Mougin Loïs, Macrae Heather Z, Taylor Lee, James Lewis J, Mears Stephen A
School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, Leicestershire, LE11 3TU, UK.
School of Sport, Exercise and Rehabilitation, Faculty of Health, University of Technology Sydney, Sydney, Australia.
Sports Med. 2025 Aug 20. doi: 10.1007/s40279-025-02294-3.
Carbohydrate metabolism during prolonged endurance exercise can be influenced by heat stress and dehydration. While heat exposure and dehydration have been shown to independently affect glycogen use and carbohydrate oxidation, their combined impact remains unclear. No previous review has systematically evaluated the effects of these factors on carbohydrate metabolism during prolonged endurance exercise or undertaken a meta-analysis.
The aim was to systematically review the literature and meta-analyse the effects of heat stress (hot compared to temperate conditions) and dehydration (dehydrated compared to hydrated status) on (1) respiratory exchange ratio, (2) carbohydrate oxidation and (3) glycogen use.
A Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)-compliant systematic review with meta-analysis was completed ( https://osf.io/uq8n5 ). PubMed/MEDLINE and SportDiscus databases were searched for original articles (published up to November 2024) that assessed changes in (main outcomes) (1) respiratory exchange ratio, (2) carbohydrate oxidation or (3) glycogen use. The population included healthy, active, trained adults (> 18 years). Interventions involved exercise in hot conditions compared to temperate conditions and/or dehydration compared to a hydrated state. The exercise duration was required to be ≥ 15 min. Meta-analysis was performed using a random-effects model to calculate standardised mean differences (SMDs) between experimental conditions (hot compared to temperate conditions and/or dehydrated compared to hydrated statuses). Heterogeneity was assessed using χ and I statistics, with significance set at P ≤ 0.05.
Fifty-one studies (502 participants; 31 females) were included. Carbohydrate oxidation (SMD 0.29, P = 0.006) and glycogen use (SMD 0.78, P = 0.006) were greater in hot conditions compared to temperate conditions. In a dehydrated state, carbohydrate oxidation (SMD 0.31, P = 0.002) and glycogen use (SMD 0.62, P = 0.003) were greater compared to in a hydrated state. Greater carbohydrate oxidation in a dehydrated compared to a hydrated state was observed in hot (SMD 0.37, P = 0.001) but not in temperate conditions (SMD 0.27, P = 0.199).
Carbohydrate utilisation increases during prolonged endurance exercise in hot conditions. Dehydration appears to increase carbohydrate use, especially when combined with heat stress; however, these effects are not consistently observed under temperate conditions. Consequently, dehydration does not appear to be the primary driver of elevated carbohydrate utilisation but may play a significant role by affecting thermoregulatory responses.
长时间耐力运动期间的碳水化合物代谢会受到热应激和脱水的影响。虽然热暴露和脱水已被证明会独立影响糖原利用和碳水化合物氧化，但其综合影响仍不清楚。此前尚无综述系统评估这些因素对长时间耐力运动期间碳水化合物代谢的影响，也未进行荟萃分析。
旨在系统回顾文献并进行荟萃分析，以研究热应激（与温和条件相比处于炎热状态）和脱水（与水合状态相比处于脱水状态）对（1）呼吸交换率、（2）碳水化合物氧化和（3）糖原利用的影响。
完成了一项符合系统评价与荟萃分析的首选报告项目（PRISMA）标准的系统评价及荟萃分析（https://osf.io/uq8n5）。在PubMed/MEDLINE和SportDiscus数据库中检索了截至2024年11月发表的评估（主要结局）（1）呼吸交换率、（2）碳水化合物氧化或（3）糖原利用变化的原始文章。研究对象为健康、活跃、经过训练的成年人（>18岁）。干预措施包括与温和条件相比在炎热条件下运动和/或与水合状态相比处于脱水状态。运动持续时间要求≥15分钟。使用随机效应模型进行荟萃分析，以计算实验条件（与温和条件相比处于炎热状态和/或与水合状态相比处于脱水状态）之间的标准化平均差异（SMD）。使用χ和I统计量评估异质性，显著性设定为P≤0.05。
纳入了51项研究（502名参与者；31名女性）。与温和条件相比，炎热条件下的碳水化合物氧化（SMD 0.29，P = 0.006）和糖原利用（SMD 0.78，P = 0.006）更高。与水合状态相比，脱水状态下的碳水化合物氧化（SMD 0.31，P = 0.002）和糖原利用（SMD 0.62，P = 0.003）更高。在炎热条件下（SMD 0.37，P = 0.001）观察到与水合状态相比脱水状态下的碳水化合物氧化更高，但在温和条件下未观察到（SMD 0.27，P = 0.199）。
在炎热条件下进行长时间耐力运动时，碳水化合物利用率会增加。脱水似乎会增加碳水化合物的利用，尤其是与热应激相结合时；然而，在温和条件下并未始终观察到这些影响。因此，脱水似乎不是碳水化合物利用增加的主要驱动因素，但可能通过影响体温调节反应发挥重要作用。
