Objectively Determined Physical Activity and Measures of Physical Function in Older Adults

Background: Aging is associated with detrimental changes in physical function (PF), leading to frailty and disability. Physical activity (PA) has been deemed a best buy for public health. Currently there is limited data on the relationships between PA assessed with body worn sensors and various objective measures of PF.

Purpose: To investigate the relationship between accelerometer-derived PA with objective measures of PF in a sample of community dwelling older adults.

Methods: PA was assessed using an accelerometer-based motion sensor (Actigraph GT3X+) worn on the hip for seven consecutive days. Data were summed into 60-second epochs to deduce moderate-vigorous physical activity (MVPA). PF was assessed by maximal quadriceps strength (QS), the short performance physical battery (SPPB), 400m walk (400W), usual gait speed (UGS), and choice step reaction time (CSRT). Body fat was assessed with dual-energy x-ray absorptiometry (GE Lunar Prodigy). Regression models to predict PF measures from MVPA were developed while controlling for potential influencing factors of age, gender, education, income, and percent body fat.

Results: Seventy-six individuals, 55 females (68.4 ± 10.1y,38.1 ± 7.2% fat) and 21 males (70.9 ± 9.8y, 28.2 ± 8.1% fat) completed the study. Initial models including age, gender, education, income and percent body fat accounted for 19.5% (QS) to 54.9% (400W) of the variance in PF. The addition of MVPA improved all models, and represented a significant contributor to SPPB(R2 change 4.3%, P = 0.022), 400W (R2 change 5.5%, P =0.003), and UGS (R2 change 4.5%, P = 0.033).

Conclusions: When controlling for other common predictors of PF, accelerometer-derived measures of MVPA suggest that quality and quantity of PA account for a significant portion of the variance in PF based on various PF outcome measures. Interventions targeting increases in MVPA are warranted, and are likely to have impactful functional benefit for older adults.