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n International SportMed Journal - Metabolic responses to multiple bouts of supra-maximal exercise in trained and untrained subjects : research article
Background : Performance and metabolic pathways used in submaximal exercise have been well examined, but not above VO2max.
Research question : To examine the pattern of energy use during supra-VO2maximal exercise, the metabolic responses of both trained and untrained subjects to repeated bouts of intense, constant power exercise, which was designed to deplete muscle glycogen, were evaluated.
Methods : Sixteen males with similar genetic aerobic capacity were studied: active but untrained (AUT), and exercise trained (TR). Subjects ran to exhaustion at 125% VO2max for 25 bouts (20 min. rest periods, water but no carbohydrate supplementation).
Results : The results are presented as mean ± SD. Total exercise time was significantly greater in TR (42.75 ± 3.85 min) than AUT (33.10 ± 6.95 min). VO2remained constant at 95% of maximum for 10 bouts in AUT and for 20 bouts in TR, after which VO2 dropped to 60-65% of maximum in AUT and to 85-90% of maximum in TR. During bouts 11-25, TR had significantly greater peak lactates (6.91±0.9 vs. 2.66±0.5 mM), greater VE/VO2 ratios (31 ± 2 vs. 25 ± 9) and greater rates of lactate accumulation (4.90±0.74 vs. 3.09±0.68 Mm.min-1) than AUT.
Conclusions : TR had significant glycolysis during all 25 exercise bouts, whereas AUT became glycogen-depleted. Trained subjects apparently spared glycogen during supra-VO2maximal exercise presumably by oxidising more fat (in slow twitch fibres). Thus athletes who participate in anaerobic events may benefit substantially from aerobic training, as well as anaerobic training.
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