![The major limiting factors during exercise in the heat are linked to inexorable increases in core temperature [25], card...](https://img5.gyms1.com/118/570/117932781185703.jpg)
14/01/2023
The major limiting factors during exercise in the heat are linked to inexorable increases in core temperature [25], cardiovascular strain [29] and/or reductions in central drive [30]. Conceptually, regarding most endurance athletes and military personnel, the capacity to dissipate heat and offset one, or all, of these eventualities in hot environments predominantly occurs via three modifiable factors: lowered metabolic heat production, enhanced skin vasodilation (i.e., convective heat loss) or evaporative heat transfer (i.e., sweating [37,38,39]). The two supplements deemed to have the strongest empirical evidence to support these mechanisms [6], and reportedly serve to aid endurance exercise performance in temperate conditions, are caffeine (1,3,7-trimethylxanthine [1, 40]) and dietary nitrate (NO3− [4]). Mechanistically, there is a sound theoretical basis for both caffeine and NO3− supplementation to offset fatigue in the heat through increased central drive (caffeine [41]), and nitric oxide’s (NO) action on eccrine sweat gland function and subcutaneous microvascular control (NO3− [42,43,44]). However, numerous studies have reported negative or null performance and thermoregulatory effects for both of these supplements during exercise in the heat
![Olympic Committee (IOC [6]), American College of Sports Medicine (ACSM [7]) and the Union of European Football Associati...](https://img5.gyms1.com/118/572/117932531185728.jpg)
