Comparison of skeletal muscle oxidative function in young, middle-aged, and older males and females with similar physical activity levels.

Optimal skeletal muscle oxidative function (microvascular reactivity and mitochondrial capacity) is an integral part of healthy aging and is related to physical function and quality of life. We aimed to extend upon the understanding of skeletal muscle oxidative function with healthy aging in males and females across the adult life span. Younger ( N = 22; 11 males), middle-aged ( N = 19; 10 males), and older ( N = 21; 10 males) adults completed this study. Time spent in moderate and vigorous physical activity was self-reported and similar among groups. Near-infrared spectroscopy was used to investigate skeletal muscle microvascular reperfusion [oxyhemoglobin-myoglobin (O 2 Hb+Mb) half-time to peak hyperemia ( T ½ )], mitochondrial capacity [muscle oxygen consumption (mV̇o 2 ) recovery rate constant], and walking tissue oxygen saturation ([Formula: see text]) of the tibialis anterior (TA) muscle at seven incremental walking speeds. Mitochondrial capacity was not significantly different across groups ( P = 0.07). Younger adults exhibited significantly slower T ½ compared with older adults ( P = 0.006) and middle-aged adults ( P = 0.025). There were no observed sex differences for mitochondrial capacity ( P = 0.442) or T ½ ( P = 0.402). Older adults exhibited significantly lower [Formula: see text] across all walking speeds compared with younger adults ( P = 0.003). Mitochondrial capacity and microvascular reperfusion are maintained in middle and older age, with no sex differences in either outcome. However, in older adults whole body functional movement, such as walking, may place an additional demand on the TA as a compensatory response to lower functional reserve not evident in distinct measures of mitochondrial capacity and microvascular reperfusion. NEW & NOTEWORTHY Compared with younger adults, mitochondrial capacity and microvascular reperfusion of the tibialis anterior (TA) muscle are well maintained in similarly physically active middle-aged and older adults, with no sex differences observed in either outcome. However, greater tissue oxygen utilization in older adults during walking highlights how whole body functional movement may place an additional demand on the TA that reveals a potential compensatory response to lower functional reserve not evident in distinct measures of mitochondrial capacity and microvascular reperfusion.