Seiler, S., & Hetlelid, K. J. (2004). Impact of rest duration on physiological and RPE responses during interval training. Medicine and Science in Sports and Exercise, 36(5), Supplement abstract 1021.

This study investigated the effect of rest duration on self-selected intensity, physiological responses, and RPE during standardized, high-intensity interval training. Well-trained male runners (N = 11) performed preliminary testing followed by three interval-training sessions on a 5% inclined treadmill. One training session, consisting of six, 4-min work bouts separated by either 1-, 2-, or 4-minute recovery periods, was completed each week in random order. Ss regulated their own work and rest intensity during all tests based on written instructions that were read before each session and described a high-intensity workout with the goal being to achieve the highest possible average running speed for the work intervals. In a fourth interval session, Ss self-selected their recovery time in response to a fixed intensity established from previous sessions.

Running velocity increased slightly when rest duration increased from one to two minutes, but showed no further increase with four minutes of rest. VO2 during the work periods (averaged over the last three minutes), was slightly higher with 2-min rest compared to 1- and 4-min. Peak blood lactate was similar for the three conditions, while peak RPE was slightly lower during the 4-min rest condition . When recovery time between work bouts was self-selected, with no knowledge of elapsed time, the average rest duration was approximately two minutes.

Under self-paced conditions, varying rest duration in a range of one to four minutes had limited impact on average running velocity, or physiological and perceptual responses during high intensity interval training consisting of repeated 4-min exercise bouts. Approximately 120s of active recovery may provide an optimal balance between intracellular restitution and maintenance of high VO2 kinetics.

Implication. Two minute rest periods are optimal for high-intensity interval running training.

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