This 2019 study, from researchers at Kobe University and University of Tsukuba in Japan, examined how endurance and intermittent exercise performances are impaired by high ambient temperatures.
The purpose of this study was to investigate the effect of wearing cooling vests which cooled torso and neck area of athletes during half-time (HT) on intermittent exercise performance that imitated intermittent athletic games. This kind of ‘intermittent effort’ simulation best describes sports like American football or Rugby in which the actions is stop and start, throughout a game. The results of the experiment indicated that wearing a cooling vest during breaks (such as half time) significantly improves intermittent exercise performance in the heat with decreased neck and mean skin temperature and improved subjective responses.
Figure 1. Perceptual Index: the perceived level of thermal strain is dampened by a cooling vest.
Figure 2. The mean power output in the 2nd trial was significantly greater with a cooling vest. Seven out of the eight participants had improved mean power output in the 3rd trial with a cooling vest vs the control, and all eight participants had improved mean power output in the 4th trial with the cooling vest compared with the control.
You can access the full study here.