Background  A population‐based prospective cohort study was undertaken to examine the predictors of functional decline in instrumental activities of daily living (I‐ADL) among non‐disabled older Japanese subjects living in a rural community during a five‐year interval from 1992 to 1997. Methods  The subjects consisted of 624 men and women aged from 65–89 years and independent in I‐ADL at baseline, who could be completely followed for five years. Independent variables were various physical factors potentially associated with higher level of functional capacity obtained from an interview survey and medical examinations at baseline. Dependent variables were functional status in I‐ADL obtained at the time of the 5‐year follow‐up. Results  Significant predictors of functional decline in I‐ADL during a 5‐year follow‐up period included: (1) older age; (2) higher blood pressure; and (3) lower maximum walking speed at baseline. Among these predictor, the maximum walking speed is likely to the strongest predictor for the decline in I‐ADL. Conclusion  The ability to walk faster in the old age is strongly associated with independence in the other I‐ADL, and walking speed should be modified by the lifestyle to strengthen muscles of the lower extremities in daily life.

The primary purposes of this study were 1) to confirm age-related deterioration of physical performance in older adults longitudinally, and 2) to predict future functional status and mortality by initial level of physical performances. The subjects were 517 older adults examined both in 1992 and 1996 in the Tokyo Metropolitan Institute of Gerontology, Longitudinal Interdisciplinary Study on Aging. The same battery consisting of muscle strength, balance, walking, and manual speed was administered to the subjects in the baseline and follow-up examinations. A significant longitudinal decline was observed in all physical performances except for grip strength. The age-related decline accelerated with aging for preferred walking velocity. Inter-subject variability in walking velocity significantly increased for 4 years period. Maximum walking velocity was a common predictor for functional status and mortality. The results suggest that physical performance measures, especially maximum walking velocity, is a valid means for physical therapy to evaluate physical functioning of community-living older persons.

The aim of this study was to investigate the use of [18F]fluorodeoxyglucose and positron emission tomography (FDG PET) for quantitative evaluation of glucose metabolism in skeletal muscle during walking. Ten young males underwent FDG PET twice during walks, which were done with or without an automated stride assistance system (SAS). Walk ratios were significantly increased by the SAS in seven subjects. Regional glucose metabolism in muscles between the crista iliaca and the planta was clearly visualized in all ten subjects. Glucose utilization increased significantly in the tibialis posterior and medial gastrocnemius muscles of the seven subjects in whom walk ratios were increased by the SAS. FDG PET is useful for analysis of muscle activity during exercise and rehabilitation.

To elucidate the effect of chronic inflammation on spinal nociceptive neurons in the elderly, we compared nocifensive behavior, peripheral inflammatory responses, and spinal dorsal horn neuronal activities between the aged (29-34 mo) and adult (7-12 mo) male rats after injection of complete Freund's adjuvant (CFA) into the hind paw. Aged rats exhibited a significantly lower mechanical paw withdrawal threshold before inflammation. However, after CFA injection mechanical allodynia developed in both adult and aged rats after CFA injection. The changes of foot temperature and thickness after CFA injection were greater and lasted longer in aged than in adult rats. Sets of 124 wide dynamic range (WDR) neurons (aged: 59, adult: 65) and 26 nociceptive specific (NS) neurons (aged: 13, adult: 13) were recorded from the lumber spinal dorsal horn. NS neurons from the inflamed adult rats showed significantly higher responses to noxious mechanical stimulation than those in aged rats, whereas WDR neurons from inflamed adult and aged rats were similar. Background activity of WDR neurons from the adult rats increased after CFA, whereas WDR neurons of aged rats and NS neurons from either group were not. The afterdischarge followed by noxious mechanical stimulation was significantly greater for WDR neurons in both adult and aged rats, whereas no significant differences were observed in NS neurons. Two days after CFA injection, Fos expression increased similarly in aged and adult rats. Thus the aged rats showed enhanced peripheral inflammatory responses to CFA injection with only a slight change in dorsal horn neuronal activity. Together with our previous finding that nociceptive neurons in aged rats exhibit hyperexcitability, these results suggest that the dorsal horn nociceptive system becomes sensitized with advancing age and its excitability cannot be further increased by inflammation.

The SAS increases walking scores in elderly people without increasing energy consumption of lower-extremity muscles. The elderly subjects with low walking speed showed higher glucose metabolism in hip-related muscles and triceps surae. Thus, this association suggested that decreased walking speed in elderly adults has a higher metabolic cost in these muscle regions.