Med Sci Sports Exerc. 2016 Aug 30;
PURPOSE: To determine how high-intensity interval training (HIIT) protocols featuring matched times but distinct sprint durations affect cardiorespiratory and metabolic responses and performance.
METHODS: Thirty-eight recreationally active men (aged 21 ± 2 years) were assigned to one of three interval training groups: long-duration high-intensity (HIIT60s; 8 × 60-s at 85%-90% V˙O2max; 120-s recovery at 30% V˙O2max), short-duration high-intensity (HIIT10s; 48 × 10-s at 85%-90% V˙O2max; 20-s recovery at 30% V˙O2max), and control (CON; regular physical activity without HIIT). Before and after a 4-wk training period (3 sessions per week), participants performed graded exercise tests and repeated-sprint tests, based on which their aerobic and anaerobic capacities were assessed. Skinfold thickness, blood and metabolic responses were also measured before and after intervention.
RESULTS: After 4-wk training, V˙O2max was significantly increased (P < 0.01) in HIIT60s (52 ± 9 ml/kg/min vs. 61 ± 12 ml/kg/min) and HIIT10s (53 ± 10 ml/kg/min vs. 61 ± 10 ml/kg/min), but no changes in CON (50 ± 7 ml/kg/min vs. 52 ± 7 ml/kg/min). Skinfold thickness in the abdomen and thigh did not differ significantly among the groups, but a significantly greater decrease in 14%-25% in HIIT60s and decrease in 20% in HIIT10s after training (P < 0.05). Blood lactate, total cholesterol, triglyceride, cortisol, and insulin concentrations were not significantly different among the three groups (P > 0.05), but testosterone concentration in the HIIT10s was higher after training than before (P < 0.05).
CONCLUSION: The higher incremental aerobic performance and lower skinfold thickness in HIIT60s versus HIIT10s reflected similar adaptations, but the higher repeated-sprint performance was observed only in responses to HIIT60s, which may elicit greater anaerobic adaptations.