B-33 Free Communication/Poster - Heat Stress

Abstract

The fat loss associated with sprint interval exercise training (SIT; 3 sessions/wk over 6 wk) cannot be explained fully by an increased 24-h energy expenditure associated with this type of training (Hazell et al 2012). Rather, a cumulative effect of reduced energy intake (EI), increased post-exercise oxygen consumption (VO2), and/or increased lipid oxidation may explain this outcome. PURPOSE: To assess the effects of acute sprint interval exercise (SIE) on EI, subjective appetite, appetite-related peptides, VO2, and whole-body substrate oxidation (RER). METHODS: Eight men (25±3 y, 79.6±9.7 kg, body fat 13±6%; mean±SD) completed two, systematically rotated 34-h treatments consisting of consecutive 10-h test days: SIE and recovery (SIEx) and no exercise control (NoEx). Between 0800-1800 h, participants remained in the laboratory for 8 breath-by-breath gas collections, 3 ad libitum buffet-type meals, 14 ratings of hunger, fullness, satiety and motivation to eat, and 4 blood samples for GLP-1, insulin, pancreatic polypeptide, and PYY. At 1800 h, participants went home with a snack bag, remained sedentary, and returned the following morning for the second test day. Area under the curve (AUC) for total (34-h) VO2 and appetite ratings was calculated with the trapezoid method. Treatment comparisons were made using two-way repeated measures ANOVA (treatment × time) or t-tests. RESULTS: Immediate, albeit short-lived (<1 h), post-exercise suppression of appetite and increase in PYY were observed during SIEx (p<0.001). However, AUC for hunger and motivation to eat were greater during SIEx (p<0.02), but this did not affect 34-h EI (SIEx: 24.6±4.8 vs NoEx: 24.9±5.4 MJ; p=0.76). RER was lower ∼6 h post-exercise (p<0.001) and total VO2 was greater during SIEx (560±88 L) vs NoEx (491±107 L; p=0.05). CONCLUSIONS: Acute SIE suppresses appetite briefly, but subsequently results in greater feelings of hunger and motivation to eat. Despite its effects on appetite and PYY, SIE did not affect 34-h EI. Therefore, following acute SIE, energy expenditure is increased but EI remains the same, suggesting that increases in energy expenditure and alterations in lipid oxidation likely explain the fat loss associated with this training modality. Supported by Gatorade Sport Science Institute, Subway, PepsiCo and Real Canadian Superstore.