human
***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVE The aim of this study was to investigate the effect of a cognitive task on st and ing postural control of the injured and non-injured leg of athletes with chronic ankle instability . METHODS Postural stability was measured by center of pressure parameters while chronic ankle instability patients ( n = 8) r and omly performed single and double leg st and ing in isolation or concurrently with a digit-backward cognitive task . RESULTS After performing a concurrent cognitive task , anteroposterior sway significantly decreased in injured leg ( P < 0.05 ) and area significantly decreased in both injured and non-injured legs ( P < 0.05 ) . There was no significant difference in all center of pressure parameters between injured and non-injured legs . CONCLUSION The findings confirm the effect of a concurrent digit-backwards memory task on single leg st and ing balance in chronic ankle instability patients but the response to cognitive loading was not significantly different between the injured and non-injured legs Study Design . Three factors mixed- design with 1 between-subject and 2 within-subject factors . Objective . To compare the main effects and interactions of postural and cognitive difficulty on quiet stance between subjects with and without nonspecific low back pain ( LBP ) . Summary of Background Data . The interference between postural control and cognitive tasks depends on factors such as sensorimotor/cognitive integrity . Changes in peripheral sensory and muscular systems as well as cognitive processes have been observed in LBP patients . It was hypothesized that the effect of cognitive task on postural performance might be different in subjects with nonspecific LBP as compared with healthy individuals . To the authors ’ knowledge this has not been investigated before . Methods . Postural stability was measured by center of pressure parameters while nonspecific LBP ( n = 22 ) and healthy ( n = 22 ) subjects r and omly performed quiet st and ing task with 3 levels of difficulty ( rigid-surface eyes open , rigid-surface eyes-closed , and foam-surface eyes-closed ) in isolation or concurrently with an easy or difficult digits backward cognitive task . Results . Subjects with nonspecific LBP had less postural sway than healthy subjects , while postural sway decreased with increase in the level of cognitive difficulty . Nonspecific LBP and healthy subjects had larger postural sway at more difficult sensory conditions such as rigid-surface eyes-closed and foam-surface eyes-closed . The response to dual-tasking was not significantly different between the 2 groups . Conclusion . The dual-tasking did not change the postural performance of nonspecific LBP subjects with low level of pain and disability differently compared to healthy subjects Background Knee reinjury after ACL reconstruction is common and increases the risk of osteoarthritis . There is sparse evidence to guide return to sport ( RTS ) decisions in this population . Objectives To assess the relationship between knee reinjury after ACL reconstruction and ( 1 ) return to level I sports , ( 2 ) timing of RTS and ( 3 ) knee function prior to return . Methods 106 patients who participated in pivoting sports participated in this prospect i ve 2-year cohort study . Sports participation and knee reinjury were recorded monthly . Knee function was assessed with the Knee Outcome Survey — Activities of Daily Living Scale , global rating scale of function , and quadriceps strength and hop test symmetry . Pass RTS criteria were defined as scores > 90 on all tests , failure as failing any . Results Patients who returned to level I sports had a 4.32 ( p=0.048 ) times higher reinjury rate than those who did not . The reinjury rate was significantly reduced by 51 % for each month RTS was delayed until 9 months after surgery , after which no further risk reduction was observed . 38.2 % of those who failed RTS criteria suffered reinjuries versus 5.6 % of those who passed ( HR 0.16 , p=0.075 ) . More symmetrical quadriceps strength prior to return significantly reduced the knee reinjury rate . Conclusions Returning to level I sports after ACL reconstruction leads to a more than 4-fold increase in reinjury rates over 2 years . RTS 9 months or later after surgery and more symmetrical quadriceps strength prior to return substantially reduce the reinjury rate Study Design . Prospect i ve assessment of return to work after low back pain . Objective . To determine which factors or combination of factors best predict recurrence of low back pain ( defined 4 different ways ) when returning to full-duty work . Summary of Background Data . Recurrent back pain is one of the more costly health problems facing industry today . Few systematic evaluations of the various factors suspected of exacerbating low back pain have been reported in the literature . Methods . A total of 206 workers who reported low back pain were evaluated as they returned to full-duty work .  Five types of assessment s were performed including : 1 ) a  low back kinematic functional assessment s  , 2 )  evaluation of job physical dem and s  , 3 )  psychosocial assessment of the job environment , 4 )  self-reported impairment including perception of symptoms and psychological measures  , and 5 )  personal ( individual ) factors . One year after return to full duty workers were interviewed to assess who had a recurrence of low back pain according to 4 different definitions of low back pain ( symptom reports , medical visits , self-reported lost days , and employer-reported lost days due to back pain ) . Multiple logistic regression models were developed to assess the best combinations of predictors . Results . The most liberal definition of recurrence , recurrent symptoms , had a significantly greater recurrence rate at 58 % than all other outcome measures ( P = 0.0001 ) . The medical visit recurrence rate of 36 % was significantly greater than the more conservative lost time measures ( P = 0.0001 ) . The recurrence rate for self-reported lost time was 15 % , whereas the more conservative employer confirmed lost time measure was significantly lower at 10 % ( P = 0.0077 ) . Multivariate predictive models associated with the various recurrence definitions yielded sensitivities varying between 78 % and 80 % and specificity between 73 % and 80 % . Conclusion . Recurrence is greatly dependent on how one defines recurrence with symptom reporting yielding 5.5 times as many recurrences compared with employer confirmed lost time . In general , more quantitative measures of worker musculoskeletal function yielded the best predictions of recurrence when predicting the more restrictive definitions of recurrence ( employer confirmed lost time ) Examining postural control while simultaneously performing a cognitive , or suprapostural task , has shown a fairly consistent trend of improving postural control in young healthy adults and provides insight into postural control mechanisms used in everyday life . However , the role of attention driven by explicit verbal instructions while dual-tasking is less understood . Therefore , the purpose of this investigation is to determine the effects of explicit verbal instructions on the postural-suprapostural interactions among various domains of working memory . A total of 22 healthy young adults with a heterogeneous history of ankle sprains volunteered to participate ( age : 22.2±5.1 years ; n=10 history of ankle sprains , n=12 no history ) . Participants were asked to perform single-limb balance trials while performing three suprapostural tasks : backwards counting , r and om number generation , and the manikin test . In addition , each suprapostural task was completed under three conditions of instruction : no instructions , focus on the postural control task , focus on the suprapostural task . The results indicate a significant effect of instructions on postural control outcomes , with postural performance improving in the presence of instructions across all three cognitive tasks which each stress different aspects of working memory . Further , postural-suprapostural interactions appear to be related to the direction or focus of an individual 's attention as instructions to focus on the suprapostural task result ed in the greatest postural control improvements . Thus , attention driven by explicit verbal instructions  influence postural-suprapostural interactions as measured by a temporal-spatial postural control outcome , time-to-boundary , regardless of the suprapostural task performed PURPOSE To evaluate health-related quality of life ( HRQL ) in patients undergoing anterior cruciate ligament ( ACL ) reconstructive surgery  by use of 2 procedures and to estimate the direct costs of surgery . METHODS We performed a 2-year r and omized , prospect i ve intervention study of 2 surgical ACL reconstruction techniques ( anatomic single bundle [ SB ] v double bundle [ DB ] ) .  Fifty-five consecutive out patients , with a mean age of 30.88 years , were r and omized to SB or DB ACL reconstruction .  The Medical Outcomes Study 36-item Short Form Health Survey ( SF-36 ) was used to measure HRQL ( primary outcome ) . ACL injuries were assessed by the International Knee Documentation Committee ( IKDC ) score ( secondary outcome ) . The use of medical re sources and their costs were evaluated . RESULTS We included 52 patients in the final analyses ( 23 in the SB group and 29 in the DB group ) . At baseline , there were no significant differences in study variables . At 2 years of follow-up , there were no significant differences in SF-36 and IKDC scores between groups . However , compared with baseline , the SF-36 physical function , physical role , bodily pain , social function , and emotional role scores were significantly better in the SB group ( P < .05 ) , whereas only the physical function dimension score was better in the DB group ( P = .047 ) . IKDC scores at 2 years improved significantly in the SB group ( P < .001 ) and DB group ( P = .004 ) compared with baseline . There was a significant correlation between the SF-36 physical function , physical role , and bodily pain dimensions and the IKDC score at 2 years ( P < .05 ) . The costs were € 3,251 for the SB group and € 4,172 for the DB group . CONCLUSIONS HRQL and medical outcomes were similar between SB and DB ACL reconstruction techniques , 2 years after surgery . However , the SB technique was more cost-effective Performing a cognitive task while balancing can result in either increased or decreased sway depending on the nature of the cognitive task , and is commonly used in pathologic population s to evaluate postural performance . A total of 39 participants were recruited into two groups : uninjured controls ( n=20 , age : 21.9±2.1 years , height : 175.0±11.2 cm , mass : 71.3±14.9 kg ) and chronic ankle instability ( n=19 , age : 22.1±5.6 years , height : 169.7±7.7 cm , mass : 72.9±17.3 kg ) . Participants were asked to perform one of three cognitive tasks while maintaining single limb balance . Cognitive tasks included backwards counting by 3 ( BC ) , the manikin test ( MAN ) , and r and om number generation ( RNG ) . Time-to-boundary minima , mean , and st and ard deviations were calculated and compared between groups as pre to post change scores . Effect sizes and 95 % confidence intervals were also calculated to test for group differences and the effect of task performance on sway . No significant main effects of Group or Group by Task interactions were identified ( p>0.05 ) . However , a significant multivariate main effect of Task was identified in BC ( p=0.001 , F(6 , 32)=4.804 ) and RNG ( p<0.001 , F(6 , 32)=6.233 ) but not for MAN ( p=0.117 ) . The results suggest that those with chronic ankle instability and uninjured controls have similar postural-suprapostural interactions across multiple cognitive task domains . Both the BC and RNG tasks result ed in less sway for all participants . Our results suggest that dual-task interference in the CAI population may not be present as previous research would suggest Recurrence quantification analysis ( RQA ) , a nonlinear method of postural analysis , was used to explore the effects of dual-tasking on postural performance in people with nonspecific low back pain ( LBP ) compared with healthy participants .  Postural performance was quantified by RQA % recurrence , % determinism , entropy and trend .  People with nonspecific LBP ( n=22 ) and unimpaired individuals ( n=22 ) r and omly performed quiet st and ing tasks with three levels of difficulty ( rigid-surface eyes open , rigid-surface eyes closed and foam-surface eyes closed ) . These tasks were performed in isolation or concurrently with an easy or difficult cognitive task . Increasing postural difficulty was associated with higher % determinism , higher entropy and lower trend in anteroposterior ( AP ) and mediolateral ( ML ) directions in people with LBP and healthy participants .  All RQA variables in the ML direction decreased as cognitive conditions became more difficult . Significant interactions between group and cognitive difficulty were shown for % recurrence , % determinism and trend in the AP direction . While healthy participants decreased % recurrence and trend by increasing the level of cognitive difficulty , the LBP patients did not . This preliminary study suggests that LBP may be one factor that modulates the posture-cognition interaction Our study aim ed to evaluate the effect of cognitive challenge on double-leg postural control under visual and surface perturbations of patients with anterior cruciate ligament reconstruction ( ACLR ) cleared to return to sport .  Double-leg stance postural control of 19 rehabilitated patients with ACLR ( age : 24.8 ± 6.7 years , time since surgery : 9.2 ± 1.6 months ) and 21 controls ( age : 24.9 ± 3.7 years ) was evaluated in eight r and omized situations combining two cognitive ( with and without silent backward counting in steps of seven ) , two visual ( eyes open , eyes closed ) and two surface ( stable support , foam support ) conditions . Sway area and sway path of the centre of foot pressure were measured during three 20-s recordings for each situation . Higher values indicated poorer postural control . Generally , postural control of patients with ACLR and controls was similar for sway area and sway path ( p >  
    Output:
    
agent
Conclusion The results of this systematic review indicate that motor performance is further impaired by placing a cognitive load on individuals in population s with musculoskeletal injury .
More dem and ing tasks such as gait appear to be more affected in injured individuals than simple balance tasks .
***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVE The aim of this study was to investigate the effect of a cognitive task on st and ing postural control of the injured and non-injured leg of athletes with chronic ankle instability . METHODS Postural stability was measured by center of pressure parameters while chronic ankle instability patients ( n = 8) r and omly performed single and double leg st and ing in isolation or concurrently with a digit-backward cognitive task . RESULTS After performing a concurrent cognitive task , anteroposterior sway significantly decreased in injured leg ( P < 0.05 ) and area significantly decreased in both injured and non-injured legs ( P < 0.05 ) . There was no significant difference in all center of pressure parameters between injured and non-injured legs . CONCLUSION The findings confirm the effect of a concurrent digit-backwards memory task on single leg st and ing balance in chronic ankle instability patients but the response to cognitive loading was not significantly different between the injured and non-injured legs Study Design . Three factors mixed- design with 1 between-subject and 2 within-subject factors . Objective . To compare the main effects and interactions of postural and cognitive difficulty on quiet stance between subjects with and without nonspecific low back pain ( LBP ) . Summary of Background Data . The interference between postural control and cognitive tasks depends on factors such as sensorimotor/cognitive integrity . Changes in peripheral sensory and muscular systems as well as cognitive processes have been observed in LBP patients . It was hypothesized that the effect of cognitive task on postural performance might be different in subjects with nonspecific LBP as compared with healthy individuals . To the authors ’ knowledge this has not been investigated before . Methods . Postural stability was measured by center of pressure parameters while nonspecific LBP ( n = 22 ) and healthy ( n = 22 ) subjects r and omly performed quiet st and ing task with 3 levels of difficulty ( rigid-surface eyes open , rigid-surface eyes-closed , and foam-surface eyes-closed ) in isolation or concurrently with an easy or difficult digits backward cognitive task . Results . Subjects with nonspecific LBP had less postural sway than healthy subjects , while postural sway decreased with increase in the level of cognitive difficulty . Nonspecific LBP and healthy subjects had larger postural sway at more difficult sensory conditions such as rigid-surface eyes-closed and foam-surface eyes-closed . The response to dual-tasking was not significantly different between the 2 groups . Conclusion . The dual-tasking did not change the postural performance of nonspecific LBP subjects with low level of pain and disability differently compared to healthy subjects Background Knee reinjury after ACL reconstruction is common and increases the risk of osteoarthritis . There is sparse evidence to guide return to sport ( RTS ) decisions in this population . Objectives To assess the relationship between knee reinjury after ACL reconstruction and ( 1 ) return to level I sports , ( 2 ) timing of RTS and ( 3 ) knee function prior to return . Methods 106 patients who participated in pivoting sports participated in this prospect i ve 2-year cohort study . Sports participation and knee reinjury were recorded monthly . Knee function was assessed with the Knee Outcome Survey — Activities of Daily Living Scale , global rating scale of function , and quadriceps strength and hop test symmetry . Pass RTS criteria were defined as scores > 90 on all tests , failure as failing any . Results Patients who returned to level I sports had a 4.32 ( p=0.048 ) times higher reinjury rate than those who did not . The reinjury rate was significantly reduced by 51 % for each month RTS was delayed until 9 months after surgery , after which no further risk reduction was observed . 38.2 % of those who failed RTS criteria suffered reinjuries versus 5.6 % of those who passed ( HR 0.16 , p=0.075 ) . More symmetrical quadriceps strength prior to return significantly reduced the knee reinjury rate . Conclusions Returning to level I sports after ACL reconstruction leads to a more than 4-fold increase in reinjury rates over 2 years . RTS 9 months or later after surgery and more symmetrical quadriceps strength prior to return substantially reduce the reinjury rate Study Design . Prospect i ve assessment of return to work after low back pain . Objective . To determine which factors or combination of factors best predict recurrence of low back pain ( defined 4 different ways ) when returning to full-duty work . Summary of Background Data . Recurrent back pain is one of the more costly health problems facing industry today . Few systematic evaluations of the various factors suspected of exacerbating low back pain have been reported in the literature . Methods . A total of 206 workers who reported low back pain were evaluated as they returned to full-duty work .  Five types of assessment s were performed including : 1 ) a  low back kinematic functional assessment s  , 2 )  evaluation of job physical dem and s  , 3 )  psychosocial assessment of the job environment , 4 )  self-reported impairment including perception of symptoms and psychological measures  , and 5 )  personal ( individual ) factors . One year after return to full duty workers were interviewed to assess who had a recurrence of low back pain according to 4 different definitions of low back pain ( symptom reports , medical visits , self-reported lost days , and employer-reported lost days due to back pain ) . Multiple logistic regression models were developed to assess the best combinations of predictors . Results . The most liberal definition of recurrence , recurrent symptoms , had a significantly greater recurrence rate at 58 % than all other outcome measures ( P = 0.0001 ) . The medical visit recurrence rate of 36 % was significantly greater than the more conservative lost time measures ( P = 0.0001 ) . The recurrence rate for self-reported lost time was 15 % , whereas the more conservative employer confirmed lost time measure was significantly lower at 10 % ( P = 0.0077 ) . Multivariate predictive models associated with the various recurrence definitions yielded sensitivities varying between 78 % and 80 % and specificity between 73 % and 80 % . Conclusion . Recurrence is greatly dependent on how one defines recurrence with symptom reporting yielding 5.5 times as many recurrences compared with employer confirmed lost time . In general , more quantitative measures of worker musculoskeletal function yielded the best predictions of recurrence when predicting the more restrictive definitions of recurrence ( employer confirmed lost time ) Examining postural control while simultaneously performing a cognitive , or suprapostural task , has shown a fairly consistent trend of improving postural control in young healthy adults and provides insight into postural control mechanisms used in everyday life . However , the role of attention driven by explicit verbal instructions while dual-tasking is less understood . Therefore , the purpose of this investigation is to determine the effects of explicit verbal instructions on the postural-suprapostural interactions among various domains of working memory . A total of 22 healthy young adults with a heterogeneous history of ankle sprains volunteered to participate ( age : 22.2±5.1 years ; n=10 history of ankle sprains , n=12 no history ) . Participants were asked to perform single-limb balance trials while performing three suprapostural tasks : backwards counting , r and om number generation , and the manikin test . In addition , each suprapostural task was completed under three conditions of instruction : no instructions , focus on the postural control task , focus on the suprapostural task . The results indicate a significant effect of instructions on postural control outcomes , with postural performance improving in the presence of instructions across all three cognitive tasks which each stress different aspects of working memory . Further , postural-suprapostural interactions appear to be related to the direction or focus of an individual 's attention as instructions to focus on the suprapostural task result ed in the greatest postural control improvements . Thus , attention driven by explicit verbal instructions  influence postural-suprapostural interactions as measured by a temporal-spatial postural control outcome , time-to-boundary , regardless of the suprapostural task performed PURPOSE To evaluate health-related quality of life ( HRQL ) in patients undergoing anterior cruciate ligament ( ACL ) reconstructive surgery  by use of 2 procedures and to estimate the direct costs of surgery . METHODS We performed a 2-year r and omized , prospect i ve intervention study of 2 surgical ACL reconstruction techniques ( anatomic single bundle [ SB ] v double bundle [ DB ] ) .  Fifty-five consecutive out patients , with a mean age of 30.88 years , were r and omized to SB or DB ACL reconstruction .  The Medical Outcomes Study 36-item Short Form Health Survey ( SF-36 ) was used to measure HRQL ( primary outcome ) . ACL injuries were assessed by the International Knee Documentation Committee ( IKDC ) score ( secondary outcome ) . The use of medical re sources and their costs were evaluated . RESULTS We included 52 patients in the final analyses ( 23 in the SB group and 29 in the DB group ) . At baseline , there were no significant differences in study variables . At 2 years of follow-up , there were no significant differences in SF-36 and IKDC scores between groups . However , compared with baseline , the SF-36 physical function , physical role , bodily pain , social function , and emotional role scores were significantly better in the SB group ( P < .05 ) , whereas only the physical function dimension score was better in the DB group ( P = .047 ) . IKDC scores at 2 years improved significantly in the SB group ( P < .001 ) and DB group ( P = .004 ) compared with baseline . There was a significant correlation between the SF-36 physical function , physical role , and bodily pain dimensions and the IKDC score at 2 years ( P < .05 ) . The costs were € 3,251 for the SB group and € 4,172 for the DB group . CONCLUSIONS HRQL and medical outcomes were similar between SB and DB ACL reconstruction techniques , 2 years after surgery . However , the SB technique was more cost-effective Performing a cognitive task while balancing can result in either increased or decreased sway depending on the nature of the cognitive task , and is commonly used in pathologic population s to evaluate postural performance . A total of 39 participants were recruited into two groups : uninjured controls ( n=20 , age : 21.9±2.1 years , height : 175.0±11.2 cm , mass : 71.3±14.9 kg ) and chronic ankle instability ( n=19 , age : 22.1±5.6 years , height : 169.7±7.7 cm , mass : 72.9±17.3 kg ) . Participants were asked to perform one of three cognitive tasks while maintaining single limb balance . Cognitive tasks included backwards counting by 3 ( BC ) , the manikin test ( MAN ) , and r and om number generation ( RNG ) . Time-to-boundary minima , mean , and st and ard deviations were calculated and compared between groups as pre to post change scores . Effect sizes and 95 % confidence intervals were also calculated to test for group differences and the effect of task performance on sway . No significant main effects of Group or Group by Task interactions were identified ( p>0.05 ) . However , a significant multivariate main effect of Task was identified in BC ( p=0.001 , F(6 , 32)=4.804 ) and RNG ( p<0.001 , F(6 , 32)=6.233 ) but not for MAN ( p=0.117 ) . The results suggest that those with chronic ankle instability and uninjured controls have similar postural-suprapostural interactions across multiple cognitive task domains . Both the BC and RNG tasks result ed in less sway for all participants . Our results suggest that dual-task interference in the CAI population may not be present as previous research would suggest Recurrence quantification analysis ( RQA ) , a nonlinear method of postural analysis , was used to explore the effects of dual-tasking on postural performance in people with nonspecific low back pain ( LBP ) compared with healthy participants .  Postural performance was quantified by RQA % recurrence , % determinism , entropy and trend .  People with nonspecific LBP ( n=22 ) and unimpaired individuals ( n=22 ) r and omly performed quiet st and ing tasks with three levels of difficulty ( rigid-surface eyes open , rigid-surface eyes closed and foam-surface eyes closed ) . These tasks were performed in isolation or concurrently with an easy or difficult cognitive task . Increasing postural difficulty was associated with higher % determinism , higher entropy and lower trend in anteroposterior ( AP ) and mediolateral ( ML ) directions in people with LBP and healthy participants .  All RQA variables in the ML direction decreased as cognitive conditions became more difficult . Significant interactions between group and cognitive difficulty were shown for % recurrence , % determinism and trend in the AP direction . While healthy participants decreased % recurrence and trend by increasing the level of cognitive difficulty , the LBP patients did not . This preliminary study suggests that LBP may be one factor that modulates the posture-cognition interaction Our study aim ed to evaluate the effect of cognitive challenge on double-leg postural control under visual and surface perturbations of patients with anterior cruciate ligament reconstruction ( ACLR ) cleared to return to sport .  Double-leg stance postural control of 19 rehabilitated patients with ACLR ( age : 24.8 ± 6.7 years , time since surgery : 9.2 ± 1.6 months ) and 21 controls ( age : 24.9 ± 3.7 years ) was evaluated in eight r and omized situations combining two cognitive ( with and without silent backward counting in steps of seven ) , two visual ( eyes open , eyes closed ) and two surface ( stable support , foam support ) conditions . Sway area and sway path of the centre of foot pressure were measured during three 20-s recordings for each situation . Higher values indicated poorer postural control . Generally , postural control of patients with ACLR and controls was similar for sway area and sway path ( p >  
    Output:
    