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.

Background. Self-congruency refers to the coherence between emotional experience (internal states) and enacted behavior (outward actions). Reduced self-congruency has been linked to vulnerability in mental health, yet its physiological correlates remain poorly characterized. Heart-brain temporal coupling may provide a candidate physiological marker of this psychological coherence. Methods. Thirty-eight healthy adults underwent resting-state functional magnetic resonance imaging while cardiac activity was simultaneously recorded using photoplethysmography to derive heart rate variability (HRV). Self-congruency was assessed using a graphic rating scale based on the spatial overlap between emotional experience and enacted behavior. Heart-brain temporal coupling between HRV and regional blood-oxygen-level-dependent (BOLD) signals was quantified using cross-covariance analysis across biologically plausible temporal shifts. Results. Heart-brain temporal coupling predominantly reflected brain-to-heart temporal ordering, particularly within regions central to the neurovisceral integration model, including the ventromedial prefrontal and anterior cingulate cortices. In contrast, higher self-congruency was associated with stronger heart-to-brain temporal coupling, notably within the right rostral middle frontal gyrus and supramarginal gyrus, regions implicated in emotion regulation and socio-emotional processing. Conclusions. While global heart-brain temporal coupling is dominated by top-down neural regulation, greater alignment between emotional experience and enacted behavior is associated with enhanced bottom-up cardiac temporal ordering on neural activity. These findings seem to identify a physiological-psychological axis that may inform original prevention-oriented approaches in mental health.

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.

Heart rate variability (HRV) is most often used as a standalone, without integration of complementary data. Yet these data are at our fingertips, and a revolution might be just around the corner. This perspective article gives insight on how integrating accelerometery and continuous blood pressure and extracting ventilatory variables may improve the use of HRV, taking it to a whole new level for elite and recreational sports, assessing fatigue, and intensity domains. Also, the use of mass data could lead to seamless measurements as precise and relevant as in elite sports, which could be made available to the public for health assessment and follow-up.

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.

Introduction & Purpose: Vertical Kilometer (VK) running is a growing discipline on extreme uphill terrain. On October 10th, 2025, both men’s (Rémi Bonnet, 27 min 21 s) and women’s (Axelle Gachet-Mollaret, 32 min 52 s) world records were broken in Fully, Switzerland—one of the steepest courses worldwide (1.9 km, 1000 m ascent, 52% slope). Although previous research has defined the energetic demands and optimal gradients for maximizing vertical velocity during uphill locomotion, the physiological determinants of elite VK performance and the transferability of laboratory treadmill tests to field performance remain poorly understood. This study examined the relationships between physiological parameters measured during a treadmill test and actual VK race performance in athletes. We hypothesized that V̇O2max and maximal vertical velocity (vVmax) would strongly predict VK race time. Methods: Eight athletes (Tier 3-5), (4 males, 4 females) from the Swiss national ski mountaineering team performed treadmill tests at 25% slope, followed by the Fully VK race 10–12 days later. Each athlete completed two 5-min submaximal bouts (4.0 km·h⁻¹ for men; 3.5 km·h⁻¹ for women) to assess VO2 kinetics and vertical running economy, followed by an incremental test to exhaustion (0.3 km·h⁻¹·min⁻¹ increments; with poles). Breath-by-breath gas exchange (Quark CPET, Cosmed, Italy) was analyzed to determine ventilatory thresholds and maximal values. Pulse oxygen saturation (SpO₂) was measured continuously. Hemoglobin mass (Hbmass) was assessed by the optimized CO-rebreathing method (OpCo, Detalo Instruments, Denmark), and body composition was estimated from six skinfolds to calculate body fat percentage (BF%) and fat-free mass (FFM). Results: V̇O2max and V̇O2max _FFM differed significantly between females and males (60.0 ± 3.1 vs. 73.7 ± 4.9 ml·kg⁻¹·min⁻¹, p < 0.001; and 69.7 ± 4.1 vs. 79.0 ± 5.5 ml·kg⁻¹·min⁻¹, p = 0.003, respectively). vVmax showed the strongest relationship with VK time (Figure 1). V̇O2max was also highly correlated with performance. Minimal SpO₂ at exhaustion (SpO2min) correlated positively with VK time, indicating that greater exercise-induced hypoxemia (EIH) was associated with poorer performance. Moreover, Hbmass was also highly correlated with VK time (r = -0.95, p = 0.011. Surprisingly, BF% did not correlate significantly with VK time (r = 0.67, p = 0.067). Discussion: As expected, vVmax, V̇O2max, and Hbmass were the strongest predictors of VK performance. In our study, EIH was associated with decreased performance, likely due to increased quadriceps fatigue, which contributes to earlier exhaustion and reduced endurance capacity (Romer et al., 2006). Normalizing V̇O2max and Hbmass to FFM did not substantially change their correlation with performance, suggesting that oxygen transport efficiency is a primary determinant independent of body composition. Conclusion: A treadmill test at 25% slope provides a valid assessment of VK performance determinants. Beyond aerobic power and maximal vertical velocity, EIH appears influential. References Romer, L. M., Haverkamp, H. C., Lovering, A. T., Pegelow, D. F., & Dempsey, J. A. (2006). Effect of exercise-induced arterial hypoxemia on quadriceps muscle fatigue in healthy humans. American Journal of Physiology. Regulatory, Integrative and Comparative Physiology, 290(2), R365-375. https://doi.org/10.1152/ajpregu.00332.2005

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.

Ski mountaineering (SkiMo) is a new Olympic sport with extreme endurance demands and altitude exposure. Previous studies have focused on traditional cardiorespiratory variables, such as maximal oxygen consumption ( V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ ) or ventilatory thresholds, but, to our knowledge, did not report haemoglobin mass (Hbmass). The aim of this study was to investigate the relationship between Hbmass and V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ in elite SkiMo athletes and compare physiological differences across performance levels. Twenty-nine Swiss national team SkiMo athletes (10 females and 19 males) were classified into Tier 3-5. Participants performed a treadmill graded exercise test (25% slope) to determine V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ and ventilatory thresholds. The Hbmass and blood volumes were assessed using a CO-rebreathing technique. Sex and tier-based comparisons were made, and correlations between haematological parameters and aerobic performance metrics were analysed. The Hbmass normalized to body mass (HbmassBM) was significantly correlated with V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ in the pooled group (r = 0.80, P < 0.001), females (r = 0.82, P = 0.007) and males (r = 0.53, P = 0.024). The Hbmass and related haematological parameters were significantly higher in males (P < 0.05). Males in Tier 5 had higher oxygen consumption at the second ventilatory threshold (63.0 ± 4.3 vs. 58.9 ± 2.8 mL min-1 kg-1; P = 0.022) and V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ (72.0 ± 4.4 vs. 67.4 ± 3.1 mL min-1 kg-1; P = 0.015) than those in Tier 3-4. The significant correlation between HbmassBM and V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ confirms the key role of Hbmass in oxygen transport and aerobic capacity. However, Tier 5 athletes achieved superior aerobic performance without higher HbmassBM, indicating that additional physiological factors underpin elite-level performance.

Exposure to high altitude can cause acute mountain sickness (AMS) characterized by headache, gastrointestinal symptoms, dizziness and fatigue, which may progress to life-threatening conditions like high-altitude cerebral edema (HACE). Although the pathophysiology and development of AMS have been intensely investigated, the risk factors and underlying mechanisms remain incompletely understood. In addition, objective criteria for the diagnosis of AMS and reliable biomarkers are missing. Here we provide an overview of the molecular and pathophysiological foundations of AMS and review which potential biomarkers have been suggested and in combination with which physiological and psychological correlates of AMS they could improve diagnosis. Moreover, we point out current knowledge gaps and discuss which future research is required to enable AMS diagnosis based on more objective biomedical and psychophysical criteria. Emphasizing the apparent heterogeneity in AMS pathogenesis, we support the classification of different AMS subtypes according to etiological parameters. We propose the hypothesis that both insufficient and excessive hypoxia responses can cause AMS and that the differentiation according to these divergent mechanisms might allow the identification of AMS subtypes that can be characterized better using biomarkers and correlates of AMS.

Ski mountaineering (SkiMo) sprints will debut as an Olympic sport in 2026, yet research on the discipline remains scarce compared to other winter sports. The demanding sprint format, with most of the race time spent on uphill sections, highlights the importance of body composition and maximal oxygen consumption (V˙O2max). While previous studies have primarily focused on male athletes, this study aimed to analyze sex differences in physiological parameters of elite SkiMo athletes, hypothesizing that differences in vertical velocities (vV) would surpass those in V˙O2 at ventilatory thresholds (VT1, VT2) and maximal intensity (MAX), respectively. Twenty elite/worldclass Swiss SkiMo athletes (6 women, 14 men, aged 20–32 years) participated in the study. They performed a graded exercise test to exhaustion on a treadmill set at a 25% slope, with breath-by-breath gas exchanges. Elite female SkiMo athletes had a V˙O2 value 13.6% lower at MAX (64.0 ± 3.8 vs. 72.8 ± 5.5 ml/kg/min; p = 0.002) and 15.5% lower at VT2 (54.8 ± 2.8 vs. 62.2 ± 5.8 ml/kg/min; p = 0.009) than their male counterparts. Interestingly, the sex-differences in vV at both MAX (1,825 ± 113 vs. 2,125 ± 156 m/h; p < 0.001; 16.4%) and VT2 (1,412 ± 56 vs. 1,696 ± 151 m/h; p < 0.001; 20.1%) intensities were consistently larger than the differences in V˙O2. Moreover, fat mass was higher in females (15.2 ± 1.0 vs. 6.6 ± 0.6%; p = 0.004). Additionally, vertical running energy cost at VT2 was significantly higher in females compared to males (2,329 ± 95 vs. 2,199 ± 60 ml/kg/kmv; p = 0.018). Sex differences in uphill velocities (16.4–20.1%) exceeded those in V˙O2 (13.6–16.5%). Investigation on the underlying mechanisms is required but several factors may contribute to this pronounced sex difference in uphill velocity beyond aerobic power alone. Overall, the present findings align with recent studies reporting a 16%–20% difference in performance times when investigating sex differences in uphill displacement. The performance gap between men and women appears to be larger in uphill sports.

Ventilatory acclimatization to high altitude is an important adaption to prolonged time at altitude. Changes in breathing variability over a 16 day acclimatization period to altitude, when awake, were quantified. We tested the hypothesis that the increase in ventilatory loop gain with acclimatization would exacerbate breathing variability at rest and during exercise and that these changes would be correlated with the changes in cerebrovascular CO2, chemoreceptor sensitivity and successful ventilatory acclimatization. Breath-by-breath ventilation, partial pressure of end-tidal O2 and CO2 in 21 healthy lowlanders were recorded at sea level (SL), at day 1 at high altitude (ALT1) and after 16 days of acclimatization (ALT16) to 5260 m at rest and during submaximal and maximal exercise. Power spectrum density (PSD) and the frequency of ventilatory oscillations (fmax) were compared across conditions. At rest, PSD of oscillations were significantly greater at ALT1 and ALT16 compared to SL and fmax of oscillations was significantly lower at ALT16 compared to SL and ALT1. During submaximal exercise PSD of these oscillations was also significantly greater at ALT1 and ALT16 compared to SL. Their fmax were not different between SL, ALT1 and ALT16. The area under the curve (AUC) of ventilation at SL rest and the AUC of ventilation increase from SL to ALT1 was positively associated with the increase in ventilation from SL to ALT16. These data highlight the intrinsic oscillatory nature of the closed loop ventilatory system during and after altitude acclimatization. The AUC metric at SL and acute altitude may be important for predicting successful ventilatory acclimatization with chronic altitude. KEY POINTS: The amplitude of the ventilatory oscillations in acute and chronic hypoxia were greater than at sea level (SL). The frequency of oscillations was slower after acclimatization. These changes may be a result of the increased chemosensitivity and to the closed loop system of the control of ventilation. These changes may also contribute to the adaptation of this closed loop to chronic altitude by limiting the decrease in arterial P O 2 ${{P}_{{{{\mathrm{O}}}_2}}}$ . The area under the curve (AUC) of ventilation at SL rest and the change in AUC from SL to day 1 at high altitude (ALT 1) were both positively associated with the greatest increases in VE from SL to ALT 16, highlighting the potential importance of this metric in predicting successful ventilatory acclimatization to high altitude.

This study aimed to evaluate the putative effects of hypobaria on ventilatory, cardiovascular, and muscle oxygenation during exercise in normoxia and hypoxia. Eighteen healthy air pilot trainees (26 ± 3 yr, 177 ± 10 cm, 70 ± 11 kg) performed a 6-min moderate-intensity cycling exercise (1 W/kg) in four randomized conditions, namely, normobaric normoxia (NN), hypobaric normoxia (HN), normobaric hypoxia (NH), and hypobaric hypoxia (HH) in a hypobaric chamber. Inspired oxygen pressure was matched between normoxic (NN vs. HN, 141.2 ± 0.8 vs. 141.5 ± 1.5 mmHg) and hypoxic (NH vs. HH, 75.7 ± 0.4 vs. 74.3 ± 1.0 mmHg) conditions. Gas exchanges, pulse oxygen saturation ([Formula: see text]), heart rate, middle cerebral artery blood flow velocity, cerebral and muscular oxygenation, and cerebral O2 delivery (cDO2) were recorded. [Formula: see text], brain, and muscle oxygenation were significantly lower and ventilation higher in HH than in NN and HN, and NH, during both rest and exercise (exercise [Formula: see text] 99.0 ± 1.5, 80.8 ± 4.2, 97.6 ± 1.9, and 69.2 ± 5.7% and ventilation 12.5 ± 2.3, 13.3 ± 3.1, 12.4 ± 2.6, and 14.6 ± 2.4 L/min in NN, NH, HN, and HH, respectively). cDO2 was decreased to the same extent in HH and NH compared with NN and HN (exercise 865.5 ± 147.6, 731.8 ± 152.2, 857.8 ± 157.8, and 755.8 ± 163.3 cm·mLO2/s·dLbl). Specific effects of hypobaria in normoxia were lesser than in hypoxia since only blood O2 and CO2 partial pressures were lower in HN than NN. Respiratory and cardiovascular responses and brain/muscle oxygenation were more altered in HH than in NH, which confirms the additive effects of hypobaria on exercise in severe hypoxia. However, the effects of hypobaria are likely of negligible clinical relevance in normoxia.NEW & NOTEWORTHY A hypobaric normoxia (HN) condition was used to disentangle the effects of hypoxia and hypobaria. There was an additive effect of hypobaria and hypoxia. Cerebral and muscular tissue oxygenation were lower in hypobaric normoxia than in normobaric hypoxia during rest and exercise. The effects of hypobaria were negligible in normoxia.

Introduction The autonomic nervous system (ANS) relies on two essential feedback loops: respiratory sinus arrythmia (RSA) and arterial baroreflex which are both regulated by a complex interplay of sympathetic and parasympathetic activations. The amplitude of RSA is modified by the respiratory frequency, i.e. an increase in respiratory frequency leads to a progressive decline in RSA as vagal effectors become less able to follow variations at higher frequencies. On the contrary, a reduction in the respiratory frequency can increase RSA. Slow Paced Breathing (SPB) is usually associated with deep changes in thoracic volume which increases the parasympathetic tone, and which has numerous expected beneficial effects on health. However, some studies report little or no effects. The goal of this study was to test a personalized SPB training vs. placebo to help disentangle the effects of SPB from those solely linked to breathing awareness or distraction. Methods Twenty-four young healthy volunteers participated in this study. They performed a four-week protocol of personalized SPB exercises (SPB group, n = 12) or control condition (spontaneous breathing, CON group, n = 12). Before and after the interventional period, they performed baroreflex sensitivity (BRS) and heart rate variability (HRV) assessments in our laboratory (labPRE and labPOST). During these four weeks, they performed three times per week an orthostatic test (OT) at home immediately before (hPRE) and after (hPOST) a SPB or CON exercise. The OT consisted of five minutes supine (sup) immediately followed by five minutes standing (stand). Personalized SPB was determined as the breathing frequency that elicited the greatest possible RSA, i.e., the best synchronization between breathing and heart rate. The HRV assessments included measures of heart rate (HR), root mean square of the successive differences (RMSSD), power spectrum in the low- and high-frequency bands (LF and HF). Results HFsup increased only in the SPB group (1062±686 vs 1469±905 ms2) from labPRE to labPOST. In addition, both RMSSDsup (54±29 vs. 62±19 ms) and HFsup (1369±1211 vs. 1469±905 ms2) were greater in the SPB group than the control group in labPOST. BRS increased only in the SPB group from labPRE to labPOST (12.8±3.2 vs. 15.2±2.8 ms/mmHg). LFsup decreased from hPRE to hPOST and this decrease was greater in SPB than CON. RMSSDstand increased in both groups from hPRE to hPOST and this increase was greater in CON than SPB. LFstand decreased from hPRE to hPOST. This decrease was greater by the end than at the beginning of the intervention and greater in SPB than CON. HFstand increased from hPRE to hPOST, and this increase was greater in SPB than CON. Discussion/Conclusion Four weeks of SPB training led to a larger increase in parasympathetic modulations to the heart in SPB than CON, indicating that such prolonged intervention has beneficial effects on health. These specific benefits were generally significant from week 4 onward. Further studies are required to better explore the underlying mechanisms.

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 damage (EIMD). Methods: Twenty-eight physically active males completed an individually tailored EIMD protocol immediately followed by one of the following recovery interventions: HWI (40 degrees C, HWI40), HWI (41 degrees C, HWI41) or warm water immersion (36 degrees C, CON36). Gastrointestinal temperature (T-gi), hemodynamic adjustments (cardiac output [CO], mean arterial pressure [MAP], and systemic vascular resistance [SVR]), pre-frontal cortex deoxyhemoglobin (HHb), ECG-derived respiratory frequency, and subjective perceptual measures were tracked throughout immersion. In addition, functional markers of muscle fatigue (maximal concentric peak torque [T-peak]) and muscle damage (late-phase rate of force development [RFD100-200]) were measured prior to EIMD (pre-), 24 h (post-24 h), and 48 h (post-48 h) post-EIMD. Results: By the end of immersion, HWI41 led to significantly higher T-gi values than HWI40 (38.8 +/- 0.1 vs. 38.0 degrees C +/- 0.6 degrees C, p < 0.001). While MAP was well maintained throughout immersion, only HWI41 led to increased (HHb) (+4.2 +/- 1.47 mu M; p = 0.005) and respiratory frequency (+4.0 +/- 1.21 breath.min(-1); p = 0.032). Only HWI41 mitigated the decline in RFD100- 200 at post-24 h (-7.1 +/- 31.8%; p = 0.63) and T-peak at post-48 h (-3.1 +/- 4.3%, p = 1). Conclusion: In physically active males, maintaining a core body temperature of similar to 25 min within the range of 38.5 degrees C-39 degrees C has been found to be effective in improving muscle recovery, while minimizing the risk of excessive physiological heat strain.

Background This systematic review with meta-analyses aims to assess the overall validity of the first and second heart rate variability - derived threshold (HRVT1 and HRVT2, respectively) by computing global effect sizes for agreement and correlation between HRVTs and reference – lactate and ventilatory (LT-VTs) – thresholds. Furthermore, this review aims to assess the impact of subjects’ characteristics, HRV methods, and study protocols on the agreement and correlation between LT-VTs and HRVTs. Methods Systematic computerised searches for studies determining HRVTs during incremental exercise in humans were conducted between March and August 2023 using electronic databases (Cochrane Library, EBSCO, Embase.com, Google Scholar, Ovid, ProQuest, PubMed, Scopus, SportDiscus, Virtual Health Library and Web of science). The agreements and correlations meta-analyses were conducted using a random-effect model. Causes of heterogeneity were explored by subgroup analysis and meta-regression with subjects’ characteristics, incremental exercise protocols and HRV methods variables and compared using statistical tests for interaction. The methodological quality was assessed using QUADAS-2 and STARD HRV tools. The risk of bias was assessed by funnel plots, fail-safe N test, Egger's test of the intercept and the Begg and Mazumdar rank correlation test. Results Fifty included studies (1’160 subjects) assessed 314 agreements (95 for HRVT1, 219 for HRVT2) and 246 correlations (82 for HRVT1, 164 for HRVT2) between LT-VTs and HRVTs. The standardized mean differences were trivial between HRVT1 and LT1-VT1 (SMD = 0.08, 95% CI -0.04–0.19, n = 22) and between HRVT2 and LT2-VT2 (SMD = -0.06, 95% CI -0.15–0.03, n = 42). The correlations were very strong between HRVT1 and LT1-VT1 (r = 0.85, 95% CI 0.75–0.91, n = 22), and between HRVT2 and LT2-VT2 (r = 0.85, 95% CI 0.80–0.89, n = 41). Moderator analyses showed that HRVT1 better agreed with LT1 and HRVT2 with VT2. Moreover, subjects’ characteristics, type of ergometer, or initial and incremental workload had no impact on HRVTs determination. Simple visual HRVT determinations were reliable, as well as both frequency and non-linear HRV indices. Finally, short increment yielded better HRVT2 determination. Conclusion HRVTs showed trivial differences and very strong correlations with LT-VTs and might thus serve as surrogate thresholds and, consequently for the determination of the intensity zones. However, heterogeneity across study results and differences in agreement when comparing separately LTs and VTs to HRVTs were observed, underscoring the need for further research. These results emphasize the usefulness of HRVTs as promising, accessible, and cost-effective means for exercise and clinical prescription purposes

Introduction Daily exposition to ether glycols is common. Caretakers using cleaning products are critically exposed by combining physical activity with exposition to highly concentrated products. Previous animal studies showed hemato-, respiratory and autonomic nervous system toxicity amongst others. Yet, no controlled study explored the combination of an exposition to glycol ethers with physical activity in humans. Methods 30 young healthy participants were exposed a control condition (ambient air) and to one of three vaporized glycol ethers: propylene glycol n-propyl ether (PGPE, 25 ppm, n = 10) or propylene glycol ethyl ether (PGEE, 35 ppm, n = 10) or propylene glycol monomethyl ether (PGME, 35 ppm, n = 10) in a single-blind cross-over design. They performed an orthostatic test (5-min supine, 5-min standing) and a 6-min steady-state exercise at 1.5 W/kg followed by 10-min recovery in PGPE/PGEE conditions. In addition, an incremental exercise to exhaustion followed in PGME condition. Heart rate variability (HRV) was measured throughout the protocol, Heart rate recovery (HRR) was assessed during the 10-min recovery post steady-state exercise. Root-mean-square of the successive differences (RMSSD), power spectrum of the low- (LF) and high-frequency (HF) bands, tau, amplitude and T30 were computed for HRR. Near Infrared spectroscopy (NIRS) and cardiac output (using thoracic impedance) were measured for PGME exposition. PO2, PCO2 and pH were measured regularly via arterialized and venous blood sampling. Results Resting values of supine LF (1,180 ± 851 vs. 2,993 ± 2,259 ms2) and standing RMSSD (32 ± 17 vs. 41 ± 17 ms) increased under PGEE. Supine and standing HR decreased under PGPE (65.5 ± 4.8 vs. 61.3 ± 6.9 and 83.8 ± 7.0 vs. 76.1 ± 10.0 bpm) whereas standing RMSSD (26.6 ± 10.0 vs. 37.0 ± 14.9 ms) and LF (825 ± 474 vs. 2,028 ± 1,471 ms2) increased. Parasympathetic reactivation (e.g., RMSSD, LF and HF) was increased post-exercise under exposition to all three glycol ethers. In addition, amplitude significantly increased when exposed to PGEE. However, unexpectedly, HRR was neither slowed nor speeded. Finally, no differences were observed in any NIRS variables or cardiac output. Accordingly, the modelled muscle oxygen diffusion coefficient was not modified between any solvent conditions. Arterialized blood pH (7.35 ± .06 vs. 7.39 ± .04) and PaCO2 (34.1 ± 5.0 vs. 35.7 ± 4.3 mmHg) increased whilst PaO2 (81.8 ± 9.7 vs. 77.9 ± 10.6 mmHg) decreased. Discussion/Conclusion: The decrease in supine/standing HR associated with a general increase in HRV during recovery likely indicate an increase in parasympathetic modulation, which is compatible with the sedative effects of glycol ethers previously described in animal models. However, HR recovery was not altered. Despite no change in the O2 diffusion coefficient, there was an increase in PaCO2, a decrease in PaO2 and an increase in blood pH, all indicative of potential impaired blood oxygenation during exercise, to be further investigated. To conclude, exposition to different glycol ethers induced an enhanced parasympathetic activation without any changes in HR recovery or O2 diffusion.

PurposeElite swimmers often schedule altitude training camps ahead of major events in an attempt to maximize performance. However, the relationships between altitude-induced hematological changes, markers of training adaptation, and performance changes in such context are unclear. This study assessed hematological status, markers of daily adaptation, and swimming performance in elite middle-distance and distance swimmers during a 22-day altitude training camp at 2,320 m, 2 weeks prior to World Championship qualification competition.MethodsVenous blood was obtained and total hemoglobin mass (tHbmass) measured (CO rebreathing) in 7 elite swimmers (4 females, 3 males) 8 days before and on day 22 of the altitude camp. Resting heart rate, peripheral oxygen saturation, urinary specific gravity, body mass, fatigue and self-reported sleep duration and quality were monitored daily during the altitude camp. Swimming performance was assessed through a standardized set (6 sets of 4 maximal repetitions of 100 m front crawl) on days 3, 10 and 17 of the camp, and at sea level competitions (200 m–1,500 m) immediately after the camp, and 2 weeks later.ResultstHbmass (+5.6 ± 3.3%; range: 2.1%–11.0%; p < 0.05), red blood cell count, hemoglobin concentration, hematocrit increased at the end of the training camp (p < 0.05). Performance at altitude improved throughout the camp (+1.4 ± 0.4%; range: 0.7%–2.5%; p < 0.05). No significant relationship was noted between hematological changes, the change in altitude performance and any of the monitored daily markers of adaptation during the camp. Compared to the swimmers’ previous personal best, competition performances did not improve immediately (2.5% ± 1.9% slower times) and 2 weeks after altitude (1.2% ± 1.4% slower times).ConclusionThe 22-day altitude training camp at 2,320 m was beneficial for elite swimmers’ tHbmass, hematological status and performance at altitude, but these benefits did not clearly translate into enhanced sea level performance immediately after or 2 weeks later. The present study confirms the large inter-individual variability in hematological responses to altitude training, and that the improvement in performance at altitude and sea level may depend on factors other than the increase in tHbmass alone.

BackgroundHeart rate variability (HRV) is a common means of monitoring responses to training, yet in professional cycling, one may question its usefulness, particularly during multi-day competitions such as Grand Tours.ObjectivesThis study aims to report and analyze HRV responses in a male professional cyclist over a season, including the Tour de France.MethodsA professional cyclist recorded resting and exercise inter-beat intervals during 5 months, comprising a training period with two altitude sojourns and two competition blocks, including the Tour de France. Resting recordings lasted 5 min in the supine position and were used for computation of mean heart rate (HR), root mean square of the successive differences (RMSSDs), and power in the low- and high-frequency bands (LF and HF, respectively). Training load quantification was based on recorded HR during exercise and expressed as training impulses (TRIMPSs).ResultsLF (3,319 ± 2,819 vs. 1,097 ± 1,657 ms2), HF (3,590 ± 1858 vs. 1,267 ± 1,683 ms2), and RMSSD (96 ± 26 vs. 46 ± 30 ms) were higher and HR (47 ± 4 vs. 54 ± 2 bpm) was lower during the training period when compared to the two competition blocks. The coefficient of variation (CV) was significantly lower during the training period than during the two competition blocks for RMSSD (26 vs. 72%), LF (85 vs. 160%), and HF (58 vs. 141%).DiscussionThe present study confirms that monitoring daily HRV responses during training periods is valuable in professional cycling, but questions its usefulness during the Tour de France. Moreover, the previous suggestion that CV in RMSSD would help to predict poor performance was not confirmed in a professional cyclist.

Introduction The acute mountain sickness (AMS) prevalence increases with altitude; i.e.,10-25% at 2,500 m and 50-85% at ~5,000 m (Bärtsch & Swenson, 2013). Women are more likely affected by AMS than men (Richalet et al., 2012). AMS can affect exercise performance. However, the effects of the menstrual cycle (MC) on physiological responses to exercise and on tolerance to high-altitude (HA) remain underexplored. It has been reported that ovarian hormones stimulate ventilation in normoxic conditions (Saaresranta & Polo, 2002). Early findings suggest that running economy is lower in the mid-luteal (ML) compared to the early-follicular (EF) phase in normoxia (Goldsmith & Glaister, 2020). However, cycling efficiency at HA has not been explored yet. Thus, we investigated the effects of acute HA exposure on ventilatory responses at rest and during exercise in healthy females during two different phases of their MC. Methods Sixteen eumenorrheic women (age: 33 ± 7 yr; MC length: 27 ± 2 days; not taking any hormonal contraceptive) took part in this study. First, over a 6-month period, the participants’ MC were monitored using a calendar method. Then, they reached the Torino Hut (3,375 m) by cable car and spent one night at HA on two different MC phases; i.e., during the early-follicular (EF; MC day 4 ± 1) and the mid-luteal (ML; day 20 ± 2) phases. Each time, they underwent a submaximal (1.2 W/kg) test on a cycle ergometer ~17 h after arrival at HA. In addition to this, participants filled in two questionnaires, the Lake Louise AMS Score and the Groningen Sleep Quality Scale, ~16 h after arrival at HA. Results Resting ventilation was significantly higher during EF compared to ML (15.2 ± 1.9 vs. 13.2 ± 2.5 L/min, p = 0.039), while no differences were found for ventilation during exercise (53.9 ± 13.2 vs. 53.5 ± 13.4 L/min, p = 0.695), cycling efficiency (21.7 ± 0.0% vs. 19.8 ± 0.0%, p = 0.244), saturation at rest (92.4 ± 1.3 vs. 91.3 ± 3.2%, p = 0.142) and during exercise (87.2 ± 5.7 vs. 89.0 ± 4.0%, p = 0.528). Moreover, no differences in the Lake Louise AMS (2.2 ± 1.5 vs. 1.7 ± 1.5, p = 0.266) or Groningen (8.0 ± 3.3 vs. 7.5 ± 3.4, p = 0.668) scores were noted between the two MC phases. Discussion/Conclusion Despite a slightly higher resting ventilation during EF, when both oestrogens and progesterone are at their lowest levels, there were no differences in ventilatory responses to exercise and in AMS between the different phases of the MC. Consequently, there is currently very little evidence to aptly recommend a specific MC phase for mountaineering or any other HA activities (Burtscher et al., 2023). Further investigations are requested to assess whether other physiological responses to HA may be influenced by hormonal variations. References Bärtsch, P., & Swenson, E. R. (2013). Acute high-altitude illnesses. New England Journal of Medicine, 368, 2294–2302. https://doi.org/10.1056/NEJMcp1214870 Burtscher, J., Raberin, A., Brocherie, F., Malatesta, D., Manferdelli, G., Citherlet, T., Krumm, B., Bourdillon, N., Antero, J., Rasica, L., Burtscher, M. & Millet, G. P. (2023). Recommendations for women in mountain sports and hypoxia training/conditioning. Sports Medicine. Advance online publication. https://doi.org/10.1007/s40279-023-01970-6 Goldsmith, E., & Glaister, M. (2020). The effect of the menstrual cycle on running economy. The Journal of Sports Medicine and Physical Fitness, 60(4), 610–617. https://doi.org/10.23736/s0022-4707.20.10229-9 Richalet, J.-P., Larmignat, P., Poitrine, E., Letournel, M., & Canouï-Poitrine, F. (2012). Physiological risk factors for severe high-altitude illness: A prospective cohort study. American Journal of Respiratory and Critical Care Medecine, 185(2), 192–198. https://doi.org/10.1164/rccm.201108-1396OC Saaresranta, T., & Polo, O. (2002). Hormones and breathing. American College of Chest Physicians, 122(6), 2165–2182. https://doi.org/10.1378/chest.122.6.2165

PURPOSE:Both maximal-intensity exercise and altitude exposure challenge the pulmonary system that may reach its maximal capacities. Expiratory flow limitation (EFL) and exercise-induced hypoxemia (EIH) are common in endurance-trained athletes. Furthermore, because of their smaller airways and lung size, women, independently of their fitness level, may be more prone to pulmonary limitations during maximal-intensity exercise, particularly when performed in hypoxic conditions. The objective of this study was to investigate the impact of sex and fitness level on pulmonary limitations during maximal exercise in normoxia and their consequences in acute hypoxia. METHODS:Fifty-one participants were distributed across four different groups according to sex and fitness level. Participants visited the laboratory on three occasions to perform maximal incremental cycling tests in normoxia and hypoxia (inspired oxygen fraction = 0.14) and two hypoxic chemosensitivity tests. Pulmonary function and ventilatory capacities were evaluated at each visit. RESULTS:EIH was more prevalent (62.5% vs 22.2%, P = 0.004) and EFL less common (37.5% vs 70.4%, P = 0.019) in women than men. EIH prevalence was different ( P = 0.004) between groups of trained men (41.7%), control men (6.7%), trained women (50.0%), and control women (75.0%). All EIH men but only 40% of EIH women exhibited EFL. EFL individuals had higher slope ratio ( P = 0.029), higher ventilation (V̇ E ) ( P < 0.001), larger ΔVO 2max ( P = 0.019), and lower hypoxia-related V̇ E increase ( P < 0.001). CONCLUSIONS:Women reported a higher EIH prevalence than men, regardless of their fitness level, despite a lower EFL prevalence. EFL seems mainly due to the imbalance between ventilatory demands and capacities. It restricts ventilation, leading to a larger performance impairment during maximal exercise in hypoxic conditions.