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.

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.

Air speed and direction affect metabolic and thermoregulatory responses during walking and running in a temperate environment.

Revisiting classical experiments on the impact of air resistance on metabolic rate, we aimed to overcome limitations of previous research, notably: low participant numbers ( = 1-3), highly turbulent wind, and confounding effects of rising body temperature. In a custom-built wind tunnel with reduced turbulence, 14 participants (8 males, 6 females) walked (5 km·h) and ran on a treadmill (70%V̇o) at 0, 2, 4, and 6 m·s headwind or tailwind in a counterbalanced design, with rest breaks between each exposure to avoid rises in body core temperature. Oxygen consumption (V̇o) exhibited strong linear relationships versus wind direction, dynamic pressure, and air speed squared (V), lower in magnitude for headwind than tailwind.

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.

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.

Retrofitting passive cooling strategies to combat heat stress in the face of climate change: A case study of a ready-made garment factory in Dhaka, Bangladesh.

The ready-made garment industry is critical to the Bangladesh economy. There is an urgent need to improve current working conditions and build capacity for heat mitigation as conditions worsen due to climate change. We modelled a typical, mid-sized, non-air-conditioned factory in Bangladesh and simulated how the indoor thermal environment is altered by four rooftop retrofits (1.

Human scalp hair as a thermoregulatory adaptation.

Humans are unique among mammals in having a functionally naked body with a hair-covered scalp. Scalp hair is exceptionally variable across populations within . Neither the function of human scalp hair nor the consequences of variation in its morphology have been studied within an evolutionary framework.

Optimal low-cost cooling strategies for infant strollers during hot weather.

The current study aimed to identity the optimal low-cost stroller cooling strategies for use in hot and moderately humid summer weather. A commercially available stroller was instrumented to assess the key parameters of the thermal environment. The cooling efficacy of eight different stroller configurations was examined in a counterbalanced order across 16 hot summer days (air temperature () = 33.

Quantifying the impact of heat on human physical work capacity; part IV: interactions between work duration and heat stress severity.

High workplace temperatures negatively impact physical work capacity (PWC). Although PWC loss models with heat based on 1-h exposures are available, it is unclear if further adjustments are required to accommodate repeated work/rest cycles over the course of a full work shift. Therefore, we examined the impact of heat stress exposure on human PWC during a simulated work shift consisting of six 1-h work-rest cycles.

Breaking Sitting Time with Physical Activity Increases Energy Expenditure but Does Not Alter Postprandial Metabolism in Girls.

Purpose: Young people spend a substantial proportion of their time at school sedentary; therefore, this setting represents an important target for interventions aimed at displacing sedentary time with physical activity. This study aimed to examine the postprandial metabolic effects of breaking sedentary time by accumulating walking and repeated bouts of nonambulatory standing during simulated school days in inactive adolescent girls.

Methods: Seventeen girls (mean ± SD = 12.

Influence of sex and biological maturation on the sudomotor response to exercise-heat stress: are girls disadvantaged?

Both adult females and children have been reported to have a lower sweating capacity and thus reduced evaporative heat loss potential that may increase their susceptibility to exertional hyperthermia in the heat. Compared with males, females have a lower maximal sweat rate and thus a theoretically lower maximum skin wettedness due to a lower sweat output per gland. Similarly, children have been suggested to be disadvantaged in high ambient temperatures due to a lower sweat production and therefore reduced evaporative capacity, despite modifications of heat transfer due to physical attributes and possible evaporative efficiency.

Seasonal Heat Acclimatisation in Healthy Adults: A Systematic Review.

Background: Physiological heat adaptations can be induced following various protocols that use either artificially controlled (i.e. acclimation) or naturally occurring (i.

Quantifying the impact of heat on human physical work capacity; part II: the observed interaction of air velocity with temperature, humidity, sweat rate, and clothing is not captured by most heat stress indices.

Increasing air movement can alleviate or exacerbate occupational heat strain, but the impact is not well defined across a wide range of hot environments, with different clothing levels. Therefore, we combined a large empirical study with a physical model of human heat transfer to determine the climates where increased air movement (with electric fans) provides effective body cooling. The model allowed us to generate practical advice using a high-resolution matrix of temperature and humidity.

Quantifying the impact of heat on human physical work capacity; part III: the impact of solar radiation varies with air temperature, humidity, and clothing coverage.

Heat stress decreases human physical work capacity (PWC), but the extent to which solar radiation (SOLAR) compounds this response is not well understood. This study empirically quantified how SOLAR impacts PWC in the heat, considering wide, but controlled, variations in air temperature, humidity, and clothing coverage. We also provide correction equations so PWC can be quantified outdoors using heat stress indices that do not ordinarily account for SOLAR (including the Heat Stress Index, Humidex, and Wet-Bulb Temperature).

Body mapping of sweating patterns of pre-pubertal children during intermittent exercise in a warm environment.

Purpose: To determine sweating responses of pre-pubertal children during intermittent exercise in a warm environment and create whole-body maps of regional sweat rate (RSRs) distribution across the body.

Methods: Thirteen pre-pubertal children; six girls and seven boys (8.1 ± 0.

Caffeine alters thermoregulatory responses to exercise in the heat only in caffeine-habituated individuals: a double-blind placebo-controlled trial.

To assess the impact of acute caffeine ingestion on thermoregulatory responses during steady-state exercise under moderate heat stress conditions in caffeine-habituated and nonhabituated individuals. Twenty-eight participants [14 habituated (HAB) (4 females) and 14 nonhabituated (NHAB) (6 females)] cycled at a fixed metabolic heat production (7 W·kg) for 60 min on two separate occasions 1 h after ingesting ) 5 mg·kg caffeine (CAF) or ) 5 mg·kg placebo (PLA), in a double-blinded, randomized, and counterbalanced order. Environmental conditions were 30.

Thermoregulation During Pregnancy: a Controlled Trial Investigating the Risk of Maternal Hyperthermia During Exercise in the Heat.

Objectives: Despite the well-established benefits of exercise, pregnant women are discouraged from physical activity in hot/humid conditions to avoid hyperthermia (core temperature (T) ≥ 39.0 °C). Recent epidemiological evidence also demonstrates greater risk of negative birth outcomes following heat exposure during pregnancy, possibly due to thermoregulatory impairments.

Aerobic fitness as a parameter of importance for labour loss in the heat.

Objectives: To derive an empirical model for the impact of aerobic fitness (maximal oxygen consumption; V̇O in mL∙kg∙min) on physical work capacity (PWC) in the heat.

Design: Prospective, repeated measures.

Methods: Total work completed during 1 h of treadmill walking at a fixed heart rate of 130 b∙min was assessed in 19 young adult males across a variety of warm and hot climate types, characterised by wet-bulb globe temperatures (WBGT) ranging from 12 to 40 °C.

An advanced empirical model for quantifying the impact of heat and climate change on human physical work capacity.

Occupational heat stress directly hampers physical work capacity (PWC), with large economic consequences for industries and regions vulnerable to global warming. Accurately quantifying PWC is essential for forecasting impacts of different climate change scenarios, but the current state of knowledge is limited, leading to potential underestimations in mild heat, and overestimations in extreme heat. We therefore developed advanced empirical equations for PWC based on 338 work sessions in climatic chambers (low air movement, no solar radiation) spanning mild to extreme heat stress.

Electric fans: A potential stay-at-home cooling strategy during the COVID-19 pandemic this summer?

Current public health guidance designed to protect individuals against extreme heat and the ongoing COVID-19 pandemic is seemingly discordant, yet during the northern hemisphere summer, we are faced with the imminent threat of their simultaneous existence. Here we examine the environmental limits of electric fan-use in the context of the United States summer as a potential stay-at-home cooling strategy that aligns with existing efforts to mitigate the spread of SARS-COV-2.

Short Sprints Accumulated at School Modulate Postprandial Metabolism in Boys.

Introduction: This study examined the efficacy of maximal sprint running accumulated during a typical school day to modulate postprandial metabolism in adolescent boys.

Methods: Nineteen adolescent boys completed three 2-d experimental conditions: a standard-practice control (CON), an accumulated in-school sprint running (ACC), and a single block of afterschool sprint running (BLO). On day 1, a fasting capillary blood sample was taken at 0735 h in the school.

Effects of a 12-Week Exercise Intervention on Subsequent Compensatory Behaviors in Adolescent Girls: An Exploratory Study.

Purpose: Chronic exercise programs can induce adaptive compensatory behavioral responses through increased energy intake (EI) and/or decreased free-living physical activity in adults. These responses can negate the benefits of an exercise-induced energy deficit; however, it is unclear whether young people experience similar responses. This study examined whether exercise-induced compensation occurs in adolescent girls.