Int J Sports Physiol Perform. 2019 Sep 1;14(8):1140-1146. doi: 10.1123/ijspp.2018-0854.
To analyze the diurnal variation of maximal fat oxidation (MFO) and the intensity that elicits MFO (Fatmax) in trained male athletes.
A total of 12 endurance-trained male athletes age 24.7 (4.1) y participated in the study. The authors measured MFO, Fatmax, maximum oxygen uptake (VO2max), and VO2 percentage at ventilatory threshold 2 with a graded exercise protocol performed on 2 days separated by 1 wk. One test was performed in the morning and the other in the afternoon. The authors assessed the participants' chronotype using the HÖME questionnaire.
MFO and Fatmax were greater in the afternoon than in the morning (Δ = 13%, P < .001 and Δ = 6%, P = .001, respectively), whereas there were similar VO2max and ventilatory threshold 2 in the morning, than in the afternoon test (Δ = 0.2%, P = .158 and Δ = 7%, P = .650, respectively). There was a strong positive association between VO2max and MFO in both morning and afternoon assessments (R2 = .783, P = .001 and R2 = .663, P < .001, respectively). Similarly, there was a positive association between VO2max and Fatmax in both morning and afternoon assessments (R2 = .406, P = .024 and R2 = .414, P = .026, respectively).
MFO and Fatmax may partially explain some of the observed diurnal variation in the performance of endurance sports.
分析训练有素的男性运动员最大脂肪氧化（MFO）和引发 MFO（Fatmax）的强度的日变化。
共有 12 名年龄为 24.7（4.1）岁的耐力训练男性运动员参加了这项研究。作者使用分级运动方案在相隔 1 周的 2 天内测量 MFO、Fatmax、最大摄氧量（VO2max）和通气阈 2 时的 VO2 百分比。一项测试在早上进行，另一项在下午进行。作者使用 HÖME 问卷评估参与者的昼夜型。
MFO 和 Fatmax 下午高于上午（Δ=13%，P<.001 和 Δ=6%，P=.001），而 VO2max 和通气阈 2 上午与下午测试相似（Δ=0.2%，P=.158 和 Δ=7%，P=.650）。在早上和下午的评估中，VO2max 与 MFO 之间存在强烈的正相关关系（R2=.783，P=.001 和 R2=.663，P<.001）。同样，在早上和下午的评估中，VO2max 与 Fatmax 之间存在正相关关系（R2=.406，P=.024 和 R2=.414，P=.026）。
MFO 和 Fatmax 可能部分解释了耐力运动表现中观察到的一些昼夜变化。
