Critical Assessment of the Recommended Alert Limit Curves for Occupational Heat Exposure.

Background: Occupational heat stress recommendations aim to achieve thermal equilibrium and keep core temperature (T) below 38.0°C. We assessed the recommended alert limit curves when: (1) work-rest ratios are adjusted based on wet-bulb globe temperature (WBGT) at a fixed rate of metabolic heat production (H) and (2) H is adjusted based on WBGT at a fixed work-rest ratio.

Cardiovascular and Respiratory Responses During Graded Exercise in Adolescents After Sport-Related Concussion.

Background: Symptom-limited exercise intolerance is a physiological sign of sport-related concussion. Possible etiologies include rest-induced aerobic deconditioning and/or impaired cardiopulmonary function.

Objective: This study examined cardiovascular and respiratory function at rest and during progressive cycle ergometer exercise in adolescents within 10 days of sport-related concussion compared with non-concussed athletes.

Inspiratory Muscle Warm-Up and Perceptual, Physiological, and Performance Outcomes During Exercise in Normoxia and Hypoxia.

Introduction: Some evidence shows that an inspiratory muscle warm-up (IMW) could enhance exercise performance; however, outcomes are mixed, and the mechanistic basis is unclear. Therefore, our purpose was to examine how IMW affects the sensory and affective components of dyspnea, exercise performance, and locomotor muscle oxygenation.

Methods: Thirteen recreationally active individuals (23 [5] y, 5 women) performed a cycling time-to-exhaustion test (∼80%-85% maximal oxygen uptake) preceded by either IMW (2 × 30 breaths, 40% maximal inspiratory pressure) or SHAM (2 × 30 breaths, 15% maximal inspiratory pressure) in normoxic (FIO2 = 0.

Investigating omega-3 fatty acids' neuroprotective effects in repetitive subconcussive neural injury: Study protocol for a randomized placebo-controlled trial.

Soccer (football) is the most popular sport globally, with 265 million players across all ages and sexes. Repetitive subconcussive head impacts due to heading of the soccer ball can pose threats to healthy brain development and aging. Omega-3 fatty acids, especially docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), may have neuroprotective effects, but it remains unclear what aspects of neural health benefit from DHA+EPA when faced with subconcussive head impacts.

Hot water immersion increases internal carotid artery shear rate but does not alter intracranial vascular reactivity to carbon dioxide.

Acute hot water immersion (HWI) increases cerebral blood flow, which may increase arterial shear rate and benefit cerebrovascular function. However, it is unclear whether HWI alters cerebral artery shear rate and cerebrovascular reactivity to carbon dioxide (CVR). We tested the hypotheses that HWI (39 °C) increases extracranial artery shear rate and intracranial artery hypercapnic CVR, but reduces hypocapnic CVR compared to temperate water immersion (TWI; 35 °C).

Parasympathetic Responses to Face Cooling in Adolescents with Sport-Related Concussion and After Clinical Recovery.

Face cooling (FC) initiates the mammalian dive reflex, which elicits a parasympathetic autonomic response. In our pilot study, collegiate athletes had a blunted parasympathetic response to FC within 10 days of sport-related concussion (SRC). The objective of the current study was to assess the FC response in adolescent athletes with acute SRC and after clinical recovery.

Influence of work intensity on acute kidney injury risk during simulated occupational heat stress.

Violation of the National Institute of Occupational Safety and Health (NIOSH) heat stress recommendations by exceeding the allowable wet bulb globe temperature (WBGT) for a given work intensity and work-rest ratio augments acute kidney injury (AKI) risk. Here, we tested the hypothesis that exceeding the allowable work intensity at a given WBGT and work-rest ratio would also worsen AKI risk. Twelve healthy adults completed two NIOSH recommendation compliant trials and one noncompliant trial consisting of a 4 h (half workday) exposure.

The effect of consuming a sucrose-containing sports drink on acute kidney injury risk during a 4 h simulated occupational heat stress.

Occupational heat stress increases acute kidney injury risk. Drinking a soft drink sweetened with high fructose corn syrup further elevates this acute kidney injury risk. However, the impact of sucrose, another fructose-containing sweetener, on acute kidney injury risk remains unexplored.

The independent effects of hydrostatic pressure and hypercapnic breathing during water immersion on ventilatory sensitivity and cerebrovascular reactivity.

Head-out water immersion (HOWI) induces ventilatory and hemodynamic changes, which may be a result of hydrostatic pressure, augmented arterial CO tension, or a combination of both. We hypothesized that the hydrostatic pressure and elevated CO tension that occur during HOWI will contribute to an augmented ventilatory sensitivity to CO and an attenuated cerebrovascular reactivity to CO during water immersion. Twelve subjects [age: 24 ± 3 yr, body mass index (BMI): 25 ± 3 kg/m] completed HOWI, waist water immersion with CO (WWI + CO), and WWI, where a rebreathing test was conducted at baseline, 10, 30, and 60 min, and postimmersion.

Creatinine clearance is maintained in a range of wet-bulb globe temperatures and work-rest ratios during simulated occupational heat stress.

We tested the hypothesis that compliance with the National Institute for Occupational Safety and Health (NIOSH) heat stress recommendations will prevent reductions in glomerular filtration rate (GFR) across a range of wet-bulb globe temperatures (WBGTs) and work-rest ratios at a fixed work intensity. We also tested the hypothesis that noncompliance would result in a reduction in GFR compared with a work-rest matched compliant trial. Twelve healthy adults completed five trials (four NIOSH compliant and one noncompliant) that consisted of 4 h of exposure to a range of WBGTs.

Acute moderate normobaric hypoxia does not modify circulating thyroid hormone concentrations induced by 1 h of head-out cold-water immersion.

This study tested the hypothesis that acute moderate normobaric hypoxia augments circulating thyroid hormone concentrations during and following 1 h of cold head-out water immersion (HOWI), compared with when cold HOWI is completed during normobaric normoxia. In a randomized crossover single-blind design, 12 healthy adults (27 ± 2 yr, 2 women) completed 1 h of cold (22.0 ± 0.

Relation between resting spleen volume and apnea-induced increases in hemoglobin mass.

Introduction: Indigenous populations renowned for apneic diving have comparatively large spleen volumes. It has been proposed that a larger spleen translates to heightened apnea-induced splenic contraction and elevations in circulating hemoglobin mass (Hb), which, in theory, improves O carrying and/or CO/pH buffering capacities. However, the relation between resting spleen volume and apnea- induced increases in Hb is unknown.

Renal vascular control during normothermia and passive heat stress does not differ between healthy younger men and women.

Men are likely at greater risk for heat-induced acute kidney injury compared with women, possibly due to differences in vascular control. We tested the hypothesis that the renal vasoconstrictor and vasodilator responses will be greater in younger women compared with men during passive heat stress. Twenty-five healthy adults [12 women (early follicular phase) and 13 men] completed two experimental visits, heat stress or normothermic time-control, assigned in a block-randomized crossover design.

Diagnostic accuracy of thermal, hydration, and heart rate assessments in discriminating positive acute kidney injury risk following physical work in the heat.

Occupational heat stress increases the risk of acute kidney injury (AKI). This study presents a secondary analysis to generate novel hypotheses for future studies by investigating the diagnostic accuracy of thermal, hydration, and heart rate assessments in discriminating positive AKI risk following physical work in the heat in unacclimatized individuals. Unacclimatized participants ( = 13, 3 women, age: ∼23 years) completed four trials involving 2 h of exercise in a 39.

Cool head-out water immersion does not alter cerebrovascular reactivity to hypercapnia despite elevated middle cerebral artery blood velocity: A pilot study.

Episodic increases in cerebral blood flow (CBF) are thought to contribute to improved cerebrovascular function and health. Head-out water immersion (HOWI) may be a useful modality to increase CBF secondary to the hydrostatic pressure placed on the body. However, it is unclear whether water temperatures common to the general public elicit similar cerebrovascular responses.

Activation of cardiac parasympathetic and sympathetic activity occurs at different skin temperatures during face cooling.

Sufficiently cold-water temperatures (<7°C) are needed to elicit the sympathetic response to the cold pressor test using the hand. However, it is not known if stimulating the trigeminal nerve via face cooling, which increases both sympathetic and cardiac parasympathetic activity, also has a threshold temperature. We tested the hypothesis that peak autonomic activation during a progressive face cooling challenge would be achieved when the stimulus temperature is ≤7°C.

Utility of Structured Oculomotor, Balance, and Exercise Testing in Civilian Adults With Mild Traumatic Brain Injury.

Purpose: Assessments of oculomotor, balance, and exercise function detect different responses to mild traumatic brain injury in sports-related mild traumatic brain injury. These assessments are understudied in the adult community mild traumatic brain injury population. We evaluated level 1 trauma center patients with nonsports-related mild traumatic brain injury on oculomotor functioning (near point of convergence and accommodation), balance (Balance Error Scoring System), and exercise tolerance (Buffalo Concussion Treadmill Test).

Aerobic exercise performance is reduced following prolonged cold-water immersion.

We tested the hypotheses that self-paced aerobic exercise performance is reduced following four hours of cold-water immersion when breathing air and further reduced when breathing 100% oxygen (O2). Nine healthy adults (four women; age 24 ± 3 years; body fat 17.9 ± 6.

Occupational Heat Stress Recommendation Compliance Attenuates AKI Risk Compared with a Work-Rest Ratio-Matched, Positive Control Scenario.

Occupational heat stress recommendations attenuate AKI risk compared with a work–rest ratio–matched positive control scenario. Heat-induced AKI risk is strongly related to peak core temperature. The peak change in serum creatinine largely paralleled peak changes in urinary [insulin-like growth factor-binding protein 7·tissue inhibitor metalloproteinase 2].

The modulatory role of cannabis use in subconcussive neural injury.

Cannabis use has become popular among athletes, many of whom are exposed to repetitive subconcussive head impacts. We aimed to test whether chronic cannabis use would be neuroprotective or exacerbating against acute subconcussive head impacts. This trial included 43 adult soccer players (Cannabis group using cannabis at least once a week for the past 6 months, n = 24; non-cannabis control group, n = 19).

Water consumption patterns impact hydration markers in males working in accordance with the National Institute for Occupational Safety and Health recommendations.

The impact of water consumption bolus volume and frequency on hydration biomarkers during work in the heat is unknown. In a randomized, crossover fashion, eight males consumed either 500 mL of water every 40 min or 237 mL of water every 20 min during 2 hr of continuous walking at 6.4 kph, 1.

Elevations in sweat sodium concentration following ischemia-reperfusion injury during passive heat stress.

Renal ischemia-reperfusion (I/R) injury results in damage to the renal tubules and causes impairments in sodium [Na] reabsorption. Given the inability to conduct mechanistic renal I/R injury studies in vivo in humans, eccrine sweat glands have been proposed as a surrogate model given the anatomical and physiological similarities. We tested the hypothesis that sweat Na concentration is elevated following I/R injury during passive heat stress.