ECSS Paris 2023: CP-PN07
INTRODUCTION: The energetic cost of transport (CoT) follows a U-shaped curve during walking (where the lowest walking CoT defines the economical speed (ES), intersecting with a linear running CoT at the economical transition speed (EOTS). Muscle tissue saturation index (TSI), derived from near-infrared spectroscopy (NIRS), quantifies local oxygenation and may reflect different components of the oxygen transport chain. Environmental factors such as heat and hypoxia are known to influence CoT as well as muscular TSI. The aim of the study was a) to assess the relationship between CoT and muscle TSI during human locomotion under environmental stress and b) to assess the impacts of environmental stress on energetic markers of economy (ES and EOTS). METHODS: Thirteen participants completed four randomized trials in control (CON; FiO2 20.9%, 24 °C, 50% relative humidity [RH]), heat (HOT; FiO2 20.9%, 35 °C, 50% RH), moderate normobaric hypoxia (MH; FiO2 16.8%, simulating ~1800 m altitude, 24 °C, 50% RH), and severe hypoxia (SH; FiO2 13.3%, simulating ~3600 m altitude, 24 °C, 50% RH) conditions. Each trial included eight walking stages (from 2.4 to 7.3 km·h-1) and four running stages (from 7.3 to 9.4 km·h-1). A computerized breath-by-breath system (Quark, Cosmed, Rome, Italy) was used to measure Pulmonary oxygen uptake (VO2) and carbon dioxide output (VCO2) for CoT, while the TSI of the vastus lateralis was continuously recorded using a portable NIRS device (PortaMon, Artinis Medical Systems, Zetten, the Netherlands). RESULTS: Walking and running CoT increased significantly in SH (+8.8 ± 0.95%, P = 0.003 and +6.0 ± 0.6%, P = 0.005, respectively) and in MH (+7.4 ± 0.9%, P = 0.006 and +8.1 ± 0.6%, P = 0.0002, respectively) versus CON. HOT had no significant effect during walking (-1.9 ± 0.9%, P = 0.47), and running (-3.4 ±. 0.6%, P = 0.099) versus CON. TSI in SH significantly decreased during walking (-9.9 ± 10.7%, P = <0.00001) and running (-13.8 ± 12.5%, P = 0.0009), While in MH no difference was observed during walking (-1.5 ± 8.7%, P =0.39) or running (-1.0 ± 9.7%, P =0.75), compared to CON. No significant difference observed in HOT during walking (-0.9 ± 9.1%, P =0.61) and running (-4.1 ±1 1.7%, P =0.27) compared to CON. ES and EOTS did not significantly change under any condition. CONCLUSION: These results suggest that pulmonary gas exchange limitations under SH contribute substantially to increases in CoT and reductions in muscle TSI during locomotion. MH also increases CoT but without a significant impact on TSI, indicating possible compensatory mechanisms or insufficient environmental stress to observe effects. HOT appears not to have any significant impact on either CoT or TSI, possibly due to thermoregulatory adjusments such as increased cardiac output and blood flow redistribution. The lack of change in ES and EOTS suggests that other factors maintain gait transition parameters under environmental stress.
Read CV Hubert WoronieckiECSS Paris 2023: CP-PN07
INTRODUCTION: Intermittent hypoxia (IH) is widely used to enhance athletic performance, yet evidence remains fragmented across diverse protocols (LLTH, LHTL, LHTLH) and training modalities. Recent systematic reviews (SRs), meta-analyses (MAs), and network meta-analyses (NMAs) report heterogeneous findings, limiting practical recommendations. This umbrella review aimed to synthesize and critically appraise the highest level of evidence regarding the effects of IH protocols on physical performance outcomes. METHODS: Following PRIOR guidelines (PROSPERO CRD42024465481), seven databases were searched from inception to June 2025. Eligible studies were SRs with or without MA/NMA investigating systemic IH strategies (LLTH, LHTL, LHTLH) and reporting at least one performance outcome. Methodological quality was assessed using AMSTAR-2. Overlap between reviews was quantified using the Corrected Covered Area (CCA). RESULTS: Twenty-two SRs were included, encompassing 487 unique primary studies and 5,333 participants (13–67 years). Fourteen included MAs and three included NMAs. Overall overlap was low (CCA=3.5%). IH protocols demonstrated significant improvements in aerobic and anaerobic performance. LHTL combined with low-altitude training showed large effects on V̇O₂max (SMD=1.04, 95%CI [0.47–1.61]). Simulated altitude training produced similar effects (SMD=0.91 [0.44–1.38]). Repeated sprint training in hypoxia (RSH) improved V̇O₂max (SMD=0.76 [0.29–1.23]) and repeated-sprint ability (SMD=0.46, p=0.05). Hypoxic HIIT elicited greater V̇O₂max gains than normoxia (SMD=1.14; SMD=0.68 in recent MA). RSH with voluntary hypoventilation improved sprint fatigue resistance (SMD=0.60, p=0.005). Hematological adaptations were inconsistent and primarily observed with prolonged exposure (>12 h·day⁻¹). Methodological quality was predominantly low to critically low. CONCLUSION: IH training enhances multiple domains of performance, with the strongest evidence supporting LHTL, hypoxic HIIT, and RSH for aerobic and repeated-sprint outcomes. Benefits appear largely mediated by peripheral and metabolic adaptations rather than robust erythropoiesis in most protocols. However, methodological limitations and protocol heterogeneity temper certainty. Optimizing hypoxic dose and individualizing prescriptions are critical to maximize performance benefits.
Read CV Ayoub BoularesECSS Paris 2023: CP-PN07
INTRODUCTION: A major issue using Live Low–Train High (LLTH) models of hypoxia training is the reduction in the mechanical training load required to cope with the hypoxia-induced limitation in maximal aerobic power [1-2]. The ability to achieve high mechanical power output despite limited metabolic demand in eccentric cycling (ECC) [3], might be especially relevant to maintain or enhance the mechanical training load in LLTH interventions. This study aimed to establish if combining high-intensity interval concentric (CON) and ECC cycling under hypoxia improves physiological determinants of judo performance in a well-trained judo athletes. METHODS: Twenty-three well-trained judo athletes (20+/-1 yr, 1.72+/-9m, 79+/-11kg) were divided in a hypoxic CON group (HYP) or a hypoxic CON and ECC group (HYP-ECC). Both groups underwent 2 weekly training sessions in hypoxia (3,000m) over a 6-wk period. All sessions for the HYP group involved 5 repetitions of 3-min CON cycling at 100% of hypoxic CON maximal aerobic power (MAP) with 3-min of recovery between intervals at 30% of hypoxic CON MAP. The HYP-ECC group performed the same training sessions except that the recoveries between intervals were performed in ECC at 150% of hypoxic CON MAP. Pre and post training assessments included body composition (DEXA scan), vastus lateralis thickness (VLT, echography), knee extensor maximal voluntary isometric contraction (MVC), incremental cycling tests and a repeated sprint test in normoxia (RST, 10s sprint/20s recovery). Data are presented as means +/- standard deviations and differences between groups were tested using a two-way ANOVA (time x group) on repeated measures. RESULTS: Body composition did not change with training, except for a greater VLT in the HYP-ECC group (+10%, p<0.05). Both groups improved or tended to improve power output associated to maximal oxygen uptake (+5-7%, p<0.05-0.1), to the second (+5-7%, p<0.05) and to the first ventilatory thresholds (+10-14%, P<0.05). Oxygen cost of cycling improved only in the HYP-ECC group (-5%, p<0.05). MVC did not change significantly nor did CON peak sprint power. Squat jump height improved with training in both groups (+3-5%, p<0.05) as did the number of sprints performed until exhaustion in the RST (+25-31%, p<0.05). No significant group by time interactions were observed. CONCLUSION: These data demonstrate the feasibility of a new LLTH design combining high-intensity CON and ECC cycling. The results indicate similar training-induced benefits in judo performance factors for both groups, except for VLT and oxygen cost of cycling improving only in the HYP-ECC group. Future studies should further explore this new LLTH strategy to optimize the combination of high-intensity CON and ECC cycling with the ultimate goal to enhance athletes’ performance. 1. Dufour et al. J Appl Physiol. 2006 2. Faiss et al. Brit J Sports Med. 2013 3. Isner-Horobeti et al. Sport Med. This study was supported by a grant ANR-20-STHP-0002
Read CV Stéphane P. DufourECSS Paris 2023: CP-PN07