Purpose: To compare the effects of 60-min bouts of intermittent moderate and vigorous exercise on postprandial plasma triacylglycerol (TAG) metabolism in eight healthy adolescent boys (mean ± SD age: 13 ± 0.3 yr).
Methods: Participants completed three conditions in a counterbalanced order. On day 1, they either rested for 110 min (CON), completed 6 × 10-min blocks of intermittent treadmill exercise at 53% peak V˙O2 (MOD), or 6 × 10-min blocks at 75% peak V˙O2 (VIG). On day 2 after a 12-h fast, a capillary blood sample was taken for [TAG] and [glucose] (mmol·L−1) and then a high-fat milkshake was consumed (1.50 g·kg−1 fat, 1.22 g·kg−1 CHO, and 0.22 g·kg−1 protein; 80 kJ·kg−1). Further blood samples were taken every hour for a 6-h postprandial rest period for [TAG] and [glucose].
Results: Estimated energy expenditure was 45% higher in VIG than in MOD (95% confidence interval [CI] 23-72%). Fasting [TAG] and [glucose] did not differ between the conditions. Average [TAG] for the postprandial period was lower by 24% in MOD (95% CI −47% to 9%, P = 0.06) and by 21% in VIG (95% CI −42% to 8%, P = 0.08) than CON, with no meaningful difference (4%; 95% CI −27% to 48%, P = 0.50) between MOD and VIG. The total area under the [TAG] versus time curve (mmol·L−1 6 h) was lower by 24% in MOD (95% CI −42% to 0%, P = 0.05) and by 20% in VIG (95% CI −37% to 0%, P = 0.07) than CON. MOD and VIG were not different from each other (4%; 95% CI −18% to 32%, P = 0.54).
Conclusion: Both 60 min of moderate and vigorous intermittent exercises reduced postprandial [TAG]. However, the extra energy expended in the vigorous condition did not produce a dose-related reduction compared with the moderate-intensity condition.
1Research Institute for Health and Social Change, Department of Exercise and Sport Science, Manchester Metropolitan University, Alsager; and 2Exercise and Health Research Group, School of Sport and Exercise Sciences, Loughborough University, Loughborough, UNITED KINGDOM
Address for correspondence: Keith Tolfrey, Ph.D., Research Institute for Health and Social Change, Department of Exercise and Sport Science, MMU Cheshire, Alsager, ST7 2HL, UK; E-mail: K.Tolfrey@lboro.ac.uk.
Submitted for publication September 2007.
Accepted for publication December 2007.