<p>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, VO<sub>2 peak</sub>: 46.7 ± 2.0 mL kg<sup>-1</sup> min<sup>-1</sup>) underwent 2 trials with a primed constant infusion of L-[<em>ring</em>-<sup>13</sup>C<sub>6</sub>]phenylalanine in the fasted state for each work-matched exercise intensity (LOW: cycling for 60 min at 30% W<sub>max</sub> and HIGH: 30 min at 60% W<sub>max</sub>). 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-p38<sup>Thr180/Tyr182</sup> was greater at 4.5 h after exercise compared to 0.5, 24 and 28 h post-exercise (<em>p</em> < 0.05). Additionally, a strong trend was present for phospho-mTOR<sup>Ser2448</sup> (<em>p</em> = 0.056) with 0.5 h post-exercise phosphorylation significantly higher after HIGH than after LOW exercise (<em>p </em>< 0.05). Myofibrillar protein synthesis was stimulated 1.5–fold 0.5 – 4 h post-exercise (<em>p</em> < 0.05), returning to rest in the LOW condition 24 h post-exercise, while 6 out of 8 subjects maintained increased myofibrillar FSR 24 h post HIGH exercise (<em>p</em> < 0.05). The increase in myofibrillar FSR 0.5 – 4 h post-exercise was correlated with phospho-mTOR<sup>Ser2448</sup> 0.5 h post-exercise (r = 0.698, <em>p</em> < 0.01), indicating the role of this signaling pathway in myofibrillar protein synthesis. It is concluded that aerobic exercise has an effect on myofibrillar protein synthesis and intensity may play a role in the duration of this response.</p> / Master of Science in Kinesiology
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/12408 |
| Date | 10 1900 |
| Creators | Di, Donato M Danielle |
| Contributors | Phillips, Stuart, Kinesiology |
| Source Sets | McMaster University |
| Detected Language | English |
| Type | thesis |
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