High-intensity interval training: Modulating interval duration in overweight/obese men

Introduction. High-intensity interval training (HIIT) is a time-efficient strategy shown to induce various cardiovascular and metabolic adaptations. Little is known about the optimal tolerable combination of intensity and volume necessary for adaptations, especially in clinical populations. Objectives: In a randomized controlled pilot design, we evaluated the effects of two types of interval training protocols, varying in intensity and interval duration, on clinical outcomes in overweight/obese men. Methods. Twenty-five men [body mass index (BMI) > 25 kg.m(2)] completed baseline body composition measures: fat mass (FM), lean mass (LM) and percent body fat (%BF) and fasting blood glucose, lipids and insulin (IN). A graded exercise cycling test was completed for peak oxygen consumption (VO(2)peak) and power output (PO). Participants were randomly assigned to high-intensity short interval (1MIN-HIIT), high-intensity interval (2MIN-HIIT) or control groups. 1MIN-HIIT and 2MIN-HIIT completed 3 weeks of cycling interval training, 3 days/week, consisting of either 10 x 1 min bouts at 90% PO with 1 min rests (1MIN-HIIT) or 5 x 2 min bouts with 1 min rests at undulating intensities (80%-100%) (2MIN-HIIT). Results. There were no significant training effects on FM (Delta 1.06 +/- 1.25 kg) or % BF (Delta 1.13% +/- 1.88%), compared to CON. Increases in LM were not significant but increased by 1.7 kg and 2.1 kg for 1MIN and 2MIN-HIIT groups, respectively. Increases in VO(2)peak were also not significant for 1MIN (3.4 ml.kg(-1).min(-1)) or 2MIN groups (2.7 ml.kg(-1).min(-1)). IN sensitivity (HOMA-IR) improved for both training groups (Delta-2.78 +/- 3.48 units; p < 0.05) compared to CON. Conclusion. HIIT may be an effective short-term strategy to improve cardiorespiratory fitness and IN sensitivity in overweight males.