Aprů, W., Borgenvik, M., Ekblom, B., & Blomstrand, E. (2012). Endurance exercise attenuates mTOR signaling following resistance exercise. Presentation 1144 at the 59th Annual Meeting of the American College of Sports Medicine, San Francisco, California; May 29-June 2, 2012.

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Research findings of whether endurance training blunts following resistance training are equivocal. It has been suggested that any interference may be due to an inhibitory effect of adenosine monophosphate activated protein kinase (AMPK) on anabolic signaling through the mammalian target of the rapamycin pathway.

This study if endurance exercise has a detrimental effect on the rapamycin pathway signaling following resistance exercise. Males performed either high-intensity interval cycling followed by resistance exercise or resistance exercise only. In the endurance-resistance exercise session, interval cycling consisted of five four-minute intervals at 85% of Ssí maximal oxygen consumption during three minutes of cycling at 100 W between each interval. Following 15 minutes of recovery, Ss performed 13 sets of resistance exercise at a load equal to individuals' 8-10 repetition maximum. Resistance exercise in the resistance exercise only trial was the same as in the other condition. Biopsies were taken from the vastus lateralis muscle before, immediately after, and thee hours after resistance exercise. Samples were analyzed for signaling proteins in the rapamycin pathway using the Western blot technique.

Phosphorylation of the rapamycin pathway increased twofold immediately after resistance exercise and remained elevated at three hours after with no difference between the two trials. Phosphorylation of p70S6k remained unchanged immediately after exercise in the endurance-resistance exercise session but was elevated fourfold in the resistance exercise only session. At the three-hour time point, p70S6k phosphorylation was elevated sixfold in both trials with no difference between the two. Immediately after exercise, phosphorylation of AMPK was increased by 20 and 50% in the resistance exercise only and endurance-resistance exercise sessions, respectively. However, three hours after exercise, phosphorylation levels of this protein had returned to baseline values in both trials. Similarly, phosphorylation of ACC was elevated 60 and 120% in the resistance exercise only and endurance-resistance exercise trials, respectively, with the values returning to baseline in both trials at the three-hour time point.

Implication. Anabolic signaling following resistance exercise may be blunted when resistance exercise is preceded by high-intensity interval cycling.

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