Thermoregulation and dehydration in children and youth exercising in extreme heat compared with adults.

Objective: To compare hyperthermia and physiological dehydration risk during exercise heat stress between children of different ages and adults and evaluate an existing adult sweat rate calculator in children.

Methods: 68 fit and recreationally active children aged 10-16 years (31 girls), and 24 adults aged 18-40 years (11 females) completed three separate 45 min treadmill walking/running trials at different intensities on different days at 30°C, 40% relative humidity (RH) (WARM) or 40°C, 30% RH (HOT). Exposures were randomised to elicit intensities scaled to (1) fitness, (2) mass and (3) surface area.

Influence of Exercise Heat Acclimation Protocol Characteristics on Adaptation Kinetics: A Quantitative Review With Bayesian Meta-Regressions.

The integrative influence of heat acclimation (HA) protocol characteristics and approach on adaptation kinetics and exercise capacity/performance in the heat remains unclear. Bayesian multilevel regression models were used to estimate adaptations with the number of exposures, exposure duration, ambient temperature, water vapor pressure, and HA approach (e.g.

Mixed pre-cooling improves thermal strain but not running performance in female endurance athletes exercising in the heat across the menstrual cycle.

This study investigated the effect of mixed pre-cooling (cooling vest and ice-slurry) on thermal and cardiovascular strain and performance in unacclimatized females exercising in the heat during menstrual cycle (MC) Phase-1 (low estrogen and progesterone) and Phase-4 (moderate estrogen and high progesterone). In a randomized crossover design, 11 runners completed two trials in each MC Phase: mixed pre-cooling (wearing a cooling vest around the torso for 30 min and ingesting 7.5 g.

The Addition of Glycerol and Sodium Chloride to a Hyperhydration Protocol Does Not Improve Half-Marathon Time-Trial Performance in Trained Runners in Warm Conditions.

Purpose: We examined the effect of glycerol- and sodium-induced hyperhydration on a field-based half-marathon in warm conditions.

Methods: Endurance runners (N = 13) completed a 180-minute hyperhydration (HYP) and control (CON) protocol before a maximal-effort half-marathon time trial (∼24 °C wet-bulb globe temperature) in a randomized crossover order. HYP involved ingesting 25 mL·kg body mass (BM)-1 fluid with glycerol (1.

Elevated Humidity Impairs Evaporative Heat Loss and Self-Paced Exercise Performance in the Heat.

This study investigated the effects of absolute humidity on heat dissipation and subsequent thermal, cardiovascular, and performance responses during self-paced exercise in the heat. Twelve trained male cyclists performed a 700-kJ time trial in four different humidity conditions (Low: 1.6 kPa, Moderate: 2.

Efficacy of the FIFA cooling break heat policy during an intermittent treadmill football simulation in hot conditions in trained females.

Objectives: To investigate the efficacy of the current FIFA cooling break heat policy against alternative cooling configurations in attenuating physiological strain during a football simulation in the heat.

Design: Five randomised counterbalanced experimental trials in 40 °C and 41 % relative humidity (32 °C wet-bulb globe temperature).

Methods: Twelve females (age 25 ± 5 y, V̇O 51 ± 5 mL·kg·min) completed five 90-min football simulations with different cooling configurations: regular match without cooling breaks (REG), 3-min breaks without cooling (BRK), 3-min breaks with cooling (BRK: current FIFA policy; chilled fluid and ice towel across neck/shoulders), 5-min extended half-time without cooling breaks (ExtHT), and 5-min extended half-time with 3-min cooling breaks (ExtHT).

Evidence of seasonal heat acclimatisation in recreationally active adults during a mild summer.

Objectives: To assess the magnitude of seasonal heat acclimatisation in recreationally active adults and contextualise the process by documenting the factors that influence adaptations.

Design: Longitudinal, repeated measures design.

Methods: Seventeen (7 females) recreationally active adults (28 ± 8 yr, V̇O 54 ± 8 mL·kg·min) exercising outdoors a minimum of 5 h·wk completed a 45-min heat response test running at 60 % V̇O in 40 °C and 30 % relative humidity prior to, midway through, and following summer.

Influence of acute heat mitigation strategies on core temperature, heart rate and aerobic performance in females: A systematic literature review.

This review examined the effect of acute heat mitigation strategies on physiological strain and exercise performance in females exercising in the heat. Three databases were searched for original research with an acute heat mitigation (intervention) and control strategy in active females and reporting core temperature, heart rate and/or aerobic exercise performance/capacity with ≥ 24°C wet bulb globe temperature. Hedges' effect sizes were calculated to evaluate outcomes.

Thermal and cardiovascular heat adaptations in active adolescents following summer.

This study aimed to investigate seasonal heat acclimatization in active adolescents following summer. Fifteen (5 females) active adolescents (14.6 ± 1.

Efficacy of the FIFA cooling break heat policy during an intermittent treadmill football simulation in hot conditions in trained males.

Objective: To evaluate the efficacy of the Fédération Internationale de Football Association (FIFA) cooling break policy against alternative cooling configurations in attenuating thermal strain during simulated football in the heat.

Methods: 12 males (age: 27±6 years, V̇O: 61±7 mL/kg/min) completed five 90 min intermittent treadmill football match simulations in 40°C and 41% relative humidity (32°C wet-bulb globe temperature) with different cooling configurations: regular match without cooling breaks (REG), 3 min breaks without cooling (BRK), 3 min breaks with cooling (BRK: current FIFA policy; chilled fluid ingestion and ice towel across neck and shoulders), 5 min extended half-time without cooling breaks (ExtHT) and 3 min cooling breaks with 5 min ExtHT (ExtHT). Rectal temperature (T), heart rate, whole-body sweat rate (WBSR) and rating of perceived exertion (RPE) were recorded.

Biological sex does not independently influence core temperature change and sweating of children exercising in uncompensable heat stress.

The purpose of this study was to investigate the influence of biological sex, independent of differences in aerobic fitness and body fatness, on the change in gastrointestinal temperature (ΔT) and whole body sweat rate (WBSR) of children exercising under uncompensable heat stress. Seventeen boys (means ± SD; 13.7 ± 1.

Reliability and validity of the MX3 portable sweat sodium analyser during exercise in warm conditions.

Purpose: Accurately measuring sweat sodium concentration ([Na]) in the field is advantageous for coaches, scientists, and dieticians looking to tailor hydration strategies. The MX3 hydration testing system is a new portable analyser that uses pre-calibrated biosensors to measure sweat [Na]. This study aimed to assess the validity and reliability of the MX3 hydration testing system.

Combining Heat and Altitude Training to Enhance Temperate, Sea-Level Performance.

Background: Repeated exposure to heat (ie, plasma volume expansion) or altitude (ie, increase in total hemoglobin mass), in conjunction with exercise, induces hematological adaptations that enhance endurance performance in each respective environment. Recently, combining heat and altitude training has become increasingly common for athletes preparing to compete in temperate, sea-level conditions.

Purpose: To review the physiological adaptations to training interventions combining thermal and hypoxic stimuli and summarize the implications for temperate, sea-level performance.

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.

Influence of Biological Sex and Fitness on Core Temperature Change and Sweating in Children Exercising in Warm Conditions.

Purpose: This study aimed to investigate the associations of biological sex and aerobic fitness (i.e., V̇O 2peak ) on the change in gastrointestinal temperature (∆ Tgi ) and whole-body sweat rate (WBSR) of children exercising in warm conditions.

Performance Benefits of Pre- and Per-cooling on Self-paced Versus Constant Workload Exercise: A Systematic Review and Meta-analysis.

Background And Objective: Exercise in hot environments impairs endurance performance. Cooling interventions can attenuate the impact of heat stress on performance, but the influence of an exercise protocol on the magnitude of performance benefit remains unknown. This meta-analytical review compared the effects of pre- and per-cooling interventions on performance during self-paced and constant workload exercise in the heat.

Regular physical activity across the lifespan to build resilience against rising global temperatures.

Population aging, high prevalence of non-communicable diseases, physical inactivity, and rising global temperatures are some of the most pressing issues in public health of the current century. Such trends suggest that individuals increasingly less equipped to tolerate heat will be increasingly exposed to it, which from a public health perspective is alarming. Nonetheless, future impacts of extreme heat events will depend not only on the magnitude of climate change, but on our ability to adapt by becoming less sensitive and vulnerable.

The Impact of a Short-Term Ketogenic Low-Carbohydrate High-Fat Diet on Biomarkers of Intestinal Epithelial Integrity and Gastrointestinal Symptoms.

Endurance exercise can disturb intestinal epithelial integrity, leading to increased systemic indicators of cell injury, hyperpermeability, and pathogenic translocation. However, the interaction between exercise, diet, and gastrointestinal disturbance still warrants exploration. This study examined whether a 6-day dietary intervention influenced perturbations to intestinal epithelial disruption in response to a 25-km race walk.