***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: Unilateral light fingertip touch of a stationary object has a significant stabilizing effect on postural sway during stance . The purpose of this study was to find out if this effect is enhanced by bilateral light touch of parallel stationary objects . The postural sway of 54 healthy subjects was tested in four stance conditions : no touch ; unilateral left light touch of the left h and le of a walker ; unilateral right light touch of the right h and le of the same walker ; and bilateral light touch of the two h and les . During testing , subjects stood blindfolded on two foam pads placed on the left and right force plates of the Tetrax balance system . Testing in each condition lasted 45 s and was executed twice in a r and om order . As expected , postural sway was significantly reduced by unilateral left or right light fingertip touch . It was significantly further decreased by bilateral light touch . In addition , light touch conditions were associated with a reduction in pressure fluctuations between the heel and forefoot of the same foot as well as those of the contralateral foot , with a concomitant increase in weight shift fluctuations between the two feet . The decrease in postural sway with bilateral light touch suggests cortical modulation of the bilateral touch inputs , with enhancement of the stabilizing response Objectives : To investigate the potential benefits from lightly touching an external supporting device on automatic postural responses to support surface translations , in subjects with profound sensory neuropathy in the feet due to diabetes mellitus ( DM-PN ) . Methods : Eight subjects with DM-PN and 10 age matched controls were tested under r and omly ordered conditions of no fingertip touch ( NT ) , light touch ( LT ; < 1 N ) , and heavy touch ( HT , as needed ) of a stationary touch plate , during three backward translation velocities of the support surface at 10 , 20 , and 30 cm/s . Dependent variables included response latencies , CoP velocity , and the slope of the relation between centre of pressure ( CoP ) velocity and translation velocity as a measure of response scaling . Results : Postural response latencies were significantly longer and scaling of initial response magnitude in proportion to translation velocity was significantly smaller in the DM-PN subjects compared to the control subjects . LT had no significant effect on response latencies of the DM-PN patients . Fingertip touch increased the slope of the scaling of postural response magnitude in both groups . However , DM-PN subjects had to use HT to improve response scaling , whereas control subjects improved scaling with LT as well as HT . LT significantly increased rightward CoP velocity towards the touch plate in all subjects . Conclusions : LT did not reduce the latency or improve the scaling of automatic postural responses in subjects with peripheral neuropathy . The major effect of LT on the automatic postural responses of the DM-PN subjects was in increasing CoP velocity towards the side of the supporting device . HT in neuropathy subjects and LT in age matched control subjects increased the sensitivity of initial postural response scaling , suggesting that somatosensory substitution from a cane in the h and could be used to improve the magnitude of medium latency postural responses to slips and trips BACKGROUND Postural sway during quiet st and ing reduces when somatosensorial information is provided by an active or passive " light touch " of different body parts with a surface . The contact of the safety harness with the body could induce a similar effect , leading to an undesirable side effect in the balance evaluation . METHODS This study investigated if a safety harness system , commonly used in balance studies , affects body sway during the balance evaluation . Healthy adults stood as quietly as possible for 60s in a comfortable position on a force plate . First , we performed an experiment on the light-touch effect with 10 subjects to determine the necessary sample size for the main investigation . Then , 60 subjects completed four tasks where the use of the safety harness and the visual information were manipulated . Area , root-mean square , speed , and frequency of the center of pressure displacement were analyzed . FINDINGS A light touch decreased postural sway on both visual conditions but there was no effect of the use of a safety harness on sway when quietly st and ing , independent of the visual information . Postural sway increased on both somatosensorial conditions when the visual information was not provided . INTERPRETATION This result shows that the safety harness does not interfere with the evaluation what is of major importance to method ological aspects of balance evaluation BACKGROUND AND OBJECTIVE haptic cues from fingertip light touch ( LT ) with a stationary surface reduce postural sway even at non-mechanically supportive force levels . Aim of this study was to determine the effects of LT on postural sway in older compared with younger persons . SUBJECTS twenty young ( age 20 - 29 , mean 23.9 + 2.5 ) and 20 older participants ( age 65 - 83 , mean 74.3 + 6.4 ) . METHODS subjects stood in the semi-t and em position on a firm surface , and their postural sway was quantified using a force platform . Experimental trials , r and omised across subjects , included two sight conditions ( vision and no vision ) and three contact conditions ( no touch , NT ; light touch , LT ; and force touch , FT ) . The measured parameters were the length and the area of centre of pressure sway ( COP-L and COP-A ) and the mean velocity of COP displacements in the anterior-posterior ( COP-AP ) and medial-lateral ( COP-ML ) direction . RESULTS for all variables , the analysis showed significant differences between contact conditions , sight conditions and age . Contact-age interaction was significant between NT and LT conditions , with older participants showing greater decrease in postural sway than younger participants , but not between FT and LT conditions . CONCLUSIONS results indicate that the effectiveness of LT in reducing postural sway may be greater in older than in younger persons , perhaps because in older persons haptic cues from upper extremity might counterbalance sub- clinical sensory loss in the lower extremities . This finding supports the hypothesis that older people may sometimes use a walking aid as an informative device and suggests that during balance training external aids should not be used Abstract . Light touch of the index finger with a stationary surface at non-mechanically supportive force levels ( < 100 g ) greatly attenuates the  body sway of st and ing subjects . In three experiments , we evaluated the properties of finger contact and of the contacted object necessary to produce postural stabilization in subjects st and ing heel-to-toe with eyes closed , as well as how accurately h and position can be controlled . Experiment 1 involved finger contact with flexible filaments of different bending strengths , a flat surface , and an imagined spatial position . Contact with the flat surface was most effective in attenuating sway ; the flexible filaments were much less effective but still significantly better than imagined contact . Experiment 2 compared the effectiveness of finger contact with a flexible filament , a rigid filament of the same diameter , a flat surface , and an imagined spatial position . The rigid filament and flat surface conditions were equally effective in attenuating body sway and were greatly superior to contact with the flexible filament , which was superior to imagined contact . Experiment 3 included five conditions : arms by sides ; finger " contact " with an imagined spatial position ; finger contact with a flat surface ; finger contact with a flexible filament attempting to maintain it bent ; and contact with the flexible filament attempting not to bend it . The arms by sides and finger " contact " with an imagined position conditions did not differ significantly ; all three conditions involving actual finger contact showed significantly less center of pressure and h and sway , but contact with the flat surface was most effective in attenuating both postural and h and displacement . In all three experiments , the level of force applied in fingertip contact conditions was far below that necessary to provide mechanical stabilization . Our findings indicate that : ( 1 ) stimulation of a small number of receptors in the fingertip is adequate to allow stabilization of sway , ( 2 ) fingertip force levels as low as 5–10 g provide some stabilization , ( 3 ) contact with a stationary spatial referent is most effective , and ( 4 ) independent control of arm and torso occurs when finger contact is allowed Parkinson 's disease ( PD ) de grade s balance control . Haptic ( touch and proprioception ) feedback from light contact with a stationary surface inadequate to mechanically stabilize balance improves balance control in healthy people . In this study we tested whether PD impairs use of haptic cues independent of mechanical support to control balance . We measured postural sway in thirteen individuals with PD ( H&Y 1 - 3 , median=2 , Q1=2 , Q3=2 ) and thirteen age-matched controls balancing in a widened , sharpened Romberg stance in four conditions : eyes-closed , no manual contact ; eyes-closed light-touch contact ( < 1N ) , eyes-closed , unrestricted contact ; and eyes-open , no contact .  To determine whether PD-severity affects any of these balance strategies , PD participants were tested on- and off-medication , and using the more- and less-affected body side in the stance and manual contact . Individuals with PD simultaneously maintained non-supportive fingertip contact and balance in this task without practice . PD participants swayed more than control participants ( ML CP p=0.010 ; shoulder p<0.001 ) , but manual contact reduced sway . Non-supportive manual contact stabilized balance more than vision ( p<0.05 ) . PD-severity factors had no significant effect ( p>0.05 ) . We conclude the effect of PD on balance is not specific to vision or haptic feedback . Nevertheless , haptic cues from manual contact , independent of mechanical support , improve balance control in individuals with PD . We discuss the implication that PD or associated dopaminergic pathways do not directly affect haptic feedback balance control mechanisms , including arm/posture coordination and proprioceptive integration Abstract . When a st and ing person applies a light finger touch to an external stable object ,  postural sway  is reduced . We tested a hypothesis that two factors related to touch can induce this effect , the presence of a stable reference point and the modulation of contact forces leading to tissue deformation . Force platform signals were analyzed while subjects stood quietly with or without additional light touch to an external object ( contact forces under 1 N ) . The point of touch on the body was manipulated . We also investigated the effects of active touch vs fixation of a finger at a point in external space . The results show that touch to the head or neck can be more effective in reducing body sway than a finger touch . A larger reduction in sway was observed when the finger was fixed in a clip ( the net forces between the clip and the point of its fixation to the st and were under 1 N ) as compared to a free light touch to a pad . The subjects showed a reduction in postural sway while holding a load suspended using a pulley system ; in this situation , contact with the load via the pulley provided modulation of contact forces but not a fixed reference point . This finding emphasizes the importance of such factors as stability of the contact point and modulation of contact forces , as compared to active touch or to an implicit task of stabilizing the kinematic chain . The system of postural stabilization can reduce postural sway , making use of either of two sources of sensory information associated with touch , one related to providing a fixed reference point in space , and the other related to transient force changes at the point of contact related to the sway 
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Such effect was more evident when the applied vertical force was greater than 1N , but if individuals with poor balance took more advantage of the light touch than healthy ones it depended on the source of their balance problems and not the amount of the applied force .
These findings suggested that the maintenance of the fingertip lightly touching an external surface could provide additional somatosensory information for individuals with poor balance and then it could be used as a strategy to improve the control of upright st and ing during intervention programs