***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: It is generally accepted that human bipedal upright stance is achieved by feedback mechanisms that generate an appropriate corrective torque based on body-sway motion detected primarily by visual , vestibular , and proprioceptive sensory systems . Because orientation information from the various senses is not always available ( eyes closed ) or accurate ( compliant support surface ) , the postural control system must somehow adjust to maintain stance in a wide variety of environmental conditions . This is the sensorimotor integration problem that we investigated by evoking anterior-posterior ( AP ) body sway using pseudor and om rotation of the visual surround and /or support surface ( amplitudes 0.5 - 8 degrees ) in both normal subjects and subjects with severe bilateral vestibular loss ( VL ) .  AP rotation of body center-of-mass ( COM )  was measured in response to six conditions offering different combinations of available sensory information .  Stimulus-response data were analyzed using spectral analysis to compute transfer functions and coherence functions over a frequency range from 0.017 to 2.23 Hz . Stimulus-response data were quite linear for any given condition and amplitude . However , overall behavior in normal subjects was nonlinear because gain decreased and phase functions sometimes changed with increasing stimulus amplitude . " Sensory channel reweighting " could account for this nonlinear behavior with subjects showing increasing reliance on vestibular cues as stimulus amplitudes increased . VL subjects could not perform this reweighting , and their stimulus-response behavior remained quite linear . Transfer function curve fits based on a simple feedback control model provided estimates of postural stiffness , damping , and feedback time delay . There were only small changes in these parameters with increasing visual stimulus amplitude . However , stiffness increased as much as 60 % with increasing support surface amplitude . To maintain postural stability and avoid resonant behavior , an increase in stiffness should be accompanied by a corresponding increase in damping . Increased damping was achieved primarily by decreasing the apparent time delay of feedback control rather than by changing the damping coefficient ( i.e. , corrective torque related to body-sway velocity ) . In normal subjects , stiffness and damping were highly correlated with body mass and moment of inertia , with stiffness always about 1/3 larger than necessary to resist the destabilizing torque due to gravity . The stiffness parameter in some VL subjects was larger compared with normal subjects , suggesting that they may use increased stiffness to help compensate for their loss . Overall results show that the simple act of st and ing quietly depends on a remarkably complex sensorimotor control system Conclusion . The properties of a foam surface significantly affect  body movement variance . Therefore , studies where different kinds of foam have been used may not provide congruent results . Objectives . To investigate whether different properties of foam  affect body movement variance ( 32 subjects , mean age 22.5 years ) in terms of linear head , shoulder , hip and knee movements . Subjects repeated tests with eyes open and closed , to also determine the effect of vision on the different surfaces . Subjects and methods . Body movement was captured on three different foam surfaces and on a control solid surface over 2 min using a Zebris ™ ultrasound measuring system . The foam surfaces were categorized by their firmness as firm foam , medium foam and soft foam . Results . Body movement variance increased significantly when st and ing on all foam surfaces compared with the solid surface . However , movement variance was larger when st and ing on the firm foam compared with the softer foams , except in the anteroposterior total and low frequency ranges . We also found that the body movement pattern differed when st and ing on foam and firm surfaces , with greater reliance on movements at the knee to give postural stability on foam than on the solid surface . Vision clearly reduced all body movement variances , but particularly within the high frequency range 
    Output:
    
RESULTS Based on the present review ed findings , it is impossible to conclude that children with Down syndrome present significantly lower static postural control compared to TD children .
In contrast , findings showed that adolescents with Down syndrome tended to present significantly lower static postural control compared to TD adolescents when visual and plantar cutaneous inputs were disturbed separately or simultaneously .