ECSS Paris 2023: OP-PN35
INTRODUCTION: Continuous hypoxic exposure can improve exercise capacity, yet the relative contribution of central versus peripheral adaptations remains unresolved [1,2]. This uncertainty is especially relevant in women, who are under-represented in hypoxia research despite physiological differences which may be pertinent to adaptation [3]. We investigated whether ten days of continuous hypoxic residence results in higher exercise capacity via central or peripheral mechanisms in women, and whether such effects depend on oxygen availability. METHODS: Healthy, physically active women were randomized to intervention (n=14) or control (n=13). The intervention group lived continuously in normobaric hypoxia (PiO2=98 mmHg; ~3500 m) for ten days, whereas the control group continued normoxic free-living. At baseline and post-intervention, participants completed incremental exercise tests to exhaustion in normoxia and normobaric hypoxia (PiO2=89 mmHg; ~3800 m). Gas exchange, cardiac output, and vastus lateralis tissue oxygenation were recorded via metabolic cart, bioelectrical impedance, and near-infrared spectroscopy, respectively. Outcomes were averaged across the final 20 s pre-exhaustion. Earlobe capillary samples were obtained immediately post-exercise during early active recovery, and analysed for blood gases. Outcomes were analyzed using linear mixed-effects ANCOVA models to test intervention effects (group) and their dependence on exercise condition (group*condition), with baseline values included as covariates. All values represent post-intervention baseline-adjusted estimated marginal means (±95%CI). RESULTS: Baseline-adjusted post-intervention peak oxygen uptake was higher in the intervention group compared with control (43±1 vs 40±1 ml/kg/min; group p=0.014) across both exercise conditions (interaction p=0.41). Maximal aerobic power showed a similar group-specific effect (218±7 vs 199±7 W; group p=0.001; interaction p=0.17). The intervention did not affect cardiac output (21±2 vs 20±2 L/min; group p=0.22, interaction p=0.55) or ventilation (116±5 vs 110±5 L/min; group p=0.14, interaction p=0.80). Capillary oxygen tension in early recovery was higher in the intervention group compared with control (100±5 vs 82±6 mmHg; group p<0.001), with no group*condition interaction (p=0.26). Vastus lateralis oxygenation showed a significant interaction (p<0.001), with higher values in the intervention group during normoxic (72±2 vs 69±2%) but not hypoxic (69±2 vs 71±2%) exercise. CONCLUSION: Ten days of continuous normobaric hypoxic residence at ~3500 m resulted in higher exercise capacity in women, similarly during normoxic and hypoxic exercise. The absence of clear systemic cardiorespiratory effects, alongside condition-specific changes in muscle oxygenation, indicates that peripheral mechanisms may contribute to these differences. 1. Wagner (1993) Respir Physiol, 93, 221-37. 2. Calbet et al. (2003) Am J Physiol Regul Integr Comp Physiol, 284, 291-303. 3. Raberin et al. (2024) Sports Med, 54, 271-87.
Read CV Benjamin NarangECSS Paris 2023: OP-PN35
INTRODUCTION: Neurovascular coupling (NVC) describes the relationship between cerebral blood flow (CBF) and local metabolic demand. Previous research has shown that the NVC response remains either unchanged [1,2] or elevated [3] following high altitude (HA) acclimatization. Whether sex differences exist in NVC following HA acclimatization remains unexplored given the logistical challenge of recruiting a sufficiently powered and matched sample of male and female participants sojourning to terrestrial HA. Considering females have shown higher cerebral blood velocity at sea-level [4], we hypothesized that compared to males, females would also exhibit a greater NVC response at sea-level and throughout HA acclimatization. METHODS: Twenty-five healthy participants (12F; 24±3yrs) underwent cardiorespiratory and cerebrovascular monitoring at sea-level (334m) and following early (day 3-4) and late (day 11-12) acclimatization to HA (3,800m). Posterior cerebral artery velocity (PCAv) was measured at rest and during a visual stimulus test (Where’s Waldo) using transcranial Doppler ultrasound. Beat-by-beat arterial blood pressure (finger photoplethysmography) and heart rate (HR; three-lead electrocardiogram in lead II orientation) were continuously recorded. RESULTS: At sea-level, baseline PCAv was higher in females compared to males (F: 44.24±11.39 vs. M: 32.69±10.39 cm/s; p=0.019). PCAv increased at HA (p<0.0001) and remained higher in females following acute HA exposure (F: 55±12 vs. M: 44±10 cm/s; p=0.028), however, this difference was eliminated following HA acclimatization (p=0.292). During the NVC test, absolute peak PCAv was higher in females at sea-level (p=0.032). Peak PCAv remained unchanged at HA (p=0.249) but remained higher in females following early HA exposure (p=0.048). This difference was diminished following late HA acclimatization (p=0.328). Absolute mean PCAv response to visual stimulation was higher at HA (p=0.047), but did not differ between sexes (p=0.157). CONCLUSION: These data demonstrate that resting PCAv and NVC is higher in females at sea-level and following early (3-4 days) HA acclimatization when compared to males. These differences were, however, abolished following late acclimatization to HA (11-12 days). The physiological implications of these findings warrant further investigation. 1. Caldwell et al. (2017) 2. Stacey et al. (2023) 3. Leacy et al. (2018) 4. Tegeler et al. (2012) 5. Burma et al. (2021)
Read CV Christabel Osei-BoatengECSS Paris 2023: OP-PN35
INTRODUCTION: Training interventions based on repeated sprint performed in hypoxia (RSH) have regularly demonstrated superior gains in repeated-sprint performance at sea level compared with the same programs conducted under normoxic conditions. Despite these findings, the effectiveness of a short repeated-sprint training block in hypoxia compared to normoxia has only been investigated in female athletes at a training altitude of 5,000m whereas 3,000m is preferentially used for RSH. Therefore, the present study sought to examine whether brief hypoxic repeated-sprint training induces greater improvements in repeated-sprint ability than the same training in normoxic condition in national-level female rugby union players. METHODS: Eight elite female rugby union players participated in a randomized, controlled, cross-over study design. Each athlete completed five repeated-sprint training sessions under two environmental conditions: normobaric hypoxia (RSH; simulated altitude 3,000m, FiO2 = 14.5%) and normoxia (RSN; altitude 165m, FiO2 = 20.5%). Repeated-sprint ability was assessed before and after each training condition using a cycle ergometer protocol comprising six maximal 10-second sprints separated by 20-second passive recovery periods. Peak power output (PPO; mean of the best sprint), mean power output (MPO; mean of the six sprints) were recorded and sprint decrement (Sdec; [1 - (MPO/PPO)] × 100)) was calculated. RESULTS: Following the hypoxic training condition, PPO exhibited a significant increase between pre- and post-intervention assessments (602 ± 98 to 704 ± 92 W; p = 0.007), whereas no significant change was observed after normoxic training (661 ± 91 to 673 ± 76 W; p = 0.560). MPO demonstrated a comparable response, with a significant improvement after RSH (445 ± 63 to 532 ± 51 W; p = 0.013) but not after RSN (499 ± 88 to 509 ± 63 W; p = 0.557). No meaningful alterations in Sdec were detected following either training condition (RSH: p = 0.819; RSN: p = 0.336). CONCLUSION: These findings resulting from a cross-over study indicate that only five sessions of RSH at a simulated altitude of 3,000m is sufficient to induce enhancements in repeated-sprint ability in elite female rugby union players, whereas the same training performed in normoxia does not add similar benefits.
Read CV Mélanie BabalianECSS Paris 2023: OP-PN35