Soegaard Camilla, Riis Simon, Mortensen Jesper Friis, Hansen Mette
Department for Public Health, Aarhus University, Aarhus, Denmark.
Curr Dev Nutr. 2024 Dec 10;9(1):104520. doi: 10.1016/j.cdnut.2024.104520. eCollection 2025 Jan.
Carbohydrate restriction can alter substrate utilization and potentially impair endurance performance in female athletes. Caffeine intake may mitigate this performance decrements.
The aim of this study was to test the hypothesis that maximal fat oxidation (MFO) rate would be enhanced in the carbohydrate (CHO) restricted state in trained females. Additionally, the impact of caffeine intake before exercise under conditions of low CHO availability was examined on time-trial performance.
By using a randomized, double-blinded, placebo-controlled, crossover design, 17 female endurance athletes completed 3 experimental blocks. Each block consisted of high-intensity-interval-training (HIT) in the evening, followed by a fat oxidation test to measure MFO rate and a 20-min time trial (20TT) performance the next morning. The females received standardized, isoenergetic diets with different timing of CHO intake: No CHO between exercise sessions without (FASTED) or with 300 mg caffeine (4.1-4.9 mg/kg body mass) (FASTED+CAFF) before morning exercise tests or CHO ingestion after HIT (FED).
MFO rate was higher in FASTED+CAFF (0.57 ± 0.04 g/min) than that in FED (0.50 ± 0.04 g/min, = 0.039) but not different from FASTED condition. Power output performed during the 20TT was higher after FASTED+CAFF (189 ± 9 W) than that after FASTED (+6.9%, = 0.022) and FED (+4.2%, = 0.054).
CHO restriction during recovery from HIT enhances MFO rate during subsequent exercise compared with the condition where CHOs were consumed during the recovery period, but the effect was only significant when CHO restriction was combined with caffeine supplementation before the MFO test. In addition, caffeine ingestion before exercise in the CHO-restricted state compensates for the decreased work capacity associated with the CHO-restricted state.
限制碳水化合物摄入会改变底物利用情况，并可能损害女性运动员的耐力表现。摄入咖啡因可能会减轻这种表现下降的情况。
本研究的目的是检验以下假设：在训练有素的女性中，处于碳水化合物（CHO）限制状态时，最大脂肪氧化（MFO）速率会提高。此外，还研究了在低CHO可用性条件下运动前摄入咖啡因对计时赛表现的影响。
采用随机、双盲、安慰剂对照、交叉设计，17名女性耐力运动员完成了3个实验阶段。每个阶段包括晚上的高强度间歇训练（HIT），随后在第二天早上进行脂肪氧化测试以测量MFO速率和20分钟计时赛（20TT）表现。这些女性接受了标准化的等能量饮食，CHO摄入时间不同：运动期间不摄入CHO（禁食）或在早上运动测试前摄入300毫克咖啡因（4.1 - 4.9毫克/千克体重）（禁食 + 咖啡因），或在HIT后摄入CHO（进食）。
禁食 + 咖啡因组的MFO速率（0.57 ± 0.04克/分钟）高于进食组（0.50 ± 0.04克/分钟，P = 0.039），但与禁食状态无差异。禁食 + 咖啡因组在20TT期间的功率输出（189 ± 9瓦）高于禁食组（+6.9%，P = 0.022）和进食组（+4.2%，P = 0.054）。
与恢复期间摄入CHO的情况相比，HIT恢复期间限制CHO摄入可提高后续运动期间的MFO速率，但只有在MFO测试前将CHO限制与咖啡因补充相结合时，这种效果才显著。此外，在CHO限制状态下运动前摄入咖啡因可弥补与CHO限制状态相关的工作能力下降。
