Gibala, M. J., Little, J. P., van Essen, M., Wilkin, G. P., Burgomaster, K. A., Safdar, A., Raha, S., & Tarnopolsky, M. A. (2006). Short-term sprint interval versus traditional endurance training: similar initial adaptations in human skeletal muscle and exercise performance. Journal of Physiology, 575(Part 3), 901-911.

This study examined changes in exercise capacity and molecular and cellular adaptations in skeletal muscle after low-volume sprint-interval training and high-volume endurance training. Active men (N = 16; ~21 years) were assigned to either (N = 8) of both groups. Six training sessions were performed over 14 days. In the sprint-interval group, each session consisted of either four to six repeats of 30 seconds "all out" cycling at approximately 250% of peak oxygen uptake with four minutes of recovery. In the endurance training group, 90-120 minutes of continuous cycling at approximately 65% VO2peak was completed.

Training time commitment over two weeks was approximately 2.5 hours for the sprint-interval group and approximately 10.5 hours for the endurance-training group. Total training volume was approximately 90% lower for the sprint versus the endurance training conditions ( approximately 630 versus approximately 6500 kJ). Training decreased the time required to complete 50 and 750 kJ cycling time-trials, with no difference between groups. Biopsy samples obtained before and after training revealed similar increases in muscle oxidative capacity. Training-induced increases in muscle buffering capacity and glycogen content were also similar between groups.

Implication. Higher intensity training is a time-efficient strategy that induces rapid adaptations in skeletal muscle and exercise performance that are comparable to endurance training in young active men. High-intensity training would be appropriate for athletes with time restraints (e.g., limited practice times in a week; starting late in a season; after appropriate re-introduction after injury; etc).

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