Keeping Fit Takes less time than thought

June 6, 2005

Six sessions of sprint interval training increases muscle oxidative potential

and cycle endurance capacity in humans

J Appl Physiol 98: 1985-1990, 2005. First published February 10, 2005;

Kirsten A. Burgomaster,1 C. ,1 J. F. Heigenhauser,2 Suzanne

N. Bradwell,1 and J. Gibala1

1Exercise Metabolism Research Group, Department of Kinesiology, and 2Department

of Medicine, McMaster University, Hamilton, Ontario, Canada

Submitted 1 October 2004 ; accepted in final form 1 February 2005

Parra et al. (Acta Physiol. Scand 169: 157-165, 2000) showed that 2 wk of daily

sprint interval training (SIT) increased citrate synthase (CS) maximal activity

but did not change " anaerobic " work capacity, possibly because of chronic

fatigue induced by daily training. The effect of fewer SIT sessions on muscle

oxidative potential is unknown, and aside from changes in peak oxygen uptake (O2

peak), no study has examined the effect of SIT on " aerobic " exercise capacity.

We tested the hypothesis that six sessions of SIT, performed over 2 wk with 1-2

days rest between sessions to promote recovery, would increase CS maximal

activity and endurance capacity during cycling at ~80% O2 peak. Eight

recreationally active subjects [age = 22 ± 1 yr; O2 peak = 45 ± 3 ml·kg-1·min-1

(mean ± SE)] were studied before and 3 days after SIT. Each training session

consisted of four to seven " all-out " 30-s Wingate tests with 4 min of recovery.

After SIT, CS maximal activity increased by 38% (5.5 ± 1.0 vs. 4.0 ± 0.7 mmol·kg

protein-1·h-1) and resting muscle glycogen content increased by 26% (614 ± 39

vs. 489 ± 57 mmol/kg dry wt) (both P < 0.05). Most strikingly, cycle endurance

capacity increased by 100% after SIT (51 ± 11 vs. 26 ± 5 min; P < 0.05), despite

no change in O2 peak. The coefficient of variation for the cycle test was 12.0%,

and a control group (n = 8) showed no change in performance when tested ~2 wk

apart without SIT. We conclude that short sprint interval training (~15 min of

intense exercise over 2 wk) increased muscle oxidative potential and doubled

endurance capacity during intense aerobic cycling in recreationally active

individuals.

Wingate test; citrate synthase; muscle glycogen

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