Substrate oxidation pattern during cardiorespiratory exercise prescribed by different methods

Abstract

The American College of Sports Medicine recommends intensities of between 55% and 70% heart rate reserve (HRR) for prescription of endurance exercise (EEx) aiming the body composition change. However, several studies have found that the maximal lipid oxidation (LIPox) is directly related to anaerobic threshold (AT) and occurs at intensities around 60% maximal heart rate (HRmax) and 55% maximal oxygen uptake (VO2max). The aim of this study was to compare the substrate oxidation rates from EEx prescribed by AT (direct method, mDR) and HRR (indirect method, mIND). Seven untrained healthy male subjects performed 60min of EEx at AT and 55% HRR for substrates oxidation rates by indirect calorimetry, after 8-h fasting followed by maltodextrin intake (2g/kg, 6% solution) 30-min before the onset of exercise. Our results showed dissimilar patterns of LIPox (0,23 ± 0,01 e 0,10 ± 0,01 g/min; mDR e mIND, respectively; p < 0,05); as a consequence, the relative contribution of LIP oxidation to total energy expenditure was 1.8 times higher in AT than in HRR trial (25,9 ± 0,9 e 14,6 ± 1,0 %; mDR e mIND, respectively; p < 0,05). Despite HRR underestimate the LIPox, this method indicated for applicability approaching the scientifically recommended criteria, which for strength indication in field situations may result in lower margin of error.