The impact of high-intensity intermittent exercise on resting metabolic rate in healthy males

Introduction

High-intensity intermittent exercise training (HIT) may favourably alter body composition despite low training volumes and predicted energy expenditure (EE).

Purpose

To characterise the acute impact of two common HIT protocols on EE and post-exercise oxygen consumption (11 h EPOC).

Methods

Oxygen consumption (l min^?1), respiratory exchange ratio (RER) and EE were measured in nine healthy, lean males over 12 h under three conditions: control (CON), HIT1 (10 × 1 min high-intensity cycling bouts followed by 1 min rest) and HIT2 (10 × 4 min high-intensity cycling bouts followed by 2 min rest).

Results

Total exercise period EE during HIT1 (1,151 ± 205 kJ) (mean ± SD) was significantly lower than HIT2 (2,788 ± 322 kJ; p < 0.001). EE within the 60 min after exercise was significantly albeit marginally higher after HIT1 (388 ± 44 kJ; p = 0.02) and HIT2 (389 ± 39 kJ; p = 0.01) compared with CON (329 ± 39 kJ), with no difference between exercise conditions (p = 0.778). RER during this period was significantly lower in HIT1 (0.78 ± 0.06; p = 0.011) and HIT2 (0.76 ± 0.04; p = 0.004) compared with CON (0.87 ± 0.06). During the ‘slow phase’ of EPOC (1.25–9.75 h), there were no significant differences in EE (p = 0.07) or RER (p = 0.173) between trials.

Conclusions

Single HIT sessions notably increases EE during exertion; however, the influence on metabolic rate post-exercise is transient and relatively minor.