Fat Utilization During High-Intensity Exercise: When Does It End?

Ratko Peric,Zoran Nikolovski,Marco Meucci

doi:10.1186/s40798-016-0060-1

Ratko Peric, Zoran Nikolovski + Show 1 more

Open Access

https://doi.org/10.1186/s40798-016-0060-1

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Abstract

BackgroundThis study examined substrate oxidation at high-intensity exercise and aimed to determine when fat oxidation ends (FATmin). We hypothesized the existence of a connection between the anaerobic threshold (AnT) and FATmin point.MethodsBreath-by-breath data obtained from indirect calorimetry during a graded treadmill test were used to measure substrate oxidation and maximal oxygen uptake (VO2max) on 47 males (30 athletes (ATL) and 17 non-athletes (NATL)). Pearson correlation coefficient (r) and effect size (R2) were used to test correlations between VO2 at AnT and at FATmin.ResultsMaximal oxygen uptake (VO2max) was 56.17 ± 4.95 and 46.04 ± 3.25 ml kg−1 min−1 in ATL and NATL, respectively. In ATL, AnT was observed at 87.57 ± 1.30 % of VO2max and FATmin was observed at 87.60 ± 1.60 % of VO2max. In NATL, AnT and FATmin were at 84.64 ± 1.10 % of VO2max and 85.25 ± 1.10 % of VO2max, respectively. Our data show large correlations between VO2 at AnT and VO2 at FATmin for ATL (r = 0.99, p < 0.01, 95 % CI 0.99 to 1.00) and NATL (r = 0.97, p < 0.01, 95 % CI 0.91 to 0.98). The effect size of correlations for ATL and NATL were 0.98 and 0.94, respectively.ConclusionsOur results show high correlation between AnT and FATmin in both ATL and NATL with equal substrate oxidation rates at AnT.

Highlights

This study examined substrate oxidation at high-intensity exercise and aimed to determine when fat oxidation ends (FATmin)
Fat utilization increased with exercise intensity until the aerobic threshold (AerT) was reached, followed by a decrease of total fat oxidation and an increase of CHO utilization (Fig. 1)
FATmin was obtained at 49.22 ± 6.53 ml kg−1 min−1 of Oxygen consumption (VO2) or at 87.60 ± 1.60 % of VO2max for ATL and 39.25 ± 3.44 ml kg−1 min−1 of VO2 or at 85.25 ± 1.10 % of VO2max for NATL (U = 29.00, p < 0.01)

Summary

Introduction

This study examined substrate oxidation at high-intensity exercise and aimed to determine when fat oxidation ends (FATmin). We hypothesized the existence of a connection between the anaerobic threshold (AnT) and FATmin point. It is well documented that carbohydrates (CHO) and lipids are simultaneously oxidized during energy production. Intensity of the exercise where there is maximal utilization of lipids as a fuel is referred to as FATmax, which is correlated with. In contrast to CHO oxidation, which increases together with the work rate, absolute fat oxidation rate declines at high-intensity exercises. Achten et al [1] introduced the point where fat utilization becomes negligible (FATmin)

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