counterparts. It is manifested by the higher percentage of male teachers in Cluster IV and their lower percentage in Cluster II (Tab. 1). The analysis of professional burnout level with regard to taught subjects revealed diverse tendencies. The most numerous group of respondents (burned out and non-burned out) were the PE teachers (48.4% and 17.7%, respectively). There was also a high percentage of teachers of sciences in the cluster of non-burned out teachers; but only three burned out teachers of natural sciences (5.4%) (Tab. 3).
One-fourth of the examined physics teachers (n = 15) exhibited visible burnout symptoms (26.7%); as well  The examined general education teachers featured a high index of general self-efficacy ( = 31.11: women = 30.87; men = 31.91). The sex variable did not differentiate the subjects in terms of professional burnout, and neither did job seniority, school and its geographical location, despite slightly higher values in male teachers.
Perception of self-efficacy as a personality variable is a significant factor preventing professional burnout in general education teachers (p < 0.001, χ 2 = 40.230, df = 3). This correlation is statistically significant in teachers of humanities and physical education (p < 0.05, χ 2 = 11.143 and χ 2 = 9.464 respectively, df = 3). A strong correlation can also be noted in teachers of sciences (p < 0.01,  . According to Bandura, the stronger one's conviction of possibilities to face challenges and meet standards is, the higher the resistance to failures. Disappointment with the discrepancy between the level of performance and adopted standards can also motivate one to intensify his or her efforts [2]. Table 4 presents the mean indices of general selfefficacy in the groups of non-burned out, partially burned out and burned out teachers. The correlation between perception of self-efficacy and different components of the three-dimensional burnout syndrome was assessed with the Pearson correlation coefficient (Tab. 5).
A high level of general self-efficacy most effectively prevents the loss of sense of personal accomplishment (PA) in the teachers under study (Tab. 5). Perception of self-efficacy also determines to a great extent the level of tolerated stress during intentional acts [12, 13 after 2]. It protects teachers against inevitable disorganization of actions and growing emotional exhaustion (EE), and prevents -mostly male teachers -from deterioration of interpersonal skills (Tab. 5). Depersonalization of students (DP) in conditions of intense professional stress is a defense mechanism.
The teachers of different subjects perceive differently the preventive role of self-efficacy. Generally, selfefficacy perception protects teachers against the loss of professional interests and satisfaction. The exceptions are teachers of foreign languages, especially women, in whom perception of self-efficacy is decreased considerably by emotional exhaustion (p < 0.05) (Tab. 3,5).
Professional burnout proceeds much slower in teachers of sciences (Tab. 3), in whom the preventive role of self-efficacy is highly significant (p < 0.01). The first reaction of teachers to professional stress is profound disillusionment with work at school (the highest percentage in Cluster I). Conviction of self-efficacy protects teachers (mostly women) against reduction of work satisfaction and progressive burnout (Tab. 3,5).
Perceived self-efficacy in teachers of humanities determines two components of the burnout syndrome. In this group of subjects the burnout is initiated by emotional exhaustion (Tab. 3). The sense of self-efficacy protects the teachers (male teachers, in particular) against the loss of personal accomplishment (PA) and reduces stress at work in school (EE) (Tab. 5).
The analysis of professional burnout syndrome in PE teachers shows a high percentage of both non-burned out and burned out teachers. Perception of self-efficacy of PE teachers determines all the three components of the syndrome (Tab. 5).
The obtained results point to the necessity of development of teachers' sense of self-efficacy during their university studies and in-service training. This way the protection against the professional burnout syndrome will be ensured. A high level of perception of self-efficacy enhances effective stress management and coping with professional duties; it also facilitates changes in the working environment and prevention of the burnout causes [5]. The development of self-efficacy as a means of multidimensional resistance to the burnout syndrome should be of particular concern for PE teachers. Following Tucholska [6] it is the professional group of PE teachers, that displays the highest level of dissatisfaction with the effects of their professional activities.

1.
General perception of self-efficacy protects school teachers against the professional burnout syndrome manifested by low professional satisfaction, growing emotional exhaustion and a tendency to depersonalize their students.
2. Among teachers of different subjects the preventive role of perception of general self-efficacy concerns the following burnout syndrome components: • emotional exhaustion, loss of personal accomplishment and depersonalization in physical education teachers; • emotional exhaustion and loss of personal accomplishment in teachers of humanities; • loss of personal accomplishment in teachers of sciences and natural sciences; • emotional exhaustion in teachers of foreign languages.


Comparison of Division II College Offensive and Defensive Football Players' Upper Body Strength Across One Repetition Maximum Test and The NFL-225 Test

Comparison of Division II College Offensive and Defensive Football Players' Upper Body Strength Across One Repetition Maximum Test and The NFL-225 Test The purpose of this study was to evaluate the effectiveness of predicting actual one repetition maximum (1RM) bench press strength from the National Football League (NFL) 225-test in college football players. Forty-one Division II college football players participated in this study. Participants' upper body strength scores were expressed relative to body weight and results were compared across both tests. Mayhew et al. equation was used to predict 1RM. A repeated measures ANOVA and one-way ANOVA was used to compare the groups. The present study found that the Mayhew equation overestimated relative upper body strength of college football players, while high degree of reliability was found between the actual 1RM and the NFL-225 tests [Wilks λ = 0.43, F (1,40) = 53.07, p = 0.000, Eta-squared = 0.57] and the correlation between these two tests was very high (r = 0.94, p<0.001). The present study also found that defensive players were stronger than offensive players when scores were expressed relative to body weight. The finding of this study indicates that the NFL-225 test's applicability may not be identical for all college players. This study elucidates some of the difficulties associated with predicting 1RM. However, while it is difficult to predict 1RM, testing using sub-maximal loads are far less time consuming especially when they involve a large number of athletes. The results of this study should facilitate coaches in choosing the most appropriate strength testing procedure for their programs.

Introduction
Strength is an important part of athletes' training schedule and focuses on developing an athlete's strength, speed, power and endurance in relation to the particular demands of every individual and sport. Over the past few decades, athletes' strength performance has been extremely improved. For ex-ample, the average lineman, today, run 40-yard dash faster than the average football lineman two decades ago. Strength training is most likely responsible this type of improvement. In other words, the basic elements of speed, mobility and endurance are all functions of muscular strength. A football player needs to have great relative body strength to meet the performance demands of the sport. On the other hand, the football player who can move his own body weight with the greatest ease will generally be able to perform at a higher level.
Resistance training is an essential part of athletic preparation today and an organized program can lead to the development of muscular strength of athletes (Fleck and Kramer, 1997). Many sports require athletes to have high levels of muscular strength (Atha, 1981;Wilson, 1994). The assessment of strength, therefore, is recognized by coaches as necessary for evaluation of a football players' athletic potential. The assessment of strength must be accurate. Accurate assessment of strength is especially fundamental for both occupational functional capacity evaluation and appropriate athletic and rehabilitation exercise prescription (Brown and Weir, 2001).
To compare the strength of athletes, relative strength is usually calculated (Zatsiorsky, 1995). Although absolute strength is important for the tall and heavy athletes, for sports in which the athletes' body rather than an implement is moved, relative strength is of greater importance (Zatsiorsky 1995). Football requires a solid strength foundation. Not only does the athlete have to be strong enough to move his own body weight, but he has to do it quickly. Therefore, relative strength is an important quality to develop for increased power and speed. Notably, evidence from a number of different types of research as well as observational data indicates that relative strength is strongly related to sports performances that rely on speed and motor skills (Fry et al., 1991, Stone et al., 1980. Barker et al. (1993), for example, studied a Division IAA university team and divided the players into starters and non-starters. Based on the 1 RM squat, normalized for body mass, Barker et al. (1993) statistically divided the team into 3 relative strength group levels: high, moderate and low. A continuum is evident as stronger players also had higher vertical jumps compared to moderate-and low-level relative strength groups.
One of the most popular measurements of upper body strength is the 1RM bench press (Arthur, 1982;Brzycki, 1993;Mayhew et al., 1992). Strength is normally measured by the maximal amount of weight an individual can lift in a single repetition of a movement or in one isometric contraction (Baechla, 1994). Measuring 1RM provides a trial-and-error method of manipulating weight loads until a maximal effort is achieved (Kuramoto and Payne, 1995). However, this can be time consuming and cause increased possibility of injury including fractures, torn ligaments, and deformation of growth plates in young participants (Matheson et al., 1989;Mayhew et al., 1993;Niewiadomski et al., 2008). As a result, many coaches and strength specialists have applied submaximal testing to estimate the 1RM strength in the bench press. Previous studies applying submaximal tests for estimating 1RM strength used either a generalized prediction equation or prediction equations for specific exercises including bench press, squat, and deadlift (Bryzcki, 1993;Dohoney et al., 2002;Kuramoto and Payne, 1995;Lander, 1985;Matthew et al., 2003). Regression equations typically include the number of repetitions completed (Mayhew et al., 1999), the resistance used (Kim et al., 2002) or body weight (Rose and Ball, 1992). One of the most common submaximal tests used by the National Football League (NFL) and the National Collegiate Athletic Association (NCAA) is the 225-lbs bench press with repetitions to fatigue (Mayhew et al., 1999;Mayhew et al., 2002;Sierer et al., 2008). Because this test is generally performed in the NFL, it has been called the NFL-225 test (Matthew et al., 2003;Slovak et al., 1997).
Previous studies have produced high correlations between NFL-225 repetitions and 1 RM bench press (Chapman et al., 1996;Everett et al., 1995). Chapman et al. (1996), for example, found a high correlation between NFL-225 repetitions and 1 RM bench press in Division II players. The authors recommend that the NFL-225 test may be a valid predictor of 1 RM bench press for most college players. However, these authors are concerned about the application of the NFL-225 for college players. If more data can be obtained by examining different levels of football players and this shows a strong relationship between 1 RM and the NFL-225 tests regardless of the level, the NFL-225 test will save training time and avoid exposure of the player to any potential danger from handling excessively heavy loads during maximal attempts (Chapman et al., 1996, Mayhew et al., 1999. For example, Chapman et al. (1996) noted that when testing 98 football players for the 1-RM bench press, three testers were required for the completion of the testing procedure, which took six hours with five testing stations. Such information would be of value to coaches, athletic trainers, and fitness professionals in evaluating strength and planning resistance training programs (Mayhew et al., 1999). It will also be important to assess if any differences exist between the ability to predict 1RM by position. Furthermore, examining strength differences among by B.Agbuga et al.

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© Editorial Committee of Journal of Human Kinetics player positions will be useful for coaches, athletic trainers, and fitness professionals. Therefore, the purposes of this study were (a) to determine reliability of the actual 1RM and predicted 1RM tests, (b) to examine the relationship between the actual 1RM and the NFL-225 test tests (c) to compare the actual 1RM test and the predicted one repetition maximum by the NFL-225 test, (d) to compare upper body strength of college offensive and defensive players.

Methods
This study sought to examine the effectiveness of predicting actual one repetition maximum (1RM) bench press strength from the National Football League (NFL) 225-test in college football players and to compare the upper body strength of college football offensive and defensive players across these two tests. As part of their routine off-season training, all participants performed a 1RM and as many repetitions as possible using a weight of 225 lbs.

Participants
Forty-one Division II National Collegiate Athletic Association (NCAA) college football players (24 defensive players and 17 offensive players) participated in the present study. Participants were informed of the experimental risks and signed an informed consent prior to the investigation. The investigation was approved by an Institutional Review Board for use of Human subjects. Each player had undergone a minimum of 8 weeks of heavy resistance training during the winter off-season conditioning program prior to measurement. The off-season program focused on low repetitions and heavy loads and emphasized a periodized methodology for core exercises such as the bench press, squats, deadlifts, and push presses. Players were evaluated a week after the last workout of the cycle to allow sufficient recovery for peak performance. None of the participants had a serious pre-existing injury that could hinder their performance throughout the study. All athletes participating in the study were familiar with bench press tests. Participants were experienced with weight lifting programs prior to the date of tests. Participants' ages ranged from 18 to 30 years with a mean of 20.58 (SD = 2.07).

Procedures
Anthropometry. All of the subjectsʹ body weight and height were measured. Body weight ranged from 154.80 to 336.80 lbs with a mean of 224.31 (SD = 49.90) while body height ranged from 64.50 to 81.75 inch with a mean of 71.98 (SD = 3.59) ( Table 1). After all data had been collected, the participants were tested in the 1RM bench press test and then the NFL-225 test. Data collection was completed within two weeks from the end of the training cycle, with a minimum of 48 hours between tests.
Instruments. Each participant was measured on the 1RM bench press test, and the NFL-225 test, using free weight standard Olympic plates, a sevenfoot Olympic bar and a standard Olympic flat bench. For height, Novel Products INC., Pat # DES 290237 stadiometer and for weight, TANITA BWB-G27A Class III scale was used. These instruments are certified by their manufacturers.
Administrative procedure. The tested subjects were in the supine position with their feet on the floor and buttocks on the bench during lifting. The participant then lowered the bar in a controlled manner and returned the bar to the starting position. The arms were required to extend fully on each repetition. The bar could not rest on the chest or with arms fully extended for more than two seconds (McGee and Burkett, 2003). Spotters and coaches assisted the participants during the performance of the lift. These spotters were trained to ensure the proper lifting techniques were applied. The spotters assisted the athletes in lifting the bar from the support rack, and the participant lowered the bar to the chest and returned it to full arm extension. The test terminated when the participant could not complete a repetition with fully extended arms or until the weight was racked voluntarily by the participant.
Testing procedure for 1RM bench press test. The 1 RM bench press procedure followed the standard ''touch-and-go'' protocol in which the bar was required to touch the chest before being pressed to full arms' extension (Ware et al., 1995). Each subject was required to follow a general warm-up prior to testing by jogging a quarter mile and stretching upper and lower extremities. They were also allowed a specific warm-up that consisted of performing the bench press using light weights of approximately 50 to 75% of estimated 1RM. A standard Olympic bar and plates were used for all lifts, and the player used a grip that was slightly wider (approximately 15-35 cm) than shoulder width (Wagner et al., 1992). After each successful 1RM attempt, the participants were Journal of Human Kinetics volume 21 2009, http://www.johk.awf.katowice.pl encouraged to add between 5 and 10 pounds, depending on the degree of difficulty of the previous lift. Each participant was required to find his 1RM between 2 and 7 attempts, with 3 to 10 minutes rest between attempts (Weir et al., 1994). The greatest weight lifted for each participant was recorded as the 1RM.
Testing procedure for the NFL-225 test. Each athlete was required to perform as many repetitions as possible using an Olympic barbell with a weight of 225 pounds. The same warm-up procedure as used for the 1RM test was used prior to the NFL-225 test. They were also allowed a warm-up that consisted of performing the bench press using light weights of approximately 50 to 75% of estimated 1RM. Following warm-up, each participant grasped the bar and kept his feet on the floor at the same position as during the 1RM procedure. No more than a 2-second rest was allowed during an individual attempt of the repetition test. The participant completed as many successful repetitions as possible until muscular fatigue. The test was terminated when the participant could not complete a repetition with proper form. The number of successful repetitions completed was recorded.

Statistical Analyses
Relative strength of participants was calculated in this study, because of its influence on speed and power. Relative strength was determined by taking the weight lifted and dividing it by body weight for each individual. Descriptive statistics were generated to provide an overall outlook of football players' upper body strength scores across 1RM and the NFL-225 tests. Intraclass correlation coefficient (ICC) was used to determine reliability of the actual 1RM and predicted 1RM tests. Pearson's correlation coef-ficient were calculated to examine the relationship between the actual 1RM and predicted 1RM (i.e. the NFL-225) tests. The data was analyzed through repeated measures analysis of variance and one-way analysis of variance (one-way ANOVA). The statistical mean of the data was compared through the predicted 1RM and actual 1RM tests between offensive and defensive college football players using one-way ANOVA. Each player was given two different body strength tests (i.e., 1RM and the NFL-225 test) and the hypothesis -mean body strength score will be the same in the two types of measurement was tested. Another hypothesis stated that there would not be a significant difference between offensive and defensive players' upper body strength. Because the equations derived from Mayhew et al. (1999; were reported to be most accurate for the bench press, their equation [1RM (lbs) = 226.7 + 7.1* reps] was used to predict the actual 1RM from the NFL-225 test.

Results
Participants' 1RM scores ranged from 185 to 405 lbs with a mean of 272.80 + 53.74 lbs and the NFL-225 scores ranged from 233.80 to 418.40 lbs with a mean of 300.77 + 44.07 lbs (Table 1). A high degree of reliability was found between the actual 1RM and the NFL-225 tests (ICC = 0.95 with a 95% confidence interval from 0.89 -0.97.) Correlation coefficients between these two tests are shown in Table 1. The results showed that the actual 1RM test scores were highly correlated with the NFL-225 test scores (r =0.94, p<0.001).
The result of repeated measures analysis of variance indicated that the actual 1RM (M = 1.25, SD = .24) and the predicted 1RM (M = 1.34, SD = 0.23) scores by using Mayhew et al. equation as measured The Mayhew et al. (2003) equation overestimated the upper body strength of college football players although equation showed the same trends with the actual 1RM when scores were expressed to relative body weight (Figure 1). However, statistics indicated that the relationship between these two was very high (p<0.001). The results of one-way ANOVA analysis showed that there was a significant difference between defensive players (M = 1.32, SD = .20) and offensive players (M = 1.13, SD = 0.25) when scores were expressed relative to body weight for the actual 1RM, F (1, 39) = 6.93, p = 0.012, Eta-squared = 0.15. Results of one-way ANOVA also showed that a significant difference occurred between defensive (M = 1.42, SD = 0.20) and offensive players (M = 1.23, SD = 0.22) for the predicted 1RM, F (1, 39) = 8.61, p = 0.007, Eta-squared = 0.17.

Discussion
Four conclusions were drawn from the findings of the present study: (a) A high degree of reliability was found between the actual 1RM and the NFL-225 tests (b) the correlation between these two tests was also very high, (c) Mayhew et al. (2003) equation overestimated the relative upper body strength of college football players, (d) defensive college players were stronger than offensive football players when scores were expressed to relative body weight.
The results of the present study indicate a considerable degree of consistency with previous studies that found a high correlation between the actual and predicted 1RM values. However, the finding that Mayhew et al. (2002) overestimated the relative upper body strength of college football players is contrary to most of the previous studies (Matthew et al., 2003;Rose and Ball, 1992). Slovak et al. (1997), for example, compared the actual and predicted 1RM utilizing the NFL-225 test from three different equations (i.e., Brzycki, Epley and Mayhew et al. 2003, equations). Their study indicated that the prediction of 1RM bench press in NCAA Division II football players was possible using 1RM prediction equations by Epley or Mayhew (Mayhew et al. 1999 also assessed the efficacy of the NFL-225 test to evaluate upper body strength in football players. Sixty-eight percent of the crossvalidation sample had predicted 1RM values within +/-10 lbs of their actual 1RM performance. Their study determined that muscular endurance repetitions with an absolute load of 225 pounds could be used to predict actual 1RM bench press strength in college football players, although the error in prediction increases when endurance performance exceeds 10 repetitions. Slovak et al. (1997) and Mayhew et al. (1999; findings appear to differ with the results of the present study regarding the efficacy of the Mayhew et al. (2003) equation. Therefore, the present study concludes that the Mayhew et al. (2003) equation cannot predict relative 1RM and overestimates the relative upper body strength of college football players. One possible explanation for the inconsistency could be that the Mayhew et al (2003) equation is only effective in participants whose 1 RM bench press is at least 225 pounds, and therefore may have limited utility in testing weaker subjects (Brown et al., 2001). Another possible explanation could be that the accuracy of the equation decreases as the number of repetitions increase beyond 10 repetitions (Chapman et al., 1998;Mayhew et al., 1999), which limits its efficiency in very strong participants. The last explanation could be that the NFL-225 test's predictive ability may not be the same for all college football players (Bryzcki, 1993). The validity of the NFL-225 test, for example, can vary as a prediction of the actual 1-RM test in college football players who are familiar with the work out and sufficiently conditioned to perform reps with 225 lbs (Chapman et al., 1998). Anatomical and physiological variation could also confound

Player Positions
Offensive Defensive efforts when predicting 1RM. These could include muscle fiber types, length of arms, and the depth of the chest. Although the present study seems to cover a widely studied area for understanding college football players' upper body strength, it specifically examined the upper body strength of college football offensive and defensive players across the 1RM and the NFL-225 tests. The results are consistent with the study of Berg et al. (1990) that showed the strength differences between offensive and defensive college football players. Upper body strength scores were expressed relative to body weight. The conclusion of the authors was that the defense was stronger when their scores were expressed relative to body weight. The current study findings appear to agree with the findings of Berg et al. (1990).

Estimated Marginal Means
Significantly, the only group represented in this study is 41 Division II football players. Therefore, findings of this study may not be applicable to players in the different divisions of college football. Studies that compare the 1RM and predicted 1RM between divisions are recommended. A similar study should be also performed with a larger number of participants. The results of a study of this type could possibly be more accurate in determining the prediction of 1RM from the Mayhew et al. (2003) equation. A third recommendation is to test the differences among football player positions by repetitions into two categories: (1) fewer than 11 repetitions, and (2) more than 11 repetitions. By this way, strength differences can be measured more accurately.
In order to prescribe weight-training programs for football players, their maximum lifting capacity should be assessed accurately. Although the NFL-225 test may be a valid predictor of 1 RM bench press for most college players, the current study agrees with Chapman et al. (1996) that this test's applicability may not be identical for all college players. Therefore, college football coaches, athletic trainers, and fitness professionals in evaluating strength and planning resistance training programs should be careful about the accuracy of predicted 1RM's.
If a methodology was developed that could accurately assess the 1RM from submaximal loads it could ease the process of strength testing. The standard methods for testing 1RM strength are cumbersome from a time standpoint as each athlete needs multiple attempts to achieve the 1RM. Most coaches have seen athletes attempt a weight and fail. After the failed attempt their subsequent successful maximum lift is much less than the athlete and coach expected. This could be a result of premature fatigue caused by the missed attempt and the athlete fails to recover for subsequent attempts. Estimating the 1RM accurately could obviate the instances of premature fatigue due to failed attempts at the 1RM. The NFL-225 test has the practical benefit of being less time consuming for evaluating upper body strength. The risk is that the NFL-test may not be as accurate at estimating maximal upper body strength compared to the 1RM. The final decision to use the NFL-225 test instead of a 1RM is one that is left to coaches. The practitioners must weigh the benefits and risks associated with each type of testing and decide which is the most appropriate for their program.


extfieldsofstudy: Medicine Psychology

text:
Local school policies increase physical activity in Norwegian secondary schools

SUMMARY The implementation of school policies to support the adoption of physical activity is one of the main strategies recommended to increase physical activity levels among this age group. However, documentation of the effect of such policies is so far limited. The purpose of this study was to explore policy-related practices to support physical activity in Norwegian secondary schools and their association with recess physical activity. Emphasis was given to examine the association between policies and physical activity, over and beyond, individual level interests and environmental factors and to examine cross-level interaction effects. This cross-sectional study was based on a nationally representative sample of Norwegian secondary schools and grade 8 students who participated in the Health Behaviour in School-aged Children (HBSC) 2005/06 study. The final sample comprised 68 schools and 1347 students. Data were collected through questionnaires. The results showed that schools with a written policy for physical activity and schools offering organized non-curricular physical activity several times a week had a higher proportion of students reporting daily participation in recess physical activity. Multilevel logistic regression analysis demonstrated a cross-level main effect of the policy index after controlling for sex, socio-economic status, individual-level interests and the physical environment. A significant contribution of adding the policy index to the prediction of recess physical activity above that provided by the individual-level interests and the physical environment was demonstrated. The results are encouraging and give scientific support to policy documents recommending the implementation of school policies to increase physical activity.

INTRODUCTION
The Global Strategy on Diet, Physical Activity and Health has identified physical inactivity together with poor nutrition as major risk factors for some of the leading causes of mortality (World Health Organization, 2004). Recent studies show that a large number of adolescents spend numerous hours in sedentary screen-based activities after school (Currie et al., 2008a), and a substantial proportion of youth are physically active less than the 60 min daily (Riddoch et al., 2004;Booth et al., 2006;Currie et al., 2008a), recommended to gain positive health effects (Strong et al., 2005). Physical activity, sedentary behaviours and body weight status are likely to persist from youth into adulthood (Hallal et al., 2006), and young people have therefore been identified as an important target group for physical activity promotion (World Health Organization, 2004). In the past decades, numerous interventions have aimed at increasing physical activity among adolescents. However, the most recent reviews conclude that programmes have had mostly minor or shortterm effects (Timperio et al., 2004;Salmon et al., 2007;van Sluijs et al., 2007).
A vast majority of the interventions have focused on targeting students directly and have used education as the only intervention component (van Sluijs et al., 2007). Although many of the main determinants of health can be viewed as individual behaviours and lifestyles, there is an increasing awareness within the public health field that contextual and structural factors can also be important determinants of health (Sallis and Owen, 2001). A broader ecological approach to health promotion is now widely accepted as a promising theoretical framework for better understanding factors influencing the complex behaviour associated with physical activity (Ball et al, 2006). Such an approach is also the essential structure in the health promoting schools (HPS) initiative (Stewart-Brown, 2006). In Europe, HPS now exist in more than 40 countries. A key objective is the development of school health policies, and physical activity has become one of the health promoting initiatives within these schools (Samdal, 2008).
Little is known about the influences of the environment and especially policies on physical activity (Sallis et al., 2000;Ferreira et al., 2007). Within the context of physical activity, policies have been defined as 'legislative, regulatory, or policy-making actions that have the potential to affect physical activity' . Policy development and implementation are dynamic processes that involve different phases and tend to have effects in the long run (Stahl et al., 2002). They are likely to start as informal, general agreements about the importance of making changes and to progress to written commitments and declarations.
Because virtually all young people attend school and spend a large part of the day there, the school setting has been identified by many national and cross-national policy documents as a key arena in which to promote physical activity. The implementation of school policies to support the adoption of physical activity is one of the main strategies recommended (U.S. Department of Health andHuman Services, 1997, 2001;World Health Organization, 2004;Norwegian Directorate for Health and Social Affairs, 2005).
It has been noted that the cross-national difference in school systems, infrastructure, environment and social norms most likely exist (van Sluijs et al., 2007). In the Norwegian school system, students on average are provided with recess periods for 1 h daily throughout secondary school (age 13 -16 years) (Haug et al., 2008a, b). Recess can be defined as 'regularly scheduled time for unstructured activity and play' (Wechsler et al, 2000, p. 123). Recess time, including lunch breaks, has been found to contribute considerably to daily levels of moderate to vigorous physical activity in primary school students (Ridgers et al., 2006;Verstraete et al., 2006) and is a potential arena for physical activity uptake among secondary school students. The limited research that exists on school environmental influences of physical activity mostly concerns the physical environment (Davison and Lawson, 2006;Ferreira et al., 2007); however, it is relevant to assume that organization-related policy actions might also influence physical activity behaviour.
So far, different environmental effects have been reported mainly in relation to demographic characteristics, although it has been hypothesized that psychological and behavioural factors also may moderate the environment-behaviour relationship (Brug et al., 2006;Kremers et al., 2007). Interests have been found to be an important factor that drives children to adopt certain behaviours as a response to influences in the immediate environment (Chen and Zhu, 2005). Studies testing the mechanisms underlying the interactions between specific environmental influences and individual-level factors and their influences on physical activity behaviour are needed to produce more effective interventions (Ball et al., 2006). The purpose of this study was to (i) explore policy-related organizational practices to support physical activity in Norwegian secondary schools and their association with students' participation in recess physical activity, (ii) to examine the association between policies and physical activity during recess, taking into account the simultaneous influence of students' interests in physical activity and physical environmental factors and (iii) to examine the crosslevel interaction effect between interests and organizational practices on physical activity.

Study sample and participants
The study was based on a nationally representative sample of Norwegian grade 8 students (age 13 years) participating in the Health Behaviour in School-Aged Children (HBSC) 2005/06 study. The HBSC study is a World Health Organization Cross-National Survey of 11, 13 and 15 year olds conducted every fourth year and is currently carried out in 41 countries (Roberts et al., 2007). The original nationally representative sample involving grade 8 students comprised 115 schools and 2 754 students. Seventy-nine schools (69%) chose to take part in the study with 1954 students enrolled in the sampled grade 8 classes. Eighty-two percent (1595) of the sample students participated, and absence on the day that the survey was conducted was the most frequent cause of non-response. In addition to the student survey, a school-level survey was conducted. Of the 79 participating schools, 11 did not return the school-level questionnaire. Students in these schools were therefore excluded from the analysis reported here, and the final sample for this study was 68 schools and 1347 students. Of these, 52.3% were boys and 47.7% were girls. The mean number of students enrolled in the sample schools was 301 (SD ¼ 148; range, 9-712); 43.3% of the students came from urban and 56.7% from rural school areas. The mean number of grade 8 students participating in the sampled classes was 19.8 (SD ¼ 6.8; range, 1-30). Most of the students (70.3%) were in the high socio-economic status (SES) group, 26.7% in the medium SES group and 3% in the low SES group.

Procedures
The data were collected in November-December 2005 in accordance with a standardized protocol (Roberts et al., 2007). A cluster sampling procedure was followed using the school class as the sampling unit and with one participating class from each of the sampled schools. The school principal was instructed to complete the school-level questionnaire, and teachers received instructions on how to administer the student survey. Passive consent was received from parents and guardians. The student survey was carried out as a student self-completion in-school questionnaire during an ordinary class hour (45 min). Students were informed that their participation was voluntary and that responses would be treated anonymously. National ethical approval was obtained from the Regional Committee for Medical Research Ethics.

Measurements
Recess physical activity Physical activity during recess was measured with the item: 'During recess, how OFTEN are you physically active in a way that makes you out of breath and/or makes you sweat?' The answer categories were; 'every recess', 'not every recess but every day', 'not every day but every week', 'not every week' and 'never'. The variable was dichotomized with the first two response categories defined as 'Daily physically active during recess'. The wording of the item refers to vigorous physical activity (Biddle et al., 1998;Welk et al., 2000). However, the type of activity quantified by this item should not be interpreted only as vigorous physical activity because spontaneous behaviour by children and youths in non-organized physical activities characteristically involves alternating moderate to vigorous physical activity with short rest periods (Welk et al., 2000). A separate testretest study of students age 13 and 15 years indicated moderate stability (intraclass coefficient ¼ 0.68) for the item (Torsheim et al., 1995).

Interests in school physical activity
To assess interests in school physical activity, students were asked to rate on a five-point Likert scale from 'strongly disagree' (1) to 'strongly agree' (5) how much they concurred with the following statements: 'I would like various physical activities to be offered during recesses/lunch breaks', 'I would like more PE classes at school', 'I am not interested in being more physically active during the school day', 'I would like various physical activities to be offered after school' and 'I want to have more school classes outdoors'. The score for the negatively worded item 'I am not interested in being more physically active during the school day' was reversed. Cronbach's alpha coefficient for internal consistency was 0.77. In the logistic regression model, the scores were standardized, with a score of 0 indicating the minimum and a score of 1 indicating the maximum interests score. School policies and physical activity 65 'How many computers does your family own?' ['None' (0), 'One' (1), 'Two' (2), 'More than two' (3)]. The two highest response categories ('2' and '3 or more') of the last two items (holidays and computers) were combined. The scores were added producing a scale that ranged from 0 (least affluent) to 7 (most affluent). An extensive description of the development and use of the scale has been given elsewhere (Currie et al., 2008b). For the descriptive analyses, a three-point ordinal scale was composed, using the following recoding of the scale: 0, 1, 2, or 3¼1 (low); 4 or 5¼2 (medium); and 6 or 7¼3 (high).

School environmental factors
To examine the influence of the school environment on students' physical activity during recess, the school-level questionnaire that had been developed in a cross-national collaboration for the international HBSC 2005/06 survey (Samdal et al., 2005) was applied. Below the employed indicators from this questionnaire are presented.

Physical environmental characteristics
Physical environmental characteristics were assessed with a single item: 'Which facilities for physical activity exist in the indoor school area, the school yard (within 200 m), or in the school neighbourhood (200 m to 2000 m)?' This item included a list of 16 natural or built characteristics. Availability (yes ¼ 1 and no ¼ 0) of each characteristics was assessed to generate a continuous variable labelled 'environment index'.
Involved in a physical activity project Involvement in a physical activity project was assessed based on the response to the following question: 'If the school has been or is participating in a project to increase the physical activity level of the students, to what degree have the following groups been involved?' The answering categories were: (1) 'The school does not participate in such a project'; (2) 'The principal/ school leader'; (3) 'The teachers, the physical education teacher'; (4) 'Students'; (5) 'Parents/ guardians'. Schools that marked category 1, were categorized as not being involved in a physical activity project.

Physical activity policy
To assess whether a school had a physical activity policy, the following question was asked: 'Has your school adopted a policy to increase physical activity during the school day?' The answer categories were: (1) 'Yes, there is a written policy (e.g., in the school regulations)'; (2) 'Yes, an informal policy exists (e.g., verbal agreements)'; and (3) 'No, we do not have a specific policy'. In the analyses, only the answer about a written policy was included because the content of and the obligations in an informal policy may differ considerably between schools and this may further reflect a less well-defined approach.

Physical education classes five times a week
The provision of physical education five times a week was assessed by summarizing the responses for grade 8 on the two items: (1) 'Please indicate the number of compulsory physical education classes that your school offers per week for each of the following grades' and (2) 'Please indicate the number of extracurricular physical education classes (including sport/outdoor recreational classes and similar subjects) that your school offers per week for each of the following grades'. The scale ranged from 0 to 5 classes on the first item and from 0 to 3 classes on the second item.
Organized physical activity in non-curricular school time Organized physical activity in non-curricular school time was assessed with the following question: 'Does the school organize physical activity during the school day outside the obligatory or extracurricular physical education classes?' The item included four settings: (1) 'Before school starts'; (2) 'In the lunch break or midday hour'; (3) 'During recess time'; and (4) 'After school'. For each setting, the answer categories were: (1) 'No'; (2) 'Yes, 2-3 times per month'; (3) 'Yes, 1-2 times per week'; and (4) 'Yes, 3-5 times per week'. Schools reporting any '3-5 days a week' non-curricular instance of physical activity were coded 1, the others were coded 0.
Data analysis SPSS for Windows v. 15.0 was used for descriptive analyses. A chi-square test with Yates' correction for continuity was applied to examine sex differences in physical activity participation. Preliminary inspection of the school level data revealed that several of the variables had a considerable number of missing data. Since the multilevel analysis combines data from a school-level survey and a student-level survey, missing on one independent school level variable, would result in that all cases within that school would be excluded from the analysis. In cases where the school-level model only includes a few independent variables, this problem can be avoided with the multiple imputation (MI) procedure. Multiple imputations employ missing data that are imputed based on information external to the model, thus the missing data are imputed based on a richer set of information. The multiple imputations estimation requires the generation of multiple data sets, and performs data analysis on each of these data sets. Using the software SOLAS 3.2, five data sets were imputed based on available school level information. These five data sets were merged with the individual student-survey, and prepared for analysis in Mplus. Two-level logistic regression was performed using the 'TWOLEVEL' command in Mplus. Adaptive quadrature with 15 quadrature points was used in the estimation.
A necessary requirement in multilevel modelling is that the dependent variable has variation at multiple levels. The intraclass correlation was computed using the formula for multilevel logistic models presented in Snijders and Boskers (Snijders and Boskers, 1999, p. 224). If the intraclass correlation was sufficiently high, two sets of further analysis were planned. First, a multilevel logistic regression was performed for each of the policy factors at study. The objective of this analysis was to assess the relative strength of association with physical activity, adjusting for individual differences in interests. In a second, more targeted set of analysis, hierarchical blockwise models of cross level main effects and cross-level interaction effects of policy were undertaken. The first model was labelled an 'Individual model'. In the second block, the environment index was added, to model cross-level main effects of environment on physical activity. In the last block, cross-level main effects of policy index were added, to isolate the unique association between policy and activity, over and beyond, individual and environmental factors.

RESULTS
The proportion of schools that had put in place policies to support physical activity is shown in Table 1. The provision of physical education classes five times a week and being involved in a physical activity project were cited most frequently.
Overall, 41.5% of boys and 32.6% of girls reported daily participation in physical activity during recess periods and school breaks. The cross-level relationship between organizational policy changes and participation in recess physical activity is displayed in Table 2. Schools with a written policy for physical activity and schools offering organized physical activity in noncurricular school time three times or more a week had a higher proportion of students reporting daily participation in recess physical activity. Physical activity was most frequently organized in the lunch break/mid-hour or in  School policies and physical activity 67 recess periods (results not shown). Although not significant, also being involved in a physical activity-promoting project and the provision of physical education classes five times a week were associated with a higher proportion of students being active during recess. Ecological analysis of bivariate correlations between school-level variables is presented in Table 3. School-level factors showed moderate to strong intercorrelations. For example, having a written physical activity policy was strongly correlated with involvement in a physical activity-promoting project and organized noncurricular physical activity, and moderately related to the physical environment index. Table 4 shows the results of multilevel logistic regression models using hierarchical blockwise modelling. Block 1 showed that students' interests in school physical activity was a significant predictor of recess physical activity, after controlling for sex and SES. Adding the environment index to the model (block 2) revealed that the physical environment was significantly associated with physical activity after adjusting for individual factors. Block 3 showed a crosslevel main effect of the policy index, with a change in daily recess physical activity of 0.63 logits from few to many policy-related organizational changes, demonstrating a significant contribution of adding the policy index to the prediction of recess physical activity above that provided by the individual-level interests and the physical environment (deviance 1525.03-1517.12 ¼7.91, df ¼1, p , 0.01, two-tailed test). Two-way interactions between policies and student interests and between policies and the environment index did not achieve significance (df ¼ 2).

DISCUSSION
Our data from a national sample of Norwegian secondary schools revealed that 42% of boys and 33% of girls reported performing daily physical activity during recess periods, which confirmed that the recess setting is a potential arena for physical activity uptake among secondary school students. The policy-related organizational actions were implemented partly. Schools with a written policy for physical activity and schools that frequently organize physical activity during non-curricular school time had a higher proportion of students reporting recess physical activity. Our study extends previous research by demonstrating that policies and policy-related changes can add explanatory value to the variance in physical activity above that provided by physical environmental and individual-level factors. The findings support the multilevel approach when exploring correlates for adolescent physical activity and confirm that both individual and more distal conceptual or environmental factors can impact significantly on physical activity behaviour, as proposed in the ecological theory (Sallis and Owen, 2001;King et al., 2002). An important finding was that having a written policy for physical activity had a positive effect on participation in recess physical activity. Having a formal commitment to prioritize physical activity in the school organization may function as a catalyst for stronger involvement and increased attention to and status for school physical activity. In addition, such a commitment would likely be followed by defined goals and specific plans for increasing physical activity performed by students. Our findings support these hypotheses. Having a written policy correlated with involvement in a physical activity-promoting project, and with organized physical activity in non-curricular school time, and with the physical environment index. Although it was not possible to assess the directions of these associations, one may assume that a large number of facilities for physical activity would result from a written school policy developed to promote physical activity.
Organized physical activity in non-curricular school time three times or more a week was also associated with higher participation rates in recess physical activity. In Norway, this reflects intramural recreational activities and sports involving students within one school. The results demonstrated that the schools commonly used the lunch break/mid-hour or recess periods to organize for physical activity. The structure and the content of these organized activities may have varied greatly between schools. However, the national policy documents and programmes (Norwegian Ministry of Education, 2003;The Norwegian Ministries, 2005) emphasize specifically that schools should ensure that physical activity programmes are suitable for all school children and are matched to their various skills and abilities. This may have influenced the content of the organized noncurricular physical activity programmes. Few studies have addressed the effects of distal-level policies, such as national governmental initiatives. However, a comparison study of the national physical activity policy orientation in Finland and eastern and western Germany showed that a strong policy orientation with a focus on the entire population, as in Finland, was associated with better opportunities and infrastructure for physical activity (Stahl et al., 2002). Organized facilitation of physical activity also likely includes involvement of adult staff. Teenage students emphasize the importance of having an enthusiastic adult present to supervise and facilitate physical activities in various settings (Humbert et al., 2008). In a recent study of 9-and 15-year-old Norwegian school children, physical activity specific teacher support was a significant predictor of physical activity during non-curricular school time, before entering the strong effect of age to the model (Ommundsen et al., 2006).
Although not significant, being involved in a physical activity-promoting project and providing physical education classes five times a week were both associated with a higher proportion of students being active during recess. The latter finding is important, because of the concern that many physical education classes could negatively affect physical activity during recess, because students may have less energy or feel less need for being physically active during recess.
No interaction effect was observed between the policy index and interest index nor the policy index and the environment index. This suggests that neither students' interests in physical activity in school nor the availability of facilities moderated the effect of policies. A recent study found that students' interests in school physical activity may moderate the effect School policies and physical activity 69 of available facilities in school (Haug et al., 2008a). One possible explanation for why student interests did not moderate the effect of policies could be related to a stronger focus on inclusion of all students and more equal opportunities to be physically active in the schools with a strong policy focus, resulting in less need for being highly motivated or interested to take part in physical activity.

Limitations
A limitation of the study is the use of subjective assessment of physical activity. The sometimessporadic nature of physical activity can make it difficult to recall duration, intensity and frequency accurately, and only moderate correlations have been found between self-reports and more objective measurements (Sallis, 1991;Sirard and Pate, 2001). However, in the present study, the recess physical activity item referred to a specific setting and to vigorous intensity, which could have made it easier for the students to recall more precisely. Dichotomizing the item responses may further have increased the correct classification of students. Another limitation is that the self-reported assessment of school-level variables may have been biased with respect to the social desirability of providing opportunities for physical activity in school. However, the policies in question reflect concrete organizational actions that do not allow for a broad interpretation. We do not know whether the school principals, when assessing the physical characteristics in the survey, interpreted each area in the same way and how detailed their knowledge of the school environment was. Objective monitoring of the environment and observation of the policies as implemented could have strengthened the validity of the study. It should also be recognized that the innovation of policy may involve a level selection bias and reflect individual-level factors in principals that predispose them to implement physical activity policies. The cross-sectional design of the study does not allow indication of causal inference, but is a first step in identifying correlates and understanding the mechanisms of behaviour change that can generate hypotheses for further research.
The results from the study are based on data from 13-year old. These students are the youngest attending secondary school and may, from a maturation perspective, have as much in common with the upper primary grades as their older schoolmates. We do not know if similar associations exist among the older students, therefore we cannot generalize the findings to yield for all secondary school students.

Conclusions and implications
This study adds to a relatively unexplored field by demonstrating that organizational policies may have explanatory value to the prediction of recess physical activity above that provided by individual-level interests and physical environmental factors. The findings should encourage researchers and practitioners, as well as policy makers both at the local (school) and national level, to include a stronger focus on school policies for physical activity and facilitate opportunities and time for physical activity when developing programmes and strategies. Programmes for several important health-related issues involve the school as the target setting, and the pressure to make more time available for academic subjects is high and increases with grade (Story et al., 2006). However, based on a systematic review, Trudeau and Shephard (Trudeau and Shephard, 2008) concluded that, given competent providers, up to an additional hour per day of curricular time could be allocated to physical activity programmes by taking time from other subjects without impeding students' academic achievement.
Additional studies examining the effect of policy changes on physical activity involvement are strongly warranted. Experimental studies with random allocation of 'policy' and 'nopolicy' conditions or natural experiments testing physical activity involvement pre-and postpolicy implementation would be stronger research designs to test the effect of policies in the school setting. The latter design could also detect school-level differences at pre-test that may be attributable to factors other than policy implementation. Studies are also recommended to include the effect of distal-level policies and regulations. If documented effective, this may create a stronger acceptance by school leaders and politicians to establish policies and organizational practices aimed at increasing physical activity in school. To help schools prioritize their resources, future research should identify which policies and aspects of the school environment, taking into account individual-level factors, are most likely to have the greatest impact on students' physical activity behaviour.


extfieldsofstudy:
Sociology
Physics
Engineering
Computer Science

text:
Knowledge emergence in scientific communication: from “fullerenes” to “nanotubes”

This article explores the emergence of knowledge from scientific discoveries and their effects on the structure of scientific communication. Network analysis is applied to understand this emergence institutionally as changes in the journals; semantically as changes in the codification of meaning in terms of words; and cognitively as the new knowledge becomes the emergent foundation of further developments. The discovery of fullerenes in 1985 is analyzed as the scientific discovery that triggered a process which led to research in nanotubes.

34 resolution electron microscopes, particularly the Scanning Tunneling Microscope, that research at this level could be subject of scientometric study because a field could increasingly be distinguished. In 1997 the rate of growth of scientific journal papers with the prefix "nano" in their titles was exponentially doubling over time (Braun, Schubert, & Zsindeley, 1997;Meyer & Persson, 1998). Increased attention of science and technology policies for "nano" since 2000 encouraged the continuity of this exponential growth (Schummer, 2004). Scientometric studies of the field have grown accordingly.
In this study, the focus will be on research in "fullerenes" and the fullerenelike structures "nanotubes". This field of research originated after the discovery of fullerenes in 1985 from the study of properties of carbon molecules, especially the C 60 molecule. Research about "fullerenes" can be recognized as a significant research front of nanoscience, having developed its own terminology beyond the usage of the prefix "nano" (Schummer, 2004). A series of events can be placed along the "evolution" of this research front: a Nobel Prize was awarded for the discovery of fullerene in 1996; the first issue of the journal Fullerene Science and Technology was published in 1993; the change of the name of this journal in 2002 to Fullerenes, Producing and publishing scientific texts is one of the main activities of scientists. Peer reviewing of produced texts before accepting them for publishing validates the scientists' work. Issues related to money allocation, prestige, and a scientist's field of work can also be defined in relation to the output of publications.
Through publishing, scientists select validated knowledge and differentiate their own results and conclusions to submit them for further validation. This is a continuous process triggered by its own self-referentiality as a process. The recursive process of selections and codifications carries the development of knowledge (Fujigaki, 1998a). Variation generated by new discoveries can be measured through a change in the state of relations in the journal space. However, because knowledge is a semantic (and social) construct, variation from new discoveries can also be measured in relation to changes in the semantic representation of the social construction of knowledge.
Knowledge emerges semantically in a network of relations among words selected to carry meaning (Leydesdorff & Hellsten, 2005). This process of selection generates a network-structure of co-words where the position of the words is defined by the presence and absence of relations among them (Hesse, 1980;Burt, 1982).
Thus, meaning and knowledge are intrinsic characteristics of the network: while meaning is easily measurable in the specific configuration of the network, knowledge requires a further analysis considering the time axis. Knowledge is a further codification of meaning. Meaning is information which is already codified.

36
These codifications depend on the purpose of the communication; meaning can be asymmetrically codified across domains. These asymmetries are caused by the different interpretations of meaning carried by words and co-occurrences of words across domains (Leydesdorff & Hellsten, 2005). In this study, the emergence of knowledge originating from a discovery will be considered as: (a) variation in the codes of scientific communication, (b) variation in the semantic structure of knowledge representations at different moments in time, and (c) further codification of the potentially serendipitous 8 discovery from previously constructed knowledge.
An analysis of the codification in patents will be briefly presented as an expansion into knowledge-based applications assuming that these are a consequence of the knowledge constructed through scientific communications.
Our interest particularly resides in the question of how the codification of meaning changes with time resulting in changes in the communication structures and how different meaning codifications outlay the emergence of new knowledge that builds on but differentiates from the existing body of knowledge.

Methodology
To understand structural changes derived from the emergence of new knowledge we use methods from network analysis at various levels: (a) to track changes in the network of relations of journals, (b) to measure changes of meaning through changes in the relations of words at different times and in different domains (patents), and (c) to understand the construction of knowledge as a process of selecting and differentiating from previous knowledge.

Journals
The journal space (that is, the aggregation of publications in scientific journals) defines a cognitive structure that differs from other journal spaces and contextualizes papers belonging to it (Cozzens, 1985). Network analysis allows us to pinpoint journal spaces by assuming that the citation relations are cognitive relations as well (Amsterdamska & Leydesdorff, 1989). A journal space is composed of journals that have citation relations between them.
Definition of the journal space allows limiting the environment of a specific journal identifying the journals from which it "feeds". The delineation of the environment of a journal is a relational problem that will be addressed considering the relevant environment in the overall database of citations taken from the Journal Citation Reports of the Science Citation Index. The mapping can be complemented with a factor analysis approach in order to outlay the position of the journal in a network of relations and its underlying dimensions (Leydesdorff & Cozzens, 1993).
For the special case of fullerenes research, the appearance of the journal Fullerene Science and Technology can be considered as an important breakthrough, since the journal specialized in scientific communication related to fullerene issues.
The journal's environment was delineated by considering all citations to and from this journal. The citation environment of this journal will be studied for the years 1996 (the first year in which it appeared in the Journal Citation Reports) and 2004 in order to consider changes in the construction of boundaries.
Normalization using the cosine as proposed by Salton & McGill (1983) will be applied to the journals environment defined by the matrix of citation relations.
Visualizations are optimized using the algorithm of Kamada & Kawai (1989).

Codification of meaning in time and space
The study of scientific developments through the network of relations among words in texts has already been proposed by Hesse (1980) and Callon, Law, & Rip (1986). In actor network theory, the strength of the relations of co-words depends on the network of associations that form its context (Teil & Latour, 1995). The semantic maps in this study, however, are not derived from the relations between two specific words but among any number of words in a set of titles. For this, the asymmetric matrix of words versus the retrieved titles of documents was used. The relations were normalized using the cosine among word vectors as proposed by Salton & McGill (1983). This provides us with spatial representations of how words are positioned in relation to other words.
Two different sources of information were considered to track changes of meaning in domains: the Science Citation Index (SCI) as available in the so-called Web of Science (at http://scientific.thomson.com/products/wos/); and the patents search facility made available by the United States Patent Office (USPTO) (http://www.uspto.gov/patft/). In both databases, records that matched the criteria "fullerene" (or "fullerenes") and "nanotube" (or "nanotubes") as title words were retrieved until and including 2005.
The study of the influence of time in the codification of meaning is explored only for scientific communication (i.e., the SCI) because the sets retrieved from the USPTO are too small for this purpose. Given that time is not relevant if it is not related to a series of events that may introduce variation to the codification of meaning, the number of published documents was considered as the clock-time.
Initially, the analysis was made with pragmatic cut-offs for every 1,000 documents, but for the purpose of this paper, three different moments for each set were selected with equal distances in terms of numbers of events, that is, each 2,563 documents in the case of fullerene(s), and 3,224 documents in the case of nanotubes(s).
The asymmetric matrix of words versus titles was obtained using TI.exe (at:http://www.leydesdorff.net/software.htm) that generates a word-occurrence matrix, and a normalized co-occurrence matrix from a set of titles and a word list. The matrices were then read using the software package for network analysis PAJEK (at: http://vlado.fmf.uni-lj.si/pub/networks/pajek/). All the visualizations will be based on the algorithm of Kamada & Kawai (1989), present in PAJEK. For the sets retrieved from the SCI only words that occur more than 20 times, will be considered and the cosine is set at > 0.2 in order to optimize the visualizations. For the case of the patents titles, all words occurring more than two times are used and the visualizations are optimized using only the cosine-normalized relations stronger than 0.3.

Citations
In this paper we use citation analysis to delineate the environment of a journal, as explained previously. Citations inside the set of documents retrieved are also interesting as they can be used to track the history of the development of knowledge embedded in them.
Citation relations do not always represent the scientist's use of results previously achieved. Nevertheless, through citations scientists link their work to the existing literature generating a network structure that can be used to re-write the history of scientific developments (Garfield, 1973).
Citation behaviors distinguish two different types of scientific literature: classic literature that have high citation rates independently of their age; and transient literature that becomes obsolete short after their publication and looses citing importance (Chen, 2006). In the first case, the literature belongs to the validated knowledge-base while the second type of literature is typical of the rapidly changing dynamics of the research fronts (ibid.).
For analyzing the citing relations inside our set of documents, the software package HistCite™ (http://www.histcite.com/) was used. HistCite allows to build citation histographs considering the retrieved documents from the SCI. The documents are represented by nodes, displayed historically and their size depends on the amount of citations it gets inside the set.

Results
For the case of fullerene, a search in the SCI retrieved 7,696 documents with "fullerene(s)" in their titles. The first document of the set was published in Nature by Harold W. Kroto, one of the three scientists awarded with the Nobel Prize for the discovery of fullerenes in 1996. This document was titled: "The Stability of the Fullerenes C-24, C-28, C-32, C-36, C-50, C-60 and C-70" (Kroto, 1987). Of the total set of documents, 84% were articles, 5% meeting abstracts, and 11% either reviews, letters, notes or editorial matter. For the second case, 9,672 documents were downloaded from the SCI with "nanotube(s)" in their title; 87% of them were scientific articles. The earliest document was entitled "Large Scale Synthesis of Carbon Nanotubes" (Ebbesen & Ajayan, 1992) and published in Nature.
The evolution of research in fullerenes is depicted in Figure 1 as the annual growth of documents having "fullerene(s)" or "nanotube(s)" as words in their titles.
Notable events such as the emergence of the journal, the Nobel Prize awarded to Harold W. Kroto, Richard E. Smalley and Robert F. Curl Jr. for the discovery of fullerenes, and the discovery of the one-dimensional fullerenes, that were named carbon nanotubes, are also represented in this figure. In Figure 2, the distribution of the journals publishing the 9,769 documents retrieved for "fullerene(s)" in their title is shown. Although Chemical Physics Letter published more documents, the share of fullerene-related articles in each journal is highest for Fullerene, Science and Technology (72% of the total number of articles). For the year 1996, the matrix representing the citation environment of Fullerene, Science and Technology consisted of 18 cited journals. The factor analysis of this citation environment is shown in Table 1.   factors, but leads a fourth factor as a separate grouping. Transition Metal Chemistry is also attributed to this group. In Figure 4, the citation environment just discussed with a factor analytical approach is visualized.   Figure 5 visualizes the citation environment that was factor analyzed in Table   2 on the basis of the cosine as the similarity measure. This visualization shows that a strong component of the graph is formed by six journals in the field of physical chemistry and materials chemistry. Fullerene, Nanotubes and Carbon Nanostructures is one of these six journals.   Fullerene, Nanotubes and Carbon Nanostructures might be explained by the diffusion of new discoveries in multidisciplinary journals aimed at a broader audience. We shall see below that the articles which are most cited in this field appear in Science and Nature.

Codification of meaning in time and space
Until now, the emergence of knowledge has been conceptualized in terms of variation in the structure of the journal space. New discoveries disrupt the network structure communicating scientific developments. In the following section, the evolution of the term "fullerene" will be analyzed considering semantic changes that For every case, only words occurring more than 20 times were considered, and the search terms ("fullerene(s)" and "nanotube(s)") were excluded from the analysis.
The cosine was used for the normalization. The algorithm of Kamada and Kawai (1989) available in the software PAJEK was applied to the visualization of the networks with a threshold of cosine 0.2.

Fullerene documents
For the set of fullerenes, the division was made into two subsets of 2,565 and one of 2,566 documents. The first set, Figure 7, corresponds to documents published from 1987 to 1997. A total of 4,645 words occur in the titles of these documents, and 1,905 occur more than once. For this case 90 words that appeared more than once were considered.  The analysis was made with 144 words that appeared more than 20 times in the set. . In Figure 9, the semantic map obtained from the analysis of co-occurrences of words in titles exhibits even more sophistication than the previous ones. Some of the clusters from the second set of documents remain, but new nodes and clusters appear.
The dyadic relation between carbon and nanotubes demonstrates that the carbonnanotubes as part of fullerene-related research persist from the earlier documents. The only permanent strong relation that endures from the first set is the link between molecules C 70 and C 60 . This link is associated with the production of high purity fullerenes.

Nanotubes documents
The exercise was repeated for the 9,672 documents retrieved from the SCI for the term "nanotube(s)" in their titles. In the three different sets of fullerene-related documents shown above, the association between carbon and nanotube was present in every set and remained visible using higher thresholds of the cosine (until 0.4) for the last two sets. This indicates the importance of carbon nanotubes in fullerene-related research. As has been mentioned above, carbon nanotubes can be considered as a prolongation of research in fullerenes. The codification of the sets of nanotube-related 52 documents gives insights of further codification of fullerene research when they are no longer the central objective but constitutes underlying knowledge.
For the study of the codification of the concept of "nanotube(s)", three consecutive sets of 3,224 documents were distinguished. The first set ( Figure 10) corresponds to documents published from 1992 to 2002. A total of 3,704 words occur in the titles of these documents, and 1,717 occur more than once. For this case 147 words that appeared more than 20 times were analyzed.     time. An early growth of fullerenes-applications, its stabilization and a further 'boom' in nanotubes-applications can respond to an innovation process characterized by an 11 ttl/fullerene$ ; ttl/nanotube$ 56 early science-push followed by market-push (Schmoch, 1997). What is evident from both Figure 1 and Figure 13, is that even though nanotubes is a spin-off effect of research in fullerenes, it differentiates from and forms its own research front. For the case of patents applications, just 4 documents have both the word nanotubes and fullerenes in their title.

Fullerene patent documents
For the case of fullerene, the exercise retrieved a total of 175 patents, with "fullerene(s)" in their titles, in which 411 words happened. For this analysis 117 words that occurred more than twice were used. The semantic map of the title words of these 175 patent documents is illustrated in Figure 14. From Figure 14, the codification of the meaning of fullerene does not seem to be strongly codified in relation to its envisaged applications and differently from codifications at the scientific domain. In fact just the cluster that is formed with "HIV-Viral-Infection-Treatment-Soluble" appears as a complete novelty from the frequent words in the titles of scientific communication.
The rest of the clusters seems to be related to processes of preparation and qualities and characteristics of fullerenes; words all frequent in the scientific 57 communication. The cluster formed by the words "carbon-manufacturing-nanotubesame-apparatus", should be related to the production of carbon nanotubes. A further analysis should be based on the relation between the patents and their references to examine the scientific-base in fullerenes and nanotubes patent applications.

Nanotubes patent documents
For the case of nanotubes, 407 patents with "nanotube(s)" in their titles were retrieved. As illustrated in Figure 13, nanotube applications manifest later in the patents documents, but they soon experiment increasing growing rates. The apparent decrease of this tendency for 2006 is consequence of the moment of the query.
In these titles, a total of 775 words occurred and 301 had a higher frequency than two. The analysis was made with 217 of these words that appeared more than twice, removing propositions, the term "nanotubes" and taking only the singular form of the words. The results from the analysis of the titles in the nanotube patents in Figure 15, show more relation to its expected applications in comparison to fullerene patent documents. Clustering words such as "emitter", "plasma", "signal", "fiber", "medical shielding", "nanosize transistor", "growing seed", "high energy", "emitting device", "electrical conductor", "cell, memory", "circuits", "battery electrode", and "nanowire", seem to be more related to potential applications.
Nevertheless, the permanence, when increasing the threshold of the cosine, of some clusters formed with words such as "cvd" 12 , "methodology", "discharge", "chemical", "vapor", and "deposition" are very related to nanotube production. This indicates that the tension to patent nanotube producing methods continues to be very important in relation to its further applications. In Figure 17, the citing relations for the nanotubes documents are depicted.
The total number of documents that do not cite any other document in the set is 1,035; 4,517 documents are not cited by any other document.
The citation dynamics inside each of the sets illustrates different behaviors.

Conclusions
Network analysis proves useful to understand the dynamic process of knowledge production as a further codification of information; in this text, For the semantic codification of meaning in time, while "carbon-nanotubes" constitute a dyadic relation for all the time-differentiated sets of fullerene documents, "fullerene" has weak patterns of association in the sets of nanotube documents.
Relations among words were different in each of the sets. While for fullerenes, the network became denser with more complex clusters; in nanotubes the semantic codifications in time did not acquire more complexity. This seems to prove that there are underlying processes that generate structures in the communication: some provide variation and others are more functionally oriented to create structure in the communication.
Although there were some differences in the codifications at different domains, the most frequent words were similar in scientific and patent documents.
The hype in patenting fullerene and nanotube related processes can affect the semantic codification of its commercial applications.
The citation relations showed that "fullerene" documents are among the most cited documents in the development of nanotube research. A deeper analysis of references and most cited documents of the set must be done to make further remarks about the constitution of fullerene research as the intellectual base of the nanotube research front. For the case of fullerenes, the most frequently cited articles are not the more recent ones as could be expected of a nanoscience field of research.
The different network analysis seems to converge in the conclusion that even though fullerene and nanotube research are related, nanotube research has acquired its own dynamics soon after its discovery and has been disconnected from fullerene research. This is confirmed by the fact that there is a different distribution of authoring countries in each of the sets of documents. United States and Japan have an important input in both fronts, but actors such as Switzerland, Taiwan and South Korea have stronger participation in research in nanotubes than in fullerenes; and countries like China, Germany, England, France and Italy have a relevant participation in the production of fullerene documents, but not significant for the case of nanotubes.
One of the possible reason why fullerenes and nanotubes research drift and constitute each its own dynamics and institutions is that although they are both nanometer carbon structures, the exceptionality of the molecular nature of the nanotubes in terms of their high length-to-width aspect ratio has captured the attention of further research as specialized and large-scale applications are growing constantly (Colbert, 2003).

Further work
Knowledge has become increasingly central to the progress of society and our daily lives. Industrial economies are targeting to become more knowledge-based. This justifies the importance of finding ways to operationalize the knowledge-base, to observe and measure the fluxes of information that form its foundations, to understand issues concerning the processes behind the production and application of knowledge.
Our purpose in this paper has been to understand the emergence of knowledge as a consequence of new discoveries and its disrupting effects in the structures of scientific communications; for this, we have concentrated on the relations among the codes of communication, and the changes of meaning codification in relation to time and domain. Our first assumption has been that knowledge is socially constructed through communication.
We consider time as crucial in the process of knowledge construction and application. New discoveries constitute new information that acts as a source of variation in the communication, but this can only be observed as time-dependent variation. New information can become knowledge with the introduction of time as a further degree of freedom through which the disrupted communication re-organizes.
Different properties and measures of the networks could give some hindsight into the state of development of scientific disciplines, topics of research and research fronts, and the integration of knowledge to existing knowledge bases.
In this study we have worked with the codification of two concepts related to nanoscience, an emerging field of the sciences. The analysis has been to understand the changes in scientific communication. Further steps will consider knowledge-based innovation to measure their scientific base and analyze codification processes at the interfaces as well as concepts related to medicine and the social sciences.