Search

Purpose: Cold water immersion (CWI) provides rapid cooling in events of exertional heat stroke. Optimal procedures for CWI in the field are not well established. This meta-analysis aimed to provide structured analysis of the effectiveness of CWI on the cooling rate in healthy adults subjected to exercise-induced hyperthermia., Methods: An electronic search (December 2014) was conducted using the PubMed and Web of Science. The mean difference of the cooling rate between CWI and passive recovery was calculated. Pooled analyses were based on a random-effects model. Sources of heterogeneity were identified through a mixed-effects model Q statistic. Inferential statistics aggregated the CWI cooling rate for extrapolation., Results: Nineteen studies qualified for inclusion. Results demonstrate CWI elicited a significant effect: mean difference, 0.03°C·min(-1); 95% confidence interval, 0.03-0.04°C·min(-1). A conservative, observed estimate of the CWI cooling rate was 0.08°C·min(-1) across various conditions. CWI cooled individuals twice as fast as passive recovery. Subgroup analyses revealed that cooling was more effective (Q test P < 0.10) when preimmersion core temperature ≥38.6°C, immersion water temperature ≤10°C, ambient temperature ≥20°C, immersion duration ≤10 min, and using torso plus limbs immersion. There is insufficient evidence of effect using forearms/hands CWI for rapid cooling: mean difference, 0.01°C·min(-1); 95% confidence interval, -0.01°C·min(-1) to 0.04°C·min(-1). A combined data summary, pertaining to 607 subjects from 29 relevant studies, was presented for referencing the weighted cooling rate and recovery time, aiming for practitioners to better plan emergency procedures., Conclusions: An optimal procedure for yielding high cooling rates is proposed. Using prompt vigorous CWI should be encouraged for treating exercise-induced hyperthermia whenever possible, using cold water temperature (approximately 10°C) and maximizing body surface contact (whole-body immersion).

This study examined the effects of dehydration on intermittent sprint performance and perceptual responses. Eight male collegiate baseball players completed intermittent sprints either dehydrated (DEHY) by 3% body mass or euhydrated (EU). Body mass was reduced through exercise in the heat with controlled fluid restriction occurring 1 day before the trial. Participants completed twenty-four 30-m sprints divided into 3 bouts of 8 sprints with 45 seconds of rest between each sprint and 3 minutes between each bout. Perceived recovery status (PRS) scale was recorded before the start of each trial. Heart rate (HR), ratings of perceived exertion (RPE) (0-10 OMNI scale), and perceived readiness (PR) scale were recorded after every sprint, and session RPE (SRPE) was recorded 20 minutes after completing the entire session. A 2 (condition) × 3 (bout of sprints) repeated-measures ANOVA revealed a significant main effect of condition on mean sprint time (p = 0.03), HR (p < 0.01), RPE (p = 0.01), and PR (p = 0.02). Post hoc tests showed significantly faster mean sprint times for EU vs. DEHY during the second (4.87 ± 0.29 vs. 5.03 ± 0.33 seconds; p = 0.01) and third bouts of sprints (4.91 ± 0.29 vs. 5.12 ± 0.44 seconds; p = 0.02). Heart rate was also significantly lower (p ≤ 0.05) for EU during the second and third bouts. Post hoc measures also showed significantly impaired (p ≤ 0.05) feelings of recovery (PRS) before exercise and increased (p ≤ 0.05) perceptual strain before each bout (PR) during the second and third bouts of repeated sprint work (i.e., RPE and PR) and after the total session (SRPE) in the DEHY condition. Dehydration impaired sprint performance, negatively altered perception of recovery status before exercise, and increased RPE and HR response.

Clothing targeting the exercise enthusiast has been advertised to keep individuals drier, cooler, and more comfortable during exercise in the heat. The marketing of such clothing has increased dramatically within the last decade. In hot environments, clothing acts as a barrier to thermal balance by inhibiting evaporative and convective cooling. Clothing construction, fit, and fabric are all critical influences on the amount of sweat absorbed from the skin and transported throughout the clothing. The majority of the research analyzing advertised synthetic fabrics has shown no difference in thermoregulation or clothing comfort while exercising in those fabrics in the heat compared to natural fabrics. The influence of clothing construction on thermal balance has received minimal research in regards to exercise. Further research is needed in this area, since it is poorly understood from ecologically valid human testing. Future research should also consider examining the effects of clothing characteristics on comfort during exercise and recovery. The incorporation of protocols that more closely mirror sporting and recreational activity lasting >60 min as well as simulated work-related protocols lasting >120 min is warranted.

Roux en Y gastric bypass (RYGB) surgery is currently the most effective therapy employed to treat obesity and its associated complications. In addition to weight loss and resolution of metabolic syndromes, such as diabetes, the RYGB procedure has been reported to increase alcohol consumption in humans. Using an outbred rodent model, we demonstrate that RYGB increases postsurgical ethanol consumption, that this effect cannot be explained solely by postsurgical weight loss and that it is independent of presurgical body weight or dietary composition. Altered ethanol metabolism and postsurgical shifts in release of ghrelin were also unable to account for changes in alcohol intake. Further investigation of the potential physiological factors underlying this behavioral effect identified altered patterns of gene expression in brain regions associated with reward following RYGB surgery. These findings have important clinical implications as they demonstrate that RYGB surgery leads directly to increased alcohol intake in otherwise alcohol nonpreferring rat and induces neurobiological changes in brain circuits that mediate a variety of appetitive behaviors.

Sex-specific variation in morphology (sexual dimorphism) is a prevalent phenomenon among animals, and both dietary intake and resource allocation strategies influence sexually dimorphic traits (e.g., body size or composition). However, we investigated whether assimilation efficiency (AE), an intermediate step between dietary intake and allocation, can also vary between the sexes. Specifically, we tested whether sex-based differences in AE can explain variation in phenotypic traits. We measured morphometric characteristics (i.e., body length, mass, condition, and musculature) and AE of total energy, crude protein, and crude fat in post-reproductive adult Children's pythons (which exhibit a limited female-biased sexual size dimorphism) fed both low and high dietary intakes. Meal size was negatively related to AE of energy. Notably, male snakes absorbed crude protein more efficiently and increased epaxial (dorsal) musculature faster than females, which demonstrates a link between AE and phenotype. However, females grew in body length faster but did not absorb any nutrient more efficiently than males. Although our results do not provide a direct link between AE and sexual size dimorphism, they demonstrate that sexual variation in nutrient absorption exists and can contribute to other types of sex-based differences in phenotype (i.e., sexual dimorphism in growth of musculature). Hence, testing the broader applicability of AE's role in sexually dimorphic traits among other species is warranted.

The proper maintenance of body weight and mood are two of the most prevalent health issues present in society today. Obese humans display higher levels of mood-related disorders and the causality of such an association is unknown. A common feature of obesity is the imbalance of regulatory hormones which normally act to maintain stable energy balance and body weight. The adiposity hormone leptin is one such signal elevated in obesity with the capacity to dampen feeding behavior through action on brain circuits which regulate appetite and metabolism. Recent evidence suggests that leptin may regulate motivation through its actions within brain reward circuitry. In addition, leptin signaling within central nervous system regions that regulate cognition and emotion elicits anti-depressant like effects. Together, these data indicate that leptin may regulate the decreased motivation and mood present in obesity and depression. This review describes the capacity of leptin to regulate motivation and depression through actions within brain circuits that modulate effort-based behavior and emotion, respectively.

Feeding for pleasure, or "non-homeostatic feeding", potentially contributes to the rapid development of obesity worldwide. Obesity is associated with an imbalance of regulatory hormones which normally act to maintain stable energy balance and body weight. The adiposity hormones insulin and leptin are two such signals elevated in obesity with the capacity to dampen feeding behavior through their action on hypothalamic circuits which regulate appetite and metabolism. Recent evidence suggests that both hormones achieve this degree of regulation by inhibiting the rewarding aspects of feeding behavior, perhaps by signaling within midbrain reward circuits. This review describes the capacity of both insulin and leptin to regulate reward-related behavior., (Published by Elsevier Ltd.)

Circulating angiotensin II (ANGII) elicits water intake and activates the hypothalamic-pituitary-adrenal (HPA) axis by stimulating angiotensin type 1 receptors (AT1Rs) within circumventricular organs. The subfornical organ (SFO) and the organum vasculosum of the lamina terminalis (OVLT) are circumventricular organs that express AT1Rs that bind blood-borne ANGII and stimulate integrative and effector regions of the brain. The goal of these studies was to determine the contribution of AT1Rs within the SFO and OVLT to the water intake and HPA response to increased circulating ANGII. Antisense oligonucleotides directed against the AT1R [AT1R antisense (AT1R AS)] were administered into the OVLT or SFO. Quantitative receptor autoradiography confirmed that AT1R AS decreased ANGII binding in the SFO and OVLT compared with the scrambled sequence control but did not affect AT1R binding in other nuclei. Subsequently, water intake, ACTH, and corticosterone (CORT) were assessed after administration of isoproterenol, a beta-adrenergic agonist that decreases blood pressure and elevates circulating ANGII. Delivery of AT1R AS into the SFO attenuated water intake, ACTH, and CORT after isoproterenol, whereas similar treatment in the OVLT had no effect. To determine the specificity of this blunted drinking and HPA response, the same parameters were measured after treatment with hypertonic saline, a stimulus that induces drinking independently of ANGII. Delivery of AT1R AS into the SFO or OVLT had no effect on water intake, ACTH, or CORT after hypertonic saline. The results imply that AT1R within the SFO mediate drinking and HPA responses to stimuli that increase circulating ANGII.