***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: OBJECTIVES To study electromyographic characteristics of anticipatory postural adjustment in axial and lateral , posterior and anterior trunk muscles during the performance of upper- and lower-limb flexion tasks , in subjects with hemiparesis after stroke and to determine the relationship between anticipatory activity and subjects ' motor and functional status . DESIGN A nonr and omized control study . SETTING Geriatric rehabilitation center in Israel . PARTICIPANTS Fifty poststroke hemiparetic patients and 30 healthy control subjects . INTERVENTION  Electromyographic activity of the lumbar erector spinae and of the latissimus dorsi muscles was recorded bilaterally during flexion of either arm and from the 2 rectus abdominis and obliquus externus muscles during flexion of either hip . MAIN OUTCOME MEASURES Muscles ' onset latency , cross-correlation values between the temporal activation profile of corresponding pairs and between ipsilateral muscular pairs , symmetry in activation magnitude of corresponding muscles , and relation between electromyographic activity and motor and functional performance RESULTS Onset latencies of trunk muscles were partially delayed in the patients with longest hindrance displayed by the erector spinae ipsilateral to the flexing arm ( P<.04 ) . Temporal synchronization between pertinent muscular pairs was lower in the patients than in the healthy subjects , with significant group differences ( P<.05 or lower ) in the correlations between ipsilateral pairs of trunk muscles . Activation of the corresponding lateral trunk muscles in the patients was significantly less symmetrical than in the controls ( P<.03 or lower ) because of reduced activity on the paretic body side , especially on flexing of the paretic limbs . Conversely , in the controls as well as on the nonparetic side of the patients , limb flexion was associated with increased activity in the ipsilateral lateral trunk muscle . The erector spinae muscle in both groups and on both sides was more active on the contralateral side than on the ipsilateral side to the flexing arm . The reduced activity level in trunk muscles on the paretic body side was associated with deficiencies in motor and functional abilities . CONCLUSIONS Major impairments in the activity of trunk muscles in hemiparetic subjects were manifested in the reduced activity level of the lateral trunk muscles , in delayed onset , and in reduced synchronization between activation of pertinent muscular pairs . These problems were associated with motor and functional deficits and warrant specific consideration during physical rehabilitation of post stroke hemiparetic patients OBJECTIVE To examine trunk stability in unstable sitting posture in 2 different functional activities . DESIGN A r and omized crossover design . SETTING Rehabilitation center in Italy . PARTICIPANTS Ten healthy subjects and 10 patients with multiple sclerosis . INTERVENTIONS Subjects were seated on an unstable support surface . A task in which the subjects had to keep their trunk as stable as possible was compared with tasks in which they had to track an object with the head or grasp an object . Main outcome measures Angular displacement and mean absolute angular velocity in the anteroposterior and mediolateral planes of the support surface . RESULTS Angular displacement showed differences between patients and healthy subjects both in the sagittal plane ( P<.0001 ) and frontal plane ( P<.002 ) . Velocity of angular displacement differentiated between the groups in both planes ( P<.0001 ) . Differences between velocity of angular displacement in different tasks were also detected ( P<.0001 ) . Correlation coefficients between sitting balance scores and laboratory measures were low and not statistically significant . In the healthy subjects , instability in the frontal plane correlated positively with the subjects ' weight and height . CONCLUSIONS Both patients and healthy subjects had more difficulty with frontal plane stability than with sagittal plane stability . Angular velocity for a given task showed the greatest difference between the groups and between postural challenge tasks within a group . Patients were more unstable than healthy subjects during head movements in the frontal plane ; conversely , arm movements produced larger angular displacement , especially in the sagittal plane The study assessed the effect of velocity of arm movement on anticipatory postural adjustments ( APAs ) generation in the contralateral and ipsilateral muscles of individuals with stroke in seating . Ten healthy and eight post-stroke subjects were studied in sitting . The task consisted in reaching an object placed at scapular plane and mid-sternum height at self-selected and fast velocities .  Electromyography was recorded from anterior deltoid ( AD ) , upper ( UT ) and lower trapezius ( LT ) and latissimus dorsi ( LD ) . While kinematic analysis was used to assess peak velocity and trunk displacement . Differences were found between the timing of APAs on ipsi and contralateral LD and LT in both movement speeds and in ipsilateral UT during movement of the non-affected arm at a self-selected velocity . A delay on the contralateral LD to reach movement with the non-affected arm at fast velocity was also observed . The trunk displacement was greater in post-stroke subjects . Individuals with stroke demonstrated a delay of APAs in the muscles on both sides of the body compared to healthy subjects . The delay was observed during performance of the reaching task with the fast and self-selected velocity 1 . The effects of cerebellar deficits in humans on scaling the magnitude of automatic postural responses based on sensory feedback and on predictive central set was investigated . Electromyographic ( EMG ) and surface reactive torques were compared in patients with anterior lobe cerebellar disorders and in normal healthy adults exposed to blocks of four velocities and five amplitudes of surface translations during stance .  Correlations between the earliest postural responses ( integrated EMG and initial rate of change of torque ) and translation velocity provided a measure of postural magnitude scaling using sensory information from the current displacement . Correlations of responses with translation amplitude provided a measure of scaling dependent on predictive central set based on sequential experience with previous like displacements because the earliest postural responses occurred before completion of the displacements and because scaling to displacement amplitude disappeared when amplitudes were r and omized in normal subjects . 2 . Responses of cerebellar patients to forward body sway induced by backward surface displacements were hypermetric , that is , surface-reactive torque responses were two to three times larger than normal with longer muscle bursts result ing in overshooting of initial posture . Despite this postural hypermetria , the absolute and relative latencies of agonist muscle bursts at the ankle , knee , and hip were normal in cerebellar patients . 3 . Although they were hypermetric , the earliest postural responses of cerebellar patients were scaled normally to platform displacement velocities using somatosensory feedback . Cerebellar patients , however , were unable to scale initial postural response magnitude to expected displacement amplitudes based on prior experience using central set . R and omization of displacement amplitudes eliminated the set effect of amplitude on initial responses in normal subjects , but responses to r and omized and blocked trials were not different in cerebellar patients . 4 . Cerebellar patients compensated for hypermetric responses and lack of anticipatory scaling of earliest gastrocnemius activity by scaling large , reciprocally activated tibialis and quadriceps antagonist activity with the displacement velocity and amplitude . Correlations between these antagonist EMG integrals and displacement amplitudes were preserved when amplitudes were r and omized , suggesting that feedback-dependent and not set-dependent mechanisms were responsible for scaling of antagonists by cerebellar patients . Antagonist compensation for initial hypermetric responses also could be induced in normals when they overresponded to unexpectedly small amplitudes of surface displacements . 5 . The major effects of anterior lobe cerebellar damage on human postural responses involves impairment of response magnitude based on predictive central set and not on use of velocity feedback or on the temporal synergic organization of multijoint postural coordination . ( ABSTRACT TRUNCATED AT 400 WORDS 
    Output:
    
In a sitting position , central nervous system activity precedes movement by diverse anticipatory muscular activities and shows the ability to adapt anticipatory muscular activity parameters to the movement direction , postural stability , or charge weight .
In addition , these parameters could be adapted to the speed of execution , as found for the st and ing position .
Parameters of anticipatory muscular activities ( duration , order , and amplitude of muscle contractions constituting the anticipatory muscular activity ) could be used as a predictive indicator of forthcoming movement .