Arnett, M. G. (2001). Effects of prolonged and reduced warm-ups on diurnal variation in body temperature and swim performance. Medicine and Science in Sports and Exercise, 33(5), Supplement abstract 893.

This investigation determined a) if increasing (doubling) the volume of warm-up could eliminate diurnal variation in body temperature and swim performance, and b) if reduction to 33% of the late afternoon warm-up volume would affect body temperature as reflected by tympanic temperature and swim performance. Ss (M = 6; F = 4) were competitive swimmers. A normal warm-up was used as baseline. A doubled warm-up consisted of doubling everything performed normally and a 33% warm-up consisted of reducing the normal activities by two-thirds. Each S completed one test condition per day.

There was a significant difference in tympanic temperature with the morning being lower than the late afternoon. Doubling the morning warm-up volume removed this difference. Reducing the evening warm-up volume did not reduce the temperature and the significant diurnal difference remained. No matter what warm-up was used, swimming performance in the evening was always significantly superior. Actual tympanic temperature appeared to be unrelated to performance.

Implication. Swimming performances and tympanic temperatures are different between morning and late afternoon practices. Swimming performances should be expected to be better at evening practices than at morning practices.

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