Introduction: Falls occur frequently during walking, and they often cause serious problems, particularly in the elderly. To prevent falls, determination of gait characteristics may give some useful information. During gait, ankle plantar-flexor torque plays an important functional role to propel and support the body. Few studies have assessed whether the magnitude of this torque is related to fall-risk factors.
Purpose: The purpose of this study was to describe the relationship between peak torque of ankle plantar flexors during gait and falls in the community-dwelling middle-aged and elderly.
Methods: The subjects of this study were Japanese men and women who participated in the third examination of the National Institute for Longevity Sciences-Longitudinal Study of Aging (NILS-LSA). The NILS-LSA was a comprehensive study including medical, physiological, nutritional, and psychological examination, which started in November 1997 in Japan. The third examination held from April 2002 to May 2004. The subjects were community-living adults age 40-84 years who comprised 1,170 males and 1,131 females. The subjects were asked to walk on a 10-m wooden walkway at a self-selected comfortable pace. To calculate peak torque of ankle plantar flexors during gait, 3-dimensional coordinates of body segments were obtained using an optoelectronic 6-camera system (Vicon370, Oxford Metrics) that recorded the 10 bony markers. Also, two force platforms (9286, Kistler) were embedded in the center of the walkway. The subjects were divided into two groups according to this peak torque at 59.8 Nm (the 20th percentile). Thus, the 20th percentile below group and the 20th percentile or above group were used for analysis. The history of falling during past year was determined according to self-administered questionnaires.
Results and Discussion: Chi-square test revealed that the prevalence of the falls was higher in women (11.2%) than in men (8.8%; p < .01). The fallers were significantly older (61.4 ± 12.6 yrs) than the nonfallers (59.6 ± 11.5 yrs; p < .01) by Student’s t test. The peak torque of ankle plantar flexors during gait was significantly lower in the fallers (73.8 ± 20.2 Nm) than in the nonfallers (76.4 ± 19.1 Nm; p < .05). By a multivariate logistic regression, the risk of falls was significantly higher in the 20th percentile below group than in the 20th percentile or above group, even after being controlled for age, sex, height, weight, and walking velocity (odds ratio: 1.31, 95%CI: 1.03-1.66, p < .05). These results indicated that the fallers exhibited less peak torque of the ankle plantar flexors during gait, which might connect to less momentum of center of mass of gravity and less acceleration of leg swing in the preswing phase compared with the nonfallers.
Conclusion: It is suspected that decrease in peak torque of ankle plantar flexors during walking leads to risk of falls in the community-dwelling middle-aged and elderly.