Association of Lower-Extremity Muscle Performance and Physical Activity Level and Intensity in Middle-Aged and Older Adults: A Doubly Labeled Water and Accelerometer Study

Objectives The purpose of this study was to examine if there is a relationship between lower-extremity muscle performance (LEMP) and physical activity, especially the physical activity level (PAL) value, in community-dwelling middle-aged and older adults. Design Cross-sectional study. Setting Community-based. Participants Participants were 54 community-dwelling and independent middle-aged and older individuals (aged 54–89 years). Measurements Physical activity level was calculated from the total energy expenditure of each participant obtained using the doubly labeled water method (PALDLW) and estimated basal metabolic rate. Daily step count and intensity of physical activity was monitored with a triaxial accelerometer, and LEMP was assessed using the five-repetition sit-to-stand test (STS-5) and vertical jumping (VJ). Results The results of STS-5 nearly negatively correlated with those of PALDLW when analysing the middle-aged and older man and woman, separately. VJ positively correlated with PALDLW when analysing the middle-aged and older men and woman, separately. The relationship between LEMP (e.g. STS-5 and VJ) and PAL were maintained, regardless of sex and body composition. PALDLW was significantly positively correlated with LPA, MVPA, and steps, and significantly negatively correlated with sedentary time. The relationship PALDLW and steps was described as following equation: PALDLW = 0.0000392 × steps +1.531. Conclusions These findings suggest that PALDLW is a key contributor to increasing LEMP among middle-aged and older adults. Maintaining high PALDLW may be beneficial to independent living, and participation in recreational and social activities in middle-aged and older adults.