The maintenance of postural balance depends on effective and efficient feedback from various sensory inputs. The importance of auditory inputs in this respect is not, as yet, fully understood. The purpose of this study was to analyse how the moving auditory stimuli could affect the standing balance in healthy adults of different ages. The participants of the study were 12 healthy volunteers, who were divided into two age categories: the young group (mean = 21.9 years) and the elderly group (mean = 68.9 years). The instrument used for evaluation of standing balance was a force plate for measuring body sway parameters. The toe pressure was measured using the F-scan Tactile Sensor System. The moving auditory stimulus produced a white-noise sound and binaural cue using the Beachtron Affordable 3D Audio system. The moving auditory stimulus conditions were employed by having the sound come from the right to left or vice versa at the height of the participant's ears. Participants were asked to stand on the force plate in the Romberg position for 20 s with either eyes opened or eyes closed for analysing the effect of visual input. Simultaneously, all participants tried to remain in the standing position with and without auditory stimulation that the participants heard from the headphone. In addition, the variables of body sway were measured under four conditions for analysing the effect of decreased tactile sensation of toes and feet soles: standing on the normal surface (NS) or soft surface (SS) with and without auditory stimulation. The participants were asked to stand in a total of eight conditions. The results showed that the lateral body sway of the elderly group was more influenced than that of the young group by the lateral moving auditory stimulation. The analysis of toe pressure indicated that all participants used their left feet more than their right feet to maintain balance. Moreover, the elderly had the tendency to be stabilized mainly by use of their heels. The young group were mainly stabilized by the toes of their feet. The results suggest that the elderly may need a more appropriate stimulus of tactile and auditory sense as a feedback system than the young for maintaining and control of their standing postures.

Our findings revealed several aspects regarding the circumstances surrounding falls among community-dwelling elderly people in Hokkaido.

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In this study, we described the joint angle changes of the trailing leg during the compensatory step used to recover balance following a forward slip while walking. Fifteen healthy young males walked on a walkway which incorporated a movable platform to simulate a forward slip while walking. In 12 out of the 15 subjects, the trailing leg was rapidly lowered during the swing phase and was placed on the ground behind the slipping foot following the onset of the slip. Time taken for the onset of the slip to the placing of the trailing foot was 0.28Ϯ0.03 s. The amount of hip flexion lessened after 52% of the normalized time, with 0% being the onset of the platform movement and 100% representing the placing of the trailing foot on the ground. The flexed knee began to extend at 72% of the normalized time, which continued until the foot was firmly placed. The plantarflexed ankle began to dorsiflex at 56% of the normalized time, the angle of which peaked at the moment the toe made contact with the walkway again-the end of the movement. These findings aided us in understanding the mechanism underlying the compensatory step to recover the loss of balance caused by a forward slip while walking.