FEATURE: HEAT STRESS ON FA UP Figure 1. Time course of heat acclimatisation/acclimation adaptations. Within a week plasmavolume expands and heart rate is reduced during exercise at a given work rate. Core and skintemperature are reduced when exercising at a given work rate, whereas sweat rate increases. Perceptually, the rating of thermal comfort is improved. As a result, aerobic exercise capacity is increased. The magnitude of these adaptations is dependent on the initial heat to induce state of acclimation and the protocol utilised (e.g. environmental conditions and exercise adaptation is the most intensity). Adapted with permission from Périard et al. (2015). impactful intervention an athlete or team may employ to off set the deleterious eff ects of heat stress. For example, after one week of acclimatisation where a match played in the heat was compared to one played in cool conditions the week before, the amount of high intensity running remained lower (/home/webapps/asp_au/data/asp/publications/au-sports-medecine-australia/publications/sport-health-volume-36-june-2018/sport-health-volume-36-issue-123%) (Mohr et al., 2012). However, peak sprint speed was improved by 4% in the heat, despite no diff erences being noted in the quantity or length of sprints between conditions. Moreover, the success rate of passes and crosses was enhanced in the heat. Generally, the phenotypic adaptations that develop during repeated exposure to hot environmental conditions improve submaximal exercise performance, increase maximal aerobic capacity and enhance thermal comfort in the heat. These benefi ts are achieved through plasma volume expansion, better maintenance of fl uid balance, enhanced sweating and skin blood fl ow responses, and acquired thermal tolerance (Horowitz, 2014; Périard et al., 2015). From a terminology perspective, ‘heat acclimatisation’ stems from chronic exposure to natural environments, whereas ‘heat acclimation’ refers to repeated exposure to artifi cial or laboratory settings. Whilst both elicit similar physiological responses, heat VOLUME 36 • JUNE ISSUE 2018 23 tiripsahplA/kcotsknihT