Physical Complications in Acute Lung Injury Survivors: A Two-Year Longitudinal Prospective Study Injuries during the one repetition maximum assessment in the elderly. Muscle atrophy is prevented in patients with acute spinal cord injury using functional electrical stimulation Residual effects of muscle strength and muscle power training and detraining on physical function in community-dwelling prefrail older adults: a randomized controlled trial Acute First-Time Hamstring Strains during High-Speed Running Muscle strength and physical performance as predictors of mortality, hospitalization, and disability in the oldest old. The Rapid and Progressive Degeneration of the Cervical Multifidus in Whiplash: An MRI Study of Fatty Infiltration RESPONSES OF ELBOW FLEXORS TO TWO STRENUOUS ECCENTRIC EXERCISE BOUTS SEPARATED BY THREE DAYS Mechanisms of Chronic Muscle Wasting and Dysfunction after an Intensive Care Unit Stay. A Pilot Study. Effects of a second bout of maximal eccentric exercise on muscle damage and electromyographic activity Activity and immobilization after eccentric exercise: I. Recovery of muscle function. The Effects of Repeated Maximal Voluntary Isokinetic Eccentric Exercise on Recovery from Muscle Damage Delayed Onset Muscle Soreness and Perceived Exertion After Blood Flow Restriction Exercise Randomized controlled trial of intradialytic resistance training to target muscle wasting in ESRD: the Progressive Exercise for Anabolism in Kidney Disease (PEAK) study. Rate of force development as an adjunctive outcome measure for return-to-sport decisions after anterior cruciate ligament reconstruction. DETRAINING AND TAPERING EFFECTS ON HORMONAL RESPONSES AND STRENGTH PERFORMANCE Long-term spinal cord injury increases susceptibility to isometric contraction-induced muscle injury
Objective : Survivors of severe critical illness frequently develop substantial and persistent physical complications , including muscle weakness , impaired physical function , and decreased health-related quality of life . Our objective was to determine the longitudinal epidemiology of muscle weakness , physical function , and health-related quality of life and their associations with critical illness and ICU exposures . Design : A multisite prospect i ve study with longitudinal follow-up at 3 , 6 , 12 , and 24 months after acute lung injury . Setting : Thirteen ICUs from four academic teaching hospitals . Patients : Two hundred twenty-two survivors of acute lung injury . Interventions : None . Measurements and Main Results : At each time point , patients underwent st and ardized clinical evaluations of extremity , h and grip , and respiratory muscle strength ; anthropometrics ( height , weight , mid-arm circumference , and triceps skin fold thickness ) ; 6-minute walk distance , and the Medical Outcomes Short-Form 36 health-related quality of life survey . During their hospitalization , survivors also had detailed daily evaluation of critical illness and related treatment variables . Over one third of survivors had objective evidence of muscle weakness at hospital discharge , with most improving within 12 months . This weakness was associated with substantial impairments in physical function and health-related quality of life that persisted at 24 months . The duration of bed rest during critical illness was consistently associated with weakness throughout 24-month follow-up . The cumulative dose of systematic corticosteroids and use of neuromuscular blockers in the ICU were not associated with weakness . Conclusions : Muscle weakness is common after acute lung injury , usually recovering within 12 months . This weakness is associated with substantial impairments in physical function and health-related quality of life that continue beyond 24 months . These results provide valuable prognostic information regarding physical recovery after acute lung injury . Evidence -based methods to reduce the duration of bed rest during critical illness may be important for improving these long-term impairments PURPOSE A decrease in strength , and its associated loss of functional ability is common among the elderly . Although resistance training can reverse this decline , associated injuries with frequently used strength assessment s may present a greater risk . METHODS To evaluate the injuries associated with maximal strength evaluations , 83 relatively healthy elderly subjects ( 40 men and 43 women , 65.8 + /- 6.2 years ) with and without prior weight training experience performed 1 repetition maximum testing ( 1 RM ) involving 5 different exercises : chest press , leg extension , abdominal curl , arm curl , and seated calf raise . Subjects were separated into three groups depending on weight training experience , Group 1 had no weight training experience ( n = 32 ) , Group 2 had < 6 months of training ( n = 24 ) , and Group 3 had > 6 months of training ( n = 27 ) . Injury assessment was made 30 minutes , 2 days , and 7 days posttesting . RESULTS Two Group 1 subjects sustained an injury ( 2.4 % of total subjects , 8 % of Group 1 ) . Eighty-one subjects safely completed the 1 RM assessment without injury ( 97.6 % of total ) . Forty-eight of the 83 subjects complained of muscle soreness after testing ( 58 % of total ) . This complaint alone was not sufficient to be categorized as an injury . CONCLUSIONS These results indicate that 1 RM testing is an acceptable tool in strength evaluations in the elderly . Additional pre caution s may be needed in inexperienced , elderly individuals to prevent injury Severe muscle atrophy occurs rapidly following traumatic spinal cord injury ( SCI ) . Previous research shows that neuromuscular or ‘ functional ’ electrical stimulation ( FES ) , particularly FES-cycle ergometry ( FES-CE ) can cause muscle hypertrophy in individuals with chronic SCI ( > 1 year post-injury ) . However , the modest degree of hypertrophy in these already atrophied muscles has lessened earlier hopes that FES therapy would reduce secondary impairments of SCI . It is not known whether FES treatments are effective when used to prevent , rather than reverse , muscle atrophy in individuals with acute SCI . This study explored whether unloaded isometric FES contractions ( FES-IC ) or FES-CE decreased subsequent muscle atrophy in individual with acute SCI ( <3 months post-injury ) . Twenty-six subjects , 14–15 weeks post-traumatic SCI , were assigned to control , FES-IC , or FES-CE against progessively increasing resistance . Subjects were involved in the study for 3 or 6 months . Total body lean body mass ( TB-LBM ) , lower limb lean body mass ( LL-LBM ) , and gluteal lean body mass ( G-LBM ) were determined before the study , and at 3 and 6 months using dual energy X-ray absorptiometry ( DEXA ) . Controls lost an average of 6.1 % , 10.1 % , 12.4 % , after 3 months and 9.5 % , 21.4 % , 26.8 % after 6 months in TB-LBM , LL-LBM and G-LBM respectively . Subjects in the FES-IC group consistently lost less lean body mass than controls , however , only 6 month G-LBM loss was significantly attenuated in this group relative to the controls . In the FES-CE group , LL-LBM and G-LBM loss were prevented at both 3 and 6 months , and TB-LBM loss was prevented at 6 months . In addition , FES-CE significantly increased G-LBM and LL-LBM after 6 months of training relative to pre-training levels . Within the control group , there was no significant relationship between LL-LBM loss ( 3 and 6 months ) and the number of days between injury and baseline measurement . In summary , this study shows that FES-CE , but not FES-IC , training prevents muscle atrophy in acute SCI after 3 months of training , and causes significant hypertrophy after 6 months . The magnitude of differences in regionalized LBM between controls and FES-CE subject raises hopes that such treatment may indeed be beneficial in preventing secondary impairments of SCI if employed before extensive post-injury atrophy occurs Background Although resistance exercise interventions have been shown to be beneficial in prefrail or frail older adults it remains unclear whether there are residual effects when the training is followed by a period of detraining . The aim of this study was to establish the sustainability of a muscle power or muscle strength training effect in prefrail older adults following training and detraining . Methods 69 prefrail community-dwelling older adults , aged 65–94 years were r and omly assigned into three groups : muscle strength training ( ST ) , muscle power training ( PT ) or controls . The exercise interventions were performed for 60 minutes , twice a week over 12 weeks . Physical function ( Short Physical Performance Battery = SPPB ) , muscle power ( sit-to-st and transfer = STS ) , self-reported function ( SF-LLFDI ) and appendicular lean mass ( aLM ) were measured at baseline and at 12 , 24 and 36 weeks after the start of the intervention . Results For the SPPB , significant intervention effects were found at 12 weeks in both exercise groups ( ST : p = 0.0047 ; PT : p = 0.0043 ) . There were no statistically significant effects at 24 and 36 weeks . In the ST group , the SPPB declined continuously after stop of exercising whereas the PT group and controls remained unchanged . No effects were found for muscle power , SF-LLFDI and aLM . Conclusions The results showed that both intervention types are equally effective at 12 weeks but did not result in statistically significant residual effects when the training is followed by a period of detraining . The unchanged SPPB score at 24 and 36 weeks in the PT group indicates that muscle power training might be more beneficial than muscle strength training . However , more research is needed on the residual effects of both interventions . Taken the drop-out rates ( PT : 33 % , ST : 21 % ) into account , muscle power training should also be used more carefully in prefrail older adults . Trial registration This trial has been registered with clinical trials.gov ( NCT00783159 Background Hamstring muscle strain is one of the most common injuries in sports . Still , knowledge is limited about the progression of clinical and magnetic resonance imaging characteristics and their association with recovery time in athletes . Hypothesis Knowing the anatomical location and extent of an acute first-time hamstring strain in athletes is critical for the prognosis of recovery time . Study Design Case series ( prognosis ) ; Level of evidence , 2 . Methods Eighteen elite sprinters with acute first-time hamstring strains were prospect ively included in the study . All subjects were examined , clinical ly and with magnetic resonance imaging , on 4 occasions after injury : at day 2 to 4 , 10 , 21 , and 42 . The clinical follow-up period was 2 years . Results All sprinters were injured during competitive sprinting , and the primary injuries were all located in the long head of the biceps femoris muscle . There was an association between the time to return to pre-injury level ( median , 16 ; range , 6 - 50 weeks ) and the extent of the injury , as indicated by the magnetic resonance imaging parameters . Involvement of the proximal free tendon , as estimated by MRI , and proximity to the ischial tuberosity , as estimated both by palpation and magnetic resonance imaging , were associated with longer time to return to pre-injury level . Conclusion Careful palpation during the first 3 weeks after injury and magnetic resonance imaging investigation performed during the first 6 weeks after injury provide valuable information that can be used to predict the time to return to pre-injury level of performance in elite sprinting OBJECTIVES To evaluate the predictive value of muscle strength and physical performance in the oldest old for all-cause mortality ; hospitalization ; and the onset of disability , defined as a decline in activities of daily living ( ADLs ) , independent of muscle mass , inflammatory markers , and comorbidities . DESIGN A prospect i ve , observational , population -based follow-up study . SETTING Three well-circumscribed areas of Belgium . PARTICIPANTS Five hundred sixty participants aged 80 and older were followed for 33.5 months ( interquartile range 31.1 - 35.6 months ) . MEASUREMENTS  Grip strength , Short Physical Performance Battery ( SPPB ) score , and muscle mass  were measured at baseline ; ADLs at baseline and after 20 months ; and all-cause mortality and time to first hospitalization from inclusion onward . Kaplan-Meier curves and Cox proportional hazards models were calculated for all-cause mortality and hospitalization . Logistic regression analysis was used to determine predictors of decline in ADLs . RESULTS Kaplan-Meier curves showed significantly higher all-cause mortality and hospitalization in subjects in the lowest tertile of grip strength and SPPB score . The adjusted Cox proportional hazards model showed that participants with high grip strength or a high SPPB score had a lower risk of mortality and hospitalization , independent of muscle mass , inflammatory markers , and comorbidity . A relationship was found between SPPB score and decline in ADLs , independent of muscle mass , inflammation , and comorbidity . CONCLUSION In people aged 80 and older , physical performance is a strong predictor of mortality , hospitalization , and disability , and muscle strength is a strong predictor of mortality and hospitalization . All of these relationships were independent of muscle mass , inflammatory markers , and comorbidity Study Design . Single-center prospect i ve longitudinal study . Objective . To study the ( 1 ) temporal development of muscle fatty infiltrates ( MFI ) in the cervical multifidi after whiplash , ( 2 ) differences in multifidi MFI between those who recover or report milder pain – related disability and those who report moderate/severe symptoms at 3 months , and ( 3 ) predictive value of multifidi MFI outcomes . Summary of Background Data . The temporal development of MFI on conventional magnetic resonance image has been shown to be associated with specific aspects of pain and psychological factors . The replication of such findings has yet to be explored longitudinally . Methods . Thirty-six subjects with whiplash injury were enrolled at less than 1 week postinjury and classified at 3 months using percentage scores on the Neck Disability Index as recovered/mild ( 0%–28 % ) or severe ( ≥30 % ) . A fat/water magnetic resonance imaging measure , patient self-report of pain-related disability , and post-traumatic stress disorder were collected at less than 1 week , 2 weeks , and 3 months postinjury . The effects of time and group ( per Neck Disability Index ) and the interaction of time by group on MFI were determined . Receiver operating characteristic curve analysis was used to determine a cut-point for MFI at 2 weeks to predict outcome at 3 months . Results . There was no difference in MFI across groups at enrolment . MFI values were significantly higher in the severe group than those in the recovered/mild group at 2 weeks and 3 months . The receiver operating characteristic curve analysis indicated that MFI levels of 20.5 % or above result ed in a sensitivity of 87.5 % and a specificity of 92.9 % for predicting outcome at 3 months . Conclusion . Consistent with previous evidence , muscle degeneration occurs soon after injury but only in those patients with poor functional recovery . This study provides further evidence that ( 1 ) multifidi MFI occur in t and em with known predictive risk factors ( older age , pain-related disability , and post-traumatic stress disorder ) and ( 2 ) routine imaging protocol s may need to be reconsidered in the vast majority of patients after whiplash . Level of Evidence : This study investigated whether the second eccentric exercise performed 3 days after the initial bout would exacerbate muscle damage and retard the recovery .  Fifty-one athletes performed  30 eccentric actions of the elbow flexors  using a dumbbell weighted 100 % of the maximal isometric force ( MIF ) at the elbow joint angle of 908 ( ECC1 ) . Three days after ECC1 , all subjects except those in the control group ( n = 12 ) performed the second bout ( ECC2 ) with the same ( 100 % ) intensity ( n = 12 ) , 90 % ( n = 13 ) , or 80 % ( n = 14 ) of the ECC1 . Some subjects , especially in the 100 % group , required spotting for ECC2 but made maximal effort to complete the exercise . MIF , range of motion , upper-arm circumference , muscle soreness , muscle proteins in the blood , and ultrasound images were used to assess muscle damage . Changes in these measures for 9 days following ECC1 were compared among groups by 2-way analysis of variance ( ANOVA ) with repeated measures . All criterion measures changed significantly after ECC1 ; however , no significant differences between the groups were evident for any of the changes in the measures . These results suggest that it is possible for athletes to complete the second bout if the intensity is reduced 10–20 % from the initial bout . No significant differences between the control group and other groups indicate that the second eccentric exercise performed 3 days after the initial bout does not exacerbate muscle damage and retard the recovery regardless of the intensity of the second bout . It is concluded that the elbow flexors can perform high-intensity eccentric exercise in the early stage of recovery from the initial bout and are not damaged further by performing a subsequent bout 3 days after the first RATIONALE Critical illness survivors often experience permanent functional disability due to intensive care unit (ICU)-acquired weakness . The mechanisms responsible for long-term weakness persistence versus resolution are unknown . OBJECTIVES To delineate cellular mechanisms underlying long-term weakness persistence in ICU survivors . METHODS We conducted a nested , prospect i ve study of critically ill patients mechanically ventilated for 7 days or longer . The patients were recruited from the RECOVER program  and serially assessed over 6 months after ICU discharge . Twenty-seven of 82 patients consented to participate ; 15 and 11 patients were assessed at 7 days and 6 months after ICU discharge , respectively . MEASUREMENTS AND MAIN RESULTS We assessed motor functional capacity , quadriceps size , strength , and voluntary contractile capacity and performed electromyography , nerve conduction studies , and vastus lateralis biopsies  for histologic , cellular , and molecular analyses . Strength and quadriceps cross-sectional areas were decreased 7 days after ICU discharge . Weakness persisted to 6 months and correlated with decreased function . Quadriceps atrophy resolved in 27 % patients at 6 months . Muscle mass reconstitution did not correlate with resolution of weakness , owing to persistent impaired voluntary contractile capacity . Compared with Day 7 , increased ubiquitin-proteasome system-mediated muscle proteolysis , inflammation , and decreased mitochondrial content all normalized at 6 months . Autophagy markers were normal at 6 months . Patients with sustained atrophy had decreased muscle progenitor ( satellite ) cell content . CONCLUSIONS Long-term weakness in ICU survivors results from heterogeneous muscle pathophysiology with variable combinations of muscle atrophy and impaired contractile capacity . These findings are not explained by ongoing muscle proteolysis , inflammation , or diminished mitochondrial content . Sustained muscle atrophy is associated with decreased satellite cell content and compromised muscle regrowth , suggesting impaired regenerative capacity This study examined whether a second bout of maximal eccentric exercise performed 3 days after the first exercise bout would produce further changes in muscle damage and electromyographic activity ( EMG ) . Male students ( n=26 ) were r and omly assigned to experimental 70 ( EX70 ; n=9 ) , experimental 30 ( EX30 ; n=8 ) , and control ( CON ; n=9 ) groups . The initial exercise was 30 maximal voluntary isokinetic eccentric contractions ( MAX1 ) on non-dominant elbow flexors at 60 ° s−1 ( 1.05 rad s-1 ) . The EX70 and EX30 groups performed a second bout of 70 and 30 eccentric contractions ( MAX2 ) , respectively , 3 days after MAX1 . Upper arm circumference , range of motion , strength , integrated EMG ( IEMG ) , and mean power frequency ( MPF ) were measured before , immediately after , and once a day for 9 days after MAX1 . Plasma creatine kinase ( CK ) activity and muscle soreness were assessed before and for 9 days after MAX1 . Total work , work per contraction , IEMG , and MPF were also recorded during MAX1 and MAX2 . All indicators of muscle damage changed following MAX1 for each group ( P<0.05 ) , but no indicators of additional damage ( P>0.05 ) were apparent after MAX2 for either the EX70 or EX30 groups . IEMG ( P=0.03 ) and MPF ( P=0.04 ) were lower for MAX2 compared with MAX1 for both the EX30 and EX70 groups . It is concluded that performing a second bout of eccentric exercise with damaged muscles 3 days after the initial bout does not produce further damage or retard recovery , even when the second bout of exercise is more strenuous . EMG findings were consistent with reduced activation of fast-twitch motor units during the second eccentric bout . These results may be interpreted as evidence of a neural protective mechanism PURPOSE The purpose of the present study was to determine whether activity would affect the recovery of muscle function after high-force eccentric exercise of the elbow flexors . METHODS Twenty-six male volunteers were r and omly assigned to one of three groups for a 4-d treatment period : immobilization ( N = 9 ) , control ( N = 8) , and light exercise ( N = 9 ) . Relaxed arm angle ( RANG ) , flexed arm angle ( FANG ) , maximal isometric force ( MIF ) , and perceived muscle soreness ( SOR ) were obtained for 3 consecutive days pre-exercise ( baseline ) , immediately post-exercise , and for 8 consecutive days after the 4-d treatment period ( recovery ) . During the treatment period , the immobilization group had their arm placed in a cast and supported in a sling at 90 degrees . The control group had no restriction of their arm activity . The light exercise group performed a daily exercise regimen of 50 biceps curls with a 5-lb dumbbell . RESULTS All subjects showed a prolonged decrease in RANG , increase in FANG , loss in MIF , and increase in SOR in the days after eccentric exercise . During recovery , there was no significant interaction observed among groups over time in RANG ( P > 0.05 ) or FANG ( P > 0.05 ) , but there was a significant interaction observed among groups over time in both MIF ( P < 0.01 ) and SOR ( P < 0.01 ) . Recovery of MIF was facilitated by light exercise and immobilization , whereas recovery from SOR was facilitated by light exercise and delayed by immobilization . CONCLUSIONS The recovery of MIF in both the light exercise and immobilization groups suggests that more than one mechanism may be involved in the recovery of isometric force after eccentric exercise Abstract This study investigated whether performing repeated bouts of maximal voluntary isokinetic eccentric exercise ( MAX1 ) on 3 ( MAX3 ) and 6 days ( MAX6 ) after the initial bout would produce significant changes in the indirect markers of muscle damage and total work . A secondary purpose was to determine whether participants ' psychological maximal effort was equivalent to the physiological maximal effort during muscle soreness . Male university students were assigned r and omly to a control group ( n = 12 ) and a group that repeated the exercise ( EX ; n = 12 ) . The MAX1 was 3 × 10 repetitions of the nondominant elbow flexors on the Cybex 6000 system at a speed of 60 deg/s . The EX group performed the same exercise 3 days and 6 days after MAX1 . The range of motion and maximal isometric force ( MIF ) , muscle soreness index , plasma creatine kinase , and glutamic-oxaloacetate transaminase activities were measured before and every 24 hr for 9 days after MAX1 for both groups . MIF was also assessed once before and immediately after each MAX for the EX group . There were no significant changes ( p > .05 ) between the groups for all criterion measures , except for total amount of work ( p < .05 ) . It is concluded that strenuous voluntary isokinetic eccentric exercise performed with damaged muscles does not appear to exacerbate damage or influence the recovery process . Although individuals could perform repeated MAXs , the total work performed was significantly reduced . This has practical implication s in strength training for coaches and athletes during muscle damage Abstract Br and ner , CR , and Warmington , SA . Delayed onset muscle soreness and perceived exertion after blood flow restriction exercise . J Strength Cond Res 31(11 ) : 3101–3108 , 2017—The purpose of this study was to determine the perceptual responses to resistance exercise with heavy loads ( 80 % 1 repetition maximum [ 1RM ] ) , light loads ( 20 % 1RM ) , or light loads in combination with blood flow restriction ( BFR ) . Despite the use of light loads , it has been suggested that the adoption of BFR resistance exercise may be limited because of increases in delayed onset muscle soreness ( DOMS ) and perceived exertion .  Seventeen healthy untrained males participated in this balanced , r and omized cross-over study . After 4 sets of elbow-flexion exercise , participants reported ratings of perceived exertion ( RPE ) , with DOMS also recorded for 7 days after each trial . Delayed onset muscle soreness was significantly greater for low-pressure continuous BFR ( until 48 hours postexercise ) and high-pressure intermittent BFR ( until 72 hours postexercise ) than for traditional heavy-load resistance exercise and light-load resistance exercise . In addition , RPE was higher for heavy-load resistance exercise and high-pressure intermittent BFR than for low-pressure continuous BFR , with all trials greater than light-load resistance exercise . For practitioners working with untrained participants , this study provides evidence to suggest that to minimize the perception of effort and postexercise muscle soreness associated with BFR resistance exercise , continuous low-pressure application may be more preferential than intermittent high-pressure application . Importantly , these perceptual responses are relatively short-lived ( ∼2 days ) and have previously been shown to subside after a few exercise sessions . Combined with smaller initial training volumes ( set × repetitions ) , this may limit RPE and DOMS to strengthen uptake and adherence and assist in program progression for muscle hypertrophy and gains in strength BACKGROUND To determine whether prolonged ( 24 weeks ) intradialytic progressive resistance training ( PRT ) could counteract muscle wasting more effectively than short- duration training ( 12 weeks ) in patients with end-stage renal disease . STUDY DESIGN R and omized controlled trial . SETTING & PARTICIPANTS 49 patients ( age , 62.6 + /- 14.2 years ; 0.3 to 16.7 years on hemodialysis therapy ) were r and omly assigned to PRT plus usual care for 24 weeks ( 24WK group ) or a crossover control group that received usual care for the first 12 weeks , then PRT plus usual care for the latter 12 weeks ( 12WK group ) . INTERVENTION Two sets of 10 free-weight PRT exercises were performed at a high intensity during routine thrice-weekly hemodialysis treatment under direct supervision . OUTCOMES & MEASUREMENTS Primary outcomes include thigh muscle cross-sectional area by means of computed tomography and intramuscular lipid content estimated through attenuation . Secondary outcomes include muscular strength , exercise capacity , and C-reactive protein level . RESULTS The 24WK group increased muscle cross-sectional area ( + 1.82 + /- 3.25 cm(2 ) ) compared with losses in the 12WK group ( -1.37 + /- 6.87 cm(2 ) ; relative effect size , 0.59 ; 95 % confidence interval [ CI ] , -0.27 to 6.65 ; P = 0.04 ) . However , this outcome did not achieve the level of statistical significance required ( P = 0.025 ) after Bonferroni correction for multiple primary outcomes . There was no significant change in intramuscular lipid content between groups ( + 0.19 + /- 1.32 versus + 0.16 + /- 1.69 Hounsfield units in the 24WK and 12WK groups , respectively ; P = 0.31 ) . Log C-reactive protein level tended to decrease in the 24WK group compared with the 12WK group ( relative effect size , -0.63 ; 95 % CI , -0.27 [ -0.54 to 0.00 ] ; P = 0.05 ) . The 24WK group improved muscular strength measures and exercise capacity throughout the trial . LIMITATIONS Single geographic site used ; no control group without exercise exposure ; unblinded assessment of some secondary outcome measures . CONCLUSIONS Prolonged intradialytic PRT did not significantly improve muscle cross-sectional area or intramuscular lipid content compared with a shorter duration of exercise . Future trials are required to more thoroughly investigate the clinical importance and magnitude of myogenic adaptations to PRT in this cohort STUDY DESIGN Descriptive , prospect i ve , longitudinal single-cohort study . OBJECTIVE To investigate the rate of force development to 30 % ( RFD(30 ) ) , 50 % ( RFD(50 ) ) , and 90 % ( RFD(90 ) ) of maximal voluntary isometric contraction ( MVIC ) as an adjunct outcome measure for determining readiness for return to sport following an  anterior cruciate ligament ( ACL ) reconstruction .  BACKGROUND One criterion of full recovery following an ACL reconstruction is the ability to achieve 85 % or 90 % of the maximal strength of the contralateral limb . However , the time required to develop muscular strength in many types of daily and sports activities is considerably shorter than that required to achieve maximal strength . Therefore , in addition to maximal strength , neuromuscular functions such as RFD should also be considered in the definition of recovery . METHODS Forty-five male professional soccer players who underwent an ACL reconstruction were recruited .  Assessment with the International Knee Documentation Committee ( IKDC ) Subjective Knee Evaluation Form , Tegner score , and KT1000 instrumented arthrometer  was performed postinjury/prereconstruction and at 6 and 12 months after ACL reconstruction .  MVIC , RFD(30 ) , RFD(50 ) , and RFD(90 ) testing was performed preinjury , as part of st and ard preseason assessment , and at 6 and 12 months post-ACL reconstruction . RESULTS The average MVIC value 6 months postreconstruction was 97 % of the preinjury average value . In contrast , at 6 months , the RFD(30 ) , RFD(50 ) , and RFD(90 ) values were 80 % ( P = .04 ) , 77 % ( P = .03 ) , and 63 % ( P = .007 ) , respectively , of the preinjury values . The mean RFD values for the reconstructed knee attained or exceeded 90 % of the preinjury mean values only at the 12-month post-ACL reconstruction assessment ( RFD(30 ) , P = .86 ; RFD(50 ) , P = .51 ; RFD(90 ) , P = .56 ) . CONCLUSION Despite the near recovery of MVIC strength to preinjury levels , there were still significant deficits in RFD at 6 months post-ACL reconstruction . An RFD similar to the preinjury RFD was achieved at 12 months post-ACL reconstruction , following a rehabilitation program focusing on muscle power . These results suggest that , following an ACL reconstruction , RFD criteria may be a useful adjunct outcome measure for the decision to return athletes to sports . J Orthop Sports Phys Ther 2012;42(9):772 - 780 , Epub 19 July 2012 . doi:10.2519/jospt.2012.3780 This study examined the impact of 4 weeks of either complete cessation of training ( DTR ) or a tapering period ( TAP ; short-term reduction of the strength training volume , while the intensity is kept high ) , subsequent to 16 weeks of periodized heavy resistance training ( PRT ) on strength/power gains and the underlying physiologic changes in basal circulating anabolic/catabolic hormones in strength-trained athletes . Forty-six physically active men were matched and r and omly assigned to a TAP ( n = 11 ) , DTR ( n = 14 ) , or control group ( C ; n = 21 ) , subsequent to a 16-week PRT program . Muscular and power testing and blood draws to determine basal hormonal concentrations were conducted before the initiation of training ( T0 ) , after 16 weeks of training ( T1 ) , and after 4 weeks of either DTR or TAP ( T2 ) . Short-term DTR ( 4 weeks ) results in significant decreases in maximal strength ( −6 to −9 % ) and muscle power output ( −17 and −14 % ) of the arm and leg extensor muscles . However , DTR had a significant ( p > 0.01 ) larger effect on muscle power output more than on strength measurements of both upper and lower extremity muscles . Short-term ( 4 weeks ) TAP reached further increases for leg ( 2 % ) and arm ( 2 % ) maximal strength , whereas no further changes were observed in both upper and lower muscle power output . Short-term DTR result ed in a tendency for elevation resting serum insulin-like growth factor (IGF)-1 concentrations , whereas the corresponding TAP experienced elevation in resting serum insulin-like binding protein-3 ( IGFBP-3 ) . These data indicated that DTR may induce larger declines in muscle power output than in maximal strength , whereas TAP may result in further strength enhancement ( but not muscle power ) , mediated , in part , by training-related differences in IGF-1 and IGFBP-3 concentrations Complete spinal cord injury ( SCI ) results in inactivation and unloading of affected skeletal muscles . Unloading causes an increased susceptibility of muscle to contraction-induced injury . This study used magnetic resonance imaging ( MRI ) to test the hypothesis that isometric contractions would evoke greater muscle damage to the quadriceps femoris muscle ( mQF ) of SCI subjects than that of able-bodied ( AB ) controls .  MR images were taken of the mQF prior to , immediately post , and 3 days post electromyostimulation ( EMS ) . EMS consisted of five sets of ten isometric contractions ( 2 s on/6 s off , 1 min between sets ) followed by another three sets of ten isometric contractions ( 1 s on/1 s off , 30 s between sets ) . Average muscle cross-sectional area ( CSA ) and the relative areas of stimulated and injured muscle were obtained from MR images by quantifying the number of pixels with an elevated T2 signal . SCI subjects had significantly greater relative area [ 90 (2)% versus 66 (4)% , P<0.05 ; mean ( SE ) ] but a lesser absolute area [ 16 ( 3 ) cm2 versus 44 ( 6 ) cm2 , P<0.05 ] of mQF stimulated than AB controls . During EMS , peak torque was reduced by 66 % and 37 % for SCI and control subjects , respectively . Three days post EMS , there was a greater relative area of stimulated mQF injured for the SCI subjects [ 25 (6)% versus 2 (1)% , P<0.05 ] . Peak torque remained decreased by 22 % on day 3 in the SCI group only . These results indicate that affected muscle years after SCI is more susceptible to contraction-induced muscle damage , as determined by MRI , compared to AB controls . They also support the contention that electrically elicited isometric contractions are sufficient to cause muscle damage after a prolonged period of inactivity
Conclusion Overall , our findings do not support the presence of a secondary loss of strength following an acute muscle injury , and strongly suggest that strength , on average , recovers steadily over the first 3 days post-injury
Background An immediate loss of strength follows virtually all types of muscle injury but there is debate whether the initial strength loss is maximal or if a secondary loss of strength occurs during the first 3 days post-injury .
Objective The objective of this analysis was to conduct a systematic review and meta- analysis of the research literature to determine if a secondary loss of strength occurs after an injurious initiating event .