Impaired Muscle Efficiency but Preserved Peripheral Hemodynamics and Mitochondrial Function With Advancing Age: Evidence From Exercise in theYoung, Old, and Oldest-Old

Muscle weakness in the elderly has been linked to recurrent falls and morbidity; therefore, elucidating the mechanisms contributing to the loss of muscle function and mobility with advancing age is critical. To this aim, we comprehensively examined skeletal muscle metabolic function and hemodynamics in 11 young (23 +/- 2 years), 11 old (68 +/- 2 years), and 10 oldest-old (84 +/- 2 years) physical activity-matched participants. Specifically, oxidative stress markers, mitochondrial function, and the ATP cost of contraction as well as peripheral hemodynamics were assessed during dynamic plantar flexion exercise at 40 per cent of maximal work rate (WRmax). Both the PCr recovery time constant and the peak rate of mitochondrial ATP synthesis were not significantly different between groups. In contrast, the ATP cost of dynamic contractions (young: 1.5 +/- 1.0, old: 3.4 +/- 2.1, oldest-old: 6.1 +/- 3.6 mM min(-1) W-1) and systemic markers of oxidative stress were signficandy increased with age, with the ATP cost of contraction being negatively correlated with WRmax (r = .59, p < .05). End-of-exercise blood flow per Watt rose significantly with increasing age (young: 37 +/- 20, old: 82 +/- 68, oldest-old: 154 +/- 93 mL min(-1)W(-1)). These findings suggest that the progressive deterioration of muscle contractile efficiency with advancing age may play an important role in the decline in skeletal muscle functional capacity in the elderly.