Effects of ice-slurry and carbohydrate on exercise in the heat

There is considerable interest in reducing the ergolytic effect of heat. One approach is to reduce body-heat content through ingesting ice-slurry (IS), which provides a substantially greater heat sink benefit than cool liquids because of the enthalpy of fusion absorbed in the phase change from ice to water [1]. Many studies using IS have employed a formulation containing carbohydrate [2], which is itself ergogenic during prolonged exercise in the heat [3]. Although the separate effects of IS and carbohydrate on performance in the heat are established, it is unclear if there is an interaction when co-ingested. For example, exogenous carbohydrate oxidation is impaired with hyperthermia [4], whereas IS reduces heat stress. This study examined the separate and combined effects of IS and carbohydrate on performance, thermoregulation, substrate utilisation and thermal perception during prolonged cycling exercise in the heat.