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Heart rate and spontaneous work-rest cycles during exposure to heat

1983; Taylor & Francis; Volume: 26; Issue: 12 Linguagem: Inglês

10.1080/00140138308963453

1366-5847

J. J. Vogt, J. P. Libert, Victor Candas, F. Daull, PH. MAIRJAUX,

Occupational Health and Performance

Ten young men and women performed different workloads (25-50% of VO2max) on a bicycle in ambient temperatures of 25, 35 and 45°C. Air velocity (V a) and water vapour pressure (P a) were kept constant (V a = 0.25 m s−1; p a = 2.3 k Pa). The subjects determined themselves the time and duration of the successive work and rest phases but had to perform at least 60min of cycling during the 180 min of exposure. The whole working duration was spontaneously split up into one to six working phases whose durations ranged from 9 to 146 min. Whatever the number of working phases, the duration of the last phase was about 50% of the first one, and the duration decrease occurring with exposure time was nearly proportional to the order number of the working periods. For a given pattern of work-rest cycles, work finally stops at a constant critical heart rate level. This level depends on experimental conditions and on subjects.