Objectives Substrate utilisation during exercise is an important factor for endurance performance. Higher availability of fatty acid extends endurance exercise time.1 Additionally, the anaerobic threshold (AT), which is the exercise intensity driven main energy substrate turning fat into carbohydrate, has shown a high correlation with endurance performance.2 Therefore, fat metabolism may be associated with endurance performance. Fatmax, defined as the exercise intensity that elicits the maximal fat oxidation (MFO) rate,3 and MFO are parameters relating to the ability of fat metabolism. Fatmax has been shown to be correlated with the AT4. The aim of current study was to investigate the correlations between MFO and Fatmax and endurance performance in trained runners.
Methods Participants included 14 male endurance-trained runners. All participants performed a graded exercise test on a treadmill using a short-time testing protocol which increased 1 Mets per 1 min.5 The maximal oxygen consumption (VO2max), AT, MFO, and Fatmax were measured using indirect calorimetry. The time to exhaustion in the graded exercise test was defined as a measure of endurance performance. The linear relationships between endurance performance and the physiological parameters (VO2max, AT, MFO and Fatmax) were calculated using Pearson’s correlation coefficient.
Results Table 1 shows physical characteristics of participants (Table 1). The VO2max and AT were significantly correlated with the time to exhaustion (Fig1 A, B). However, MFO and Fatmax were not significantly correlated with the time to exhaustion (Fig1C, D).
Conclusions MFO and Fatmax, parameters reflecting the ability for fat metabolism, were not associated with the time to exhaustion in the graded exercise test in trained runners. These findings suggest that fat metabolism may not determine endurance performance.
Acknowledgment This study was supported by Grant-in-Aid from the Japan Society for the Promotion of Science Fellows (2016) and the research laboratory allowance of Waseda University.
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