RELATIONSHIP BETWEEN STRIDE TIME VARIABILITY OF WALKING AND FALL EXPERIENCE IN MIDDLE AGED AND ELDERLY WOMAN / 体力科学

This study was carried out in order to compare stride time (gait) variability of walking not only between young and older adults, but also between “fallers” and “non-fallers”. Moreover, this study aimed to clarify the relationship between stride time variability, balance ability, muscular strength and fall experience. The subjects were 12 young women aged 21.2±2.2 years (young group) and 27 older women aged 66.6±4.4 years (older group). The older group included 14 fallers and 13 non-fallers. They wore an accelerometer on their back and walked at a slow, preferred or fast pace. The time of heel contact was detected by acceleration waveform, and stride time was estimated. The stride time variability was computed by the coefficient of variance (CV) of stride time. The subjects underwent balance tests and muscular strength tests. The CV of stride time at the preferred and fast pace were significantly larger in the older group than in the young group, even though there was no difference in any of the gait speeds between the two. The CV of stride time was significantly larger in fallers than in non-fallers at the fast pace. Path analysis showed that fall experience was affected by an increase in the CV of stride time and decreased balance ability, but less affected by decreased muscular strength. Therefore, this study suggested that stride time variability when walking fast is useful as an early assessment of fall risk in middle-aged and elderly people and that fall experience was affected by stride time variability and balance ability.

AGING EFFECTS ON CO-CONTRACTION OF ANKLE MUSCLES DURING VOLUNTARY SWAY TASK / 体力科学

The aim of this study was to compare co-contraction of ankle muscles between older and young adults performing a voluntary sway task, and identify any relationships between co-contraction, balance ability and muscular strength. The task involved displacement of the center of mass backwards and forwards continually during upright stance under three amplitude conditions, large, small and preferred, with sway speeds of slow, medium and fast. The participants comprised 17 older (64.1±2.9 years) and 14 young (21.3±3.3 years) women. Electromyographic recordings were obtained from the tibialis anterior and the medial gastrocnemius muscles during task performance to calculate the co-contraction index (CCI) and evaluate the relative level of co-contraction of antagonist muscle. Additional measurements were obtained from balance tests including body sway tests, functional reach, gait tests, and the EquiTest (Neurocom), and also muscular strength of plantar flexion and dorsiflexion. The CCI was highest under large sway amplitude, but did not differ among sway speeds. The CCI was higher in the older group (23%) than in the young group (15%). Multiple regression analysis revealed that the CCI correlated with body sway in the EquiTest and functional reach, and dorsiflexion strength. Therefore, this study suggested that co-contraction of ankle muscles increased with aging and related to not only static and dynamic balance abilities, but also ankle dorsiflexor strength.

EFFECTS OF BALANCE EXERCISES ON BALANCE ABILITIES OF COMMUNITY-DWELLING OLDER WOMEN; A RANDOMIZED CONTROLLED TRIAL / 体力科学

This study was to investigate the effects of balance exercises on among static, dynamic and reactive balance ability in community-dwelling older women. Participants comprised 26 community-dwelling older women in Japan, randomized for age and gait speed to the exercise group (n=13) or the control group (n=13). The exercise group performed structured balancing exercises on the sponge and the G ball, once weekly for 24 weeks. The control group performed stretching exercises once per month. Static balance ability was assessed by measuring postural sway and standing on one leg; dynamic balance ability was assessed by measuring functional reach, timed up and go, and gait; and reactive balance ability was assessed using the EquiTest. We also measured knee and ankle strength using an isokinetic machine.At baseline, the two groups were well matched in physical characteristics and in all balance ability and strength tests. After 24 weeks, step length of preferred speed walking (p=0.049) only improved, and peak torque of knee flexion (p=0.050) tended to improve in the exercise group. Any correlations were not found between step length of preferred speed walking and knee flexion strength.These results suggest that these structured balance exercises are effective in improving dynamic, but not static or reactive balance ability. Improvements in dynamic balance ability were not dependent on improved muscle strength.