Sports Performance Research Institute New Zealand (SPRINZ), Auckland University of Technology, Auckland, NEW ZEALAND.
AUT-Roche Diagnostics Laboratory, School of Science, Auckland University of Technology, Auckland, NEW ZEALAND.
Med Sci Sports Exerc. 2019 Oct;51(10):2135-2146. doi: 10.1249/MSS.0000000000002008.
We investigated the effect of a 31-d ketogenic diet (KD) on submaximal exercise capacity and efficiency.
A randomized, repeated-measures, crossover study was conducted in eight trained male endurance athletes (V˙O2max, 59.4 ± 5.2 mL⋅kg⋅min). Participants ingested their habitual diet (HD) (13.1 MJ, 43% [4.6 g⋅kg⋅d] carbohydrate and 38% [1.8 g⋅kg⋅d] fat) or an isoenergetic KD (13.7 MJ, 4% [0.5 g·kg⋅d] carbohydrate and 78% [4 g⋅kg⋅d] fat) from days 0 to 31 (P < 0.001). Participants performed a fasted metabolic test on days -2 and 29 (25 min) and a run-to-exhaustion trial at 70% V˙O2max on days 0 and 31 following the ingestion of a high-carbohydrate meal (2 g⋅kg) or an isoenergetic low-carbohydrate, high-fat meal (<10 g CHO), with carbohydrate (55 g⋅h) or isoenergetic fat (0 g CHO⋅h) supplementation during exercise.
Training loads were similar between trials and V˙O2max was unchanged (all, P > 0.05). The KD impaired exercise efficiency, particularly at >70% V˙O2max, as evidenced by increased energy expenditure and oxygen uptake that could not be explained by shifts in respiratory exchange ratio (RER) (all, P < 0.05). However, exercise efficiency was maintained on a KD when exercising at <60% V˙O2max (all, P > 0.05). Time-to-exhaustion (TTE) was similar for each dietary adaptation (pre-HD, 237 ± 44 vs post-HD, 231 ± 35 min; P = 0.44 and pre-KD, 239 ± 27 vs post-KD, 219 ± 53 min; P = 0.36). Following keto-adaptation, RER >1.0 vs <1.0 at V˙O2max coincided with the preservation and reduction in TTE, respectively.
A 31-d KD preserved mean submaximal exercise capacity in trained endurance athletes without necessitating acute carbohydrate fuelling strategies. However, there was a greater risk of an endurance decrement at an individual level.
我们研究了 31 天生酮饮食（KD）对亚极量运动能力和效率的影响。
这是一项在 8 名训练有素的男性耐力运动员（V˙O2max，59.4±5.2ml·kg·min）中进行的随机、重复测量、交叉研究。参与者摄入习惯饮食（HD）（13.1MJ，43%[4.6g·kg·d]碳水化合物和 38%[1.8g·kg·d]脂肪）或等能量 KD（13.7MJ，4%[0.5g·kg·d]碳水化合物和 78%[4g·kg·d]脂肪），时间从第 0 天到第 31 天（P＜0.001）。参与者在第-2 天和第 29 天进行空腹代谢测试（约 25 分钟），在第 0 天和第 31 天在摄入高碳水化合物膳食（2g·kg）或等能量低碳水化合物、高脂肪膳食（＜10g CHO）后，以 70%的 V˙O2max 进行力竭跑步试验，在运动期间进行碳水化合物（约 55g·h）或等能量脂肪（0g CHO·h）补充。
试验之间的训练负荷相似，V˙O2max 没有变化（均，P＞0.05）。KD 降低了运动效率，尤其是在＞70%的 V˙O2max 时，这表现为能量消耗和氧气摄取的增加，而呼吸交换率（RER）的变化无法解释（均，P＜0.05）。然而，当以＜60%的 V˙O2max 进行运动时，KD 上的运动效率仍能维持（均，P＞0.05）。每次饮食适应的力竭时间（TTE）相似（HD 前，237±44min；HD 后，231±35min；P=0.44；KD 前，239±27min；KD 后，219±53min；P=0.36）。在酮适应后，V˙O2max 时的 RER＞1.0 与＜1.0 分别与 TTE 的保持和减少相一致。
31 天的 KD 保持了训练有素的耐力运动员的亚极量运动能力，而无需采用急性碳水化合物供能策略。然而，在个体水平上，耐力下降的风险更大。
