The Effect of Exercise Intensity on Substrate Metabolism and Energy Expenditure for Health Benefits
Cardiff Metropolitan University
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The purpose of this study was to determine the optimal exercise intensity for substrate metabolism and energy expenditure for health benefits, with a focus on fat metabolism. This study used a sample of 4 physically active and healthy subjects (3 women, 1 man; 21 ± 2.2 years; 175.7 ± 5.6 cm; 79.3 ± 13.5 kg; 47.2 ± 8.7 ml.kg.min VO2peak), all of which were university students. Subjects attended 4 laboratory sessions, each separated by at least 24 hours. During the first sessions subjects completed a maximal oxygen consumption test using a treadmill, in which speed was increased by 1km/h until exhaustion. The following 3 sessions consisted of a 12-minute steady state exercise bout, at intensities 40%, 60% and 80% VO2max. Respiratory gases and respiratory exchange ratio were recorded for the duration of each exercise condition to determine substrate metabolism and energy expenditure. A one-way repeated measures ANOVA test was used to determine significance of substrate metabolism and energy expenditure between exercise conditions, significance was set at p<0.05. Analysis identified a non-significant difference in fat metabolism between exercise conditions (p<0.05), with 40% VO2peak identifying the greatest amount of fat metabolism (11.72 ± 2.95 g.l.min, p<0.05). A significant difference was identified in carbohydrate between exercise conditions (p<0.05), with 80% VO2peak identifying the greatest carbohydrate metabolism (38.583 ± 7.818 g.l.min, p<0.05). A significant difference was also identified in energy expenditure between exercise conditions (p<0.05) with 80% VO2peak identifying the greatest caloric energy expenditure (180 ± 45.4 kcal.l.min (p<0.05). These findings suggest that for health benefits subjects should exercise at lower intensities at steady state for maximal fat metabolism, with an ideal intensity of 60% VO2max to ensure caloric energy expenditure for health purposes.
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