***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: BACKGROUND Women have higher rates of knee ligament injury than men . Co-contraction of knee muscles is proposed to be an important mechanism to protect the joint from injuries . HYPOTHESIS Females have lower co-contraction levels when compared to males . STUDY DESIGN Exploratory , cross-sectional design . METHODS Thirty-six men and women equally divided into four groups according to gender and activity level ( sedentary and athletic ) were compared in relation to vastus lateralis and biceps femoris co-contraction before heel strike during level walking and before floor contact during l and ing from a jump . Muscular co-contraction was assessed by surface electromyography .  Correlations between co-contraction and ligament laxity , extensor and flexor work , and flexion/extension torque ratio were also analyzed . RESULTS No differences between genders were found in the studied situations ( p0.381 ) . During walking , co-contraction was greater in sedentary women compared to athletic women ( p=0.002 ) . A moderate inverse correlation was found between co-contraction during walking and women extensor ( r=-0.613 ; p=0.007 ) and flexor ( r=-0.575 ; p=0.012 ) work . During l and ing from a jump , no variables correlated to co-contraction in any of the groups tested ( r0.477 ; p0.061 ) . CONCLUSION Co-contraction levels were not different between genders . Results suggest that women compensate strength deficits by means of increasing activation levels , possibly to generate adequate joint stiffness to meet stabilization dem and s. However , this is not evident in a more stressful activity like l and ing from a jump . CLINICAL RELEVANCE This study contributes to a better underst and ing of the factors related to joint protection in females , who are at a greater risk of ligament injuries Background and Purpose — The purpose of this study was to compare treadmill and electromechanical gait trainer therapy in subacute , nonambulatory stroke survivors . The gait trainer was design ed to provide nonambulatory subjects the repetitive practice of a gait-like movement without overexerting therapists . Methods — This was a r and omized , controlled study with a crossover design following an A-B-A versus a B-A-B pattern . A consisted of 2 weeks of gait trainer therapy , and B consisted of 2 weeks of treadmill therapy .  Thirty nonambulatory hemiparetic patients , 4 to 12 weeks after stroke , were r and omly assigned to 1 of the 2 groups receiving locomotor therapy every workday for 15 to 20 minutes for 6 weeks . Weekly gait ability ( functional ambulation category [ FAC ] ) , gait velocity , and the required physical assistance during both kinds of locomotor therapy  were the primary outcome measures , and other motor functions ( Rivermead motor assessment score ) and ankle spasticity ( modified Ashworth score ) were the secondary outcome measures . Follow-up occurred 6 months later . Results — The groups did not differ at study onset with respect to the clinical characteristics and effector variables . During treatment , the FAC , gait velocity , and Rivermead scores improved in both groups , and ankle spasticity did not change . Median FAC level was 4 ( 3 to 4 ) in group A compared with 3 ( 2 to 3 ) in group B at the end of treatment ( P = 0.018 ) , but the difference at 6-month follow up was not significant . The therapeutic effort was less on the gait trainer , with 1 instead of 2 therapists assisting the patient at study onset . All but seven patients preferred the gait trainer . Conclusions — The newly developed gait trainer was at least as effective as treadmill therapy with partial body weight support while requiring less input from the therapist . Further studies are warranted OBJECTIVE To establish whether functional recovery of gait in patients with post-stroke hemiparesis coincides with changes in the temporal patterning of lower extremity muscle activity and coactivity during treadmill walking . METHODS  Electromyographic ( EMG ) data from both legs , maximum walking speed , the amount of swing phase asymmetry and clinical measures were obtained from a group of post-acute patients with hemiparesis , as early as possible after admission in a rehabilitation centre ( mean time post-stroke 35 days ) and 1 , 3 , 6 , and 10 weeks later , while all patients participated in a regular rehabilitation program .  EMG data from the first assessment were compared to those obtained from a group of healthy controls to identify abnormalities in the temporal patterning of muscle activity . Within subject comparisons of patient data were made over time to investigate whether functional gait recovery was accompanied by changes in the temporal patterns muscle (co-)activity . RESULTS EMG patterns during the first assessment showed a number of abnormalities on the paretic side , namely abnormally long duration s of activity in biceps femoris ( BF ) during the single support ( SS ) phase and in gastrocnemius medialis ( GM ) during the first double support phase ( DS1 ) . Furthermore , in both legs a prolongation of the activity was seen in the rectus femoris ( RF ) during the SS phase . In addition , the duration of BF-RF coactivation was longer on the paretic side than it was in controls . Over time , the level of ambulatory independence , body mobility , and maximum walking speed increased significantly , indicating that substantial improvements in gait ability occurred . Despite these improvements , duration s of muscle ( co- ) activity and the level of swing phase asymmetry did not change during rehabilitation . More specifically , timing abnormalities in muscle (co-)activity that were found during the first assessment did not change significantly , indicating that these aberrations were not an impediment for functional gait improvements . CONCLUSIONS Normalization of the temporal patterning of gait related muscle activity in the lower extremities is not a prerequisite for functional recovery of gait in patients with post-stroke hemiparesis . Apparently , physiological processes other than improved temporal muscular coordination must be important determinants of the restoration of ambulatory capacity after stroke . SIGNIFICANCE Recovery of walking ability in post-stroke hemiparesis is not necessarily associated with , or dependent on , reorganization in the temporal control of gait related muscle activity . Normalization of the temporal coordination of muscle activity during gait may not be an important clinical goal during post-acute rehabilitation OBJECTIVE The purpose of this study was to compare the kinematics , muscle activation , and force production between Parkinson 's patients and healthy , age-matched participants during sit-to-st  and transfers  . DESIGN This cross-sectional study employed a 2x2x3 multivariate analysis of variance to test for significant differences between and within groups . BACKGROUND The underlying mechanisms that predispose an individual to lose strength during the clinical progression of Parkinson 's disease have proved to be elusive , especially during performance of functional tasks such as the sit to st and transfer . METHODS Twenty-four men ( mean age : 71.5 years ) categorized as Parkinson 's patients ( n = 13 ) and healthy adults ( n = 11 ) participated in this study . Two force platforms measured antero-posterior and vertical force components as well as peak torque . Muscle activation was measured by a six channel , bilateral electromyography system . A lower-body kinematic assessment was conducted utilizing a high-speed motion analysis system . RESULTS No statistically significant differences were found between groups for the outcome variables measured . However , Parkinson 's patients did exhibit significant within-group bilateral differences for the variables of knee angle at seat-off , peak vertical force and peak torque . CONCLUSION Data from this study reveal that persons with mild to moderate Parkinson 's disease exhibit moderately altered bilateral mechanics when performing a sit to st and transfer compared to their healthy peers . RELEVANCE The inability to produce constant equilateral force when performing functional tasks could be an indicator for the increased propensity of falls or other instabilities in this population OBJECTIVE To compare the gait of hemiparetic subjects walking on a treadmill  with various body weight supports and walking on the floor . DESIGN Hemiparetic subjects  walked on a treadmill , secured in a harness , with no body weight support and with 15 % and 30 % body weight relief , and walked on a floor . SETTING Kinematic laboratory of a department of rehabilitation . SUBJECTS Eighteen hemiparetic stroke patients . MAIN OUTCOME MEASURES Gait cycle parameters and kinesiologic electromyogram of six muscles of the affected side and of two muscles of the nonaffected side . RESULTS On the treadmill , patients walked more slowly because of a reduced cadence , with a longer single stance period of the paretic limb , more symmetrically , and with a larger hip extension ( multivariate profile analysis , p<.05 ) . The mean functional activities of the gastrocnemius muscle and of the first crest of the erector spinae of the paretic side were smaller on the treadmill ( univariate test , p<.05 ) . Further , the premature activity of the gastrocnemius muscle , indicating spasticity , was less on the treadmill ( univariate test , p<.05 ) ; correspondingly the qualitative muscle pattern analysis revealed less co-contraction between the gastrocnemius and tibialis anterior muscles in 11 of the 18 subjects . CONCLUSIONS Treadmill training with partial body weight support in hemiparetic subjects allows them to practice a favorable gait characterized by a greater stimulus for balance training because of the prolonged single stance period of the affected limb , a higher symmetry , less plantar flexor spasticity , and a more regular activation pattern of the shank muscles as compared with floor walking Information on the dynamic properties ( joint stiffness , viscosity and limb inertia ) of the human knee joint is scarce in the literature , especially for actively contracting knee musculature . A joint driving device was developed to apply small-amplitude r and om perturbations to the human knee  at several flexion angles with the subject maintaining various levels of muscle contraction . It was found that joint stiffness and viscosity increased with muscle contraction substantially , while limb inertia was constant . Stiffness produced by the quadriceps was highest at 30 degrees flexion and decreased with increasing or decreasing flexion angle , while knee flexors produced highest stiffness at 90 degree flexion . When knee flexion was < 60 degrees , stiffness produced by the quadriceps was higher than that of the hamstrings and gastrocnemius at the same level of background muscle torque , while knee flexor muscles produced higher stiffnesses than the quadriceps at 90 degree flexion . Similar but less obvious trends were observed for joint viscosity . Passive joint stiffness at full knee extension was significantly higher than in more flexed positions . Surprisingly , as the knee joint musculature changed from relaxed to contracting at 50 % MVC , system damping ratio remained at about 0.2 . This outcome potentially simplifies neuromuscular control of the knee joint . In contrast , the natural undamped frequency increased more than twofold , potentially making the knee joint respond more quickly to the central nervous system comm and s. The approach described here provides us with a potentially valuable tool to quantify in vivo dynamic properties of normal and pathological human knee joints Background . Little is known about whether changes in coordination patterns of muscle activation after stroke are related to functional recovery of walking . Objective . The present study investigated the longitudinal relationship between changes in neuromuscular activation patterns of paretic muscles in hemiplegic gait and improvement in walking ability after stroke . Methods . Thirteen patients diagnosed with a first unilateral ischemic stroke had their recovery of walking measured by the Rivermead Mobility Index , Functional Ambulation Categories , Barthel Index , Trunk Control Test , Motricity Index , and comfortable walking speed . Surface electromyography ( SEMG )  of the erector spinae , gluteus maximus , gluteus medius , rectus femoris , vastus lateralis , semitendinosus , gastrocnemius , and tibialis anterior muscles of both legs was used to quantify coordination patterns in comfortable walking mode . All clinical and electromyography-related measurements were taken at 3 , 6 , 9 , 12 , and 24 weeks poststroke . Timing parameters of the SEMG patterns were calculated , using an objective burst detection algorithm , and analyzed with the measures of functional recovery . Results . All functional measures , except Trunk Control Test , showed statistically significant improvement over time , whereas SEMG patterns did not change significantly over time . Conclusion . The lack of significant change in SEMG patterns over time suggests that functional gait improvements may be more related to compensatory strategies in muscle activation of the unaffected leg and biomechanical changes than by restitution of muscle coordination patterns in the affected leg 
    Output:
    
There is some controversy in MCo results , however subjects with stroke tended towards longer MCo in both lower limbs in both the acute and chronic stages , when compared with healthy controls .
A higher level of post-stroke walking ability ( speed ; level of independence ) was correlated with longer thigh MCo in the non-affected limb .
CONCLUSIONS Subjects with stroke commonly present longer MCo during walking , probably in an attempt to improve walking ability .