Effects of light finger touch to the upper legs on postural sway and muscle activity during quiet standing

Abstract

The purpose of the present study was to investigate the effects of light finger touch (LT) to one's own body on postural sway and ankle muscle activity during quiet standing. In the first part of the present study, 24 healthy men (19 ± 1 years) stood upright with their eyes closed on a pneumatic balance disk under 3 different conditions. In the first condition, the participants kept their hands in loose fists, and contact between the fingers/palms and the legs was avoided. In the second condition, the participants touched the lateral sides of upper legs lightly (without applying force for mechanical support) with all fingers. In the third condition, the participants again held their hands in loose fists. Postural sway was significantly decreased during second condition compared to first condition. Further, it also tended to decrease in third condition (P = 0.08). The second part of the present study was designed to investigate the mechanisms underlying the association between postural sway and LT by analyzing electromyographic data. Data were obtained from 12 healthy men (20 ± 1 years). During quiet stance on the stable surface, soleus activity did not significantly change by LT. However, tibialis-anterior activity significantly decreased with LT. These results suggest that LT to the upper part of one's own legs decreases postural sway (during and after touching) during a still stance by decreasing co-activation of the ankle muscles.

The Effect of Lightly Gripping a Cane on the Dynamic Balance Control

“…It is greater in the elderly than in young adults [ 26 - 28 ], with eyes closed than with eyes open [ 29 ], and on an unstable surface than on a stable surface [ 30 ]. However, some researcher reported that plantar flexor (soleus) activity was not significantly changed by a light touch during quiet stance [ 8 , 9 ].…”

“…During the bipedal stance, muscle co-activation of the ankle joint increased with age [ 26 , 27 ], and persons with less physical function during postural control tasks showed higher muscle co-activation of the ankle joints [ 27 , 31 ]. Further, Oshita and Yano [ 9 ] reported that although soleus (plantar flexor) activity did not significantly change with a light touch during quiet stance, tibialis anterior (dorsiflexor) activity significantly decreased. Therefore, a light touch during quiet stance might improve postural stability by decreasing co-activation of the ankle muscles, and provide information about the movement of the body segments.…”

“…By contrast, lightly touching a cane does not reduce muscular force outputs while maintaining posture because contact force levels are insufficient for providing mechanical body support. Furthermore, some studies revealed that the association between postural control and haptic input through light touching affects motor learning [ 9 , 36 ]. These reports suggest that light touching is a potential training tool to acquire postural control ability.…”

“…Further, researchers have made efforts to improve these variables through various procedures. Researchers have found that providing additional tactile sensory input through the hand or finger improves postural stability during quiet standing [ 1 - 9 ]. Jeka and Lackner [ 2 ] showed that lightly touching the tip of the index finger on a fixed surface at waist height (contact force levels that are insufficient for providing mechanical body support; <1 N) resulted in decreased postural sway during tandem Romberg stance.…”

“…Riley et al [ 5 ] reported that a light finger touch to a cloth curtain decreased postural sway. It has also been found that lightly touching a finger to the upper part of the thighs significantly decreases postural sway during quiet stance [ 6 , 9 ]. Furthermore, lightly touching a stable surface can improve the quality of postural responses to slips or trips during quiet standing on a platform by triggering a more rapid corrective response to a sudden displacement of the platform [ 10 ].…”