Effects of Heat Acclimation on Time Perception

Heat acclimation attenuates the increased sensations of fatigue reported during acute exercise-heat stress

“…Interestingly, the within-session change in fatigue scores during ODHA were lower compared to TDHA, with reductions during TDHA only found following session 10 (Table 3). Nonetheless, the sensations of fatigue were lower following MTHA when implementing ODHA, in agreement with previous literature [9,48], and during non-consecutive TDHA, although between-group differences remain in the time-scale for perceptual improvements. Therefore, whilst ODHA and TDHA induce comparable physiological adaptations and exercise performance improvements [24], distinct differences arise in time-scales for improved sensations of fatigue.…”

“…Nonetheless, whilst attenuated changes in perceived fatigue scores for session 10 were observed for both HA protocols, physiological signals from T re continued to be an indicator of perceived fatigue during TDHA. Our findings agree with chronic heat exposure data within an occupational setting [25], but contrast data from STHA [10] and MTHA studies [9], which indicated heat acclimated individuals were less affected by temperature modulation, resulting in lower perceived fatigue. In agreement with the sensory association hypothesis for T re [25] and disassociation of T re signals following STHA [10], an intriguing interpretation of our data indicates a potential sensory associated learning and/or training effect during HA, where mean T re was maintained yet larger sensations of fatigue were not observed.…”

“…This is in keeping with the contribution of skin temperature to TSS, reflecting the relative magnitude of perceived ambient temperature [53] and TC reflecting the perceptual indifference between T re and the environmental conditions [54,51]. Therefore, improvements in the sensations of fatigue are in part, likely explained by the repeated experience of exercise-heat stress [9], and conceivably, the induced physiological (i.e. reductions in resting T re and sweat setpoint, and augmented WBSL) and perceptual adaptations (i.e.…”

“…Additionally, a better understanding of the effects of acute heat stress on perceived fatigue is necessary, because HA interventions are commonly implemented alongside ongoing technical training and other physical preparation priorities. Previously, lower sensations of fatigue have been reported following four [10], seven [23], ten [9] and ten/eleven days of HA [22], alluding to a desirable negative relationship with the length of HA. However, in these experiments the HA method did not reflect the empirically recommended medium-to long-term isothermic model (e.g.…”

“…increased rectal temperature [T re ], heart rate [HR] and/or inflammatory/stress markers), which can further augment the magnitude of perceptual strain experienced [7,8]. For example, greater perceived fatigue has been found during exercise-heat stress (running at 60% of peak oxygen uptake [VȮ 2peak ] in 42°C, 18% relative humidity [RH]) compared to temperate conditions (22°C, 35% RH) [7,9]. Similarly, increased General and Physical Fatigue scores were reported whilst cycling at 2 W•kg −1 during the first of four sessions of exercise-heat stress (45°C, 30% RH), with reported symptoms of augmented lethargy and tiredness [10], which were correlated with an increased T re (~39.0°C).…”