The Effects of Fitness Level and Sex on EPOC Following High Intensity Interval and Moderate Intensity Aerobic Exercise

THE EFFECTS OF FITNESS LEVEL AND SEX ON EPOC FOLLOWING HIGH INTENSITY INTERVAL AND MODERATE INTENSITY AEROBIC EXERCISE Rachel Lauren Simmons Old Dominion University, 2016 Chair: Dr. David P. Swain In the past few years, much attention has been directed toward shorter-duration vigorous intensity aerobic exercise as opposed to longer-duration moderate intensity exercise. There is conflicting evidence as to whether vigorous exercise can result in a greater excess post-exercise oxygen consumption (EPOC) and thus more calories burned when compared to moderate continuous exercise performed for a longer duration. In addition, the literature contains a dearth of information isolating and investigating male and female response to these exercises, as well as fit and unfit subjects. The purpose of this study was to quantify EPOC following moderate intensity aerobic exercise (MOD) and high intensity aerobic intervals (HIAI) of equal energy expenditure. It was hypothesized that (1) EPOC following HIAI would be greater than following MOD, (2) EPOC of males and females would not differ, and (3) more fit subjects would have less of an increase in EPOC from MOD to HIAI than less fit subjects, predicted as a negative correlation between subjects’ VO2max and delta EPOC. Eleven subjects (5 male, 6 female; age 25.1 + 2.0 yr; height 169 + 3 cm; mass 67.6 + 3.0 kg; VO2max 41.0 + 1.9 mL minkg ) participated in MOD and HIAI trials in a counterbalanced order separated by at least 48 hours. HIAI was ten 1-min intervals at 90% maximal aerobic power (Pmax), alternated with 1-min intervals at 60% Pmax. MOD was 30 min at 50% Pmax. Warm-ups and cooldowns were also matched for total work. All exercise was performed on a cycle ergometer. Data are reported as mean + SE. VO2 at rest was 4.0 + 0.3 mL·min ·kg preceding the MOD trial, and 4.1 + 0.4 mL·min·kg for HIAI. Net VO2 during exercise (inclusive of warm-ups and cool-downs) was 52.7 + 3.6 L MOD, and 52.0 + 3.9 L HIAI. There was a weak trend (p = 0.164) for EPOC over 41 min of recovery to be greater in the HIAI trial (3.02 + 0.48 L) than the MOD trial (1.98 + 0.56 L). EPOC during minutes 0-10 post-exercise was significantly greater (p = 0.009) following HIAI (2.28 + 0.32 L) than MOD (1.37 + 0.43 L). Following a one-min water break, EPOC during minutes 1141 post-exercise was 0.74 + 0.28 L HIAI, and 0.56 + 0.43 L MOD, which were statistically similar (p = 0.807). For EPOC expressed relative to body mass, males had a significantly greater (p = 0.035) EPOC over the entire 41-min recovery period than females (HIAI males: 58.0 + 8.7, females: 32.5 + 4.9 mL∙kg; MOD males: 44.9 + 14.0, females: 18.7 + 10.6 mL∙kg). For the separate time periods of 0-10 min and 11-41 min, there were trends for males to have higher EPOC than females (p = 0.086 and 0.053, respectively). When total EPOC was corrected for fat free mass there was no significant difference between male and female responses to either condition (p = 0.162). There was no correlation between VO2max and absolute ∆EPOC (L), whether using the total time frame (0-41 min, p = 0.958), or the early (0-10 min, p = 0.958) or late (11-41 min, p = 0.281) phases of EPOC. In conclusion, EPOC consisted of only 3.7% of the net oxygen consumption during the MOD exercise trial, and only 5.8% of the net oxygen consumption during the HIAI trial. While the HIAI EPOC was significantly greater than the MOD EPOC, neither EPOC contributes substantially to the overall energy cost of the exercise, and is thus unlikely to have significant effects on weight loss or other health outcomes. When prescribing exercise to those who are less fit or are new to exercising, it is important to consider the intensity and time that is most tolerable when the primary goal is weight loss.