Exercise-heat acclimation in young and older trained cyclists

Best, Stuart; Thompson, Martin W.; Caillaud, Corinne; Holvik, Liv; Fatseas, George; Tammam, Amr H.

doi:10.1016/j.jsams.2013.10.243

Cited by 30 publications

(34 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Several investigators have observed improved sudomotor function in older adults following heat acclimation or acclimatisation (Armstrong & Kenney, 1993; Best et al., 2014; Inoue et al., 1995; Wagner, Robinson, Tzankoff, & Marino, 1972). This also occurred in the current study, with local and whole‐body sweat rate, and the resulting evaporative heat loss, increasing in both groups following acclimatisation (Table 2), likely due to functional adaptations in the sweat gland itself (Inoue, Havenith, Kenney, Loomis, & Buskirk, 1999).…”

Section: Discussionmentioning

confidence: 99%

Evidence for age‐related differences in heat acclimatisation responsiveness

Notley

Meade

Akerman

et al. 2020

Experimental Physiology

View full text Add to dashboard Cite

New Findings What is the central question of this study?Repeated heat exposure during the summer months can enhance heat loss in humans (seasonal heat acclimatisation), but does the magnitude of that enhancement differ between young and older adults when assessed during passive heat exposure? What is the main finding and its importance?While seasonal heat acclimatisation enhanced evaporative heat loss (i.e. sweating) in both young and older adults, those improvements led to a greater reduction in body heat storage in older adults. These outcomes indicate that heat acclimatisation may confer greater thermoregulatory benefits with increasing age. Abstract Repeated heat exposure throughout summer can enhance heat loss in humans (seasonal heat acclimatisation), although the effect of ageing on those improvements remains unclear. We therefore sought to assess thermoregulatory function in young and older adults during environmental heat exposure prior to and following seasonal heat acclimatisation, hypothesizing that the magnitude of adaptation would be greater in older relative to young adults. To achieve this, 14 young (19–27 years) and 10 older adults (55–72 years), who resided in a temperate humid‐continental climate, completed a 3 h resting heat exposure (44°C, ∼30% relative humidity) in the winter–spring months as part of a larger investigation (pre‐acclimatisation), before being re‐evaluated using the same heat stress test following the summer months (post‐acclimatisation). Whole‐body dry and evaporative heat exchange, and metabolic rate were measured throughout using direct and indirect calorimetry (respectively), and used to quantify body heat storage (metabolic rate + dry heat gain – evaporative heat loss). Evaporative heat loss increased in both groups following acclimatisation, but those improvements led to a decrease in body heat storage in older (mean difference (95% CI); 213 (295, 131) kJ; P < 0.001), but not young adults (−25 (−94, 44) kJ; P = 0.458). Thus, body heat storage was greater in older compared to young adults before (222 (123, 314) kJ; P < 0.001), but not following acclimatisation (34 (−55, 123) kJ; P = 0.433). Although there is a need for larger and more controlled confirmatory studies, our findings indicate that seasonal heat acclimatisation may induce greater thermoregulatory adaptation in older compared to young adults.

show abstract

Section: Discussionmentioning

confidence: 99%

Evidence for age‐related differences in heat acclimatisation responsiveness

Notley

Meade

Akerman

et al. 2020

Experimental Physiology

View full text Add to dashboard Cite

show abstract

“…In addition, older adults are often less physically fit and have more illnesses and disabilities what makes them also more susceptible to heat-related morbidity and mortality (Koppe et al, 2004). However, older adults are able to acclimatize to the heat (Inoue et al, 1999;Best et al, 2014) when a sufficient number of days for adaptation is allowed (Daanen and Herweijer, 2015). Furthermore, they may be more resilient to heat in hot cities than in colder cities (Worfolk, 2000).…”

Section: Introductionmentioning

confidence: 99%

Long Term Adaptation to Heat Stress: Shifts in the Minimum Mortality Temperature in the Netherlands

et al. 2020

View full text Add to dashboard Cite

It is essentially unknown how humans adapt or will adapt to heat stress caused by climate change over a long-term interval. A possible indicator of adaptation may be the minimum mortality temperature (MMT), which is defined as the mean daily temperature at which the lowest mortality occurs. Another possible indicator may be the heat sensitivity, i.e., the percentage change in mortality per 1 • C above the MMT threshold, or heat attributable fraction (AF), i.e., the percentage relative excess mortality above MMT. We estimated MMT and heat sensitivity/AF over a period of 23 years for older adults (≥65 years) in the Netherlands using three commonly used methods. These methods are segmented Poisson regression (SEG), constrained segmented distributed lag models (CSDL), and distributed lag non-linear models (DLNM). The mean ambient temperature increased by 0.03 • C/year over the 23 year period. The calculated mean MMT over the 23-year period differed considerably between methods [16.4 ± 1.2 • C (SE) (SEG), 18.9 ± 0.5 • C (CSDL), and 15.3 ± 0.4 • C DLNM]. MMT increased during the observed period according to CSDL (0.11 ± 0.05 • C/year) and DLNM (0.15 ± 0.02 • C/year), but not with SEG. The heat sensitivity, however, decreased for the latter method (0.06%/ • C/year) and did not change for CSDL. Heat AF was calculated for the DLNM method and decreased with 0.07%/year. Based on these results we conclude that the susceptibility of humans to heat decreases over time, regardless which method was used, because human adaptation is shown by either an increase in MMT (CSDL and DLNM) or a decrease in heat sensitivity for unchanged MMT (SEG). Future studies should focus on what factors (e.g., physiological, behavioral, technological, or infrastructural adaptations) influence human adaptation the most, so it can be promoted through adaptation policies. Furthermore, future studies should keep in mind that the employed method influences the calculated MMT, which hampers comparability between studies.

show abstract

“…Furthermore, the metabolic heat produced by the exercising legs may increase core temperature due to the connective transfer (González-Alonso et al, 1999). In this sense, reduced heat exchange during exercise could lead to a reduction in performance and an increase in the risk of exertional heat stroke (Best et al, 2014;Nybo, 2010).…”

Section: Introductionmentioning

confidence: 99%