Caffeine ingestion compromises thermoregulation and does not improve cycling time to exhaustion in the heat amongst males

ConclusionThe greater heat production and storage, as indicated by a sustained increase in core temperature, corroborate previous research showing a thermogenic effect of caffeine ingestion. When exercising at the pre-determined gas exchange threshold in the heat, 5  mg/kg of caffeine did not provide a performance benefit and increased the thermal strain of participants.
Source: European Journal of Applied Physiology - Category: Physiology Source Type: research