Purpose: Team sports contain high-intensity sprints separated by active recovery (AR) and passive recovery (PR). The beneficial effects of AR on repeated-sprint performance, for short exercise duration, in thermoneutral environments, are well known. However, team sports are often performed in hot environments for prolonged periods. Therefore, the aim was to investigate the thermal strain of AR versus PR during prolonged, intermittent-sprint exercise.
Methods: Eight men performed two intermittent-sprint tests in the heat (35°C, 44% relative humidity (RH)), with either AR or PR.
Results: No differences were found between conditions for mean work (AR: 3739.5 ± 204.7 J; PR: 3814.0 ± 161.3 J) or power per sprint (AR: 1257 ± 64 W; PR: 1245 ± 47 W). AR was associated with a significantly higher heart rate (HR), muscle (Tmu), rectal temperature (Tre), body temperature (Tb), and skin temperature (Tsk) after 7, 10, and 25 min, respectively. Body heat storage, and physiological and cumulative heat-strain indices, were significantly higher in AR compared with PR. The differences in Tmu and thermoregulatory strain between AR and PR were greater than the differences in Tre and Tb.
Conclusions: These results likely can be attributed to a greater rate of whole-body heat loss during the AR protocol. Because AR has previously been associated with a greater muscle pump, a greater blood flow to surface veins and inactive musculature may have been maintained, allowing greater heat dissipation than during PR, when blood was likely to be pooling in the legs. Despite the greater increase in body temperature and heat strain in AR than in PR, there was no difference in performance, possibly because critical temperature levels were not reached in this study.