Exercise Intensity, Energy Expenditure And Enjoyment During Variable High Intensity Exercise In Healthy Adults.

Abstract

Variable high-intensity exercise bouts may generate similar energy expenditures and possibly be favored over moderate-intensity exercise as an alternative to obtain optimal health benefits. PURPOSE: To examine exercise intensity, energy expenditure and perceptual responses to work-matched moderate-intensity steady-state exercise (MIE) and variable-intensity exercise (VIE) conditions in healthy adults (n = 6, age = 24.3 ± 5.4 yrs). METHODS: A graded exercise test on the cycle ergometer to maximal exertion was utilized to determine maximal oxygen uptake (VO2), maximal heart rate (HR) and work rate max (WRmax) for subsequent conditions. The two experimental conditions (MIE and VIE) were randomized and performed on separate days. MIE consisted of continuous moderate-intensity exercise at 40% of 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 total work were matched between conditions. VO2, heart rate (HR) were averaged over the entire bout for both conditions. OMNI ratings of perceived exertion (RPE) and affect, via Feelings Scale, were measured during exercise and enjoyment was measured post-exercise using the physical activity enjoyment scale. Reponses between conditions were analyzed using paired t-tests. Significance was established if p<0.05. RESULTS: During VIE and MIE, HR (156 ± 10 bpm vs. 141 ± 12 bpm) and percent of maximal HR (81.6 ± 3.2% vs. 73.3 ± 4.1%) were significantly different. Absolute VO2 during VIE and MIE were 1.42± 0.22 L∙min-1 and 1.27 ± 0.24 L∙min-1 (p=0.13). The intensities relative to VO2max were similar between bouts (VIE = 50.9 ± 10.3%; MIE = 44.9 ± 8.0%). Total energy expenditure of VIE and MIE were 212.5 ± 32.3 kcals and 189.4 ± 36.3 kcals, respectively (p=0.12). While perceived exertion (VIE = 4.6 ± 0.9; MIE = 3.6 ± 1.3) was similar between trials, in-exercise affect and post-exercise enjoyment were greater in VIE (2.0 ± 0.9 and 92.2 ± 3.3) compared to MIE (1.7 ± 1.0 and 77.2± 5.8). CONCLUSION: In healthy adults, VIE was perceived as more positive and enjoyable, while eliciting a greater HR response and similar energy expenditure compared to MIE. VIE may be an alternative exercise to MIE to obtain health benefits.