Associations Between Physical Fatigability, Vo 2 Peak And Measures Of Muscle Strength In Older Adults

Abstract

Age related declines in cardiorespiratory fitness (VO2 peak) and muscle strength lead to impaired physical function and frailty in older adults. Higher levels of perceived fatigue, fatigability, exacerbate impairments in physical function and frailty in older adults. However, the independent and combined associations between VO2 peak, muscle strength and fatigability remain incompletely defined. PURPOSE: This study examined the cross-sectional associations between VO2 peak, muscle strength, and self-reported physical fatigability among untrained older adults. METHODS: The present analyses included, twenty (13F, 7M), older adults (X±SD, 71±4y) participating in an ongoing exercise intervention (REALPA). VO2 peak was determined using a graded exercise test on treadmill. Isometric and isokinetic knee extensor strength was assessed on the non-dominant leg using a Biodex Dynamometer. Peak isometric torque was measured at an angle of 60°, while peak isokinetic torque was measured at 60°/second. Physical fatigability were determined using the Pittsburgh Fatigability Scale. We used multiple linear regression to measure the association between the Physical Fatigability Score (0-50, no fatigue to extreme fatigue), VO2 peak, peak isometric strength, and peak isokinetic strength after adjusting for age. RESULTS: The X±SD for body mass index (BMI), VO2 peak, peak isometric torque, and peak isokinetic torque, were 28±4 kg/m2, 20±4 ml/kg/min, 149±34 Nm, and 119±40 Nm, respectively. The physical fatigability scores were 12±7, ranging from 2 to 26. Before adjusting for age, peak isometric and isokinetic strength were inversely correlated with physical fatigability (r= -0.42, p = 0.07 and r = -0.41 p = 0.07, respectively). After adjusting for age, the partial correlations became statistically significant (r= -0.48, p=0.04 and r= -0.50 p = 0.03, respectively). In contrast, VO2 peak was not correlated to physical fatigability. CONCLUSION: The present results suggest that untrained older adults with lower measures of peak isometric and isokinetic strength report higher perceived physical fatigability. Further studies should examine the impact of increased skeletal muscle strength and its effect on perceived physical fatigability in older adults. This study was supported by the NIH 5R21AG058181-02.