Dehydration Lowers Performance In Running Time Trial In Heat

Most studies on the effects of dehydration on endurance performance in the heat are conducted in a controlled, laboratory environment. Researchers from the University of Connecticut recently sought to determine the effects of dehydration on running performance in the heat in the field.

Seventeen runners were recruited to complete 12 km trail runs on four occasions. Two of the runs were time trials; one of them was performed in a fully hydrated state, the other in a dehydrated state. The other two runs were moderate efforts; again, one was performed in a hydrated state and the other in a dehydrated state.

On average, the runners completed the 12 km time trial roughly 4.5 percent faster when fully hydrated. The runners ran the same pace in the two moderate-pace runs, but their core body temperature and heart rate were higher in the dehydrated run. The authors of the study, which was published in the Journal of Athletic Training, concluded, “A small decrement in hydration status impaired physiologic function and performance while trail running in the heat.”