Optimizing Heat Acclimation for Endurance Athletes: High- Versus Low-Intensity Training

Abstract

HA-H can quickly induce functional overreaching in nonacclimatized endurance athletes. As it was associated with a weak subsequent performance supercompensation, coaches and athletes should pay particular attention to training monitoring during a final preparation in the heat and reduce training intensity when early signs of functional overreaching are identified.

Impairment of Cycling Capacity in the Heat in Well-Trained Endurance Athletes After High-Intensity Short-Term Heat Acclimation

“…The main findings from the present study indicate that five consecutive days of high intensity HA results in small reductions in actual and perceived strain but impairs subsequent exercise capacity. The capacity decrements reported in the current study are in line with other high intensity STHA data 13 ; however, this is the first high-intensity STHA investigation to observe lower core body temperatures following such HA. We observed a small reduction in resting core temperature between HST1 and HST2 indicating partial adaptation (Table 3); however, we did not observe changes in HR, PV, aldosterone, or SR.…”

“…Seven days of low-intensity/moderate-volume (60 min, 50% VȮ2max) HA reduced oxygen consumption, heart rate and core temperature to a similar extent as a moderate-intensity/lowvolume protocol (~35 min, 75% VȮ2max) suggesting that elevating the exercise intensity can reduce the duration required for heat adaptation 11 . The effect of these physiological adaptations on subsequent exercise performance was not investigated in that study but recent data suggest that high intensity STHA can improve explosive exercise performance in the heat 14 and either has no effect 14 or impairs 13 prolonged exercise performance. Unfortunately, physiological data were limited in each study and discrepancies exist in the protocols used making it difficult to ascertain whether the performance adaptations are specific to HA adaptations or to the exercise type used in the HA.…”

“…Traditional HA protocols have consisted of lowintensity/high volume exercise 4 and have attempted to induce a sufficient thermal impulse by increasing the frequency and/or duration of heat exposure 3,4 . Manipulation of the exercise intensity of HA protocols has received less attention, and the few studies that have investigated different HA intensities have reported equivocal adaptation and exercise performance data [11][12][13][14] . Seven days of low-intensity/moderate-volume (60 min, 50% VȮ2max) HA reduced oxygen consumption, heart rate and core temperature to a similar extent as a moderate-intensity/lowvolume protocol (~35 min, 75% VȮ2max) suggesting that elevating the exercise intensity can reduce the duration required for heat adaptation 11 .…”

“…Minimal physiological adaptations were observed and it is worth noting that the thermal strain experienced (peak tympanic temperature = ~38°C) may not have been sufficient for adaptation 15 . Schmit et al 13 prescribed min of high-intensity HA based upon the participant's highest intensity training sessions and observed positive physiological adaptations to the heat but reported that they were offset by functional overreaching-related maladaptation. Short-duration, high-intensity HA is an attractive proposition for a time-short athlete; however, data regarding its efficacy are less attractive.…”

Sports Dietitians Australia Position Statement: Nutrition for Exercise in Hot Environments

“…Although heat acclimation is the most important intervention that athletes can undertake in preparation for competing in the heat (Racinais et al, 2015), the process of becoming acclimated can be challenging. Notably, athletes may need to adjust absolute training intensity and volume during heat training sessions compared with typical sessions undertaken in cooler conditions, or risk overreaching (Schmit et al, 2018) and experiencing lethargy and sleep disturbances (Taylor & Cotter, 2006). However, different approaches can be adopted based on available time and resources, as well as when the athletes will be arriving to the competition venue (Saunders et al, 2019).…”