Stepto, N. K., Hawley, J. A., Dennis, S. C., & Hopkins, w. g. (1999). Effects of different interval-training programs on cycling time-trial performance. Medicine and Science in Sports and Exercise, 31, 736-741.

Male endurance cyclists (N = 20) were exposed to interval training of varying intensities and then assessed for any effects on a 40-km time-trial.

Ss were first measured on a 25-kJ sprint test, an incremental test to determine peak aerobic power, and a simulated 40-km time-trial on a Kingcycle ergometer. Five randomly selected groups were formed, each featuring a different format of interval training: 12 x 30 seconds at 175% peak aerobic power; 12 x 60 seconds at 100% of peak aerobic power; 12 x 2 minutes at 90% of peak aerobic power; 8 x 4 minutes at 85% of peak aerobic power; and 4 x 8 minutes at 80% of peak aerobic power. Six sessions were completed over three weeks in addition to usual aerobic base training. All measurements were repeated.

The greatest effects were observed in the 85% and 175% groups. Intervals performed at 80% , 90%, and 100% did not produce performance enhancements.

This investigation hints at the value of moderate, relatively continuous work of stimulating nature (85%) and very-short interval work (175%) as being the most effective training formats/intensities.

Implication. Interval training performed at close to race pace intensities, enhance 40-km time trial performance (an example of the principle of specificity). Intervals at 175% peak aerobic intensity also improve performance, but by a different and presently unexplained mechanism.

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