The contribution of light touch sensory cues to corrective reactions during treadmill locomotion

Abstract

The arms play an important role in balance regulation during walking. In general, perturbations delivered during walking trigger whole-body corrective responses. For instance, holding to stable handles can largely attenuate and even suppress responses in the leg muscles to perturbations during walking. Particular attention has been given to the influence of light touch on postural control. During standing, lightly touching a stable contact greatly reduces body sway and enhances corrective responses to postural perturbations, whereas light touch during walking allows subjects to continue to walk on a treadmill with the eyes closed. We hypothesized that in the absence of mechanical support from the arms, sensory cues from the hands would modulate responses in the legs to balance disturbing perturbations delivered at the torso during walking. To test this, subjects walked on a treadmill while periodically being pulled backwards at the waist while walking. The amplitude of the responses evoked in tibialis anterior to these perturbations was compared across 4 test conditions, in a 2 × 2 design. Subjects either (a) lightly touched or (b) did not touch a stable contact, while the eyes were (c) open or (d) closed. Allowing the subjects to touch a stable contact resulted in a reduction in the amount of fore-aft oscillation of the body on the treadmill, which was accompanied by a reduction in the ongoing electromyographic activity in both tibialis anterior and soleus during undisturbed walking. In contrast, the provision of touch resulted in an increase in the amplitude of the evoked responses in tibialis anterior to the backward perturbations that was more evident when subjects walked with the eyes closed. These results indicate that light touch provides a sensory cue that can be used to assist in stabilizing the body while walking. In addition, the sensory information provided by light touch contributes to the regulation of corrective reactions initiated by balance disturbances encountered during walking.

The effect of light touch on balance control during overground walking in healthy young adults

“…The increased muscle activity during normal walking may also be due to the change in the attentional demands as proposed above [22] but research investigating the effect of an added task on muscle activity during walking has shown mixed results [ 23 , 24 , 25 ]. Previous studies investigating the effect of added haptic input have also found mixed results for changes in muscle activity [ 7 , 10 , 26 , 27 ]; however, those studies were completed using treadmill walking[ 10 , 26 , 27 ], and/or with individuals who have had a stroke [ 7 , 27 ]. The absence of a significant difference in muscle activity with added touch for the tandem and balance beam conditions could be due to increased muscular requirements for the more difficult walking tasks.…”

Human bipedal instability in tree canopy environments is reduced by “light touch” fingertip support

“…This light touch effect is produced by cutaneous receptors sensing small differences in shear forces through skin deformation 5, 25 and it substantially increases postural stability on firm supports during quiet standing and after a perturbation to balance 8, 25–27 . It has also been shown to improve gait efficiency by reducing muscle activity in the lower leg during treadmill walking before and after a gait perturbation 28 . However, no study has assessed if it is beneficial in environments where participants are exposed simultaneously to challenging physical and visual environments, and where the structures available for the provision of tactile information are highly flexible.…”

Split-Belt walking induces changes in active, but not passive, perception of step length

“…Subjects performed the active perceptual task as they walked while lightly touching (<2N, enforced with verbal feedback) an instrumented handrail located in front of the treadmill. This was done to ensure that individuals would maintain their position on the treadmill while walking with the virtual reality headset 34 . Recall that the Short-MidSpeed and Long-MidSpeed groups performed the step length tasks at a mid-walking speed (1.0 m/s), whereas the Short-SlowSpeed group performed the step length tasks at a slow walking speed (0.5 m/s).…”