BackgroundAn 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).MethodsIn 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.ResultsAnth