– Written by Julien D. Périard, Qatar

Extremely hot conditions took over Rod Laver Arena and the rest of the tennis grounds in Melbourne Park during the 2014 Australian Open.  After days of sweltering hot weather and temperatures reaching 43ºC, play was suspended for several hours when organisers invoked the Extreme Heat Policy.

The stoppage in play, however, occurred only after a plastic bottle had reportedly started melting on court, a ball boy and a male player fainted, a female player experienced cramping and vomiting, and several notable players expressed their concerns regarding the safety of continuing to compete in such conditions.

Unfortunately, the sequence of events that played out on the international stage in Australia is mirrored worldwide each year in numerous lower-profile events, highlighting the challenges and consequences of competing under severe heat stress. In effect, the development of hyperthermia during exercise in the heat has been shown to impair endurance1 and intermittent exercise performance (e.g. soccer)2,3. These performance impairments occur in conjunction with elevations in physiological and perceptual strain, relative to when exercise is performed in cooler conditions. During the development of hyperthermia, progressive dehydration can also occur if fluids are not sufficiently consumed, which can in turn exacerbate the rise in thermal strain.


The rise in body core temperature during exercise is mediated by relative intensity/workload and the prevailing environmental conditions. In conditions within the prescriptive zone – ambient temperatures in which deep body core temperature remains stable during exercise7 – core temperature increases safely up to 38.3°C during match-play tennis8-10. This suggests that in temperate environments, both autonomic (e.g. sweating) and behavioural (e.g. adjustments in play and recovery) thermoregulation successfully regulate core temperature. However, in hot ambient conditions core temperatures above 39.5ºC have been reported during play8,11-13. The development of this thermal strain, along with the concomitant increase in physiological and perceptual strain (Figures 1 and 2), is characterised by a reduction in effective playing time10,13, which is the percentage of total match time spent with the ball in play. This reduction stems from both a decrease in point duration10 and/or an increase in time between points (e.g. Table 1)13. Accordingly, these adjustments in match-play characteristics in hot ambient conditions have been suggested to represent behavioural strategies adopted to minimise or offset the sensation of environmental conditions being rated as difficult. In essence, these adjustments allow players a certain measure of self-regulation with regard to the rate of heat production in environmental conditions that contribute to increased core temperature during exercise.

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