View clinical trials related to Heat Stress.
Filter by:The investigators are studying the dangers that farmworkers face while working in the fields and at home. The investigators goals are: 1. Measure how much heat and chemicals farmworkers in Imperial County are exposed to. The investigators will ask the participants to wear a special belt under their clothes during work to measure heat. The investigators will also put two small temperature monitors in the participant's home for a day. The investigators will collect a urine sample to check hydration, and also measure the participants height, weight, blood pressure, and some blood markers for diseases using a simple finger-prick test. To measure chemicals, the investigators will give the participants a wristband to wear for a week and hang another in the participants home. The investigators will also collect dust from each participant's home with a vacuum. Then, the investigators will analyze everything at San Diego State University. After collecting samples, a trained community health worker will ask the participants a few questions about their work, lifestyle, health symptoms, and any hazards they face. The investigators will meet the participants twice at their homes to distribute the tools which will later be collected. Once the tools are collected, the investigators will have the chance to follow up with the participants if they have any questions. 2. Provide help to lower heat and chemical exposure with the help of community health workers. 3. Measure heat and chemicals again using the same methods to see if the project made a difference. 4. Talk to participants about what they liked and how the investigators can make future projects better.
This study will examine the effect of heat stress on factors that influence musculoskeletal injury risk in firefighters. Participants will attend 4 data collection sessions. 1: informed consent, screening, and familiarization. 2: pre-tests (strength, balance, and movement quality). 3: heat stress (rapid or gradual) followed by post-tests (strength, balance, and movement quality). 4: heat stress (rapid or gradual) followed by post-tests.
As the ongoing progression of climate change exposes individuals to elevated temperatures and an escalating frequency of extreme heat events, the risk of more intense and prolonged heat waves raises significant concerns for public health, particularly among vulnerable populations. The physiological response to acute heat stress involves involuntary thermolytic reactions that may strain the cardiovascular system, especially in individuals with pre-existing vulnerabilities. Heat acclimation has been identified as a potential strategy to enhance thermoregulation and mitigate the adverse effects of heat stress. While existing research primarily focuses on athletes and military, this study aims to investigate the impact of a practical heat acclimation strategy, combining passive and active heat exposure, on thermophysiological, cardiovascular and metabolic parameters in healthy overweight adults. The study targets a population at increased risk for heat-related complications, seeking to provide realistic guidelines for broader application when a heat wave appears on the weather forecast.
With the increasing regularity and intensity of hot weather and heat waves, there is an urgent need to develop heat-alleviation strategies able to provide targeted protection for heat-vulnerable older adults. While air-conditioning provides the most effective protection from extreme heat, it is inaccessible for many individuals. Air-conditioning is also energy intensive, which can strain the electrical grid and, depending on the source of electricity generation, contribute to green house gas emissions. For these reasons, recent guidance has recommended the use of electric fans as a sustainable cooling alternative. While fans may increase sweat evaporation and heat loss in healthy, young adults, evidence supporting their use in older adults is scarce. Further, studies show that when environmental temperature exceeds skin temperature, fans are not effective and can even exacerbate hyperthermia in older adults. While older adults only account for ~13% of the population, they account for ~40% off all hospitalizations. In the context of sustainable cooling interventions, this is of particular importance given that many hospitals and long-term care homes do not have air-conditioning and rely on ceiling fans to enhance sweat evaporation while participants are bed-resting. While recent biophysical modelling has suggested that pedestal fans likely provide a clinically meaningful cooling effect (proposed to be ≥0.3°C) in temperatures below ~34°C in older adults, the efficacy of ceiling fans in mitigating heat strain in these conditions is currently unknown. To address these knowledge gaps, this randomized crossover trial will evaluate body core temperature, cardiovascular strain, orthostatic intolerance, dehydration, and thermal comfort in adults aged 65-85 years exposed for 8-hours to conditions experienced during indoor overheating occurring during a heat wave in a temperate continental climate (31°C, 45% relative humidity). Each participant will complete two randomized exposures that will differ only in the airflow generated by a ceiling fan: no airflow (control) or standard airflow. Participants will remain in a supine position for the duration of the 8-hour exposure period, except for during hour 7 when they will complete a series of cardiovascular autonomic response tests.
Three male and three female semi-professional athletes, ranging in age from 22 to 27, participated in a study that was done at Lund University in Sweden to examine their physiological responses. The temperature and relative humidity were adjusted at 40 degrees Celsius for hot, dry conditions and 31 degrees Celsius for hot, wet conditions, respectively. The participants were instructed to engage in physical activity on a treadmill within the chamber for 70 minutes, or until participants were able to continue their exercise without difficulty within the allotted period. Participants were instructed to walk (5 kph) and run (8 kph). Participants pulse rate, breathing rate, oxygen consumption, and subjective reactions were all recorded. On the basis of the Wet Bulb Globe Temperature (WBGT), a heat stress index, the American College of Sports Medicine has made certain suggestions. The technique used to determine the temperature on a Celsius scale took into account the influences of relative humidity, air temperature, wind, and direct sunlight radiation. The American College of Sports Medicine advises delaying athletic competition when the WBGT is above 28 degrees. In the climate control chamber, the trials were carried out in high-risk circumstances (28 degrees Celsius WBGT). According to the study's findings, exercise is influenced by weather, and as air temperature rises, so do the intensity of exertion and thermal feeling.
The global populace is at growing risk of heat-related illness due to climate change and accompanying increases in the intensity and regularity of extremely hot temperatures. In heat-exposed persons, heat gain from the environment and metabolism initially exceeds the rate of heat dissipation from the skin. Heat is stored in the body, causing core and skin temperatures to rise, which in turn triggers autonomically mediated elevations in cutaneous blood flow and sweating to facilitate heat loss. If conditions are compensable, heat loss increases until it balances total heat gain. At this point, the rate of heat storage falls to zero (i.e., heat balance is achieved) and body temperature stabilizes, albeit at a level elevated from thermoneutral conditions. If, however, the maximal achievable rate of heat dissipation is insufficient to offset heat gain, conditions are uncompensable, and prolonged exposure will cause a continual rise in core temperature that can compromise health if left unchecked. The environmental limits of compensability (i.e., the temperatures/humidities above which heat balance can not be maintained) are therefore an important determinant of survival during prolonged heat exposure. Evaluating this limit and how it can be modified (e.g., by behavior or individual factors like age or sex) is an increasingly important and active field of study. Contemporary evaluations of the environmental limits of compensability utilize "ramping protocols" in which participants are exposed to increasing levels of temperature or humidity (in 5-10 min stages) while core temperature is monitored. It is generally observed that core temperature is relatively stable (or rises slightly) in the early stages of exposure but undergoes an abrupt and rapid increase as heat stress becomes more severe. The conditions (e.g., wet-bulb temperature or wet-bulb globe temperature) at this "inflection point" are taken as the limits of compensability. That is, it is assumed that inflection corresponds to the demarcation point, below which core temperature would remain stable for prolonged periods (theoretically indefinitely if hydration is maintained) but above which heat loss is insufficient to offset heat gain, causing core temperature to rise continuously. Despite the increasing use of these protocols, no study has clearly demonstrated their validity for identifying the environmental limits of compensability. The goal of this project is therefore to assess the validity of ramping protocols for determining the ambient conditions above which thermal compensation is not possible. Enrolled participants will complete four experimental trials in a climate-controlled chamber: one ramping protocol followed by three randomized fixed-condition exposures. In the ramping protocol, participants will rest in 42°C with 28% relative humidity (RH) for 70 min, after which RH will be increased 3% every 10 min until 70% RH is achieved. The core (esophageal) temperature inflection point will be determined. For the fixed-condition exposures, participants will rest in i) 42°C with RH ~5% below their individual inflection point (below-inflection condition), ii) 42°C with RH ~5% above their individual inflection point (above-inflection condition), and iii) 26°C with 45% RH (control condition). Comparing the rate of change in esophageal temperature between each fixed-condition exposure will provide important insight into the validity of ramping protocols for identifying the limits of compensability.
Military personnel are called upon to serve in hot, dry or humid climates, which places great demands on their ability to tolerate heat. Induced heat stress can impair performance and lead to pathologies. Faced with the challenges of global warming, this issue is becoming increasingly important in the practice of sport. While hyperthermia is known to impair endurance performance, the underlying thermophysiological responses and regulatory mechanisms during prolonged exercise remain poorly understood. The effects of hyperthermia on mental performance raise questions about the degradation of interoceptive capacities and the deleterious impact on behavioral regulation, an important component of thermal risk management in ultra-endurance exercise. What's more, despite the muscular and hydromineral consequences (rhabdomyolysis, renal failure, dehydration) of prolonged exercise, few data are available on recovery kinetics. A better understanding of the factors conditioning recovery quality could help limit the deleterious consequences of ultra-endurance exercise.
Aging is associated with impairments in heat loss responses of skin blood flow and sweating leading to reductions in whole-body heat loss. Consequently, older adults store more body heat and experience greater elevations in core temperature during heat exposure at rest and during exercise. This maladaptive response occurs in adults as young as 40 years of age. Recently, heat acclimation associated with repeated bouts of exercise in the heat performed over 7 successive days has been shown to enhance whole-body heat loss in older adults, leading to a reduction in body heat storage. However, performing exercise in the heat may not be well tolerated or feasible for many older adults. Passive heat acclimation, such as the use of warm-water immersion may be an effective, alternative method to enhance heat-loss capacity in older adults. Thus, the following study aims to assess the effectiveness of a 7-day warm-water immersion (~40°C) protocol in enhancing whole-body heat loss in older adults. Warm-water immersion will consist of a one-hour immersion in warm water with core temperature clamped at 38.5°C. Improvements in whole-body heat loss will be assessed during an incremental exercise protocol performed in dry heat (i.e., 40°C, ~15% relative humidity) prior to and following the 7-day passive heat acclimation protocol. The incremental exercise protocol will consist of three 30 minute exercise bouts performed at increasing fixed rates of metabolic heat production (i.e., 150, 200, and 250 W/m2), each separated by 15-minutes of recovery, with exception final recovery will be 1-hour in duration) performed in a direct calorimeter (a device that provides a precise measurement of the heat dissipated by the human body).
Epidemiological studies based on Danish registries have observed that Danish male firefighters have more cardiovascular disease, infertility diagnose and a trend to increased risk of cancer than other Danish employed males. Firefighting activities include a combination of stressors such as strenuous work under heat, smoke and soot known to be able to affect cardiovascular and reproductive health, with smoke and soot also being known to increase the risk of cancer. The training facilities of real-fire extinguishing exercises in Denmark operate using wood or natural gas fire, which will have differential gradients of smoke, soot and possibly heat. The investigators will use different training conditions to create gradients of the different stressors and investigate health effects thereof. With this approach, the investigators expect to be able to evaluate the individual contribution of the different stressors in markers of cardiovascular, cancer and reproductive health risk. The project will include approx. 35 young conscript participants on a firefighting course, followed in four sessions, three firefighting training sessions under different fire conditions (no fire, wood fire and gas fire) and one control scenario.
With the increasing regularity and intensity of hot weather and heat waves, there is an urgent need to develop heat-alleviation strategies able to provide targeted protection for heat-vulnerable older adults. While air-conditioning provides the most effective protection from extreme heat, it is inaccessible for many individuals. Air-conditioning is also energy intensive, which can strain the electrical grid and, depending on the source of electricity generation, contribute to increasing green house gas emissions. For these reasons, recent guidance has advocated the use of electric fans as a simple and sustainable alternative to air-conditioning. To date, however, only one study has assessed the efficacy of fan use in older adults and demonstrated that fans accelerate increases in body temperature and heart rate in a short-duration (~2 hours) resting exposure to 42°C with increasing ambient humidity from 30-70%. While subsequent modelling has suggested that fans can improve heat loss via sweat evaporation in healthy older adults at air temperatures up to 38°C, there is currently no empirical data to support these claims. Further, that work assumed older adults were seated in front of a pedestal fan generating an airflow of 3·5-4·5 m/s at the front of the body. This airflow cannot be attained by most marketed pedestal fans. Studies are therefore needed to evaluate the efficacy of fans for preventing hyperthermia and the associated physiological burden in older adults in air temperatures below 38°C and determine whether the cooling effect of fans, if any, is evident at lower rates of airflow. To address these knowledge gaps, this randomized crossover trial will evaluate body core temperature, cardiovascular strain, dehydration, and thermal comfort in adults aged 65-85 years exposed for 8 hours to conditions experienced during hot weather and heat waves in North America simulated using a climate chamber (36°C, 45% relative humidity). Each participant will complete three randomized exposures that will differ only in the airflow generated at the front of the body via an electric pedestal fan: no airflow (control), low airflow (~2 m/s), and high airflow (~4 m/s). While participants will spend most of the 8-hour exposure seated in front of the fan, they will also complete 4 x 10 min periods of 'activities of daily living' (~2-2.5 METS, light stepping) at ~2 hour intervals to more accurately reflect activity patterns in the home.