2003•Medicine & Science in Sports & ExerciseRequires access
EFFECT OF ORDER OF EXERCISE INTENSITY ON PHYSIOLOGICAL AND PERCEPTUAL RESPONSES DURING EXERCISE OF MIXED INTENSITY
Jie Kang, Justin S. Schweitzer, Jay R. Hoffman
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Abstract
An exercise of mixed intensity would be of interest to those who want to maximize exercise benefits in a relatively short period of time and are able to perform exercise at a moderate intensity. However, whether the order in which intensities are presented would affect physiological and perceptual responses remains unclear. PURPOSE To examine the effect of order of exercise intensity upon physiological and perceptual responses during exercise of mixed intensity. METHODS Eight males and 4 females served as subjects for the study. All subjects completed a peak oxygen uptake (VO2peak) test and two bouts of submaximal exercise of mixed intensity. During each submaximal exercise, subjects performed either 15-min of exercise at 70% VO2peak followed by 15-min exercise at 50% VO2peak (H/L) or 15-min of exercise at 50%VO2peak followed by 15-min of exercise at 70% VO2peak (L/H). The order of exercise intensity was randomly determined. Oxygen uptake (VO2), respiratory exchange ratio (RER), expired ventilation (VE), heart rate (HR) and ratings of perceived exertion (RPE) were measured every 5 min throughout exercise. Caloric expenditure (CE) and carbohydrate (CO) and fat oxidation (FO) were calculated from VO2 adjusted for substrate metabolism using RER and then accumulated for each phase of exercise intensity as well as for the entire exercise session. RESULTS VO2 and HR were higher (p < 0.05), while RER was lower (p < 0.05) at the lower intensity in H/L than L/H. Ve and RPE were lower (p < 0.05) at the higher intensity in H/L than L/H. While no differences in CE and CO between the two trials were observed, FO was higher (p < 0.05) both at the lower intensity and for the entire trial in H/L than L/H. CONCLUSION It appears that during exercise of mixed intensity, placing some periods of moderate intensity exercise the first is more favorable sequence in that it can elicit a greater fat oxidation while being felt less exertional.