Taking this very very low tech... I ran a 5 day running race in 40-50C heat this summer. By grabbing ice cubes at the control points during each stage and holdi

Taking this very very low tech... I ran a 5 day running race in 40-50C heat this summer. By grabbing ice cubes at the control points during each stage and holding them in my hands - as opposed to putting them under my cap like most runners - I was able to drop my heart rate by 3-6 beats per minute until the ice melted. The Swedish company Craft made an "ice glove" for triathlete Torbjørn Sindballe who had trouble from the heat when running in Hawaii...