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.

"Living High-Training Low" for Olympic Medal Performance: What Have We Learned 25 Years After Implementation?

Background: Altitude training is often regarded as an indispensable tool for the success of elite endurance athletes. Historically, altitude training emerged as a key strategy to prepare for the 1968 Olympics, held at 2300 m in Mexico City, and was limited to the "Live High-Train High" method for endurance athletes aiming for performance gains through improved oxygen transport. This "classical" intervention was modified in 1997 by the "Live High-Train Low" (LHTL) model wherein athletes supplemented acclimatization to chronic hypoxia with high-intensity training at low altitude.

Fluid balance during physical work in the heat is not modified by the menstrual cycle when fluids are freely available.

We tested the hypothesis that women may be more at risk of becoming dehydrated during physical work in the heat in the early follicular phase (EF), compared with the late follicular (LF) and mid-luteal (ML) phases of the menstrual cycle when allowed free access to drink. Twelve healthy, eumenorrheic, unacclimated women (26 ± 5 yr) completed three trials (EF, LF, and ML phases) involving 4 h of exposure to 33.8 ± 0.

Increased spleen volume provoked by temperate head-out-of-water immersion.

This study tested the hypotheses that ) spleen volume increases during head-out-of-water immersion (HOWI) and returns to pre-HOWI values postdiuresis, and ) the magnitude of apnea-induced spleen contraction increases when preapnea spleen volume is elevated. Spleen volume was measured before and after a set of five apneas in 12 healthy adults (28 ± 5 yr, 3 females) before, during (at 30 and 150 min), and 20 min after temperate temperature (36 ± 1°C) HOWI. At each time point, spleen length, width, and thickness were measured via ultrasound, and spleen volume was calculated using the Pilström equation.

Dyspnea Is Attenuated by Auditory Distraction via Music with Headphones during Exercise in Healthy Individuals.

Purpose: This study aimed to determine whether listening to music through headphones (a) affects the sensory (breathing intensity [BI]) and/or affective (breathing unpleasantness [BU]) components of dyspnea during exercise at different intensities and (b) affects exercise performance.

Methods: Twenty-two recreationally active individuals (24 ± 3 yr, 10 women) performed two 5-min constant loads (10% below/above gas exchange threshold [GET]) and an 8-km cycling time trial with ambient laboratory noise or self-selected music in a randomized crossover design. BI, BU, and ventilation ( V̇E ) were measured at each minute of the constant loads and every 2 km of the time trial.

High Intraindividual Variability in the Response of Serum Erythropoietin to Multiple Simulated Altitude Exposures.

Baranauskas, Marissa N., Timothy J. Fulton, Alyce D.

A Narrative Analysis of the Progression in the Top 100 Marathon, Half-Marathon, and 10-km Road Race Times from 2001 to 2019.

Purpose: This study aimed to characterize and describe finishing time trends of the fastest 100 performers in the men's and women's marathon, half-marathon, and road 10-km each year from 2001 to 2019 and assess the underlying basis for recent performance improvements.

Methods: The top 100 performers for each sex, event, and year were partitioned into four arbitrary ranking groups: 1-10, 11-25, 26-50, and 51-100. The percent improvement in mean performance time for each year beyond 2001 was calculated for each ranking group, event, and sex.

Nedocromil sodium and diphenhydramine HCl ameliorate exercise-induced arterial hypoxemia in highly trained athletes.

Introduction: Exercise-induced arterial hypoxemia (EIAH) has been observed in highly trained endurance athletes during near maximal exercise, which may be influenced by a histamine-mediated inflammatory response at the pulmonary capillary-alveolar membrane. In order to test this hypothesis, we examined whether the mast cell stabilizer nedocromil sodium (NS) and H -receptor antagonist diphenhydramine HCL (DH) would ameliorate EIAH and mitigate the drop in arterial oxyhemoglobin saturation (S O ) during intensive exercise.

Methods: Seven highly trained male cross country runners (age, 21 ± 2 years; V̇O , 74.

World Championship and Olympic Games Experience Influences Future Medal Performance in Track-and-Field Athletes.

Unlabelled: Some track-and-field national governing bodies send athletes to World Championship and Olympic Games (WC/OG) to gain experience that may positively impact future success, even though athletes may not be expected to place high or medal. However, it is unclear if this strategy is advantageous for future medal attainment.

Purpose: To determine if participation and/or advancement at a track-and-field athlete's first WC/OG influences the odds of future medaling.

Variation in Heart-Rate Profile During a Prolonged, Submaximal Swim Bout.

Purpose: To describe the heart-rate (HR) response during a prolonged, submaximal, multirepetition swimming bout (ie, typical early-season swimming training), as there is currently little or no literature on this topic.

Methods: A total of 12 collegiate swimmers were instructed to complete sixty 91.4-m (100-yd) freestyle repetitions at their fastest sustainable pace, allowing between 5 and 10 seconds of rest between repetitions.

Influence of Zinc on the Acute Changes in Erythropoietin and Proinflammatory Cytokines with Hypoxia.

Baranauskas, Marissa N., Joseph Powell, Alyce D. Fly, Bruce J.

Respiratory Muscle Fatigue Alters Cycling Performance and Locomotor Muscle Fatigue.

Purpose: This study aimed to determine if preexisting respiratory muscle fatigue (RMF) alters motoneuronal output, locomotor muscle fatigue, and cycling performance.

Methods: Eight trained male cyclists performed 5-km cycling time trials after a resistive breathing task that induced RMF and under control conditions (CON). Motoneuronal output was estimated using vastus lateralis surface electromyography, and locomotor muscle fatigue was quantified as the change in potentiated quadriceps twitch force from preexercise to postexercise.

Heat Versus Altitude Training for Endurance Performance at Sea Level.

Environmental stressors, such as heat or altitude, elicit dissimilar physiological adaptations to endurance training programs. Whether these differences (i.e.

Attentional focus does not impact locomotor-respiratory coupling in trained runners.

Purpose: The purpose of this study was to explore relationships between attentional strategies and LRC, running economy, perceived exertion, and dyspnea.

Methods: 25 endurance-trained males ([Formula: see text]Omax = 68.2 ± 4.

Ventilatory Responsiveness during Exercise and Performance Impairment in Acute Hypoxia.

Introduction: An adequate increase in minute ventilation to defend arterial oxyhemoglobin saturation (SpO2) during hypoxic exercise is commonly viewed as an important factor contributing to large inter-individual variations in the degree of exercise performance impairment in hypoxia. Although the hypoxic ventilatory response (HVR) could provide insight into the underpinnings of such impairments, it is typically measured at rest under isocapnic conditions. Thus, we aimed to determine whether 1) HVR at rest and during exercise are similar and 2) exercise HVR is related to the degree of impairment in cycling time trial (TT) performance from normoxia to acute hypoxia (∆TT).

Serum ferritin distribution in elite athletes.

Objectives: It is not uncommon for athletes to be diagnosed with iron deficiency, yet there remains uncertainty whether the prevalence of suboptimal iron status in elite athletes differs from the normal population or warrants routine screening. The purpose of this study is to describe the distribution of serum ferritin (SF) in a cohort of elite athletes.

Design: Retrospective cohort study.

Iron insufficiency diminishes the erythropoietic response to moderate altitude exposure.

The effects of iron stores and supplementation on erythropoietic responses to moderate altitude in endurance athletes were examined. In a retrospective study, red cell compartment volume (RCV) responses to 4 wk at 2,500 m were assessed in athletes with low ( = 9, ≤20 and ≤30 ng/mL for women and men, respectively) and normal ( = 10) serum ferritin levels ([Ferritin]) without iron supplementation. In a subsequent prospective study, the same responses were assessed in athletes ( = 26) with a protocol designed to provide sufficient iron before and during identical altitude exposure.

"Train-High Sleep-Low" Dietary Periodization Does Not Alter Ventilatory Strategies During Cycling Exercise.

The purpose of this study was to investigate the effects of "train-high sleep-low" (THSL) dietary periodization on ventilatory strategies during cycling exercise at submaximal and maximal intensities. In a randomized crossover design, 8 trained men [age (mean ± SEM) = 28 ± 1 y; peak oxygen uptake = 56.8 ± 2.

Inspiratory Muscle Training: Improvement of Exercise Performance With Acute Hypoxic Exposure.

Unlabelled: Endurance exercise performance in hypoxia may be influenced by an ability to maintain high minute ventilation (V˙E) in defense of reduced arterial oxyhemoglobin saturation. Inspiratory muscle training (IMT) has been used as an effective intervention to attenuate the negative physiological consequences associated with an increased V˙E, resulting in improved submaximal-exercise performance in normoxia. However, the efficacy of IMT on hypoxic exercise performance remains unresolved.

Special Environments: Altitude and Heat.

High-level athletes are always looking at ways to maximize training adaptations for competition performance, and using altered environmental conditions to achieve this outcome has become increasingly popular by elite athletes. Furthermore, a series of potential nutrition and hydration interventions may also optimize the adaptation to altered environments. Altitude training was first used to prepare for competition at altitude, and it still is today; however, more often now, elite athletes embark on a series of altitude training camps to try to improve sea-level performance.

Ischemic Preconditioning, O2 Kinetics, and Performance in Normoxia and Hypoxia.

Introduction: Ischemic preconditioning (IPC) before exercise has been shown to be a novel approach to improve performance in different exercise modes in normoxia (NORM). Few studies have been conducted examining potential mechanisms behind these improvements, and less has been done examining its influence during exercise in hypoxia (HYP). Oxygen uptake and extraction kinetics are factors that have been implicated as possible determinants of cycling performance.

Effect of carbohydrate ingestion on central fatigue during prolonged running exercise in moderate hypoxia.

To determine whether acute exposure to moderate hypoxia alters central and peripheral fatigue and to test whether carbohydrate ingestion impacts fatigue characteristics, 12 trained runners completed three running trials lasting 1 h each at 65% of normoxic maximum oxygen uptake. The first trial was performed in normoxia [inspired O fraction ( ) = 0.21], and the last two trials were completed in hypoxia (  = 0.