Comparable rates of integrated myofibrillar protein synthesis between endurance-trained master athletes and untrained older individuals

Background: An impaired muscle anabolic response to exercise and protein nutrition is thought to underpin age-related muscle loss, which may be exacerbated by aspects of biological aging that may not be present in older individuals who have undertaken long-term high-level exercise training, or master athletes (MA). The aim of this study was to compare rested-state and exercise-induced rates of integrated myofibrillar protein synthesis (iMyoPS) and intracellular signaling in endurance trained MA and healthy age-matched untrained individuals (Older Controls). Methods: In a parallel study design, iMyoPS rates were determined over 48 h in the rested-state and following a bout of unaccustomed resistance exercise (RE) in OC (n = 8 males; 73.5 ± 3.3 years) and endurance-trained MA (n = 7 males; 68.9 ± 5.7 years). Intramuscular anabolic signaling was also determined. During the iMyoPS measurement period, physical activity was monitored via accelerometry and dietary intake was controlled. Results: Anthropometrics, habitual activity, and dietary intake were similar between groups. There was no difference in rested-state rates of iMyoPS between OC (1.47 ± 0.06%·day ⁻¹ ) and MA (1.46 ± 0.08%·day ⁻¹ ). RE significantly increased iMyoPS above rest in both OC (1.60 ± 0.08%·day ⁻¹, P < 0.01) and MA (1.61 ± 0.08%·day ⁻¹, P < 0.01), with no difference between groups. Akt ^Thr308 phosphorylation increased at 1 h post-RE in OC (P < 0.05), but not MA. No other between-group differences in intramuscular signaling were apparent at any time-point. Conclusion: While our sample size is limited, these data suggest that rested-state and RE-induced iMyoPS are indistinguishable between MA and OC. Importantly, the OC retain a capacity for RE-induced stimulation of skeletal muscle remodeling.