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Life in space is completely void of physical and environmental stress. It is well known that living things need regular physical stress (e.g. exercise) to remain strong, functional and healthy. More and more research is showing that regular environmental stress, for example heat and hypoxia, can further improve physical health. Astronauts aboard the international space station (ISS) exercise for 1-2 hours every day to avoid physical deconditioning that would otherwise cause them to age rapidly in space. Although physical exercise is very effective in remedying this deconditioning, today's astronauts still have physiological changes that indicate accelerated aging. This is a cause for concern given NASA's priority to travel to mars within the next decade; a mission that will require at least double the duration in space for our astronauts. The investigators think that the complete absence of environmental stress, i.e., heat, may be contributing to the accelerated aging that occurs during spaceflight. Our study will assess the health effects of adding heat stress to exercise that could be performed in space by astronauts. The goal is to inform best practice for astronauts to avoid physical deconditioning during long-duration spaceflight. This information will also be relevant to life on earth as spaceflight is a model of inactivity here on earth. Therefore, the potential benefits of adding heat stress will likely translate to life in space and on earth.
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.
Patients with autonomic failure are characterized by disabling orthostatic hypotension (low blood pressure on standing), and at least half of them also have high blood pressure while lying down (supine hypertension). Exposure to heat, such as in hot environments, often worsens their orthostatic hypotension. The causes of this are not fully understood. The purpose of this study is to evaluate whether applying local heat over the abdomen of patients with autonomic failure and supine hypertension during the night would decrease their nocturnal high blood pressure while lying down. This will help us better understand the mechanisms underlying this phenomenon, and may be of use in the treatment of supine hypertension.
This study will test the hypothesis that the drugs propranolol and metoprolol will result in greater increases in core body temperature during 3 hours of extreme heat exposure in older adults.
Extreme heat causes a disproportionate number of hospitalizations and deaths in older adults relative to any other age group. Importantly, many hospitalizations and deaths are primarily due to cardiovascular events such as myocardial infarction. Previous data indicate that older adults have attenuated skin blood flow and sweating responses when exposed to heat, resulting greater increase in core body temperature. Despite these observations, relatively little is known about the risk for myocardial ischemia potentially contributing to the aforementioned higher morbidity and mortality in older adults during heat waves. The broad objective of this work is to determine the impact of ambient heat exposure on myocardial blood flow and flow reserve in young and older adults. Aim 1 will test the hypothesis that older adults exhibit attenuated myocardial flow reserve compared to young adults during heat stress. Aim 2 will determine if the percent of maximal myocardial flow reserve (assess via vasodilator stress) during heat exposure is higher in older adults compared to young adults. The expected outcome from this body of work will improve our understanding of the consequences of aging on cardiovascular responses to ambient heat stress.
This clinical trial aims to determine whether heat stress alters 24-hour breast milk production and composition following an acute bout of exercise in the heat among lactating women. The main questions are: 1. To ascertain whether heat stress alters 24-hour breast milk production following acute exercise in the heat among lactating women. We hypothesize that breast milk production will decrease to a greater extent following acute exercise in the heat compared to acute exercise with no heat stress. Lactating mothers will complete an acute exercise bout at 40% of their peak oxygen consumption (VO2peak) for 60 mins in a hot (36 °C, 40% relative humidity) and thermoneutral environment (20 °C, 20% relative humidity). Participants will record their total breast milk production in a 24-hour period using an infant scale. 2. to discover whether heat stress impacts the energy composition of breast milk following acute exercise in the heat among lactating women. We hypothesize that energy density will decrease to a greater extent following acute exercise in the heat compared to acute exercise with no heat stress. Participants will use a manual expression breast pump to collect 10 mL of breast milk from each breast immediately and 24 hours post-exercise. Energy density (lactose, protein, and lipid content) will be assessed via enzyme-linked immunosorbent assays. Participants will complete the following visits: 1) initial consent visit 2) baseline testing; 3) acute exercise in the hot condition (HOT; 36C, 40% relative humidity), and 4) acute exercise in the temperate, thermoneutral condition (TEMP; 20C, 20% relative humidity). The baseline testing day will measure participant anthropometrics including height, weight, and body composition measured by a DEXA scan. For both experimental trials, participants will be asked to walk on a treadmill at based on their metabolic heat production (8W/kg) for 60 minutes. Heart rate (HR), mean skin temperature (Tsk), core temperature (Tcore), sweat loss (SL), and fluid intake will be measured throughout the exercise protocol. Breast milk composition will be measured through milk expression using a manual expression breast pump immediately and 24 hours post-exercise. Participants will log their breast milk production for 24 hours following the exercise using an infant scale to measure their infants before and after each feed.
The investigators are assessing how seasonal changes affect kidney function biomarkers in post-menopausal women, an understudied group. While heat stress can reduce kidney function, previous research has not accounted for physical activity, diet, hydration, or sun exposure.
The purpose of this study is to determine if, compared to non-depressed adults, differences exist in skin blood flow and sweating responses to passive heat stress in adults with clinically diagnosed depression, those with depression who are prescribed and taking SSRIs and those with depression who are prescribed and taking SNRIs.
The frequency and severity of heat waves has increased in the last decades. Older adults (over 65 years) have impaired responses to heat stress making them at increased risk for adverse events. Previous heat waves report that women over 65 experience worse health outcomes than any other age group and age matched men. Aging and reproductive hormones, specifically estrogen, independently alter responses to heat stress. However, the combined effects of low estrogen following menopause and aging on the response to heat stress are unknown. In this study, the investigators will identify the role of estrogen in pre and post menopausal women on thermoregulatory responses to heat stress.