***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: The reported association of low-back pain and musculoskeletal disorders contributed to the examination of the lumbar spine and hip extensor activation patterns in back pain sufferers during walking . Seventeen idiopathic low-back pain male subjects and 16 healthy volunteers participated in the study .  Hip joint ROMs in the sagittal plane and neuromuscular activities of erector spinae [ L3 , T12 ] , gluteus maximus and biceps femoris were recorded on one r and omly selected body side in each group . Analysis using the Student 's t-test revealed significant differences for hip joint range of motion , stride time and significantly earlier onsets of the lumbar spine and hip extensors of the back pain sufferers compared with the healthy controls . It is assumed , that low-back disorders are related to changes of the lumbar spine and hip extensor recruitment pattern OBJECTIVE To investigate the recruitment of the vastus medialis obliquus ( VMO ) and vastus lateralis during voluntary tasks that challenge the stability of the knee and to evaluate whether there is a change in the coordination of the postural response by the central nervous system in subjects with patellofemoral pain syndrome ( PFPS ) . DESIGN Cross-sectional . SETTING University laboratory in Australia . PARTICIPANTS Thirty-seven subjects with PFPS and 37 asymptomatic sex-matched controls . INTERVENTIONS Not applicable . MAIN OUTCOME MEASURES Recordings of electromyographic activity of the VMO , vastus lateralis , tibialis anterior , and soleus were made by using surface electrodes . Subjects rose onto their toes ( rise task ) or rocked back on their heels ( rock task ) in a visual choice-reaction time task .  Electromyographic onsets were determined by using a computer algorithm and were verified visually . RESULTS Our results confirm that , in asymptomatic subjects , contraction of the VMO and vastus lateralis occurs as part of the feed-forward postural response associated with ankle movements in st and ing , and the contraction of these separate heads of the quadriceps group occurs simultaneously . However , when subjects with PFPS perform identical tasks , the electromyographic onset of the vastus lateralis occurs before that of the VMO . CONCLUSION These findings indicate a difference in motor control in subjects with PFPS . They also support the hypothesized relation between changes in the timing of activity of the vastii and PFPS and provide the theoretic rationale to support physiotherapy treatment commonly used in the management of PFPS Background Inappropriate control of the vastus medialis oblique and vastus lateralis muscles by the central nervous system can contribute to maltracking of the patella . Hypothesis The activation timing and amplitude of the vastus medialis oblique and vastus lateralis muscles will be different between normal subjects and patients with patellofemoral pain . Study Design Controlled laboratory study . Methods Subjects with patellofemoral pain and asymptomatic control subjects performed maximum voluntary knee extension contractions initiated from a flexed and an extended position . The activation timing and amplitude of the vastus lateralis and vastus medialis oblique muscles were quantified from the recorded electromyographic signals . Results There were no between-group differences in activation timing . The activation amplitude of the vastus medialis oblique and vastus lateralis muscles of the patellofemoral pain subjects was altered to the greatest extent during eccentric contractions and differed significantly from that of control subjects . Conclusions The activation amplitudes of the vastus medialis oblique and vastus lateralis muscles of subjects with patellofemoral pain are consistent with a laterally tracking patella during eccentric contractions . Clinical Relevance The findings suggest the clinical importance of determining whether altered activation patterns are sensitive to rehabilitation , and , if so , if subjective reports of knee joint pain and function parallel changes in the activation patterns as a result of rehabilitation BACKGROUND AND PURPOSE Physical therapy rehabilitation strategies are commonly directed at the alteration of muscle recruitment in functional movements . The aim of this study was to investigate whether feedforward strategies of the vasti in people with patellofemoral pain syndrome can be changed by a physical therapy treatment program in a r and omised , double blind , placebo controlled trial . SUBJECTS Forty ( 25 female , 15 male ) subjects aged 40 yrs or less ( 27.2+/-7.8 yrs ) . METHODS Subjects were allocated to either a placebo treatment or a physical therapy intervention program . The postural challenge used as the outcome measure was not included in the training program . Electromyography ( EMG ) onsets of vastus medialis obliquus ( VMO ) , vastus lateralis ( VL ) , tibialis anterior and soleus were assessed before and after the six week st and ardised treatment programs . RESULTS At baseline the EMG onset of VL occurred prior to that of VMO in both subject groups . Following physical therapy intervention there was a significant change in the time of onset of EMG of VMO compared to VL with the onsets occurring simultaneously . This change was associated with a reduction in symptoms . In contrast , following placebo intervention the EMG onset of VL still occurred prior to that of VMO . CONCLUSION AND DISCUSSION The results indicate that the feedforward strategy used by the central nervous system to control the patella can be restored . Importantly , the data suggest that this intervention produced a change that was transferred to a task that was not specifically included in the training program . Furthermore , the change in motor control was associated with clinical improvement in symptoms Objective To examine the effect of the application of tape over the patella on the onset of electromyographic ( EMG ) activity of vastus medialis obliquus ( VMO ) relative to vastus lateralis ( VL ) in participants with and without patellofemoral pain syndrome ( PFPS ) . Design R and omised within subject . Setting sUniversity laboratory . Participants Ten participants with PFPS and 12 asymptomatic controls . Interventions Three experimental taping conditions : no tape , therapeutic tape , and placebo tape . Main Outcome Measures Electromyographic onset of VMO and VL assessed during the concentric and eccentric phases of a stair stepping task . Results When participants with PFPS completed the stair stepping task , the application of therapeutic patellar tape was found to alter the temporal characteristics of VMO and VL activation , whereas placebo tape had no effect . In contrast , there was no change in the EMG onset of VMO and VL with the application of placebo or therapeutic tape to the knee in the asymptomatic participants . Conclusions These data support the use of patellar taping as an adjunct to rehabilitation in people with PFPS OBJECTIVE To determine the effects of a weight-bearing rehabilitation program on quadriceps and gluteus medius electromyographic activity , pain , and function in subjects diagnosed with patellofemoral pain syndrome ( PFPS ) . DESIGN Pretest and posttest 6-week intervention study . SETTING Musculoskeletal research laboratory . PARTICIPANTS Fourteen subjects diagnosed with PFPS and 14 healthy control subjects volunteered to participate in this study . No subjects withdrew from the study because of adverse effects . INTERVENTION Subjects diagnosed with PFPS participated in a 6-week rehabilitation program . The rehabilitation program consisted of weight-bearing exercises that focused on strengthening the quadriceps and hip abductor musculature . MAIN OUTCOME MEASURES Electromyographic onsets of the vastus medialis oblique ( VMO ) and vastus lateralis and onset and duration of the gluteus medius were collected during a stair-stepping task that was performed during the pretest and posttest . A visual analog scale ( VAS ) and Functional Index Question naire ( FIQ ) were administered at pretest and posttest and each week of the intervention . RESULTS Vastus lateralis and VMO onset timing differences ( vastus lateralis electromyographic onset minus VMO electromyographic onset ) and VAS and FIQ scores significantly improved for patients diagnosed with PFPS . Vastus lateralis and VMO onset timing in the PFPS group were significantly different from those in the control group at baseline and were not significantly different from the control group after the intervention . We did not find differences in gluteus medius onsets or duration of activity . CONCLUSIONS Subjects diagnosed with PFPS responded favorably and quickly to a therapeutic exercise program that incorporated quadriceps and hip musculature strengthening . The efficacy of the therapeutic exercise program used in this study should be further investigated in a larger subject population Many variables have retrospectively been associated with the presence of anterior knee pain . Very few prospect i ve data exist , however , to determine which of these variables will lead to the development of anterior knee pain . It was our purpose in this study to determine the intrinsic risk factors for the development of anterior knee pain in an athletic population over a 2-year period . Before the start of training , 282 male and female students enrolled in physical education classes  were evaluated for anthropometric variables , motor performance , general joint laxity , lower leg alignment characteristics , muscle length and strength , static and dynamic patellofemoral characteristics , and psychological parameters . During this 2-year follow-up study , 24 of the 282 students developed  patellofemoral pain . Statistical analyses revealed a significant difference between those subjects who developed patellofemoral pain and those who did not concerning quadriceps and gastrocnemius muscle flexibility , explosive strength , thumb-forearm mobility , reflex response time of the vastus medialis obliquus and vastus lateralis muscles , and the psychological parameter of seeking social support . However , only a shortened quadriceps muscle , an altered vastus medialis obliquus muscle reflex response time , a decreased explosive strength , and a hypermobile patella had a significant correlation with the incidence of patellofemoral pain . We concluded that the latter four parameters play a dominant role in the genesis of anterior knee pain and we therefore deem them to be risk factors for this syndrome 
    Output:
    
A trend was demonstrated towards a delayed onset of VMO relative to VL in those with AKP in comparison to those without .
However not all AKP patients demonstrate a VMO-VL dysfunction , and this is compounded by normal physiological variability in the healthy population .