Ventilatory Thresholds And Usual-paced 400 m Walk In Older Adults: Study Of Muscle, Mobility And Aging

Usual-paced 400 m walking is a key marker of mobility status among older adults. Examining the association between usual-paced 400 m walking and ventilatory threshold (VT), an indicator of the inflexion point of anaerobic metabolism transition during exercise, is critical to understand whether older adults adapt their walking speed to their physiological reserve. PURPOSE: We examined whether VT was associated with usual-paced 400 m long-distance corridor walk walking speed (400 m WS) among adults age ≥ 70 using cross-sectional data in the Study of Muscle, Mobility and Aging (SOMMA). METHODS: Participants completed a usual-paced 400 m long-distance corridor walk (walking speed = 400 m/completion time in seconds) and a treadmill cardiopulmonary exercise test (CPET) using a modified symptom-limited protocol at baseline. VT1 and VT2 were both calculated from the ventilatory variables of the CPET with breath-by-breath resolution. Linear regressions were adjusted for sex, age (years), clinic site, total activity counts (total counts/min, 7-day free-living from non-dominant wrist-worn accelerometer), and perceived physical fatigability (Pittsburgh Fatigability Scale, range 0-50, higher = greater fatigability). RESULTS: Participants (n = 640 with both VT1 and VT2, 75.9 ± 4.6 years, 56.7% Women, 87.0% White, 20.6 ± 4.9 mL/kg/min VO2peak) had mean VT1 of 12.4 ± 2.6 mL/kg/min, mean VT2 of 17.1 ± 4.1 mL/kg/min, and mean 400 m WS of 1.07 ± 0.17 m/s. 400 m WS was moderately correlated with VT1 (r = 0.45, p < 0.0001) and VT2 (r = 0.50, p < 0.0001). One standard deviation mL/kg/min higher VT1 and VT2 were associated with a 0.22 and 0.25 m/s faster 400 m WS, respectively (VT1: β = 0.22, VT2: β = 0.25, p < 0.001) after covariate adjustment. Our final model explained 34% of the variance in 400 m WS. Of this, VT1 explained 2% and VT2 explained 26%. CONCLUSIONS: In older adults, performance in the 400 m WS test correlates with VT1 and VT2, suggesting that usual walking speed may be physiologically connected to aerobic limits at higher exercise intensities. Optimizing submaximal metabolic capacity in older adults may have functional benefits. SOMMA funding: NIA AG059416, P30 AG024827, P30 AG021332, and UL1 TR001420. NIH/NIA funding listed in the abstract