PURPOSE:This study investigated the effects of repeated sprint training in hypoxia (RSH) induced by voluntary hypoventilation (VHL) on sport-specific performance in elite epee fencers. METHODS:Twenty-two elite-level fencers (national to international level) were randomly assigned to 8 sessions of repeated sprint training over 4 weeks. Training was performed either in hypoxia induced by VHL (RSH-VHL, n = 11) or with unrestricted breathing (repeated sprint in normoxia [RSN], n = 11). It consisted of repeated 15-second maximal fencing sprints with 15-second semiactive recovery (work:rest ratio 1:1). Performance was assessed before (pre) and after (post) the intervention using a dual-component fencing test that involved repeated maximal lunges (sprints) immediately followed by a technical task (reaction time and accuracy assessment on an electronic target) before the next repetition. RESULTS:Both groups showed similar significant improvements in best sprint time (RSH-VHL: -5.1%; RSN: -5.7%), mean sprint time (RSH-VHL: -6.8%; RSN: -7.0%), and sprint decrement score (RSH-VHL: -31.6%; RSN: -23.1%) (P ≤.003). However, physiological and technical adaptations differed. In the RSH-VHL group, maximal and mean heart rates decreased significantly (-4.7% and -5.7%, respectively) (P < .001), whereas no significant changes were observed in the RSN group (-0.7% and -0.5%, respectively). Additionally, RSH-VHL prevented the increase in technical alteration under fatigue observed in RSN (reaction time decrement: -3.0% vs 15.7%; P = .005). CONCLUSION:RSH-VHL training mitigates the decline in technical performance (reaction time) under fatigue and improves cardiovascular efficiency in elite epee fencers. These findings suggest that VHL is a valuable, equipment-free method to enhance both physical and technical resilience during high-intensity fencing bouts.

Abstract Lung and muscle oxygen diffusion capacities (DLO2 and DMO2, respectively) are difficult to measure at maximal-intensity exercise and at altitude and they are scarcely reported in the literature, yet they are key components of the O2 transport cascade. The goal of the present study was to compute DLO2 and DMO2 at simulated increasing altitudes between sea-level and Mount Everest. Literature data were compiled to compute DLO2 and DMO2 at maximal exercise using a forward iterative algorithm. These computations were repeated every 250 m of increasing altitude between seal level and the altitude of Mount Everest. Computed DLO2 increased from sea-level to 5500 m and then decreased to the altitude of Mount Everest; yet remaining higher than sea-level values. DMO2 increased from sea-level to 3500 m and then progressively decreased to values lower than sea-level. The computed variations in DLO2 and DMO2 fit with the ability of the lung and muscle to increase their diffusion capacity at altitude, which seemingly indicates an existing diffusion capacity reserve. The muscle reserve seems depleted at a lower altitude than the lung reserve. The clinical relevance of the proposed model requires further investigation.

Human acclimatization to both high-altitude and microgravity is crucial for terrestrial and space exploration. Although these extreme environments elicit several similar physiological responses, including autonomic imbalance, metabolic stress, and reduced exercise capacity, the underlying central mechanisms remain unclear. However, these effects appear to be linked to chemoreflex control. This review summarizes current evidence and proposed potential similarities and bioconvergent mechanisms underlying human responses to both terrestrial and extraterrestrial environments.

Blood flow restriction (BFR) is a widely used exercise modality in sport; however, evidence supporting its use in individuals with overweight remains limited. This study evaluated whether home-based BFR training provides additional benefits over conventional resistance training in this population. Twenty-seven participants were assigned to BFR (n = 13) or non-BFR (n = 14) groups for a 6-week (3x/week) home-based strength program via videoconference. Assessments included body composition (DEXA), glucose and lipid metabolism, knee extensor/flexor strength, and gait analysis (energetics, biomechanics and preferred walking speed). No group × time interactions were observed for any outcome, indicating no BFR-induced benefits. Across both groups, trunk lean mass increased (BFR: 27.2 ± 4.3 to 27.9 ± 4.5 kg; non-BFR: 25.4 ± 4.0 to 25.8 ± 4.4 kg; P = 0.007). HDL-cholesterol decreased (P = 0.008) and glycated haemoglobin increased (P < 0.001), both statistically significant but clinically negligible and directionally unfavourable. Isometric knee-extension peak torque increased (BFR: 186 ± 50 to 222 ± 80 Nm; non-BFR: 183 ± 81 to 204 ± 90 Nm; P < 0.001), with parallel gains in isokinetic concentric extension and flexion at 30°/s, 90°/s, and 180°/s (all P ≤ 0.032). Gait analysis showed no changes. Six weeks of remotely supervised bodyweight resistance training improved knee extensor and flexor strength in sedentary adults with overweight or obesity. Under the present conditions, adding BFR did not provide evidence of additional benefit for strength, body composition, metabolic markers, or walking outcomes. The trial was registered in advance at ClinicalTrials.gov with the identifier NCT05371119 on 12 May 2022.

Mountain ultra-marathons (MUM) impose multiple stressors on pulmonary function inducing risk of airway epithelial damage. This study aimed to assess the magnitude of pulmonary function changes and the associated risks of airway damage induced by such a race. Thirteen volunteers completed the MUM (330 km, 24,000 m elevation gain). Pulmonary function was assessed using standardized procedures before (pre-) and within 1 h after (post-) the race. Assessments included forced inhalation and exhalation maneuvers, as well as maximal inspiratory pressure (MIP) measurements. Venous blood samples were collected for the analysis of plasma club cell secretory protein 16 (CC16). Blood volume was determined using the carbon monoxide rebreathing method. From pre- to post-, forced vital capacity (FVC) (-7.5

PurposeSki mountaineering (SkiMo) sprint is a new Olympic discipline. This study aimed to investigate the performance determinants at the Milan-Cortina Olympic Sprint Test Event through the analysis of overall sprint time in quarterfinals (SPT), section-specific contributions, and associations with laboratory-derived physiological parameters.MethodsSPT and seven section splits were analyzed across quarterfinal rounds in qualified athletes (n = 36). The course included uphill (U), transition (T), and downhill sections. A subgroup of Swiss elite male sprinters (n = 9, Tier 4–5) underwent laboratory testing of aerobic power and lactate kinetics.ResultsTime on uphill ski and foot section (UT) in quarterfinals accounted for the largest proportion of SPT variability (81.5%) and was strongly correlated with SPT (r = 0.89, P < 0.001), particularly during U1, the first U section of the race (r = 0.91, P < 0.001).Time in T1 showed a moderate association with SPT (r = 0.62, P = 0.021), whereas no significant associations were observed for the remaining U, T, or downhill sections time.Among the top 18 of the 36 qualified athletes, T time contributed more to SPT variability than in athletes ranked 19th to 36th (respectively 46.8% and 18.4%).For the subgroup tested in the laboratory, UT was best predicted by maximal vertical velocity (r = −0.76, P = 0.018) and by maximal oxygen uptake relative to body mass (V˙O2max) (r = −0.75, P = 0.021), and a multiple stepwise regression identified V˙O2max and lactate removal capacity as the best UT predictors (R2 = 0.82, P = 0.006).DiscussionThese findings suggest that sprint performance in SkiMo is associated with both high aerobic capacity, and strong performance in the early sections of the race (U1 and T1). Interestingly, lactate removal capacity was also associated with sprint performance, suggesting a potential role of peripheral muscle characteristics associated with lactate kinetics on fatigue resistance during a SkiMo sprint. Finally, the relatively greater contribution of T to sprint performance among world-class athletes highlights that SkiMo sprint is not only about physiological capacity but also about fast and error-free T under maximal effort.

Near-infrared spectroscopy (NIRS) has emerged as a potential alternative method for determination of breakpoints equivalent to lactate thresholds. However, the optimal NIRS location remains unclear, particularly in Nordic skiing, which requires both upper- and lower-limb contributions. This study aimed to evaluate the feasibility and accuracy of NIRS-derived breakpoints determination (i.e., BP1 and BP2) compared to first (LT1) and second (LT2) lactate thresholds and to compare different muscle sites in male and female world-class Nordic skiers. Fifty-two world-class Nordic skiers (29 males, 23 females) performed an incremental treadmill test on roller skis. NIRS sensors were located simultaneously on four muscles: vastus lateralis (VL), biceps femoris (BF), biceps brachii (BB), and triceps brachii (TB). Oxygen saturation ( S m O 2 ${S_{{\mathrm{m}}{{\mathrm{O}}_2}}}$ ) was collected and analysed to detect BP1 and BP2 vs. LT1 and LT2. First, BP1 was too often undetectable or inaccurately detected, suggesting an unsuitable practical use. Second, BP2 was detected in VL (88.5%), BF (96.2%) and BB (86.5%) but not in TB (24.1%). Third, there was a very good accuracy (i.e., bias [95% CI] in heart rate between BP2 and LT2 in VL (-0.6 bpm [-8.9, 7.8]), BF (+1.3 bpm [-2.8, 4.2]) and BB (+1.0 bpm [-7.5, 9.5]). Finally, no significant differences were found between male and female athletes. NIRS appears as an effective non-invasive method for detecting breakpoint equivalent to LT2 in both male and female world-class Nordic skiers, especially if positioned on both BB and BF.

Atherosclerosis-induced oxidative stress drives skeletal muscle myopathy in peripheral artery disease, yet the combined effects of hypoxia and hypoxia sprint interval training (SIT) remain unclear. The present study was designed to evaluate how a six-week regimen of hypoxia exposure and SIT influences redox balance and myokine production in the skeletal muscle of high-fat diet (HFD) (21

Exogenous ketosis, induced via ketone monoester (KE) ingestion, has been shown to attenuate hypoxia-induced blood, muscle, and brain deoxygenation and augment oxygen uptake (V̇o2) under acute normobaric hypoxia. However, its effects on exercise responses during early acclimatization at terrestrial high-altitude remain unexplored. Thirty-four healthy, active adults completed four exercise sessions: one near sea level and then once per day during a 3 day altitude sojourn (3,375 m), with regular KE or placebo ingestion. Pulmonary gas exchange, minute ventilation, cardiac output, pulse oxygen saturation, skeletal muscle tissue saturation index (TSI), and brain TSI were measured during moderate- and heavy-intensity exercise. KE ingestion induced ketosis at the start of each exercise session (group × time interaction: P < 0.001). However, compared with placebo, KE resulted in a comparable (group × time interaction: P = 0.501) high-altitude-induced slowing of the primary phase time constant of V̇o2 kinetics during heavy-intensity exercise (time effect: P < 0.001). Moreover, both groups exhibited similar (all group × time interactions: P > 0.123) hypoxia-related decreases in gas exchange and increases in minute ventilation, accompanied by reductions in pulse oxygen saturation and brain TSI during both moderate- and heavy-intensity exercise across the 3 days (all time effects: P < 0.015). Notably, KE ingestion increased cardiac output during moderate-intensity exercise on the first altitude day (group × time interaction: P = 0.042). Whole-body energy efficiency was preserved across time at 3,375 m (time effect: P = 0.060) in both groups (group × time interaction: P = 0.084). These data indicate that intermittent exogenous ketosis does not attenuate altitude-induced alternations in V̇o2 kinetics or tissue oxygenation, nor improves whole-body efficiency, during moderate- or heavy-intensity exercise across 3 days at 3,375 m.NEW & NOTEWORTHY This study demonstrates that intermittent exogenous ketosis does not alter the high-altitude slowing of the primary phase of V̇o2 kinetics during the transition to heavy-intensity exercise, nor does it change ventilatory, gas exchange, blood or tissue oxygenation responses, or whole-body efficiency across 3 days at 3,375 m. However, preexercise ketone monoester ingestion increased cardiac output during moderate-intensity exercise on arrival to 3,375 m and after 24 h, but this did not translate to broader physiological benefits.

PurposeTo analyze if the “Munz Floor”® fascial stretching method significantly modifies the autonomic nervous responses at rest. We tested the hypothesis of a positive influence on the parasympathetic activity.MethodsHeart rate variability (HRV) was measured in thirty three (including nine females) healthy participants during a tilt test (i.e., 5-min supine followed by 5-min standing) before (pre-) and immediately after (post-) 60 min in either a control condition and 3 days later a “Munz Floor”® session. Time-domain (heart rate, HR); root mean square of the successive differences between RR intervals, (RMSSD), non-linear (standard deviations, SD1, SD2), and frequency-domain (spectral frequencies in very low, VLF; low, LF and high bands) parameters as well as the detrended fluctuation analysis (DFAα1) were measured.ResultsIn supine position (SU), HRSU decreased to la larger extent (−12.4% ± 7.6% vs. −3.8% ± 4.0%, p < 0.001) in the “Munz Floor”® group (62.3 ± 8.7 vs. 54.4 ± 7.3 bpm, p < 0.001, Effect Size (ES) = 0.83) than in the control group (60.8 ± 8.7 vs. 58.4 ± 8.3 bpm, p < 0.01, ES = 0.27). Significant increases in RMSSDSU (50.1 ± 30.1 vs. 73.3 ± 48.0 m, p < 0.001, ES = 0.59), HFSU (1,212 ± 1,078 vs. 2,672 ± 2,388 m2, p < 0.001, ES = 0.72) were reported in the Munz Floor”® but not in the control group. In the standing position (ST): HRST decreased in both the Munz Floor”® (76.6 ± 11.0 vs. 68.8 ± 9.6 bpm, p < 0.001, ES = 0.62) and the control (77.2 ± 12.7 vs. 74.7 ± 11.9 bpm, p < 0.01, ES = 0.20) but the relative change was larger in the “Munz Floor”® (−9.6% ± 9.4% vs. −2.9% ± 6.4%, p < 0.01). Significant increases in RMSSDST (29.5 ± 23.8 vs. 39.9 ± 27.5, p < 0.01, ES = 0.38) and in (LF + HF)ST (2,132 ± 2,464 vs. 3,065 ± 3,382 m2, p < 0.01, ES = 0.31) were observed only in the “Munz Floor”® group.ConclusionThe “Munz Floor”® fascial stretching method was effective for acutely increasing the parasympathetic activity. These results suggest “Munz Floor”® fascial stretching as a potential strategy for improving recovery and reducing the impact of stress and fatigue.

Altitude exposure can promote beneficial physiological adaptations but may also lead to altitude-related illnesses. Despite decades of research, the mechanisms explaining why some individuals acclimatize successfully whereas others do not remain incompletely understood. Traditional models of altitude acclimatization focus on the steps of the oxygen cascade but only partially account for the marked interindividual variability observed in acclimatization.In this perspective, the concept of regulatory reserve, defined as the capacity of integrated physiological control systems to maintain homeostasis during environmental hypoxia is proposed. Successful acclimatization would not only depend on the functional reserves of organs at each step of the oxygen cascade, but also on the coordinated regulation of respiratory, cardiovascular, cerebrovascular, autonomic, and diffusive processes. Conversely, altitude-related illnesses may arise when this regulatory reserve becomes insufficient, exhausted, or dysregulated. Examples from ventilatory control and pulmonary diffusion are used to highlight how adaptive responses can become maladaptive when this regulatory reserve fails. The discussion focuses on how dynamic physiological markers, including breathing variability, loop gain, heart rate variability, baroreflex sensitivity, and diffusion reserve may improve the prediction of altitude acclimatization. In addition, a systems physiology approach in which acclimatization is viewed as an emergent property of interacting control networks is outlined. Such concepts may provide new insights into altitude acclimatization, maladaptation, and the prediction of human responses to altitude.

OBJECTIVE:This study aimed to investigate the sex difference in uphill performance of Master runners. We tested the hypothesis that aging would reduce this difference, with the aging-induced performance decline being smaller in females than in males. We also analyzed changes in female participation over the past 20 years, with the hypothesis that increasing participation would be associated with a narrowing of sex differences during this period. METHODS:Data were extracted from the uphill races of the World Masters Mountain Running Championships between 2004 and 2024 and consisted of n = 116 top-3 performances in male and female Master runners (aged 35-69), across 5-year age categories. RESULTS:The sex differences in uphill performance of Master runners were 22.2% (4.9%) and remained similar across ages. Over the 20-year period, sex differences remained constant. There was a linear relationship between the number of female participants and the sex-based performance differences (r = -.31, P < .05). DISCUSSION:The 22% sex difference reported in Master mountain runners is comparable to that reported in elite athletes. Contrary to our hypotheses, sex differences in uphill running performance did not change across age categories and remained stable over the past 20 years. However, sex differences appeared to narrow as female participation increased, possibly due to the small female sample (approximately 20 on average), where individual performances may have had a greater proportional impact.

Intermittent exogenous ketosis via ketone monoester (KE) ingestion has been shown to enhance physiological responses and reduce acute mountain sickness (AMS) symptoms during acute normobaric hypoxia. Its effects during early acclimatization to terrestrial high-altitude, however, remain unclear. Thirty-four participants were randomised to an intermittent exogenous ketosis (IEK, n=17) or placebo (PLA, n=17) group and underwent a near sea level trial (295 m) without supplementation, followed by a four-day sojourn at 3375 m during which they received regular KE (IEK) or placebo (PLA) supplements. AMS symptoms, hematological markers, and resting ventilatory, cardiovascular, and cerebral tissue oxygenation responses were assessed each day upon waking, at midday, and before sleep throughout the exposure. KE consistently elevated circulating β-hydroxybutyrate post-ingestion (P<0.001), confirming intermittent exogenous ketosis in the IEK group. AMS incidence peaked at 25–35

Exposure to environmental stressors such as hypoxia or heat has emerged as an effective strategy to stimulate physiological adaptations, enhance sport/physical performance and promote health. Both environmental stressors activate shared molecular pathways, notably through the stabilisation of hypoxia-inducible factor-1 alpha and the induction of heat shock proteins, which mediate cellular protection and systemic molecular adaptation. However, hypoxia and heat differ in several aspects, including induction modalities, monitoring methods, metrics used to assess physiological strain and substantial intra- and inter-individual variability. Together, these differences challenge direct comparison and/or combination. Therefore, this current opinion highlights research gaps by critically presenting the common and distinct physiological responses and adaptations to hypoxia and heat exposure. It also emphasises the importance of monitoring internal physiological strain rather than external environmental stress to better account for individual variability. Finally, we propose future research perspectives to address current methodological challenges.

PURPOSE:Premature birth (< 37 weeks gestation) is associated with lower exercise capacity. However, the specific underlying mechanisms remain poorly defined. This study investigated the mechanisms of exercise limitation across the oxygen transport chain in preterm-born adults with normal resting cardiopulmonary function but exertional dyspnea. METHODS:10 preterm born (6F, age: 30 ± 5 years, body mass index [BMI]: 27.0 ± 6.3 kg/m2, gestational age: 30 ± 3 weeks) and 8 term born (3F, age: 29 ± 5 years, BMI: 25.4 ± 4.6 kg/m2, gestational age: 40 ± 0 weeks) adults performed resting spirometry and a cardiopulmonary exercise test, consisting of two 5-min submaximal cycling exercises (30 and 60 W), followed by an incremental protocol to exhaustion. We measured breath-by-breath gas exchange (custom designed system), heart rate (HR, 12-lead ECG), cardiac output (Q̇c, acetylene rebreathe), and calculated arterial-venous oxygen difference (a-vO2diff, Fick equation). RESULTS:Oxygen uptake (V̇O2) was similar between groups at rest, 30 and 60 W. At peak, compared to term-born peers, preterm adults showed lower power output (108 ± 18 vs. 208 ± 69 W, p < 0.001), V̇O2 (1.58 ± 0.29 vs. 2.52 ± 0.85 L/min, p = 0.017), Q̇cindex (7.5 ± 1.0 vs. 8.9 ± 1.6 L/min/m2, p = 0.057), while a-vO2diff (12.6 ± 1.7 vs. 14.1 ± 1.6 mL/dL, p = 0.096) and HR were similar between groups (175 ± 16 vs. 185 ± 8 bpm, p = 0.104). The increase in stroke volume index from rest to peak exercise was blunted in preterm compared to term-born adults (8 ± 7 vs. 15 ± 6 mL/m2, p = 0.032). CONCLUSION:Preterm born adults present with lower exercise capacity compared to age-matched peers born at term. Central mechanisms, primarily stroke volume, underlie exercise limitation in this population.

Introduction Elite cross-country (XC) skiers undergo standardized testing to monitor their performance development and to calibrate training prescriptions. However, the long-term progression of performance indicators, such as maximal oxygen uptake (VO2max), performance at the second lactate threshold (LT2), and time-trial performance over an athlete's career remains unclear. This study aimed to investigate the longitudinal data from > 15 years of exercise testing with the Swiss XC ski national team to examine the trajectories of key performance indicators across the careers of male and female skiers. Methods The longitudinal development of VO2max, LT2, and 24-minute double poling performance (24-min DP), described in further detail elsewhere (Bucher et al., 2023), was analyzed in 72 male and 49 female current and former Swiss XC-ski national team athletes. The performance trajectories were modeled using mixed-effects approaches, with a linear random intercept for VO2max, a linear random slope for LT2, and a third-degree polynomial for 24-min DP. Fixed effects included age, sex, and their interaction, with random effects at the individual level. The study included 357 observations (n = 27 females, 48 males) for VO2max, 911 (n = 46 females, 65 males) for LT2, and 601 (n = 49 females, 70 males) for 24-min DP. Results VO2max in females tended to increase by 0.16 mL/kg/min per year (p=0.085), with no increase in males (0.03 ml/kg/min, p=0.627). Males had a higher baseline VO2max at age 18 (70.8 vs. 58.2 mL/kg/min, 21.6% difference), but the rate of change with age was not significantly different between the sexes (p=0.259). LT2 improved significantly with age for both sexes: females gained 0.038 W/kg per year (p<0.001) and males 0.052 W/kg per year (p<0.001). At age 18, males had a 23.2% higher baseline LT2 (3.34 vs. 2.71 W/kg). In the 24-min DP test, both sexes initially improved significantly (p<0.001). However, there was a notable decrease in the rate of improvement in males, as indicated by the quadratic age term (p<0.001). On the other hand, females showed a consistent linear performance trajectory throughout their careers, with no significant quadratic age term (p=0.430). Female skiers showed a baseline performance of 3820 m at age 18, while this value was at 4788 m in males, with males outperforming females by 968 m (25.3%). Discussion/Conclusion VO₂max, LT2, and 24-min DP showed distinct developmental trajectories across age and sex in elite XC skiers. While VO₂max remained unchanged, LT2 continuously increased throughout their career. On the other hand, 24-min DP followed a non-linear progression in males, with a slowdown in performance improvement as they transitioned from the U23 to the senior age category. These results highlight the importance of high initial VO₂max at the junior level and the greater trainability of LT2 and aerobic time-trial performance with the accumulation of specific training as athletes progress in their careers. References Bucher, E., Millet, G. P., Wehrlin, J. P., & Steiner, T. (2023). Test-retest reliability of ski-specific aerobic, sprint, and neuromuscular performance tests in highly trained cross-country skiers. Scandinavian Journal of Medicine and Science in Sports, 33, 2482–2498. https://doi.org/10.1111/sms.14473