Associations Between Timing Of Physical Activity With Functional Fitness And Body Composition In Older Adults

BACKGROUND: Moderate-to-vigorous physical activity (MVPA) is effective for preventing/delaying the functional decline and adverse changes in body composition that occur with aging. Nevertheless, whether the timing of MVPA can produce further benefits on physical function and body composition has been less explored. PURPOSE: Determine the relationship of MVPA with strength and functional ability tests and body mass index (BMI) in Portuguese older adults. METHODS: 679 older adults (men: 75.6 yrs ± 7.4 yrs; women: 75.3 yrs ± 7.1 yrs) from the national surveillance of physical activity (PA) and sports of Portugal had objective PA, strength, functional fitness, and BMI cross-sectionally evaluated. Strength was measured with a handgrip dynamometer, while functional fitness was assessed using part of the Senior fitness test (i.e., 30 s chair stand, arm curl, 8-ft up-and-go, and 6-min walk). Morning and afternoon MVPA were defined as 7 to 12 AM and 12 PM to 7 PM, respectively, and determined by summing the mean MVPA for each hour. Morning and afternoon MVPA were additionally adjusted for accelerometer wear time. Linear regression models were fit and included age, sex and both morning and afternoon MVPA. We additionally compared the beta coefficients from the morning and afternoon MVPA models by using a linear hypothesis test. RESULTS: Morning MVPA was associated with higher handgrip strength [β = 0.19 kg; (IC 95%: 0.07; 0.30)], while afternoon MVPA was associated with lower BMI [β = -0.29 kg·m-2 (IC 95%: -0.44; -0.13)]. Regarding functional fitness, both morning and afternoon MVPA were beneficially associated with the 30 s chair stand, arm curl, 8-ft up-and-go, and 6-min walk. However, morning MVPA had a stronger relationship with the arm curl, 6-min walk, and BMI outcomes (P < 0.05) compared to afternoon MVPA. CONCLUSIONS: MVPA accumulated in the afternoon was favorably associated with BMI, whereas morning MVPA had only a relationship with handgrip strength. Both morning and afternoon MVPA had a positive influence on functional fitness, although stronger associations were observed for afternoon MVPA compared to morning MVPA, suggesting that accumulating MVPA during this time of the day might have additional benefits for upholding the functional ability of older adults.