Adaptation to Heat and Exercise Performance Under Cooler Conditions: A New Hot Topic

Abstract

Chronic exposure to a stressor elicits adaptations enhancing the tolerance to that stressor. These adaptive responses might also improve tolerance under less stressful conditions. For example, historically there has been much interest in the adaptive responses to high-altitude, or hypoxia, and their ergogenic potential under sea-level, or normoxic, conditions. In contrast, the influence of the adaptive responses to heat on exercise under cooler conditions has received relatively little interest. Heat acclimation/acclimatization (HA) is known to increase work capacity in hot environments. Yet, aerobic exercise performance can progressively deteriorate as ambient temperature increases beyond ~10 °C, indicating a thermal limitation even under relatively cool conditions. The improved thermoregulatory capability induced by HA might attenuate this thermal decrement in a manner similar to that seen when exposed to hotter temperatures. Moreover, the suite of adaptations elicited by HA has the potential to increase maximal oxygen uptake, lactate threshold and economy, and thus may be ergogenic even under conditions where performance is not thermally limited. Indeed, evidence is now emerging to support an ergogenic effect of HA but the number of studies is limited and in some instances lack appropriate control, are confounded by methodological limitations, or do not address the mechanisms of action. Nevertheless, these tantalising insights into the ergogenic potential of heat will likely generate considerable interest in this new 'hot topic'. Future research will need to employ well-designed studies to clarify the exercise conditions under which ergogenic effects of HA are apparent, to elucidate the precise mechanisms, and to optimise HA strategies for performance.

Effect of Permissive Dehydration on Induction and Decay of Heat Acclimation, and Temperate Exercise Performance

“…However, irrespective of drinking regimen, there was no effect of HA on VO 2max , LT, or GME, but given the similarity in the adaptive response to heat, the lack of between-groups differences is unsurprising. This finding is in contrast to a number of studies that have shown an effect of HA on these parameters (Sawka et al, 1983, 1985; Lorenzo et al, 2010), although these studies have often lacked adequate control and often a simple training effect cannot be excluded (Corbett et al, 2014). The possibility of a training effect was reduced in the present study by the recruitment of competitive athletes, although this may have diminished the adaptation potential due to a ceiling effect, whilst the perception based prescription of work rate during the ISO session and modest hypohydration resulted in similar cardiovascular strain and training stimulus in each group.…”

“…The effect of ambient temperature on aerobic exercise is a continuum, with an exponential performance decline at temperatures above ~10°C (Galloway and Maughan, 1997). Although it is clear that HA attenuates the performance decrement in hot environments, it has been hypothesized that the improved thermoregulatory capability with HA should also attenuate the heat-related performance decrement evident under more temperate conditions (Corbett et al, 2014). Indeed significant reductions in thermal-strain were evident in the sub-maximal exercise preceding the GXT, but none of these changes were correlated with the performance improvement, and the T re at exercise termination was similar pre vs. post HA, and below the levels associated with impaired performance.…”

“…Studies also provide indication that HA elicits improvements in VO 2max (Sawka et al, 1985; Lorenzo et al, 2010), exercise economy (Sawka et al, 1983) and lactate threshold (Lorenzo et al, 2010) in temperate conditions; together these are key determinants of endurance performance (Joyner and Coyle, 2008). However, many of these studies have been criticized for inadequate control (Corbett et al, 2014) and this ergogenic effect has not been replicated in recent experiments employing more appropriate controls (Karlsen et al, 2015; Keiser et al, 2015). Moreover, the influence of PV expansion on VO 2max depends on the balance between increased cardiac output and the haemodilution effect on O 2 -carrying capacity, which may be unfavorable in an already hypervolemic population.…”

Periodizing heat acclimation in elite Laser sailors preparing for a world championship event in hot conditions

“…Power output during submaximal cycling (∼ aerobic threshold) was similar (within 5–12 W) following HA and during the decay period, but increased in both athletes (20 W; very likely increase) following RA during the reduced volume week prior to departure (Table 1). While the relationship between PV expansion and aerobic performance in the literature is unclear, 22 our findings showed a very large (r = 0.70) relationship between PV change and submaximal power output. While supercompensation following heavy-build weeks and a subsequent download week cannot be ignored, 23 this increase was larger than what is normally seen in these athletes during a focused sailing block, where aerobic gains are not expected, thus highlighting the potential ergogenic ‘boost’ that frequent HA sessions could produce within an athlete's season 4 …”

Physiology of Soccer in the Heat

“…Skuat tuan rumah telah terbiasa dengan kondisi bermain di bawah suhu yang panas. Bermain di tempat yang panas dapat meningkatkan laju keringan dan vasodilatasi perifer untuk membuang kelebihan suhu di dalam tubuh, yang dapat berakibat dehidrasi dan kebutuhan metabolisme tubuh yang sedang memerlukan banyak energi (Corbett et al 2014;. Kebutuhan yang segera ini dapat dilatih dengan cara aklimatisasi panas, dengan mekanisme peningkatan volume plasma dan laju keringat untuk memfasilitasi pendinginan suhu inti tubuh dan denyut jantung (Périard et al 2015).…”