ECSS Paris 2023: OP-PN30
INTRODUCTION: High intensity interval training (HIIT) in hypoxia has been demonstrated to improve peak oxygen uptake (VO2peak) in athletes to a greater extent than when performed in normoxia. Further, training under hypoxia reduces the mechanical load required to elicit similar physiological responses. These characteristics of HIIT in hypoxia have obvious appeal for overweight and sedentary populations. Accordingly, the aim of this investigation was to determine the effects of an 8-week HIIT in hypoxia intervention on markers of physical fitness in overweight and sedentary individuals. METHODS: Thirty sedentary (<100 min weekly moderate physical activity) overweight and obese (BMI: 33.9±6.5) individuals (36±7 y) were recruited for a 10-week training program (three HIIT sessions and two resistance training sessions per week). In the first two weeks, all exercise was performed in normoxia. For the following eight weeks, HIIT was completed in either normoxia (n=10, five dropouts) or hypoxia (n=15). All participants completed 1-repetition maximum (1RM) testing in four exercises and a graded exercise test for the determination of VO2peak and submaximal fat oxidation rates (Fatox) prior to and following the intervention period. HIIT consisted of four to six repetitions of 1-min cycling bouts performed at a fixed rating of perceived exertion (RPE; 16/20), interspersed with 4-min of active recovery (10/20 RPE) in either normoxia (FiO2: ~0.21) or hypoxia (FiO2: ~0.14). All resistance training was performed in normoxia, and sessions consisted of four different exercises. Linear mixed models were used with condition, time and interaction defined as the fixed effects and participants as random effects. RESULTS: VO2peak significantly improved following training (hypoxia: +0.38±0.42 L/min; normoxia: +0.22±0.28 L/min, pooled effect: g=0.67), with no significant interaction found between condition and time (p=0.30). Fatox at 50 W, 75 W, and 100 W also significantly increased following training, again with no between-group differences (50 W: +0.09±0.14 g/min, 75 W: +0.11±0.12 g/min, 100 W: +0.10±0.11 g/min, pooled effect: g=0.45-1.15). Finally, 1RM also increased similarly in both conditions (Pre-post pooled group average: leg press: +43±45%, p=0.001, g=0.42; bench press: +15±13%, p<0.001, g=0.36; shoulder press: +12±16%, p=0.003, g=0.23; lat pulldown: +15±13%, p<0.001, g=0.47). CONCLUSION: A 10-week training program consisting of HIIT (3/week) and resistance training (2/week) significantly improved VO2peak, submaximal Fatox, and strength (1RM) in sedentary overweight and obese individuals. While the magnitude of VO2peak improvement was nearly 2x greater in the hypoxic HIIT group, no significant differences were found compared to performing matched training in normoxia. While our data do not support the addition of hypoxia to HIIT as a way to augment physical fitness outcomes in this population, they suggest further research may be warranted.
Read CV Paul GoodsECSS Paris 2023: OP-PN30
INTRODUCTION: The AlterG treadmill allows weight reduction during running, which lowers mechanical stress, and metabolic strain. In this context, we previously demonstrated that hypoxia compensated body weight reduction for physiological stress (Chambion-Diaz et al., 2025). However, there is no strong evidence regarding the effect of AlterG running on redox balance, inflammation and muscle damage. Hypoxia is well known to increase oxidative stress, and physiological stress. To date, there is no study investigating redox balance and inflammation in response to this type of exercise. The aim of this study is to characterize the biochemical response in this exercise combination. METHODS: Twenty-six participants completed a high-intensity interval training (HIIT) session on an AlterG treadmill in the following 5 experimental conditions in randomized order: normoxia at 100% body weight (BW); normoxia at 80% BW; normoxia at 60% BW; hypoxia (FiO2=14%) at 80% BW; hypoxia at 60% BW. The HIIT session included 3 sets of 8 repetitions of 30 seconds of effort performed at 110% of the maximum aerobic speed, interspersed with 30 seconds of passive recovery. Blood samples were taken before and after each session for measurement of oxidative stress markers (AOPP, Isoprostanes, MDA, MPO, XO) antioxidant (SOD, GPx, Catalase, FRAP, UA), inflammation (CRP, IL-6, IL-1b, TNF-α), muscle damage (CK, myoglobin). RESULTS: Catalase, MPO, FRAP and myoglobin increased post-HIIT global time effect; p<0.05). More specifically, Catalase, MPO and FRAP increased only in Control (p=0.0147; p=0.0047 and p=0.0432 respectively) and post-Hyp80% (p=0.0203; p=0.0002 and p=0.0009 respectively). These results suggest that the oxidative stress modulation by the body weight reduction could be compensated by hypoxia . All the other circulating markers are not affected by neither HIIT session nor condition. CONCLUSION: These data confirm that such HIIT session can affect circulating redox status and moderately impact muscle damage markers. In addition, it seems that similarly to physiological stress (Chambion-Diaz et al., 2025), the reduction of oxidative stress in response to HIIT session by body weight reduction is compensated by hypoxia but only on the 80% body weight. Finally, circulating muscle damage markers and inflammation were not impacted by neither weight reduction nor hypoxia. References : Chambion-Diaz M et al., 2025. Journal of Sports Sciences
Read CV Marie Chambion-DiazECSS Paris 2023: OP-PN30
INTRODUCTION: Repeated-sprint training in hypoxia (RSHyp) is often used by team-sport athletes to improve repeated-sprint ability. Similar training in the heat (RSHot) has also been suggested to be effective. However, little is known about their respective cross-talk. This study therefore aimed to analyze the effect of RSHyp and RSHot on repeated-sprint performance in either normobaric hypoxic or normoxic hot conditions in reference to a normoxic thermoneutral condition. METHODS: Seventeen French elite athletes (rugby sevens national team (n = 11 females), BMX (n = 4 males and 2 females)) performed 6 repeated-sprint training sessions (3 × 5 7-10-s sprints with 20-23-s passive recovery on a cycle ergometer) in either hypoxic (FiO2 = 14.3%, 20°C, n = 8, 6 females) or hot (FiO2 = 20.9%, 36°C, n = 9, 7 females) ambient conditions over two weeks. Pre- and Post-tests (1 week after) included a repeated-sprint ability test (8 × 10-s sprints with 20-s passive recovery) in either a normobaric hypoxic (FiO2 = 14.3%, 20°C), normoxic hot (FiO2 = 20.9%, 36°C) or normoxic thermoneutral (FiO2 = 20.9%, 20°C) environment. Maximal (Pmax) and average (Pmean) power outputs were measured for each sprint. Capillary blood samples were taken before and after the first and last training session and analyzed for pH and bicarbonate concentration [HCO3-]. RESULTS: Pmax and Pmean, averaged for all eight sprints, increased following both RSHyp and RSHot across all testing conditions from 759 ± 207 (Pre) to 849 ± 226 W (Post) for Pmax (Time effect: F = 40.0296, p=0.001) and from 564 ± 166 to 609 ± 157 W for Pmean (F=40.2696, p=0.001). The improvement in Pmax did not differ according to the training group (F=0.0304, p = 0.889) nor testing condition (F=0.956, p = 0.403) while Pmean tended to improve more in the normoxic hot (+14.8%) compared to the normoxic thermoneutral (+9.2%) and normobaric hypoxic (+10.3%) testing condition (F = 3.0765, p = 0.050). No difference was observed between training groups in acute post-training pH (RSHyp: 7.20 ± 0.11, RSHot: 7.16 ± 0.15, F = 0.041, p = 0.844) nor [HCO3-] (RSHyp: 10.8 ± 2.4 mmol.L-1, RSHot: 9.1 ± 1.7 mmol.L-1, F = 0.012, p = 0.912). CONCLUSION: Adding either normobaric hypoxia or heat in repeated-sprint training resulted in an ~11% improvement in repeated-sprint performance in elite athletes across all sprints and testing conditions with a more pronounced improvement in normoxic hot (+14.8%) conditions. The effect was independent of the training group. This indicates an effective cross-talk effect of each respective training condition on the other environmental stress. The similar acute training-induced changes in pH and [HCO3-] values between training groups seem indicative of a similar metabolic stimulus despite different responses in normobaric hypoxic (lower oxygen saturation) or heat (higher core temperature) conditions.
Read CV FRANCK BROCHERIEECSS Paris 2023: OP-PN30