Thermoregulatory Adaptations following Sprint Interval Training

Traditional endurance training typically involves weeks of long-duration (60–90 min) exercise performed at a moderate to vigorous intensity. An alternative paradigm, sprint interval training, is characterized by multiple bouts of short-duration, high-intensity exercise. Similar fitness benefits from the two paradigms have been demonstrated, but whether sprint interval training—like traditional endurance training—induces heat acclimation remains unclear. Purpose To test the hypothesis that sprint interval training performed over six sessions results in measureable thermoregulatory and cardiovascular adaptations consistent with heat acclimation. Methods Seven untrained men [mean ± SD, 13 ± 5% body fat, 22 ± 3 y, 3.1 ± 0.3 L/min peak oxygen uptake (V̇O2peak)] performed 6 sprint interval training sessions over 12 days with 48­–72 h between sessions. Sessions consisted of 4–6 thirty-second Wingate Anaerobic Tests separated by ~4 min. Before and after the two-week training protocol, participants cycled for 30 min at 65% V̇O2peak in 25 °C to assess the effects of sprint interval training on heat acclimation. Results Main outcome variables (onset of sweating, sweat sensitivity, heart rate at end of exercise, percent change in plasma volume, and core temperature change from pre- to post-exercise) were not different from pre- to post-training (all p > 0.05). Conclusion Two weeks of sprint interval training performed under the conditions specified does not result in heat acclimation.