The effect of short sprint interval training on skeletal muscle metabolism and performance during intense aerobic cycling

Abstract

Two weeks of sprint interval training (SIT) increased maximal aerobic power (VO2peak), however maximal anaerobic power (Wmax; 30-sec “all out” Wingate test) was unaffected, possibly due to chronic fatigue induced by 14 daily training bouts (Rodas et al. Eur. J. Appl. Physiol. 82:480-86,2000). The effect of fewer SIT bouts on these parameters is unknown, and no study has assessed changes in performance or muscle metabolism during intense aerobic exercise after SIT. PURPOSE: We examined whether 6 bouts of SIT, performed over 2 wks with 1-2 d rest between bouts, elicited changes in endurance performance or metabolism during a “challenge ride” to exhaustion @ ~80% VO2peak· METHODS: 8 subjects (6 men; 23±2 yr) were studied before and 2-3 d following the SIT protocol (6 bouts x 4-8 Wingate tests, 4 min rest). RESULTS: VO2peak was unchanged by SIT (Post: 45.5 ± 5 vs. Pre: 44.6 ±3.2 ml/kg/min) as was mean power during 4 repeated Wingate tests (Post: 574.8 ± 29.9 vs. Pre: 569.8 ±31.3 W). Wmax during 4 repeated Wingate tests increased by 14% following SIT (Post: 1067.0 ± 234 vs. Pre: 934.3 ± 173.6 W; p < 0.05). Most strikingly, cycle time to exhaustion increased by 101% after SIT (Post: 51.1 ± 30.8 vs. Pre: 25.4 ± 14.4 min, p < 0.01). Biopsies obtained prior to, and during the challenge rides revealed that resting muscle glycogen was higher after SIT (Post: 614 ± 39 vs. Pre: 489 ± 57 mmol/kg dry wt., p < 0.02), and glycogen degradation during exercise was attenuated (p < 0.05). The maximal activity of CS was 29% higher following training (Post: 16.7 ± 2.3 vs. Pre: 11.5 ± 1.8 mmol/kg wet wt., p < 0.05) which is indicative of a higher muscle oxidative potential. CONCLUSION: 6 bouts of SIT (~15 min total exercise time) markedly increased intense aerobic cycling performance and peak anaerobic power. The physiological mechanisms that account for these improvements remain to be fully elucidated, but include alterations in glycogen metabolism and an increased muscle oxidative potential.