The Effects of Moderate versus Variable High Intensity Cycling on Metabolic Responses during Recovery

PURPOSE: Examine oxygen consumption (VO2), energy expenditure and respiratory exchange ratio (RER) during recovery following moderate-intensity exercise (MIE) and variable high intensity exercise (VIE) in healthy adults. METHODS: The two conditions were randomized and performed on separate days fasted. Both protocols commenced after 15-min seated rest. MIE protocol was at 40% of maximal work rate (WRmax). VIE consisted of sixteen 10-sec supramaximal sprints (120% WRmax), sixteen 20-sec high intensity bouts (60% WRmax) and low-intensity recovery (20% WRmax) interspersed throughout the exercise. Total duration and work were matched. There was 75 minutes of seated recovery. VO2 and RER were recorded during exercise and every 15-minutes of recovery. Energy expenditure (EE) and fat oxidation were calculated. Significance if p≤0.05. RESULTS: During recovery, NET VO2 decreased in both conditions from exercise to 75 minutes. There were no differences in NET VO2 between conditions during recovery. Net EE during recovery was lower in MIE than VIE. During VIE and MIE, RER was 1.02 ± 0.4 and 0.96 ± 0.06, respectively (P=0.06). During recovery, RER was lower in VIE compared to MIE at 30 and 45 minutes but was similar at 15 and 60 minutes. At the end of recovery, RER for VIE and MIE were 0.89 ± 0.08 and 0.95 ± 0.09, respectively (p = 0.08). Fat oxidation at the end of recovery was significantly greater in VIE than MIE. CONCLUSION: Although, NetVO2 and EE were similar during recovery, VIE appears to alter fuel utilization patterns during recovery towards a lower RER and greater fat oxidation