Aerobic exercise can stimulate mixed muscle protein synthesis (MPS) acutely post-exercise; however, the types of proteins synthesized as a result of aerobic exercise are not known by studying changes in mixed MPS. We aimed to study the effect of aerobic exercise intensity on the 4 and 24 h post-exercise fractional synthesis rate (FSR) of myofibrillar proteins. Using a within-subject design, eight males (21 ± 1 years, VO2 peak: 46.7 ± 2.0 mL kg-1 min-1) underwent 2 trials with a primed constant infusion of L-[ring-13C6]phenylalanine in the fasted state for each work-matched exercise intensity (LOW: cycling for 60 min at 30% Wmax and HIGH: 30 min at 60% Wmax). Muscle biopsies were obtained to determine resting, 4 and 24 h post-exercise myofibrillar FSR. We also studied the phosphorylation of signaling proteins involved in protein synthesis at each time point using immunoblotting methods. Phospho-p38Thr180/Tyr182 was greater at 4.5 h after exercise compared to 0.5, 24 and 28 h post-exercise (p Ser2448 (p = 0.056) with 0.5 h post-exercise phosphorylation significantly higher after HIGH than after LOW exercise (p p p Ser2448 0.5 h post-exercise (r = 0.698, p Master of Science in Kinesiolog
