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Exercise Heat

Shih-Sung Lin, Chien-Wu Lan, Hao-Yen Hsu, Sheng-Tao Chen
When exercising in a high-temperature environment, heat stroke can cause great harm to the human body. However, runners may ignore important physiological warnings and are not usually aware that a heat stroke is occurring. To solve this problem, this study evaluates a runner's risk of heat stroke injury by using a wearable heat stroke detection device (WHDD), which we developed previously. Furthermore, some filtering algorithms are designed to correct the physiological parameters acquired by the WHDD. To verify the effectiveness of the WHDD and investigate the features of these physiological parameters, several people were chosen to wear the WHDD while conducting the exercise experiment...
December 9, 2018: Sensors
Antonia Kaltsatou, Andreas D Flouris
Patients with multiple sclerosis experience many complications that gradually lead them to comorbidity and disability. Exercise could prevent and ameliorate the symptoms that comorbidity or inactivity generate. However, until recently it was suggested that multiple sclerosis patients should not participate in exercise training programs because these patients are characterized by thermoregulatory failure and the heat stress due to physical work could exacerbate the disease symptoms. Furthermore, taken into account that 60-80% of the multiple sclerosis patients present adverse clinical symptoms when their body temperature is increased (not only due to physical working but even when immerse in hot water or by exposure to infrared lamps or to the sun), the need for the development of treatment strategies to overcome the thermoregulatory problem in these patients is crucial...
November 13, 2018: Multiple Sclerosis and related Disorders
Alexandros Sotiridis, Tadej Debevec, Urša Ciuha, Ola Eiken, Igor B Mekjavic
What is the central question of this study? Controlled-hyperthermia heat acclimation protocols induce an array of thermoregulatory and cardiovascular adaptations that facilitate exercise in hot conditions. We investigated whether this ergogenic potential can be transferred to thermoneutral normoxic or hypoxic exercising conditions. What is the main finding and its importance? We show that heat acclimation did not affect maximal cardiac output or maximal aerobic power in thermoneutral normoxic/hypoxic conditions...
December 11, 2018: Experimental Physiology
Regina C Casper
Anorexia nervosa (AN) is uncommon as a syndrome, despite widespread dieting or voluntary food restriction, especially among female adolescents. This suggests that restriction of caloric intake might not be the only component driving weight loss in AN. Historical observations and experimental evidence from energy expenditure studies and recordings from movement sensors reviewed in this paper reveal that AN is associated with motor activity levels and with an energy output not significantly different from that in normal-weight healthy age-matched controls...
2018: Frontiers in Psychology
Mauricio Krause, Domenico Crognale, Karl Cogan, Serena Contarelli, Brendan Egan, Philip Newsholme, Giuseppe De Vito
This investigation sought to determine the effects of twelve weeks of resistance exercise training in addition to protein supplementation on body composition, markers of muscle atrophy/hypertrophy and heat shock response (HSR) in healthy older adults. Thirty-eight healthy sedentary participants (M/F, 18/20; age, 63.5 ± 4.4 y) were randomly assigned to four groups: I) PLACEBO: no training, receiving placebo sachets; II) NUTRITION: no training, receiving protein supplementation sachets; III) EXERCISE PLACEBO: training, placebo sachets and IV) EXERCISE NUTRITION: training, receiving protein sachets...
December 5, 2018: Experimental Gerontology
Guilherme Veiga Guimãraes, Miguel Morita Fernandes-Silva, Luciano Ferreira Drager, Lais Galvani de Barros Cruz, Rafael Ertner Castro, Emmanuel Gomes Ciolac, Edimar Alcides Bocchi
BACKGROUND: Heated water-based exercise (HEx) promotes a marked reduction of blood pressure (BP), but it is not entirely clear whether its effects on BP persist after cessation of HEx. METHODS: We analyzed the effects of cessation of HEx on 24-hour ambulatory BP monitoring (ABPM) in patients with resistant hypertension (RH). Thirty-two patients (aged 53 ± 6 years) with RH (4 to 6 antihypertensive drugs) were randomly assigned to HEx (n = 16) or control (n = 16) groups...
December 2018: Canadian Journal of Cardiology
Craig G Crandall, Caroline A Rickards, Blair D Johnson
Hemorrhage is a leading cause of death in the military and civilian settings and approximately 85% of potentially survivable battlefield deaths are hemorrhage related. Both Soldiers and civilians are exposed to a number of environmental and physiological conditions that have the potential to alter tolerance to a hemorrhagic insult. The objective of this review article is to summarize the known impact of commonly encountered environmental and physiological conditions on hemorrhagic tolerance, primarily in humans...
December 5, 2018: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
Emily R Watkins, Jemma Gibbons, Yanoula Dellas, Mark Hayes, Peter Watt, Alan J Richardson
Heat tolerance tests identify those susceptible to heat illnesses and monitor heat adaptations. Currently, tolerance tests do not replicate the uncompensable heat strain environments experienced in some occupations. In addition, tests can take up to 2 h to complete, and cannot offer intra and inter individual comparisons, due to the use of a fixed exercise intensity. This study aimed to assess the validity and reliability of a new heat occupational tolerance test (HOTT: 40 min at 6 W kg-1 metabolic heat production, 50 °C 10% RH, in protective clothing) to the standard heat tolerance test (HTT: 2 h walk at 5 km h-1 1% gradient, 40 °C 40% RH, in shorts and t-shirt)...
December 2018: Journal of Thermal Biology
John Elson, Steve Eckels
Quantifying the impact of clothing thermal and evaporation resistance is essential to providing representative boundary conditions for physiological modeling. In many models, sweat is assumed to drip off the skin surface to the environment and is not captured in clothing. In high metabolic rate and high temperature and humidity conditions the sweat produced by the body has the potential to saturate semipermeable clothing ensembles, changing the assumptions of the model. Workers, athletes and soldiers commonly wear encapsulating versions of such clothing to protect against environmental hazards...
December 2018: Journal of Thermal Biology
Michael W Schleh, Brent C Ruby, Charles L Dumke
Heat acclimation lowers physiological strain when exercising in the heat, and may be enhanced by promoting dehydration during acclimation. The purpose was to compare fluid intake during heat acclimation by promoting dehydration (DEH=0.5 mL kg-1 15 min-1 , ~2.4% dehydration per acclimation session) compared to euhydration (EUH=2.0 mL kg-1 15 min-1 , ~1.4% dehydration per acclimation session) following four heat acclimation bouts on thermal strain, and exercise performance. Thirteen males completed 90 min heat stress tests (HST) at 50% VO2max (40 °C, 30%RH) before and after three 90 min heat acclimation trials, involving consecutive bouts with 4-fold less fluid (DEH) or EUH...
December 2018: Journal of Thermal Biology
Sean R Notley, Sheila M Dervis, Martin P Poirier, Glen P Kenny
Menstrual cycle phase has long been thought to modulate thermoregulatory function. However, information pertaining to the effects of menstrual phase on time-dependent changes in whole-body dry and evaporative heat exchange during exercise-induced heat stress and the specific heat load at which menstrual phase modulates whole-body heat loss remained unavailable. We therefore used direct calorimetry to continuously assess whole-body dry and evaporative exchange in twelve habitually active, non-endurance trained, eumenorrheic females (21±2 years) within the early-follicular, late-follicular and mid-luteal menstrual phases during three, 30-min bouts of cycling at increasing fixed exercise intensities of 40% (Low), 55% (Moderate) and 70% (High) V̇O2peak , each followed by a 15-min recovery, in hot, dry conditions (40°C, 15% relative humidity)...
November 29, 2018: Journal of Applied Physiology
Robert D Meade, Sean R Notley, Andrew W D'Souza, Sheila Dervis, Pierre Boulay, Ronald J Sigal, Glen P Kenny
AIM: Aging and hypohydration independently attenuate heat dissipation during exercise; however, the interactive effects of these factors remain unclear. We assessed the hypothesis that aging suppresses hypohydration-induced reductions in whole-body heat loss during exercise in the heat. METHODS: On two occasions, eight young (mean [SD]: 24 [4] years) and eight middle-aged (59 [5] years) men performed 30-min bouts of light (heat production of 175 W·m-2 ) and moderate (275 W·m-2 ) cycling (separated by 15-min rest) in the heat (40°C, 15% relative humidity) when euhydrated and hypohydrated (~4% reduction in body mass)...
November 27, 2018: Acta Physiologica
Hidenori Otani, Mitsuharu Kaya, Akira Tamaki, Heita Goto, Ronald J Maughan
High radiant heat load reduces endurance exercise performance in the heat indoors, but this remains unconfirmed in outdoor exercise. The current study investigated the effects of variations in solar radiation on self-regulated exercise intensity and thermoregulatory responses in the heat outdoors at a fixed rating of perceived exertion (RPE). Ten male participants completed 45-min cycling exercise in hot outdoor environments (about 31 °C) at a freely chosen resistance and cadence at an RPE of 13 (somewhat hard)...
November 21, 2018: Physiology & Behavior
Mark A Faghy, Mitch Lomax, Peter I Brown
BACKGROUND: Swimming requires sustained high performance, with limited recovery between heats, recovery strategies are essential to performance but are often self-regulated and sub- optimal. Accordingly, we investigated a physiologically determined recovery protocol. METHODS: Fifteen (m=9, f=6) international junior age group swimmers participated in this study. The average age of the participants was 15.8 ± 1.5 years. All participants completed a lactate elevation protocol (8 x 50 m sprints), followed by one of three recovery strategies, 1) velocity at lactate threshold (VLT), 2) coach prescribed protocol (COA) and 3) national governing body recommendations (NGB) and thereafter a 200-m time trial...
November 21, 2018: Journal of Sports Medicine and Physical Fitness
Matthias Lambert, Bruno Bastide, Caroline Cieniewski-Bernard
Skeletal muscle represents around 40% of whole body mass. The principal function of skeletal muscle is the conversion of chemical energy toward mechanic energy to ensure the development of force, provide movement and locomotion, and maintain posture. This crucial energy dependence is maintained by the faculty of the skeletal muscle for being a central place as a "reservoir" of amino acids and carbohydrates in the whole body. A fundamental post-translational modification, named O-GlcNAcylation, depends, inter alia , on these nutrients; it consists to the transfer or the removal of a unique monosaccharide (N-acetyl-D-glucosamine) to a serine or threonine hydroxyl group of nucleocytoplasmic and mitochondrial proteins in a dynamic process by the O-GlcNAc Transferase (OGT) and the O-GlcNAcase (OGA), respectively...
2018: Frontiers in Endocrinology
Mike J Price, Michelle Trbovich
Spinal cord injury results in physiologic adaptations affecting heat production (reduced muscle mass) and heat dissipation (blood redistribution and reduced sweating capacity below the level of lesion). However, it is the balance between these factors which determines whether heat balance is achieved. Core temperature estimates are generally consistent with those for the able-bodied, with cooler values reported in some instances. More notable differences are demonstrated through cooler lower-body skin temperatures at rest and a loss of anticipatory control during exposure to heat and cold when compared to the able-bodied...
2018: Handbook of Clinical Neurology
Glen P Kenny, Thad E Wilson, Andreas D Flouris, Naoto Fujii
Heat exhaustion is part of a spectrum of heat-related illnesses that can affect all individuals, although children, older adults, and those with chronic disease are particularly vulnerable due to their impaired ability to dissipate heat. If left uninterrupted, there can be progression of symptoms to heatstroke, a life-threatening emergency. Signs and symptoms of heat exhaustion may develop suddenly or over time. Exposure to a hot environment for a prolonged period and performing exercise or work in the heat can overwhelm the body's ability to cool itself, causing heat exhaustion...
2018: Handbook of Clinical Neurology
Junichi Suzuki
NEW FINDINGS: What is the central question of this study? Intermittent hyperbaric exposure (1.3 ATA with 20.9% O2 ) has been shown to facilitate endurance capacity by facilitating oxidative and glycolytic capacities in skeletal muscle. It currently remains unclear whether this strategy enhances endurance performance in well-trained individuals. What is the main finding and its importance? Hyperbaric exposure (1.3 ATA with 20.9% O2 ) with endurance training enhanced oxidative and glycolytic capacities and protein levels of mitochondrial transcription factor A, dynamin-related protein-1, and heat shock protein 70...
November 20, 2018: Experimental Physiology
Hiroshi Nose, Yoshi-Ichiro Kamijo, Shizue Masuki
Humans are unique in their ability to control body temperature with a large amount of skin blood flow and sweat rate while exercising in an upright position. However, cutaneous vasodilation in the body reduces total peripheral resistance and blood pooling in cutaneous veins decreases venous return to the heart and cardiac filling pressure. In addition, hypovolemia by sweating accelerates the reduction in cardiac filling pressure. These may threaten the maintenance of blood pressure if they are not compensated for...
2018: Handbook of Clinical Neurology
Matthew D White
The human autonomic nervous system participates in the control of thermoregulatory responses that are employed to regulate core temperature following deviations of skin temperature and/or core temperature from their respective resting values. This permits a regulation of the core temperature (TC ) at 37.0 ± 1°C with superimposed circadian variations in both sexes and menstrual cycle-associated variations in premenopausal women. When rendered hyperthermic, passively by heat exposure while at rest or actively during exercise, humans engage heat loss or thermolytic responses, including eccrine sweating and cutaneous vasodilatation...
2018: Handbook of Clinical Neurology
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