The ECW/TW ratio increases in the lower leg with age. The results suggest that the expansion of ECW relative to ICW and the LV masked actual muscle cell atrophy with aging.

A standardized method for assessing the physical fitness of elderly adults has not yet been established. In this study, we developed an index of physical fitness age (fitness age score, FAS) for older Japanese adults and investigated sex differences based on the estimated FAS. Healthy elderly adults (52 men, 70 women) who underwent physical fitness tests once yearly for 7 years between 2002 and 2008 were included in this study. The age of the participants at the beginning of this study ranged from 60.0 to 83.0 years. The physical fitness tests consisted of 13 items to measure balance, agility, flexibility, muscle strength, and endurance. Three criteria were used to evaluate fitness markers of aging: (1) significant cross-sectional correlation with age; (2) significant longitudinal change with age consistent with the cross-sectional correlation; and (3) significant stability of individual differences. We developed an equation to assess individual FAS values using the first principal component derived from principal component analysis. Five candidate fitness markers of aging (10-m walking time, functional reach, one leg stand with eyes open, vertical jump and grip strength) were selected from the 13 physical fitness tests. Individual FAS was predicted from these five fitness markers using a principal component model. Individual FAS showed high longitudinal stability for age-related changes. This investigation of the longitudinal changes of individual FAS revealed that women had relatively lower physical fitness compared with men, but their rate of physical fitness aging was slower than that of men.Electronic supplementary materialThe online version of this article (doi:10.1007/s11357-011-9225-5) contains supplementary material, which is available to authorized users.

1. Fibre type distributions of the slow soleus and fast plantaris muscles were investigated in 5-, 9- and 20-week-old male Goto-Kakizaki (GK) rats, as an animal model of non-obese diabetes, and were compared with those of age-matched non-diabetic Wistar rats. 2. Bodyweight and both soleus and plantaris muscle weights were lower in GK rats than in Wistar rats, regardless of age. In addition, both relative soleus and plantaris muscle weights per bodyweight were lower in GK rats than in Wistar rats, regardless of age. 3. In the soleus muscle, a higher percentage of type I fibres and a lower percentage of type IIA fibres were observed in 5- and 9-week-old GK rats. In addition, there were no type IIA fibres in 20-week-old GK rats. 4. In the plantaris muscle, there were no differences in fibre type distribution of 5-week-old GK rats. However, a higher percentage of type IIB fibres and a lower percentage of type I and type IIA fibres were observed in 9- and 20-week-old GK rats. In addition, there were no type I fibres in 20-week-old GK rats. 5. These results indicate that the decreased percentage of high-oxidative fibres (e.g. type IIA fibres in the soleus muscle and type I and type IIA fibres in the plantaris muscle) of the diabetic animals is concerned with an impairment in insulin sensitivity and glucose metabolism and is not related to bodyweight.

This study was conducted to identify biomarkers of aging and to construct an index of biological age in humans. Healthy adult men (n = 86) who had received an annual health examination from 1992 through 1998 were studied. From 29 physiological variables, five variables (forced expiratory volume in 1 second, systolic blood pressure, hematocrit, albumin, blood urea nitrogen) were selected as candidate biomarkers of aging. Five candidate biomarkers expressed substantial covariance along one principal component. The first principal component obtained from a principal component analysis was used to calculate biological age scores (BAS). Individual BAS showed high longitudinal stability of age-related changes. Age-related changes of BAS are characterized by three components: age, peak functional capacity, and aging rate. A logistic regression analysis suggested that aging rate was influenced by environmental factors, but peak functional capacity was almost independent of environmental factors.