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. Fat_max, 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. Fat_max has been shown to be correlated with the AT⁴. The aim of current study was to investigate the correlations between MFO and Fat_max 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 Fat_max 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 Fat_max) 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 Fat_max were not significantly correlated with the time to exhaustion (Fig1C, D).

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Abstract P-56 Table 1

Physical characteristics of participants

Conclusions MFO and Fat_max, 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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Abstract P-56 Figure 1

Relationship between time to exhaustion in the graded exercise test and physiological parameters (A) VO₂ max, (B) AT, (C) MFO and (D) Fat_max-

References

1. Hickson RC, Rennie MJ, Conlee RK, Winder WW, Holloszy JO. Effects of increased plasma fatty acids on glycogen utilisation and endurance. Journal of Applied Physiology 1977 Nov:43(5):829–833.

2. Kumagai S, Tanaka K, Matsuura Y, Matsuzaka A, Hirakoba K, Asano K. Relationships of the anaerobic threshold with the 5 km, 10 km, and 10 mile races. European journal of applied physiology and occupational physiology 1982 June:49(1):13–23.

3. Achten J, Gleeson M, Jeukendrup AE. Determination of the exercise intensity that elicits maximal fat oxidation. Medicine and science in sports and exercise 2002 Jan:34(1):92–97.

4. Venables MC, Achten J, Jeukendrup AE. Determinants of fat oxidation during exercise in healthy men and women: a cross-sectional study. Journal of applied physiology 2005 Jan:98(1):160–167.

5. Takagi S, Sakamoto S, Midorikawa T, Konishi M, Katsumura T. Determination of the exercise intensity that elicits maximal fat oxidation in short-time testing. Journal of sports sciences 2014 Jan:32(2):175–182.