The Association of Muscular Strength and Treadmill-Based Walking Economy in Older Men and Women.

Abstract

Ageing is linearly associated with increased body fat percentage (BF%) and decreased muscular strength, which may lead to lower force production and decreased physical function (PF) in older adults (age 60+ yrs.). The magnitude at which age-related decrements affect energy expenditure associated with walking economy (WE) is not well understood. A better understanding of the relationship between BF%, lower body muscular strength (LBMS), and PF, and the degree to which these variables are related to WE is important for the clinical exercise approach with older adults. PURPOSE: To determine the association of BF%, LBMS, and PF on WE in older adults when walking at three separate treadmill speeds. METHODS: Twenty-three older adults (12 men, 11 women; age 70 ± 6 yrs.) were recruited to participate. Session 1 included screening, protocol familiarization, and body composition assessment measure (BodPod®). During sessions 2 and 3, participants performed either a treadmill walking (TMW) protocol (three separate 6-minute TMW bouts at set speeds of 0.45, 0.89, and 1.34 m·sec-1) or a LBMS measure (1RM Leg Press) and PF test battery (SPPB). Session, walking speed, and strength/functional testing order was counter-balanced and WE was calculated as an index (kcal·min-1[BULLET OPERATOR]W-1). Steady state oxygen uptake was used to calculate energy expenditure for all TMW bouts. A linear mixed effects model was used to determine associations between BF%, LBMS, and PF on WE at the three TMW bouts. An a priori alpha of p ≤ 0.05 was set for statistical significance. RESULTS: Twenty-one older adults (11 men, 10 women; age 70 ± 6 yrs.) completed the study. There were no significant correlations for BF% (r1 = 0.19, p1 = 0.41), LBMS (r1 = -0.07, p1 = 0.78), and PF (r1 = 0.14, p1 = 0.55) on WE at the 0.45 m·sec-1 speed. Correlations were also not significant on WE at the 0.89 m·sec-1 speed [BF% (r2 = -0.22, p2 = 0.34), LBMS (r2 = 0.01, p2 = 0.96), and PF (r2 = 0.18, p2 = 0.44)] and the 1.34 m·sec-1 speed [BF% (r3 = 0.09, p3 = 0.71), LBMS (r3 = 0.14, p3 = 0.54), and PF (r3 = -0.26, p3 = 0.25)]. CONCLUSION: BF%, LBMS, and PF may not be associated with age-related decrements in WE with older adults during treadmill walking. Future research is needed to better determine the interactions of these variables on WE in older adults.