Nicotine exacerbates exertional heat strain in trained men: a randomized, placebo-controlled, double-blind study.

To determine whether using nicotine exacerbates exertional heat strain through an increased metabolic heat production (H) or decreased skin blood flow (SkBF), 10 nicotine-naïve trained males [37 ± 12 yr; peak oxygen consumption (V̇o): 66 ± 10 mL·min·kg] completed four trials at 20°C and 30°C following overnight transdermal nicotine (7 mg·24 h) and placebo use in a crossover, double-blind design. They cycled for 60 min (55% V̇o) followed by a time trial (∼75% V̇o) during which measures of gastrointestinal (T) and mean weighted skin ([Formula: see text]) temperatures, SkBF, H, and mean arterial pressure (MAP) were made. The difference in ΔT between nicotine and placebo trials was greater during 30°C (0.

Sleeping for One Week on a Temperature-Controlled Mattress Cover Improves Sleep and Cardiovascular Recovery.

Body temperature should be tightly regulated for optimal sleep. However, various extrinsic and intrinsic factors can alter body temperature during sleep. In a free-living study, we examined how sleep and cardiovascular health metrics were affected by sleeping for one week with (Pod ON) vs.

Comparisons of cell proliferation and cell death from tornaria larva to juvenile worm in the hemichordate Schizocardium californicum.

Background: There are a wide range of developmental strategies in animal phyla, but most insights into adult body plan formation come from direct-developing species. For indirect-developing species, there are distinct larval and adult body plans that are linked together by metamorphosis. Some outstanding questions in the development of indirect-developing organisms include the extent to which larval tissue undergoes cell death during the process of metamorphosis and when and where the tissue that will give rise to the adult originates.

Effects of heat acclimation on cardiac function in the intertidal mussel Mytilus californianus: can laboratory-based indices predict survival in the field?

Thermal performance curves are commonly used to investigate the effects of heat acclimation on thermal tolerance and physiological performance. However, recent work indicates that the metrics of these curves heavily depend on experimental design and may be poor predictors of animal survival during heat events in the field. In intertidal mussels, cardiac thermal performance (CTP) tests have been widely used as indicators of animals' acclimation or acclimatization state, providing two indices of thermal responses: critical temperature (Tcrit; the temperature above which heart rate abruptly declines) and flatline temperature (Tflat; the temperature where heart rate ceases).

Accuracy of Algorithm to Non-Invasively Predict Core Body Temperature Using the Kenzen Wearable Device.

With climate change increasing global temperatures, more workers are exposed to hotter ambient temperatures that exacerbate risk for heat injury and illness. Continuously monitoring core body temperature (T) can help workers avoid reaching unsafe T. However, continuous T measurements are currently cost-prohibitive or invasive for daily use.

Effect of breathing cooled air during cycling on physiology and performance in the heat.

Background: The aim of this study was to determine the physiological, perceptual, and exercise performance responses to breathing cooled air during and following exercise in the heat.

Methods: Twelve trained male cyclists (26±4 y; 180.5±5.

A single heat-stress bout induces rapid and prolonged heat acclimation in the California mussel, .

Climate change is not only causing steady increases in average global temperatures but also increasing the frequency with which extreme heating events occur. These extreme events may be pivotal in determining the ability of organisms to persist in their current habitats. Thus, it is important to understand how quickly an organism's heat tolerance can be gained and lost relative to the frequency with which extreme heating events occur in the field.

Mussel acclimatization to high, variable temperatures is lost slowly upon transfer to benign conditions.

Climate change is increasing the temperature variability animals face, and thermal acclimatization allows animals to adjust adaptively to this variability. Although the rate of heat acclimatization has received some study, little is known about how long these adaptive changes remain without continuing exposure to heat stress. This study explored the rate at which field acclimatization states are lost when temperature variability is minimized during constant submersion.

Establishing typical values for hemocyte mortality in individual California mussels, Mytilus californianus.

Hemocytes are immune cells in the hemolymph of invertebrates that play multiple roles in response to stressors; hemocyte mortality can thus serve as an indicator of overall animal health. However, previous research has often analyzed hemolymph samples pooled from several individuals, which precludes tracking individual responses to stressors over time. The ability to track individuals is important, however, because large inter-individual variation in response to stressors can confound the interpretation of pooled samples.

Impact of heating rate on cardiac thermal tolerance in the California mussel, .

Intertidal communities of wave-swept rocky shores have served as a powerful model system for experiments in ecology, and mussels (the dominant competitor for space in the mid-intertidal zone) play a central role in determining community structure in this physically stressful habitat. Consequently, the ability to account for mussels' physiological responses to thermal stress affects ecologists' capacity to predict the impacts of a warming climate on this ecosystem. Here, we examined the effect of heating rate on cardiac thermal tolerance in the ribbed mussel, , comparing populations from high and low sites in the intertidal zone where emersion duration leads to different mean daily heating rates.

The effect of passive heat stress on distress andself-control in male smokers and non-smokers.

In the current study, we tested the effects of core body temperature increases (e.g. heat stress) on affect, self-reported physical discomfort, and subsequent self-control in male smokers and nonsmokers using a novel passive heat stress paradigm, within a distress tolerance framework.

Obesity, but not hypohydration, mediates changes in mental task load during passive heating in females.

Background: The independent effects of hypohydration and hyperthermia on cognition and mood is unclear since the two stresses often confound each other. Further, it is unknown if obese individuals have the same impairments during hyperthermia and hypohydration that is often observed in non-obese individuals.

Methods: The current study was designed to assess the independent and combined effects of mild hypohydration and hyperthermia on cognition, mood, and mental task load in obese and non-obese females.

Effect of a Cooling Kit on Physiology and Performance Following Exercise in the Heat.

Context: Exercising in the heat leads to an increase in body temperature that can increase the risk of heat illness or cause detriments in exercise performance.

Objective: To examine a phase change heat emergency kit (HEK) on thermoregulatory and perceptual responses and subsequent exercise performance following exercise in the heat.

Design: Two randomized crossover trials that consisted of 30 minutes of exercise, 15 minutes of treatment (T), performance testing (5-10-5 pro-agility test and 1500-m run), and another 15 minutes of treatment (T) identical to T.

Hydration status influences the measurement of arterial stiffness.

Consensus guidelines have attempted to standardize the measurement and interpretation of pulse wave velocity (PWV); however, guidelines have not addressed whether hydration status affects PWV. Moreover, multiple studies have utilized heat stress to reduce arterial stiffness which may lead to dehydration. This study utilized two experiments to investigate the effects of dehydration on PWV at rest and during passive heat stress.

Effect of hypohydration on postsynaptic cutaneous vasodilation and sweating in healthy men.

Hypohydration decreases cutaneous vasodilation and sweating during heat stress, but it is unknown if these decrements are from postsynaptic (i.e., sweat gland/blood vessel) alterations.

Effects of obesity and mild hypohydration on local sweating and cutaneous vascular responses during passive heat stress in females.

The purpose of this study was to evaluate the effect of obesity and mild hypohydration on local sweating (LSR) and cutaneous vascular conductance (CVC) responses during passive heat stress in females. Thirteen obese (age, 24 ± 4 years; 45.4% ± 5.

Effects of mild hypohydration on cooling during cold-water immersion following exertional hyperthermia.

Purpose: We investigated the effects of mild hypohydration compared to euhydration on the cooling efficacy of cold-water immersion (CWI).

Methods: Fourteen participants (eight male, six female; age 26 ± 5 years; ht 1.77 ± 0.

Acute citrulline malate supplementation improves upper- and lower-body submaximal weightlifting exercise performance in resistance-trained females.

Purpose: Citrulline malate (CM) is a nonessential amino acid that increases exercise performance in males. However, based on physiological differences between genders, these results cannot be extrapolated to females. Therefore, the purpose of this investigation was to evaluate effects of acute CM supplementation on upper- and lower-body weightlifting performance in resistance-trained females.

No Change in 24-Hour Hydration Status Following a Moderate Increase in Fluid Consumption.

Purpose: To investigate changes in 24-hour hydration status when increasing fluid intake.

Methods: Thirty-five healthy males (age 23.8 ± 4.

Effects of 28-Day Beta-Alanine Supplementation on Isokinetic Exercise Performance and Body Composition in Female Masters Athletes.

Beta-alanine (BA) supplementation increases exercise performance due to increases in the intramuscular lactate buffer, carnosine. Females are more sensitive to these increases and results are further pronounced in trained individuals. Baseline intramuscular carnosine levels also naturally decrease with age; therefore, trained older females may experience augmented benefits from BA supplementation.

Effects of Acute Beta-Alanine Supplementation on Anaerobic Performance in Trained Female Cyclists.

Longitudinal beta-alanine (BA) supplementation can improve exercise performance in males through increases in carnosine; however, females experience greater relative increases in carnosine compared to males. This potentially allows females to benefit from acute BA doses; however, effects of an acute BA dose on performance in females remain unknown. The purpose of this investigation was to evaluate how an acute dose of 1.

Forearm cutaneous vascular and sudomotor responses to whole body passive heat stress in young smokers.

The purpose of this study was to compare smokers and nonsmokers' sudomotor and cutaneous vascular responses to whole body passive heat stress. Nine regularly smoking (SMK: 29 ± 9 yr; 10 ± 6 cigarettes/day) and 13 nonsmoking (N-SMK: 27 ± 8 yr) males were passively heated until core temperature (TC) increased 1.5°C from baseline.

Hydration status affects mood state and pain sensation during ultra-endurance cycling.

Laboratory-based studies indicate mild dehydration adversely affects mood. Although ultra-endurance events often result in mild to moderate dehydration, little research has evaluated whether the relationship between hydration status and mood state also exists in these arduous events. Therefore, the purpose of this study was to evaluate how hydration status affected mood state and perceptual measures during a 161 km ultra-endurance cycling event.

Hydration Status over 24-H Is Not Affected by Ingested Beverage Composition.

Objective: To investigate the 24-h hydration status of healthy, free-living, adult males when given various combinations of different beverage types.

Methods: Thirty-four healthy adult males participated in a randomized, repeated-measures design in which they consumed: water only (treatment A), water+cola (treatment B), water+diet cola (treatment C), or water+cola+diet cola+orange juice (treatment D) over a sedentary 24-h period across four weeks of testing. Volumes of fluid were split evenly between beverages within each treatment, and when accounting for food moisture content and metabolic water production, total fluid intake from all sources was equal to 35 ± 1 ml/kg body mass.

Increasing humidity affects thermoregulation during low-intensity exercise in women.

Introduction: Women increasingly occupy manual labor jobs. However, research examining women working under hot-humid conditions is lacking. Therefore, the purpose of our study was to assess how increasing relative humidity (RH) affects women's thermoregulation during low-intensity exercise characteristic of 8 h self-paced manual labor.