Gregoire P Millet

University of Lausanne | UNIL · Institute of Sports Science

Significance: Oxygen is indispensable for aerobic life but its utilization exposes cells and tissues to oxidative stress; thus, tight regulation of cellular, tissue and systemic oxygen concentrations is crucial. Here, we review the current understanding of how the human organism (mal-)adapts to low (hypoxia) and high (hyperoxia) oxygen levels and...

Hypoxia is caused by insufficient oxygen availability for the organism leading to reduced oxygen delivery to tissues and cells. It has been regarded as a severe threat to human health and it is indeed implicated in pathophysiological mechanisms involved in the development and progression of many diseases. Nevertheless, the potential of controlled h...

Adequate oxygen supply is essential for the human brain to meet its high energy demands. Therefore, elaborate molecular and systemic mechanism are in place to enable adaptation to low oxygen availability. Anxiety and depressive disorders are characterized by alterations in brain oxygen metabolism and of its components, such as mitochondria or hypox...

Older individuals represent a growing population, in industrialized countries, particularly those with cardiovascular diseases, which remain the leading cause of death in western societies. Aging constitutes one of the largest risks for cardiovascular diseases. On the other hand, oxygen consumption is the foundation of cardiorespiratory fitness, wh...

Sex differences in physiological responses to various stressors, including exercise, have been well documented. However, the specific impact of these differences on exposure to hypoxia, both at rest and during exercise, has remained underexplored. Many studies on the physiological responses to hypoxia have either excluded women or included only a l...

Purpose : One hundred years ago, Hill and Lupton introduced the concept of maximal oxygen uptake ( ), which is regarded as “the principal progenitor of sports physiology.” We provide a succinct overview of the evolvement of research on , from Hill and Lupton‘s initial findings to current debates on limiting factors for and the associated role of co...

The muscle molecular adaptations to different exercise intensities in combination with hypoxia are not well understood. This study investigated the effect of low- and supramaximal-intensity hypoxic training on muscle metabolic gene expression in mice. C57BL/6 mice were divided into two groups: sedentary and training. Training consisted of 4 weeks a...

Intermittent hypoxia (IH) is commonly associated with pathological conditions, particularly obstructive sleep apnoea. However, IH is also increasingly used to enhance health and performance and is emerging as a potent non-pharmacological intervention against numerous diseases. Whether IH is detrimental or beneficial for health is largely determined...

Pre‐term birth is associated with physiological sequelae that persist into adulthood. In particular, modulated ventilatory responsiveness to hypoxia and hypercapnia has been observed in this population. Whether pre‐term birth per se causes these effects remains unclear. Therefore, we aimed to assess pulmonary ventilation and blood gases under vario...

Purpose Hot water immersion (HWI) has gained popularity to promote muscle recovery, despite limited data on the optimal heat dose. The purpose of this study was to compare the responses of two exogenous heat strains on core body temperature, hemodynamic adjustments, and key functional markers of muscle recovery following exercise‐induced muscle dam...

Purpose: Total hemoglobin mass (tHbmass) and blood volume (BV) are important determinants of maximal oxygen uptake and endurance capacity. Higher-caliber endurance athletes usually possess higher tHbmass and BV values. This study aimed to compare tHbmass and BV among swimmers of diverse competitive calibers and distances. Methods: Thirty swimmer...

Purpose Laboratory tests are commonly performed by cross‐country (XC) skiers due to the challenges of obtaining reliable performance indicators on snow. However, only a few studies have reported reliability data for ski‐specific test protocols. Therefore, this study examined the test–retest reliability of ski‐specific aerobic, sprint, and neuromusc...

The objective of this study was to determine whether the relationships between energy cost of running (Cr) and running mechanics during downhill (DR), level (LR) and uphill (UR) running could be related to fitness level. Nineteen athletes performed four experimental tests on an instrumented treadmill: one maximal incremental test in LR, and three r...

Background: Elite sport is continuously evolving. World records keep falling and athletes from a longer list of countries are involved. Purpose: This commentary was designed to provide insights into present and future trends associated with world-class endurance training based on the perspectives, experience, and knowledge of an expert panel of...

Feedback of power during running is a promising tool for training and determining pacing strategies. However, current power estimation methods show low validity and are not customized for running on different slopes. To address this issue, we developed three machine-learning models to estimate peak horizontal power for level, uphill, and downhill r...

Reduced oxygen availability (hypoxia) can lead to cell and organ damage. Therefore, aerobic species depend on efficient mechanisms to counteract detrimental consequences of hypoxia. Hypoxia inducible factors (HIFs) and mitochondria are integral components of the cellular response to hypoxia and coordinate both distinct and highly intertwined adapta...

Objectives: Repeated-sprint training in hypoxia (RSH) is an effective way of improving physical performance compared with similar training in normoxia. RSH efficiency relies on hypoxia severity, but also on the oxidative-glycolytic balance determined by both sprint duration and exercise-to-rest ratio. This study investigated the effect of 2 types...

The year 2023 marks the 100th anniversary of the ‘maximum oxygen intake’ (VO2max), first described by Hill and Lupton in the QJM in 1923.¹ These authors suggested an upper limit to oxygen intake depending on the capability of the cardiorespiratory system to deliver inspired oxygen to the working muscles. Since then, whether the cardiorespiratory sy...

Premature birth is associated with endothelial and mitochondrial dysfunction, and chronic oxidative stress, which might impair the physiological responses to acute altitude exposure. We assessed peripheral and oxidative stress responses to acute high-altitude exposure in preterm adults compared to term born controls. Post-occlusive skeletal muscle...

Exercise training is an important therapeutic strategy for lower extremity peripheral artery disease (PAD). However, the effects of different exercise frequency on physiological adaptations remain unknown. Thus, this study compared the effects of a 7-week moderate-intensity aerobic training performed either three or five times/week on skeletal musc...

Huntington disease (HD) is a debilitating, currently incurable disease. Protein aggregation and metabolic deficits are pathological hallmarks but their link to neurodegeneration and symptoms remains debated. Here, we summarize alterations in the levels of different sphingolipids in an attempt to characterize sphingolipid patterns specific to HD, an...

A spring mass model is often used to describe human running, allowing to understand the concept of elastic energy storage and restitution. The stiffness of the spring is a key parameter and different methods have been developed to estimate both the vertical and the leg stiffness components. Nevertheless, the validity and the range of application of...

Introduction The prevalence of acute mountain sickness (AMS) is increasing with altitude (i.e., 10-25% at 2,500 m and 50-85% at ~ 5,000 m; Bärtsch & Swenson, 2013). While there is no error-free test to predict its occurrence, several risk factors and tests have been proposed. For example, the hypoxic ventilatory response (HVR) measures the ratio b...

Introduction Matches and high-intensity training put important load on elite football players, which may result in performance decrease and physiological alterations (Meeusen et al., 2013). Positive correlations between heart rate variability (HRV) athletic performance have been reported (Buchheit et al., 2012) but the measurements were not relat...

Introduction Repeated sprints exercise (RSE) performed in hypoxia (RSH) induce greater performance improvement than in normoxia (Brocherie et al., 2017). It has been previously argued that RSH efficiency depend on the oxidative-glycolytic balance which is influenced by sprint duration and exercise-to-rest-ratio (E:R). Indeed, we recently showed th...

Purpose: Previous research has shown that maximal oxygen uptake (VO2max) significantly influences performance in trail-running races up to 120 km but not beyond. Similarly, the influence of running economy on performance in ultratrail remains unclear. The aim of our study was, therefore, to determine the physiological predictors of performance in...

Among the people most affected by coronavirus disease 2019 (COVID-19) are those suffering from hypertension (HTN). However, pharmacological therapies for HTN are ineffective against COVID-19 progression and severity. It has been proposed that exercise training (EX) could be used as post-COVID treatment, which does not rule out the possible effects...

Dear Editor, We read with great interest the recent systematic review on the emerging topic of "maximal aerobic exercise capacity and lung function in prematurely born adults" by Thomas Gostelow and Dr Eric J. Stöhr [1]. We congratulate the authors for their excellent analysis of the growing body of literature on the topic, which corroborates the c...

Purpose: Oxygen uptake kinetics (VO2kinetics) is a measure of an athlete's capacity to respond to variations in energy demands. Faster VO2kinetics is associated with better performance in endurance sports, but optimal training methods to improve VO2kinetics remain unclear. This study compared the effects of 2 high-intensity interval-training (HIIT...

Background: Altitude sojourns increasingly attract individuals of all ages and different health status due to the appeal of high-altitude destinations worldwide and easy access to air travel. The risk of acute mountain sickness (AMS) when flying to high altitude destinations remains underemphasized. Thus, this mini-review aims to evaluate the alti...

High-altitude illnesses (HAIs) result from acute exposure to high altitude/hypoxia. Numerous molecular mechanisms affect appropriate acclimatization to hypobaric and/or normobaric hypoxia and curtail the development of HAIs. The understanding of these mechanisms is essential to optimize hypoxic acclimatization for efficient prophylaxis and treatmen...

Mitokines are signaling molecules that enable communication of local mitochondrial stress to other mitochondria in distant cells and tissues. Among those molecules are FGF21, GDF15 (both expressed in the nucleus) and several mitochondrial-derived peptides, including humanin. Their responsiveness to mitochondrial stress induces mitokine-signaling in...

Purpose: To compare the acute performance and psychophysiological responses of repeated cycling sprints to exhaustion with a short exercise-to-rest ratio (1:6), between different effort durations and inspired oxygen fractions. Methods: On separate visits, 10 active participants completed 6 repeated cycling sprint exercises to exhaustion with 3 d...

Neuropeptide Ys (NPYs) contribute to sympathetic‐adreno stimulation: NPY1‐36 potentiates the effects of catecholamines (CATs), whereas NPY3‐36 inhibits CAT release. We sought to investigate whether inhibiting dipeptidyl‐peptidase‐4 (DPP4), cleaving NPY1‐36 into NPY3‐36, leads to increased NPY1‐36 potentiating effects and reduced NPY3‐36 inhibitory...

Moderate altitude (1000–2000 m above sea level) residence is emerging as a protective factor from the mortality of various causes, including of cardiovascular diseases. Conversely, mortality from certain respiratory diseases is higher at these altitudes than in lowlands. These divergent outcomes could indicate either beneficial or detrimental effec...

Baroreflex sensitivity (BRS) is a measure of cardiovagal baroreflex and is lower in normobaric and hypobaric hypoxia compared to normobaric normoxia. The aim of this study was to assess the effects of hypobaria on BRS in normoxia and hypoxia. Continuous blood pressure and ventilation were recorded in eighteen seated participants in normobaric normo...

Objective: To determine whether the altitude of birth/childhood influences the values in peak power output (PPO) and estimated maximum oxygen uptake (estVO2max) in male Colombian road cyclists of different performance levels. This study also aimed to determine whether cyclists born at high altitudes tend to be more successful. Methods: Eighty rider...

Aiming to improve the translation of applied sport science findings to evidence-based practice in real-life sport performance environments, Frontiers has launched a series of 'Evidence to Practice' research topics that bridge the gap, for instance, in injury prevention, sport nutrition or environmental challenges. Based on the scientific interest i...

Purpose: Premature birth induces long-term sequelae on the cardiopulmonary system, leading to reduced exercise capacity. However, the mechanisms of this functional impairment during incremental exercise remain unclear. Also, a blunted hypoxic ventilatory response was found in preterm adults, suggesting an increased risk for adverse effects of hypo...

Highlights •Resistance exercise (RE) is an important physical activity modality conferring major health benefits that are partially complementary to benefits from endurance exercise. •Recent meta-analyses reveal a U-shaped relationship between RE volumes and mortality, with optimal benefits achieved at about 60 min of RE per week. •The mechanisms f...

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease with a characteristic of abnormal lipid metabolism. In the present study, we employed apolipoprotein E knockout (ApoE KO) mice to investigate the effects of hypoxia exposure on hepatic fatty acid metabolism and to test whether a high-fat diet (HFD) would suppress the benefici...

Purpose: To investigate differences in athletes' knowledge, beliefs, and training practices during COVID-19 lockdowns with reference to sport classification and sex. This work extends an initial descriptive evaluation focusing on athlete classification. Methods: Athletes (12,526; 66% male; 142 countries) completed an online survey (May-July 2020...

Purpose: This study investigates the effects of normobaric hypoxia on repeated sprint exercise (RSE) with different balance between oxidative (phosphocreatine and oxidative pathway) and glycolytic contributions. Therefore, performance and psycho-physiological responses were compared during RSE to exhaustion with the same exercise-to-rest ratio (1:...

italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Objective: Continuous monitoring of biosignals via wearable sensors has quickly expanded in the medical and wellness fields. At rest, automatic detection of vital parameters is generally accurate. However, in conditions such as high-intensity exercise,...

Purpose The aim of this study was to provide a theoretical model to predict the vertical loading rate (VLR) at different slopes and speeds during incline running. Methods Twenty-nine healthy subjects running at least once a week performed in a randomized order 4-min running trials on an instrumented treadmill at various speeds (8, 10, 12, and 14 k...

Elite masters endurance athletes are considered models of optimal healthy aging due to the maintenance of high cardiorespiratory fitness (CRF) until old age. Whereas a drop in VO2max in masters athletes has been broadly investigated, the modifying impact of training still remains a matter of debate. Longitudinal observations in masters endurance at...

The pre-term birth survival rate has increased considerably in recent decades, and research investigating the long-term effects of premature birth is growing. Moreover, altitude sojourns are increasing in popularity and are often accompanied by various levels of physical activity. Individuals born pre-term appear to exhibit altered acute ventilator...

Purpose: Hypoxia is one major environmental factor, supposed to mediate central motor command as well as afferent feedbacks at rest and during exercise. By using a comparison of normobaric (NH) and hypobaric (HH) hypoxia with the same ambient pressure in oxygen, we examined the potential differences on the cerebrovascular and muscular regulation in...

The aim of this research was to investigate the role of trait emotional intelligence (EI) in recovery stress states in a mountain ultra-marathon (MUM) race. Recovery stress states of 13 finishers were assessed before, during, and immediately after the end of an extreme MUM, whereas emotional intelligence was assessed 2 days before the MUM race. Tem...