Efficacy of Isothermic Conditioning over Military-Based Heat Acclimatization and Interval Training in Tropical Native Males

The roles of ACE I/D and ACTN3 R577X gene variants in heat acclimation

Roles of genes in heat acclimation (HA, repeated exercise-heat exposures) had not been explored. ACE I/D and ACTN3 R577X genetic polymorphisms are closely associated with outstanding exercise performances. This study investigated whether the two polymorphisms influenced the response to HA. Fifty young Han nationality male subjects were selected and conducted HA for 2 weeks. Exercise indicators (5-km run, push-up and 100-m run) were tested and rest aural thermometry (RTau) was measured before and after HA. ACE gene was grouped by I homozygote and D carrier, and ACTN3 gene was grouped by R homozygote and X carrier. Results showed that there were no differences between groups in age, body mass index, exercise indicators and RTau before HA. After HA, RTau of ACE I homozygote was lower than that of D carrier [F (1, 48) = 9.12, p = 0.004, η = 0.40]. Compared with RTau before HA, that of I homozygote decreased after HA (Δ = -0.26 °C, 95 % CI -0.34-0.18, p < 0.001), while that of D carrier did not change. There was a ACE gene × HA interaction in RTau [F (1, 48) = 14.26, p < 0.001, η = 0.48]. No effect of ACTN3 gene on RTau was observed. For exercise indicators, there were no differences between groups after HA, and no gene × HA interactions were observed. There may be a strong interaction of ACE gene and HA in the change of rest core temperature. I homozygote may have an advantage on improving heat tolerance.

Quantifying Exercise Heat Acclimatisation in Athletes and Military Personnel: A Systematic Review and Meta-analysis

BACKGROUND

Athletes and military personnel are often expected to compete and work in hot and/or humid environments, where decrements in performance and an increased risk of exertional heat illness are prevalent. A physiological strategy for reducing the adverse effects of heat stress is to acclimatise to the heat.

OBJECTIVE

The aim of this systematic review was to quantify the effects of relocating to a hotter climate to undergo heat acclimatisation in athletes and military personnel.

ELIGIBILITY CRITERIA

Studies investigating the effects of heat acclimatisation in non-acclimatised athletes and military personnel via relocation to a hot climate for < 6 weeks were included.

DATA SOURCES

MEDLINE, SPORTDiscus, CINAHL Plus with Full Text and Scopus were searched from inception to June 2022.

RISK OF BIAS

A modified version of the McMaster critical review form was utilised independently by two authors to assess the risk of bias.

DATA SYNTHESIS

A Bayesian multi-level meta-analysis was conducted on five outcome measures, including resting core temperature and heart rate, the change in core temperature and heart rate during a heat response test and sweat rate. Wet-bulb globe temperature (WBGT), daily training duration and protocol length were used as predictor variables. Along with posterior means and 90% credible intervals (CrI), the probability of direction (Pd) was calculated.

RESULTS

Eighteen articles from twelve independent studies were included. Fourteen articles (nine studies) provided data for the meta-analyses. Whilst accounting for WBGT, daily training duration and protocol length, population estimates indicated a reduction in resting core temperature and heart rate of - 0.19 °C [90% CrI: - 0.41 to 0.05, Pd = 91%] and - 6 beats·min-1 [90% CrI: - 16 to 5, Pd = 83%], respectively. Furthermore, the rise in core temperature and heart rate during a heat response test were attenuated by - 0.24 °C [90% CrI: - 0.67 to 0.20, Pd = 85%] and - 7 beats·min-1 [90% CrI: - 18 to 4, Pd = 87%]. Changes in sweat rate were conflicting (0.01 L·h-1 [90% CrI: - 0.38 to 0.40, Pd = 53%]), primarily due to two studies demonstrating a reduction in sweat rate following heat acclimatisation.

CONCLUSIONS

Data from athletes and military personnel relocating to a hotter climate were consistent with a reduction in resting core temperature and heart rate, in addition to an attenuated rise in core temperature and heart rate during an exercise-based heat response test. An increase in sweat rate is also attainable, with the extent of these adaptations dependent on WBGT, daily training duration and protocol length.

PROSPERO REGISTRATION

CRD42022337761.

Exertional Heat Illness-From Identifying Heat Rash to Treating Heat Stroke

Heat-related illness commonly affects adolescent patients, especially as summer approaches and global temperature extremes worsen. Basic counseling on sunburn prevention can decrease the risk for future malignancies, and rapidly preventing, identifying, and treating heat stroke can prevent severe morbidity and mortality. This article will review the epidemiology of exertional heat-related illness and the variations in presentations and pathology, from heat rash and sunburn to heat exhaustion and heat stroke. By the end of this review clinicians should be able to identify and treat different heat-related illnesses in adolescents and potentially save a life. [Pediatr Ann. 2024;53(1):e17-e21.].

[Expert consensus on the prevention and treatment of heatstroke in children (2023)]

Due to the immature development of temperature regulation in the central nervous system, children have a weakened ability to regulate heat and are susceptible to heatstroke, which can lead to organ damage. Based on the evidence evaluation criteria of the Oxford Centre for Evidence-Based Medicine, this expert consensus group evaluated the current evidence on heatstroke in children, and formed this consensus through thorough discussion with the aim of providing reference for the prevention and treatment of heatstroke in children. This consensus includes classifications, pathogenesis, prevention measures, as well as pre-hospital and in-hospital treatment plans for heatstroke in children.