***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: Study Design . A prospect i ve study of the sagittal st and ing posture of 766 adolescents . Objective . To determine whether posture subgroups based on photographic assessment are similar to those used clinical ly and to previous , radiographically determined subgroups of sagittal st and ing posture , and whether identified subgroups are associated with measures of spinal pain . Summary of Background Data . Relatively little research has been performed toward a classification of subjects according to sagittal spinal alignment . Clinical descriptions of different st and ing posture classifications have been reported , and recently confirmed in a radiographic study . There is limited epidemiological data available to support the belief that specific st and ing postures are associated with back pain , despite plausible mechanisms . As posture assessment using radiographic methods are limited in large population studies , successful characterization of posture using 2-dimensional photographic images will enable epidemiological research of the association between posture types and spinal pain . Methods . Three angular measures of  thoraco-lumbo-pelvic alignment  were calculated from lateral st and ing photographs of subjects with retro-reflective markers placed on bony l and marks . Subgroups of sagittal thoracolumbar posture were determined by cluster analysis of these 3 angular measures . Back pain experience was assessed by question naire . The associations between posture subgroups and spinal pain variables were evaluated using logistic regression . Results . Postural subtypes identified by cluster analysis closely corresponded to those subtypes identified previously by analysis of radiographic spinal images in adults and to those described clinical ly . Significant associations between posture subgroups and weight , height , body mass index , and gender were identified . Those adolescents classified as having non-neutral postures when compared with those classified as having a neutral posture demonstrated higher odds for all measures of back pain , with 7 of 15 analyses being statistically significant . Conclusion . Meaningful classifications exist for adolescent sagittal thoraco-lumbo-pelvic alignment , and these can be determined successfully from sagittal photographs . More neutral thoraco-lumbo-pelvic postures are associated with less back pain Study Design . A r and omized controlled trial . Objective . To investigate feed-forward activation or timing of abdominal muscle activation in response to rapid shoulder flexion after 8 weeks with core stability exercises , sling exercises , or general exercises in chronic nonspecific low back pain ( LBP ) patients . Summary of Background Data . Delayed onset in abdominal muscles has been associated with LBP . Low load exercises to volitionally activate the transversus abdominis were introduced to restore trunk muscle activation deficits . More forceful co-contraction exercises have been advocated by others . This study explored whether abdominal muscle onset changed after low-load core stability exercises , high-load sling exercises , or general exercises . Methods . Subjects ( N = 109 ) with chronic nonspecific LBP of at least 3 months ' duration were r and omly assigned to 8 weekly treatments with low-load core stability exercises , high-load stabilizing exercises in slings , or general exercises in groups . Primary outcome was onset recorded bilaterally by m-mode ultrasound imaging in the deep abdominal muscles in response to rapid shoulder flexion . Results . No or small changes were found in onset after treatment . Baseline adjusted between group differences showed a 15 ms ( 95 % confidence interval [ CI ] , 1–28 ; P = 0.03 ) and a 19 ms ( 95 % CI , 5–33 ; P < 0.01 ) improvement with sling relative to core stability and general exercises , respectively , but on 1 side only . There was no association between changes in pain and onset over the intervention period ( R2 ⩽ 0.02 ) . Conclusion . Abdominal muscle onset was largely unaffected by 8 weeks of exercises in chronic LBP patients . There was no association between change in onset and LBP . Large individual variations in activation pattern of the deep abdominal muscles may justify exploration of differential effects in subgroups of LBP Abstract Practice guidelines recommend various types of exercise and manipulative therapy for chronic back pain but there have been few head‐to‐head comparisons of these interventions . We conducted a r and omized controlled trial to compare effects of general exercise , motor control exercise and manipulative therapy on function and perceived effect of intervention in patients with chronic back pain . Two hundred and forty adults with non‐specific low back pain ⩾3 months were allocated to groups that received 8 weeks of general exercise , motor control exercise or spinal manipulative therapy . General exercise included strengthening , stretching and aerobic exercises . Motor control exercise involved retraining specific trunk muscles using ultrasound feedback . Spinal manipulative therapy included joint mobilization and manipulation . Primary outcomes were patient‐specific function ( PSFS , 3–30 ) and global perceived effect ( GPE , −5 to 5 ) at 8 weeks . These outcomes were also measured at 6 and 12 months . Follow‐up was 93 % at 8 weeks and 88 % at 6 and 12 months . The motor control exercise group had slightly better outcomes than the general exercise group at 8 weeks ( between‐group difference : PSFS 2.9 , 95 % CI : 0.9–4.8 ; GPE 1.7 , 95 % CI : 0.9–2.4 ) , as did the spinal manipulative therapy group ( PSFS 2.3 , 95 % CI : 0.4–4.2 ; GPE 1.2 , 95 % CI : 0.4–2.0 ) . The groups had similar outcomes at 6 and 12 months . Motor control exercise and spinal manipulative therapy produce slightly better short‐term function and perceptions of effect than general exercise , but not better medium or long‐term effects , in patients with chronic non‐specific back pain Objective To determine the effectiveness of lessons in the Alex and er technique , massage therapy , and advice from a doctor to take exercise ( exercise prescription ) along with nurse delivered behavioural counselling for patients with chronic or recurrent back pain . Design Factorial r and omised trial . Setting 64 general practice s in Engl and . Participants 579 patients with chronic or recurrent low back pain ; 144 were r and omised to normal care , 147 to massage , 144 to six Alex and er technique lessons , and 144 to 24 Alex and er technique lessons ;  half of each of these groups were r and omised to exercise prescription . Interventions Normal care ( control ) , six sessions of massage , six or 24 lessons on the Alex and er technique , and prescription for exercise from a doctor with nurse delivered behavioural counselling . Main outcome measures Rol and Morris disability score ( number of activities impaired by pain ) and number of days in pain . Results Exercise and lessons in the Alex and er technique , but not massage , remained effective at one year ( compared with control Rol and disability score 8.1 : massage −0.58 , 95 % confidence interval −1.94 to 0.77 , six lessons −1.40 , −2.77 to −0.03 , 24 lessons −3.4 , −4.76 to −2.03 , and exercise −1.29 , −2.25 to −0.34 ) . Exercise after six lessons achieved 72 % of the effect of 24 lessons alone ( Rol and disability score −2.98 and −4.14 , respectively ) . Number of days with back pain in the past four weeks was lower after lessons ( compared with control median 21 days : 24 lessons −18 , six lessons −10 , massage −7 ) and quality of life improved significantly . No significant harms were reported . Conclusions One to one lessons in the Alex and er technique from registered teachers have long term benefits for patients with chronic back pain . Six lessons followed by exercise prescription were nearly as effective as 24 lessons . Trial registration National Research Register N0028108728 . How does the Alex and er Technique work ? What are the authors findings about the clinical and cost effectiveness of the treatment ? Watch this video to find out ( 12 mins ) . Design . R and omized prospect i ve study of the effects of three types of active therapy on back muscle function in chronic low back pain patients . Objectives . To quantify the effects of 3 months active therapy on strength , endurance , activation , and fatigability of the back entensor muscles . Summary of Background Data . Many studies have documented an association between chronic low back pain and diminished muscular performance capacity . Few studies have quantified the changes in these measures following interventions using objective measurement techniques or related them to changes in clinical outcome . Methods . A total of 148 individuals ( 57 % women ) with chronic low back pain ( age , 45.0 ± 10.0 years ; duration of low back pain , 10.9 ± 9.5 years ) were r and omized to a treatment that they attended for 3 months : active physiotherapy , muscle reconditioning on devices , or low-impact aerobics . Before and after therapy , assessment s were made of the following : trunk muscle strength ( in flexion , extension , lateral bending , and axial rotation ) , erector spinae activation ( maximal , and during forward bending movements ) , back extensor endurance ( Biering-S/orensen test ) , and erector spinae fatigability ( determined from changes in the median frequency of the surface electromyographic signal ) during isometric and dynamic tests . Results . A total of 132 of 148 patients ( 89 % ) completed the therapy . Isometric strength in each movement direction increased in all groups post-therapy ( P < 0.0008 ) , most notably in the devices group . Activation of the erector spinae during the extension tests also increased significantly in all groups and showed a weak , but significant , relationship with increased maximal strength ( P = 0.01 ) . Pretherapy 55 % of the subjects showed no relaxation of the back muscles at L5 when in the fully flexed position ; no changes were observed in any group post-therapy . Endurance time during the Biering-S/orensen test increased significantly post-therapy in all groups ( P = 0.0001 ) , but there were no significant changes in EMG-determined fatigability . Fatigability of the lumbar muscles at L5 ( EMG median frequency changes ) during the dynamic test increased post-therapy ( P = 0.0001 ) without group differences . Conclusion . Significant changes in muscle performance were observed in all three active therapy groups post-therapy , which appeared to be mainly due to changes in neural activation of the lumbar muscles and psychological changes concerning , for example , motivation or pain tolerance Objectives Although motor control exercises have been shown to be effective in the management of  low back pain ( LBP ) the mechanism of action is unclear . The current study investigated the relationship between the ability to recruit transversus abdominis and clinical outcomes of participants in a clinical trial . Methods Ultrasonography was used to assess the ability to recruit transversus abdominis in a nested design : a sample of 34 participants with chronic LBP was recruited from participants in a r and omised controlled trial comparing the efficacy of motor control exercise , general exercise and spinal manipulative therapy .  Perceived recovery , function , disability and pain were also assessed . Results Participants with chronic LBP receiving motor control exercise had a greater improvement in recruitment of transversus abdominis ( 7.8 % ) than participants receiving general exercise ( 4.9 % reduction ) or spinal manipulative therapy ( 3.7 % reduction ) . The effect of motor control exercise on pain reduction was greater in participants who had a poor ability to recruit transversus abdominis at baseline . There was a significant , moderate correlation between improved recruitment of transversus abdominis and a reduction in disability ( r = −0.35 ; 95 % CI 0.02 to 0.62 ) . Conclusion These data provide some support for the hypothesised mechanism of action of motor control exercise and suggest that the treatment may be more effective in those with a poor ability to recruit transversus abdominis BACKGROUND The aim of this paper is to test " corset " model of spinal stability , specifically the hypothesis that feed forward transversus abdominis activity is bilaterally symmetrical and independent of the direction of perturbation to posture due to arm . This study will assess transversus abdominis electromyographical activity bilaterally . METHODS Feed forward intramuscular transversus abdominis electromyographical data  and reaction forces on the thorax due to the arm movement were collected and processed for 6 healthy subjects during 6 trials  of  8 types of arm movements ( r and omised order ) .  Reciprocal transversus abdominis indices were calculated as the difference between the normalised integrated feed forward transversus abdominis electromyographical data from each side of the trunk . FINDINGS The main finding of the study was that the reciprocal transversus abdominis index was significantly related to the axial rotational forces on the thorax due to arm movement ( F=109.991 , p<0.001 ) . Right arm movements produced clockwise axial rotation forces on the thorax and dominant left transversus abdominis muscle activity . INTERPRETATION The consequence of this finding is that feed forward  transversus abdominis  activity is not bilaterally symmetrical and is not independent of the direction of perturbation to posture due to arm movement . Transversus abdominis forms part of a synergy of muscles contributing to the generation of axial rotation forces in the core that oppose the forces due to arm movement . These findings indicate that training bilateral pre-activation of the transversus abdominis prior to rapid movement is not justified and may potentially be problematic for the production of normal movement patterns Study Design . A r and omized clinical trial with 1-year and 3-year telephone question naire follow-ups . Objective . To report a specific exercise intervention ’s long-term effects on recurrence rates in acute , first-episode low back pain patients . Summary of Background Data . The pain and disability associated with an initial episode of acute low back pain ( LBP ) is known to resolve spontaneously in the short-term in the majority of cases . However , the recurrence rate is high , 
    Output:
    
Results The included trials showed inconsistent , mostly small to moderate intervention effects on targeted movement patterns .
Conclusions Movement-based interventions were infrequently effective for changing observable movement patterns .
A relationship between changes in movement patterns and improvement in pain or activity limitation was also infrequently observed .
No independent studies confirm any observed relationships .