Use it or lose it: A four-year follow-up to assess whether engagement with physical activity close to one's physical capacity may protect against decline in physical functioning among older adults

PURPOSE: Physical activity (PA) is distinct from physical capacity (PC), even though they are correlated in old age. PC defines the limits for PA, while activities in daily life typically remain submaximal. Individuals whose intensity of daily activities is close to physical capacity may be better protected from future decline in physical function compared to those who do not, although prospective research to support this hypothesis is lacking. Therefore, this study compared changes in physical function over a four-year follow-up between community-dwelling older adults categorized based on their combined baseline PC and PA. METHODS: This was a four-year longitudinal follow-up study of older adults aged 75-85 years at baseline (N = 312, 60% women). Baseline PC was determined based on 5-second Mean Amplitude Deviation (MAD) epoch value during the maximal 10-meter walking test, and PA was determined based on the peak 75-minutes MAD intensity threshold from thigh-worn accelerometer monitoring over 3-7 days. Baseline values of PA and PC were categorized into lowPC-lowPA, lowPC-highPA, highPC-lowPA, and highPC-highPA profiles. Physical function was evaluated using the Short Physical Performance Battery (SPPB) at baseline and at the follow-up, with total score and 5 x Sit-To-Stand (5xSTS) test time as the primary outcomes. Nonparametric tests and generalized estimating equations were used for analyses. RESULTS: From baseline to follow-up, statistically significant changes in the SPPB total score and 5xSTS test time were observed in all profiles (p<0.05) except the low PC-high PA profile. Over the follow-up period, the decrease was greater for low versus high PA profiles within both PC profiles for SPPB total score (high PC: B -0.61, SE 0.24, 95% CI -1.08, -0.15; low PC: B -0.96, SE 0.35, 95% CI -1.62, -0.32), but not for 5xSTS time. No statistically significant difference was observed in the change in 5xSTS test time between the low and high PA profiles for either PC profile. CONCLUSIONS: The findings suggest that engaging in demanding PA regardless of baseline PC may help to protect against a decline in physical functioning in old age. Consequently, older adults should be encouraged to engage in physically demanding activities that could potentially enhance their functional capacity.