IMPACT OF NOCTURNAL OXYGEN ENRICHMENT ON HIGH-ALTITUDE ACCLIMATIZATION.

Nocturnal oxygen enrichment improves sleep at high-altitude but may impair acclimatization. Determine if nocturnal oxygen enrichment impacts acclimatization. A 7-day acclimatization protocol occurred at a field-based research site between 0-4200m.

Cold Ambient Temperature Does Not Alter Subcutaneous Abdominal Adipose Tissue Lipolysis and Blood Flow in Endurance-Trained Cyclists.

This study sought to investigate the effect of cold ambient temperature on subcutaneous abdominal adipose tissue (SCAAT) lipolysis and blood flow during steady-state endurance exercise in endurance-trained cyclists. Ten males (age: 23 ± 3 years; peak oxygen consumption: 60.60 ± 4.

Alaska Backcountry Expeditionary Hunting Promotes Sustained Muscle Protein Synthesis.

Introduction: We have previously described negative energy balance (ie, -9.7±3.4 MJ/d) and weight loss (Δ-1.

Training in a Hot Environment Fails to Elicit Changes in the Blood Oxidative Stress Response.

Environmental temperature can impact exercise-induced blood oxidative stress; however, the effects of heat acclimation on this response have not been fully elucidated. The purpose of the study was to investigate the effects of hot (33°C) and room temperature (20°C) environments on post-exercise blood oxidative stress responses following 15 temperature acclimation sessions. Untrained participants (n = 38, 26 ± 7 years, VO = 38.

Physiology of the Wildland Firefighter: Managing Extreme Energy Demands in Hostile, Smoky, Mountainous Environments.

Wildland firefighters (WLFFs) are inserted as the front-line defense to minimize loss of natural resources, property, and human life when fires erupt in forested regions of the world. The WLFF occupation is physically demanding as exemplified by total daily energy expenditures that can exceed 25 MJ/day (6000 calories). WLFFs must also cope with complex physical and environmental situations (i.

Total Energy Expenditure and ad Libitum Fluid/Nutrient Intake During a 24-Hour Mountain-Bike Event: A Case Study.

Unlabelled: Previous studies have used the doubly labeled water method to evaluate the total energy expenditure (TEE) during Ironman, ultramarathon trail runs, and competitive road cycling. However, the technique has not been applied to a 24-hour cross-country mountain-bike event.

Purpose: This case study aimed to measure the TEE, cycling metrics, and ad libitum nutrient/fluid intake during a 24-hour cross-country mountain-bike race.

Independent effects of acute normobaric hypoxia and hypobaric hypoxia on human physiology.

The purpose of this study was to examine the effects of acute normobaric (NH, decreased FiO) and hypobaric (HH, 4200 m ascent) hypoxia exposures compared to sea level (normobaric normoxia, NN). Tissue oxygenation, cardiovascular, and body fluid variables measured during rest and a 3-min step-test following 90-min exposures (NH, HH, NN). Muscle oxygenated hemoglobin (OHb) decreased, and muscle deoxygenated hemoglobin (HHb) increased environmentally independent from rest to exercise (p < 0.

Heat Acclimation in Females Does Not Limit Aerobic Exercise Training Outcomes.

Recent aerobic exercise training in the heat has reported blunted aerobic power improvements and reduced mitochondrial-related gene expression in men. It is unclear if this heat-induced blunting of the training response exists in females. The purpose of the present study was to determine the impact of 60 min of cycling in the heat over three weeks on thermoregulation, gene expression, and aerobic capacity in females.

Septuagenarians Approach 4 Times the Basal Metabolic Rate During Race Across America.

Background: Previous data have demonstrated that Tour de France riders maintain total daily energy expenditure (TDEE) between 3.5 and 5.5 times the basal metabolic rate (×BMR).

Nutrient Intake of Wildland Firefighters During Arduous Wildfire Suppression: Macronutrient and Micronutrient Consumption.

Unlabelled: Wildland firefighters (WLFFs) perform in adverse environments making rapid adjustments to dietary needs. The National Mobile Food Services (NMFS) contract details WLFF dietary provisions on wildfire incidents.

Objective: Determine the nutrient content of food and drink provided to and consumed by WLFFs under the NMFS contract.

The Acute Effects of Exercise and Temperature on Regional mtDNA.

A reduced mitochondrial DNA (mtDNA) copy number, the ratio of mitochondrial DNA to genomic DNA (mtDNA:gDNA), has been linked with dysfunctional mitochondria. Exercise can acutely induce mtDNA damage manifested as a reduced copy number. However, the influence of a paired (exercise and temperature) intervention on regional mtDNA (MINor Arc and MAJor Arc) are unknown.

Impact of Hypoxic Exercise Recovery on Skeletal Muscle Glycogen and Gene Expression.

Slivka, Dustin, Charles Dumke, Walter Hailes, and Brent Ruby. Impact of hypoxic exercise recovery on skeletal muscle glycogen and gene expression. .

Workshift Changes in Hydration Status During Wildfire Suppression.

Objective: Document wildland firefighters (WLFFs) hydration status during a singular workshift (13.7 ± 1.4 hours).

Evaluation of Environmental Conditions on Self-Selected Work and Heat Stress in Wildland Firefighting.

Introduction: The purpose of this study was to evaluate heat stress occurring in wildfire management activities with variable environmental conditions.

Methods: Direct observation and real-time wireless physiological monitoring allowed for weather and physiological metrics, including heart rate, core temperature (T), skin temperature, and physiological strain index (PSI), of male (n=193) and female (n=28) wildland firefighters (WLFFs) to be recorded during wildfire management activities. Accelerometry data were used to categorize intensity level of activity.

Exercise in the heat blunts improvements in aerobic power.

Introduction: PGC-1a has been termed the master regulator of mitochondrial biogenesis. The exercise-induced rise in PGC-1a transcription is blunted when acute exercise takes place in the heat. However, it is unknown if this alteration has functional implications after heat acclimation and exercise training.

Influence of Fluid Delivery Schedule and Composition on Fluid Balance, Physiologic Strain, and Substrate Use in the Heat.

Introduction: Wildfire suppression is characterized by high total energy expenditure and water turnover rates. Hydration position stands outline hourly fluid intake rates. However, dose interval remains ambiguous.

Blood oxidative stress and post-exercise recovery are unaffected byhypobaric and hypoxic environments.

Hypobaria and hypoxia exert independent effects on oxidative stress during exercise, while combined effectson the post-exercise recovery period remain unclear.Accordingly, this study examined the recovery period during lab-simulated hypoxic and hypobaric conditions following exercise-induced oxidative stress. Participants (n=13) performed 60-minutes of cycling (70% watts max) in a normobaric normoxic environment followed by a four-hour recovery under three conditions; 1000m normobaric normoxia (NN, 675mmHg), 4400m normobaric hypoxia (NH, 675mmHg), or 4400m hypobaric hypoxia (HH, 440mmHg).

Total Energy Intake and Self-Selected Macronutrient Distribution During Wildland Fire Suppression.

Introduction: Wildland firefighters (WLFF) work long hours in extreme environments, resulting in high daily total energy expenditure. Increasing work-shift eating episodes and/or providing rations that promote convenient eating has shown augmented self-selected work output, as has regular carbohydrate (CHO) consumption. It remains unclear how current WLFF feeding strategies compare to more frequent nutrient delivery.

Males and females exhibit similar muscle glycogen recovery with varied recovery food sources.

Purpose: Research has elucidated the impact of post-exercise carbohydrate nutrition and environmental conditions on muscle glycogen re-synthesis. However, research has minimally considered the implications of glycogen recovery in females and has mostly focused on commercial sport nutrition products. The purpose of this study was to determine the effects of varied mixed macronutrient feedings on glycogen recovery and subsequent exercise performance in both sexes.

Effects of 7°C environmental temperature acclimation during a 3-week training period.

Cold environmental temperatures during exercise and recovery alter the acute response to cellular signaling and training adaptations. Approximately 3 wk is required for cold temperature acclimation to occur. To determine the impact of cold environmental temperature on training adaptations, fitness measurements, and aerobic performance, two groups of 12 untrained male subjects completed 1 h of cycling in 16 temperature acclimation sessions in either a 7°C or 20°C environmental temperature.

Skeletal Muscle mRNA Response to Hypobaric and Normobaric Hypoxia After Normoxic Endurance Exercise.

The physiological effects of hypoxia may be influenced by how hypoxia is achieved. The purpose of this study was to determine the effects of recovery in hypobaric hypoxia (HH), normobaric hypoxia (NH), and normobaric normoxia (NN) after endurance exercise on gene expression related to mitochondrial biogenesis, myogenesis, and proteolysis. Fifteen recreationally trained subjects each cycled for 1 hour before recovering for 4 hours in NN (laboratory atmospheric conditions, 975 m), HH (depressurized to simulate 4420 m), and NH (fraction of O reduced to simulate 4420 m).