Scientific Programme
Physiology & Nutrition
IS-PN05 - Effects of environmental heat stress on human performance and health across the lifecourse
Date: 03.07.2025, Time: 15:15 - 16:30, Session Room: Arco
Description
The effects of environmental heat stress on physiological functions (in particular, cardiovascular and muscle functions) and its associated consequences on sport performances have largely been investigated in young adults. Epidemiological data have indicated that children and older people are vulnerable to heat. Yet comparatively little research has examined physiological responses to environmental heat stress to fully elucidate its impact on performance and health in young and older populations. With temperatures rising across the globe and people of all ages exposed more commonly to hot and extreme temperatures, it is imperative that those promoting and delivering physical activity for health or exercise for performance understand differences in physiological responses/adaptations to environmental heat stress at various stages of the lifecourse. The aim of this symposium is therefore to present the latest research on the impact of environmental heat stress on the performance and health of young people (i.e. children and adolescents), young adults (focusing here on a widely understudied organ, i.e. the lungs) and older adults.
Chair(s)
Pascale Kippelen
Liverpool John Moores University, School of Sport and Exercise Sciences
United Kingdom
Speaker A
Julien Périard
University of Canberra, Research Institute for Sport and Exercise
Australia
Read CVECSS Rimini 2025: IS-PN05
Are children at a thermoregulatory disadvantage when exercising in the heat?
Global surface temperature is projected to increase by 3 to 5ºC by 2100, along with the frequency, severity, and duration of life-threatening heatwaves. These changes in climate will present a significant challenge to human thermoregulation, especially in those with greater vulnerability to extreme heat. Historically, children have been suggested to have an underdeveloped sweating response (i.e. lower maximal sweat rate) and different regional sweat patterns to adults, increasing their vulnerability to hyperthermia during exercise under heat stress, wherein sweat evaporation is the primary avenue for heat loss. Biological sex and maturation have also been suggested to affect sweating during exercise in response to physiological changes that occur during puberty in males (i.e. elevated testosterone), as well as a greater sweat gland output in adult males relative to females and prepubertal boys. However, isolating the independent effect of sex and/or maturation on the sudomotor response to exercise is complex due to differences in physical and physiological characteristics between individuals. Indeed, previous research that has reported differences in thermoregulation between sexes or with maturation is often confounded by body size, aerobic fitness and body composition differences between participants. Few studies have addressed these confounding factors when comparing the sweating response and change in core temperature between boys and girls, and children and adults, to determine if children are truly at greater risk of exertional heat illness. This presentation will therefore: 1) contextualise the current understanding of age and biological sex-related differences in the sudomotor response and change in core temperature (i.e. risk of hyperthermia) during exercise in the heat, 2) highlight the importance of biophysical factors when comparing independent groups, and 3) present recent research findings demonstrating that children did not have a lower sweating capacity and greater vulnerability to heat stress than adults. Following the presentation, the audience (e.g. sports scientists, sports medicine physicians, allied health professionals) will have a better appreciation of the confounding effects of morphological differences and metabolic heat production on thermoregulatory sweating in compensable and uncompensable conditions; understand how to investigate the change in core temperature, whole-body sweat rate and local sweat rate when comparing independent groups; learn that active adolescents demonstrate thermal and cardiovascular heat adaptations following summer that are commensurate to those of adults; and that children are not at a thermoregulatory disadvantage. Ultimately, the content of the presentation will allow for the audience to better discern the impact environmental heat stress on performance and health in young athletes.
Speaker B
Pascale Kippelen
Liverpool John Moores University, School of Sport and Exercise Sciences
United Kingdom
Read CVECSS Rimini 2025: IS-PN05
Blowing hot air – impact of environmental heat stress on respiratory health and performance
Changes in pulmonary function and ventilatory responses to exercise do occur when humans are exposed to environmental heat, yet airflow and ventilatory variables are under-reported in the literature and sport scientists often under-appreciate the consequences of heat-related respiratory changes. Further, coaches, support staff and athletes themselves often neglect the risk of bronchoconstriction associated with exercise in the heat (despite asthma/exercise-induced bronchoconstriction being the number one chronic medical condition in children and elite athletes). The aim of this presentation is to raise awareness within the sporting community of the significant changes happening to human lungs during prolonged exposure to environmental heat. In this presentation, we will first consider the influence of ambient temperature and humidity on the air conditioning process and exercise-induced bronchoconstriction. One of the primary functions of the lungs is to bring inhaled air to 37ºC and 100% humidity before it reaches the alveoli. Exposure to hot environmental conditions minimises conditioning requirements, thereby limiting thermal and osmotic stress within the airways. In children and young adults (incl. athletes) with asthma, breathing hot humid air (up to 37ºC) during exercise has therefore been shown to be beneficial, i.e. reducing risk and severity of osmotic/inflammatory-driven bronchoconstriction. However, when outdoor temperature rises above 39ºC, negative consequences may arise – i.e., those suffering from asthma are likely to develop (cholinergic-mediated) reflex bronchoconstriction. Beside bronchoconstriction, humans face another respiratory challenge during uncompensable heat stress – i.e. when core temperature rises, humans start spontaneously to hyperventilate. Through excess removal of carbon dioxide, hyperventilation disturbs acid-base balances and reduces cerebral perfusion and oxygenation. Whether hyperthermic-hyperventilation limits exercise performance remains however a matter of debate. Finally, during prolonged heat exposure, humans often get dehydrated. Under controlled laboratory conditions, we previously demonstrated that acute dehydration causes small airway impairment, and that rehydration reverses this impairment. We will therefore reflect on the biological plausibility of heat-induced dehydration to contribute to the high burden of morbidity and mortality from respiratory illnesses (particularly apparent in older adults) during heatwaves. Following this presentation, the audience will be able to: differentiate between hot and cold air-induced bronchoconstriction; consider implications of environmental conditions for exercise-induced bronchoconstriction treatment; recognise the multiple physiological consequences of heat-related respiratory changes; and better account for respiratory changes in the design of temperature-controlled laboratory-based experiments.
Speaker C
Craig Crandall
University of Texas Southwestern Medical Center, Internal Medicine
United States
Read CVECSS Rimini 2025: IS-PN05
Elevated heat risk in older humans – what can be done about it?
Cutaneous vasodilation and sweating are the primary mechanisms by which humans maintain body temperature within a relatively narrow range. However, should heat gain (e.g., exercise and/or environmental heat exposure) exceed the capacity of these heat loss mechanisms to dissipate the heat, body temperature will progressively rise, culminating in a heat-related injury or death. In parallel with the elevations in global temperatures, the number of individuals 65+ years is escalating. Thus, a greater number of older individuals will be exposed to progressively higher environmental temperatures, including more frequent and intense heatwaves, over the ensuing decades. Notably, older individuals are at a greater risk for heat-related injuries and death, likely due (in part) to age-related reductions in the aforementioned heat dissipating capabilities coupled with cardiovascular limitations. Given that background, the objectives of this presentation are to: 1) provide a comprehensive review on the effects of aging (65+ years) on thermoregulatory function and associated cardiovascular stress during extreme heat exposure, 2) provide insight on the mechanisms responsible for the greater heat-related risk in older individuals, and 3) present research findings on possible low-energy demand heat mitigation strategies to reduce the risk of heat-related injuries/death in older individuals exposed to extreme heat conditions. Upon the conclusion of the presentation the audience will have a greater understanding of how humans regulate body temperature during extreme heat conditions; will understand that in older adults impaired cutaneous vasodilation and sweating, coupled with cardiovascular limitations, are the primary mechanisms responsible for their greater risk for heat related injuries/death; and will learn about low-energy cooling approaches that can reduce excessive rises in core and skin temperatures for older adults facing extreme heat conditions. The provided information will be directed to an audience having a limited understanding of human thermoregulation and cardiovascular function.