Purpose: Walking abilities decline with aging and the associated decrease of muscle strength, partly due to reductions in usual physical activities. On the other hand, recent studies have emphasized the importance of fat mass in relation to age-related decline in physical function. In addition, obesity is a component of metabolic syndrome and is a risk factor for future cardiovascular disease; and it suggests abnormality of body composition as well as physical function. The purpose of this study was to find out about age, muscle strength, and metabolic risk markers that determine walking speed in middle-aged and older adults.
Methods: Subjects were 193 middle-aged and older adults (65 men and 128 women; mean age of 55.6 years; and range of 34-69 years). We evaluated as anthropometric measurements body mass index (BMI), waist circumference (WAC), hip circumference (HIC) and waist-to-hip ratio (WHR). As regional body composition, trunk lean mass (TLM) and fat mass (TFM), lower extremities lean mass (LLM) and fat mass (LFM) were assessed by dual energy X-ray absorptiometry (QDR-2000; Hologic). Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were recorded at rest. High-density lipoprotein cholesterol (HDL-C), triglyceride (TG) and fasting glucose (FG) were analyzed from blood samples. As muscle strength of the lower extremity, isometric knee extension strength (KES) was measured by handheld dynamometer (µTas MF-1; ANIMA). Walking speed was calculated from maximal walk time of 10 m.
Results: Simple linear analysis showed that walking speed was significantly correlated with age (r = -.30, p = .014) and KES (r = .30, p = .017) in men. On the other hand, walking speed was significantly correlated with age (r = -.29, p = .001), log [TG] (r = -.21, p = .019) and KES (r = .44, p < .001) in women. When stepwise multiple regression analysis was performed, walking speed was significantly correlated with age (β = -0.32, p = .009), LFM (β = -0.30, p = .013) and KES (β = 0.26, p = .029) in men. On the other hand, walking speed was significantly correlated with age (β = -0.20, p = .011), BMI (β = -0.31, p < .001) and KES (β = 0.52, p < .001) in women.
Conclusion: Results of this study indicate that age and muscle strength of the lower extremities are main determinants of walking speed common to older men and women. However, the influence on walking speed of characteristics of fat storage may be different between the sexes. This study suggested that maintenance or increase of muscle strength and reduction of fat mass are likely to play an important role in the prevention of walking disabilities in the future.