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KIMBERLY BOWMAN MSc Candidate, University of British Columbia Canadian Sport Institute Pacific Sport Physiologist Intern


any elite team sport athletes face the physiological challenge of having to compete in extremely hot weather conditions [4]. Exercising in the heat induces a large stress on the body’s cardiovascular and thermoregulatory system, as metabolic heat generated from intense exercise is coupled with environmental heat [11]. Soccer in particular is a physically demanding sport requiring technical skill, strong endurance, and repeated sprint ability [3,11-12]. Mohr and colleagues (2010) highlighted the impact of an added thermal load when observing soccer match performance in a hot condition (~40˚C) compared to that in mild weather (~21˚C). Specifically, reductions in total distance (-7%), high intensity running (-26%), and running velocity (-3%) [11].

Benefits of Heat Acclimatization Heat acclimatization (HA) involves exercising at a target core temperature stimulus (~38.5˚C) in a hot environmental condition over 1-2 weeks [9]. Repeated heat exposures allow adaptations to develop that attenuate the negative effect of heat stress through improvements in exercise capacity and perceptions of thermal load [4]. More recent studies have shown heat acclimatization to be ergogenic in both mild and hot conditions, therefore, cold weather sports may also benefit from utilizing a heat protocol prior to competition [10]. The magnitude of heat adaptation is determined by: intensity, duration, frequency, number of heat exposures, and environmental condition [4, 9].


HP SIRCuit Summer 2016

Performance Tests and Monitoring Metrics in Heat Athletes performing at high intensities in Acclimatization Thermoregulatory & cardiovascular adaptation

competitive games commonly have sweat rates ≥2.5L/h [16]. Heat acclimatization improves thermoregulatory efficiency via a lowered sweating threshold and a reduction in the core temperature threshold for sweating (~0.15 to 0.29˚C) [4]. Acute acclimatization regimes have also reported a greater cardiovascular stability while exercising in the heat via a plasma volume increase (3-27%) [9].


Telemetric heart rate (HR) chest monitors (Polar Electro) used to monitor HR response act as an indirect assessment for change in cardiac efficiency, aerobic capacity, and training intensity [1]. Common HR metrics include i) Exercise HR (HRex): the mean HR in the final 30sec of the 5-minute running period and ii) Recovery HR (HRR): the mean drop in HR over a 1-minute rest period post-run [1-2]. Additionally, a GPSaccelerometer (Global Positioning System, Catapult Minimax S4) can be used to track soccer-specific external load metrics in real-time [11, 18]. The S4-GPS device can monitor; total distance covered, meters per minute (m/min), number of high-speed runs (>16.5km/h), and high IMA or accelerations/

HP SIRCuit Summer 2016  
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