Systemic Effect On Myotube Size After Sprint Exercise Combined With Nutrients

• PURPOSE: To study systemic effects of sprint exercise combined with nutrient ingestion on muscle cell hypertrophy. It was hypothesized that the size of human muscle cells increases when they are exposed to post-exercise serum in nutrient but not in placebo condition. Previously studies have shown that oral ingestion of essential amino acids (EAA) and carbohydrate results in higher activation of Akt/mTOR signalling and higher rate of muscle protein synthesis following sprintexercise in humans. Both local and systemic factors may contribute to these effects. Moreover, If the nutrient-induced effects on signalling and muscle protein synthesis result into muscle hypertrophy is not known. In this study we “isolate” the systemic effects by exposing cultured muscle cells for post sprint exercise serum from either nutrient ingestions or placebo.METHODS: This study is based on a previous study, were healthy subjects performed three 30-s sprints with 20 minutes rest in between. Subjects ingested a flavoured drink containing EAA and maltodextrin (nutrient) or only flavoured water (placebo) during the sprint exercise session up to 15 min after the last sprint in a randomized order with one month interval. Blood samples were collected before during and up to 200 minutes after the last sprint and were analyzed for EEA, insulin lactate and glucose. Human myoblasts were isolated from vastus lateralis and differentiated into multinucleated myotubes, which were cultured in serum collected from 5 subjects fromthe sprint exercise study described above. Blood samples, obtained at 80 min after the last sprint, were chosen since the peak values for the accumulation of insulin and EAA occur approximately atthat time point.RESULTS: Both serum insulin (6-fold; P<0.05) and plasma leucine levels (2.6-fold; P<0.01) were higher after nutrient compared to placebo 80 min post-exercise. Plasma lactate and glucose levels did not differ between the conditions. Myotube size was 16% larger after exposure to post sprint exercise serum obtained during nutrient as compared to placebo (P<0.05).CONCLUSIONS: Systemic factors may stimulate muscle hypertrophy after sprint exercise when combined with nutrient ingestion. If such a systemic effect may be counteracted by intracellular metabolic perturbations after sprint exercise is not known.

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MEDICIN OCH HÄLSOVETENSKAP  -- Hälsovetenskap -- Idrottsvetenskap (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Health Sciences -- Sport and Fitness Sciences (hsv//eng)

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