Acute progressive hypoxia: effects on endurance performance and its physiology

Introduction Hypoxia is defined as a reduction in the amount of oxygen (O2) available to any cell, tissue, or organism (Semenza, 2009). Research examined the effects of this reduction on endurance performance [see (Fulco et al., 1998) for review] and the benefits deriving from the exposure (and training) in hypoxia on the sea level endurance performance [see (Millet et al., 2010) for review]. However, endurance and ultra-endurance performances can also be performed in hypoxic environments. This is an intrinsic feature of those performances that either start from an altitude level and finish at a higher one or where the altitude profile changes during the race (e.g. uphill cycling time trial, running vertical kilometres, etc.). Accordingly, to date less is known about the determinants of performance where the severity of hypoxia changes during the trial (i.e. Progressive Hypoxia, PH). Therefore, the aim of this project was to investigate the effects of acute progressive hypoxia on the endurance performance and fatigue. A secondary aim was to determine the main physiological responses during these tasks in PH at different intensities of effort. Study I There are competitions like the mass start events (e.g. running and ski mountaineering vertical kilometres, cycling stages with uphill arrival, etc.) that take place in hypoxia, or even in progressive hypoxia, with the final high intensity effort at a higher altitude compared with the starting one. The aim of the study was to understand if a different hypoxic stimulus, during a submaximal cycling exercise (50% of relative Peak Power Output, PPO) impairs the high intensity performance of the final high intensity effort. After a maximal ramp test to obtain the PPO and baseline measurements of endurance performance (time to exhaustion, TTE) in a non-fatigued state (both in normoxia and in hypoxia) 8 subjects completed an 1-hour cycling protocol in normoxia (at 50% of PPO obtained in normoxia, N), constant hypoxia and progressive hypoxia (FiO2 = 13.4%, and FiO2 starting from 16.25 to 13.4%, at 50% of PPO obtained in hypoxia, Hcost and HH, respectively). TTE duration was reduced both after the N and Hcost session (-27.9% P=0.03 and -21.6% P=0.007, respectively) with no effect after HH. Higher oxygen saturation (SpO2) was observed during cycling exercise in N compared to the other two conditions. Hcost resulted in a lower SpO2 compared to HH, until the end of the 1-h bout, where Hcost and HH presented similar SpO2 due to similar altitude levels reached. Oxygen consumption was similar during the HH and Hcost condition, but Hcost is lower than in N (P=0.03). Rate of perceived exertion was similar in the three conditions. The primary finding of this study was that an impairment of ~25% in the endurance performance (tested through a TTE test and compared to a non-fatigued trial at baseline) was observed after both a normoxic (P=0.03) and a constant hypoxic (P=0.007) task; no effects after 1-h in HH. A possible explanation to the different effect of HH and Hcost on TTE performance can be related to the hypoxic dose (5.25 VS 3.75 kilometres/hour in Hcost VS HH, respectively). Study II There are competitions that take place in progressive hypoxia at a submaximal intensity throughout the entire duration with the final part of the race at a higher altitude compared to the starting one. The aim of this study was to investigate the effects of an 1-h exposure at different cycling submaximal intensities at progressive hypoxia on fatigue and endurance performance (tested through a Time To Exahustion, TTE). Peak power output (PPO) and baseline duration in a TTE were obtained in a non-fatigued state (both in normoxia and in hypoxia) in 11 subjects. Subsequently, in three separated days, they completed an 1-h protocol under the same progressively hypoxic stimulus (FiO2 starting from 16.25 to 13.4%, simulating an increase in altitude from 2000 to 3500 m) at different intensities: no effort (H_NoPO), 50% of the PPO in hypoxia (HH) and 50% of the PPO in normoxia (HN). Oxygen consumption, heart rate, blood lactate, cerebral blood flow and pulse oxygen saturation were monitored during each session. Neuromuscular fatigue was assessed pre and post the 1-h intervention as well as after the subsequent TTE. We observed a reduced duration of TTE only after 1-h HN, when compared to baseline and H_NoPO (-37.2% P<0.001 and -30.8% P=0.016). One of the reason of this impairment in performance can be the higher blood lactate accumulation and the higher RPE during 1-h HN. The general reduction in SpO2 during the three interventions may be one of the causes of the reduction in voluntary activation, as an index of central fatigue, even though cerebral blood flow increased with time without any differences between conditions. The novelty of this study was to investigate the acute effects on performance and fatigue at different submaximal intensities when athletes are exposed to a progressively increased hypoxia. The main finding was that the endurance performance (assessed by means of TTE, that can be considered as the final high intensity effort at a higher altitude compared with the starting one) was only compromised after 1-h of cycling at 50% of the absolute peak power output obtained in normoxia. Therefore, it can be a good practice to test athletes that need to perform at altitude, in simulated condition. General conclusion Progressive hypoxia is a condition encountered during several endurance and ultra endurance performances. The understanding of the effects driven by a PH exposure at different intensities on a subsequent endurance performance can be useful for coaches and athletes that need to plan and pace their efforts in similar environments. We need to be conscious that in altitude, and especially in PH, the threshold between choosing the correct intensity of an effort and the intensity that can results in a subsequent impairment during an endurance performance (TTE) is really thin. Therefore, it can be a good practice to test athletes that need to perform at altitude, in a similar condition. Finally, we can conclude that a small step forward in the understanding of efforts during a progressive hypoxic stimulus has been provided. More work is needed, and the next step could be to study PH in field performances

Talent development in young cross-country skiers: longitudinal analysis of anthropometric and physiological characteristics

Introduction: Very little is known about talent development and selection processes in young cross-country skiers. Aim: (1) to analyze the effect of age on anthropometric and physiological parameters in medium-to-high level cross-country skiers during the late teenage period; (2) to describe parameters' trend in selected talents after the late teenage period; (3) to define which characteristics during the late teenage period could discriminate against further talent selection. Method: We found 14 male (M) and nine (F) athletes in our database, identified as talents by regional teams during the late teenage period, who performed the same diagonal-stride roller-skiing incremental test to exhaustion at 17 and 18 years old. Of these, four M and three F teenagers performed four further evaluations, and were selected by the national team. Age effect during the late teenage period was verified on anthropometric and physiological parameters measured at maximal intensity (MAX), first (VT1), and second (VT2) ventilatory thresholds, and 3\ub0 and 6\ub0 of treadmill incline. An observational analysis allowed to evaluate parameters' trend after the late teenage period in selected athletes, and to determine possible characteristics early discriminating further selection. Results: During the late teenage period, height, weight, and BMI was still raising in M as well as V'O2 at VT2 and 6\ub0 of treadmill incline (all P &gt; 0.05). In F, mass-scaled V'O2 MAX increased while heart rate (HR) at MAX and VT2 decreased (all P &gt; 0.05). Since the late teenage period, all selected males showed maximal ventilation volumes, absolute V'O2 at MAX, VT1, and VT2 that were within or above the 75th percentile of their group; the same was found in selected females for mass-scaled V'O2 MAX, VT1, and VT2 time. After the late teenage period, all selected athletes showed an increasing trend for VT2 time, while a decreasing trend for sub-maximal energetic cost, %V'O2 and HR. Discussion: During the late teenage period, males are still completing their maturation process. Since the late teenage period, some physiological parameters seem good indicators to early discriminate for further talents. A progressive increase in skiing efficiency was demonstrated in developing talents of both sexes after the late teenage period

Post-exercise cardiac autonomic and cardiovascular responses to heart rate-matched and work rate-matched hypoxic exercise

PURPOSE: This study investigated the effect of performing hypoxic exercise at the same heart rate (HR) or work rate (WR) as normoxic exercise on post-exercise autonomic and cardiovascular responses.METHODS: Thirteen men performed three interval-type exercise sessions (5*5-min; 1-min recovery): normoxic exercise at 80% of the WR at the first ventilatory threshold (N), hypoxic exercise (FiO2=14.2%) at the same WR as N (H-WR) and hypoxic exercise at the same HR as N (H-HR). Autonomic and cardiovascular assessments were conducted before and after exercise, both at rest and during active squat-stand manoeuvres (SS).RESULTS: Compared to N, H-WR elicited a higher HR response (83% vs 75%HRmax, p&lt;0.001) and H-HR a reduced exercise WR (-21.1\ub19.3%, p&lt;0.001). Cardiac parasympathetic indices were reduced 15min after exercise and recovered within 60min in N and H-HR, but not after H-WR (p&lt;0.05). H-WR altered cardiac baroreflex sensitivity (cBRS) both at rest and during SS (specifically in the control of blood pressure fall during standing phases) in the first 60min after the exercise bout (p&lt;0.05). Post-exercise hypotension (PEH) did not occur in H-HR (p&gt;0.05) but lasted longer in H-WR than in N (p&lt;0.05).CONCLUSIONS: Moderate HR-matched hypoxic exercise mimicked post-exercise autonomic responses of normoxic exercise without resulting in significant PEH. This may relate to the reduced WR and the limited associated mechanical/metabolic strain. Conversely, WR-matched hypoxic exercise impacted upon post-exercise autonomic and cardiovascular responses, delaying cardiac autonomic recovery, temporarily decreasing cBRS and evoking prolonged PEH

Validity of the SenseWear Armband\u2122 to assess energy expenditure in graded walking.

Background: Accurate assessments of physical activity and energy expenditure (EE) are needed to advance research on positive and negative graded walking. Purpose: To evaluate the validity of two SenseWear\u2122 Armband monitors (Pro3 and the recently released Mini) during graded walking. Methods: Twenty healthy adults wore both monitors during randomized walking activities on a motorized treadmill at seven grades (0%, \ub15%, \ub115% and \ub125%). Estimates of total EE from the monitors were computed using different algorithms and compared to values derived from indirect calorimetry methodology using a 2-way mixed model ANOVA (Device x Condition), correlation analyses and Bland-Altman plots. Results: There was no significant difference in EE between the two armbands in any of the conditions examined. Significant main effects for device and condition as well as a consistent bias were observed during positive and negative graded walking, with a greater over- and under-estimation at higher slope. Conclusions: Both the armbands produced similar EE values and seem to be not accurate in estimation of EE during activities involving uphill and downhill walking. Additional work is needed to understand factors contributing to this discrepancy and to improve the ability of these monitors to accurately measure EE during graded walking

Ski mountaineering: perspectives on a novel sport to be introduced at the 2026 Winter Olympic Games

Ski mountaineering is a rapidly growing winter sport that involves alternately climbing and descending slopes and various racing formats that differ in length and total vertical gain, as well as their distribution of downhill and uphill sections. In recent years, both participation in and media coverage of this sport have increased dramatically, contributing, at least in part, to its inclusion in the 2026 Winter Olympics in Milano-Cortina. Here, our aim has been to briefly describe the major characteristics of ski mountaineering, its physiological and biomechanical demands, equipment, and training/testing, as well as to provide some future perspectives. Despite its popularity, research on this discipline is scarce, but some general characteristics are already emerging. Pronounced aerobic capacity is an important requirement for success, as demonstrated by positive correlations between racing time and maximal oxygen uptake and oxygen uptake at the second ventilatory threshold. Moreover, due to the considerable mechanical work against gravity on demanding uphill terrain, the combined weight of the athlete and equipment is inversely correlated with performance, prompting the development of both lighter and better equipment in recent decades. In ski mountaineering, velocity uphill is achieved primarily by more frequent (rather than longer) strides due primarily to high resistive forces. The use of wearable technologies, designed specifically for analysis in the field (including at elevated altitudes and cold temperatures) and more extensive collaboration between researchers, industrial actors, and coaches/athletes, could further improve the development of this sport

Model of CD45 isoforms-mediated IL-6 signaling in multiple myeloma cells.

<p>Engagement of IL-6R with IL-6 leads to complex formation of IL-6R, gp130, Lyn as well as CD45RO/RB in raft microdomains. In response to IL-6 stimulation, CD45RO/RB moves into lipid rafts to induce dephosphorylation of the negative regulatory of Tyr507, phosphorylation of Tyr396, and subsequent conformation change and Lyn activation [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0119780#pone.0119780.ref017" target="_blank">17</a>]. We confirmed our hypothesis that lipid rafts-targeted CD45RO/RB facilitates IL-6-induced STAT3 and Lyn/PKC/NF-κB activation in rafts microdomains, while raft-excluded CD45RA remains outside of lipid rafts after IL-6 stimulation and negatively regulates ERK-activation.</p

COM displacement influences the energetic cost of lococmotion during the double poling technique

Double poling technique (DP) is a particular type of skiing locomotion due to the extensive use of the upper body. Cost of locomotion is generally related to metabolic adaptations to training, but also biomechanical strategies can concur to set the amount of energy spent to travel at a given speed. The aim of this investigation was to analyze metabolic and biomechanical characteristics of two differently skilled groups of cross-country skiers, in relation to the energetic cost of DP locomotion

Cost of force generation as an index of performance ability in cross coun try skiers

Metabolic power depends on mean force applied to the ground during a cycle , on rate of force application and on cost of force generation. This cost is constant at different speeds and describe the amount of energy spent to perform a Newton of muscular force In a sport where energy consumption, muscular capabilities and force application strategies can influence performance capabilities, the computation of cost of force generation could be a good index of performance ability

Relationship Between Cognitive Appraisal of Control and Cardiac Vagal Regulation During an Unsupported Ski Crossing of Greenland

International audiencePurpose The aim of the present study was to investigate the relationships between Perceived Control (PC) and Heart rate variability (HRV) during a 27-day expedition, during which an unsupported crossing was made from the west coast to the east coast of Greenland (across the Ice Sheet); and that therefore a high PC represents a favourable factor for recovery and stress management. Methods Four subjects participated in the study. PC was measured on alternated days in the evening at the end of the day, using the Pearlin Mastery Scale; and the next day, upon waking, heart rate using a wrist heart rate monitor and a chest strap. Together with the PC, the perceived effort was measured through the CR-100 Borg scale and each subject was asked to indicate the most emotionally significant event of the day. Time and frequency domain indices for heart rate variability were calculated. Results Several correlations were observed between PC and HRV indices. In particular two indices in the time domain, standard deviation of all NN intervals (SDNN) (rrm = 0.51) and root mean square of successive (RMSSD) (rrm = 0.46), showed a significant and strong positive correlation. Conclusion The existence of a positive correlation between PC and cardiac vagal regulation is of great interest to individuals immerged into extreme situations, because it can affect performance or prevents maladaptive states or injuries. To improve stress management, it could be convenient for members of extreme expeditions to adopt forms of cognitive training that modify their cognitive appraisal in order to raise their perception of control

Effect of new type of compression garments on sub-maximal and maximal cycling performance in the heat (32\ub0 C)

This study investigated the effect of compression garments (X) on cycling performance in the heat (32 _C) and tested the hypothesis that X would not negatively affect cycling performance in the heat by comparing X and traditional cycling garments (C). Seven amateur cyclists and triathletes performed an incremental test followed by 20 min cycling performance test at a power that elicited the subject\u2019s pre-determined 80 % of ventilatorthreshold and then a time to exhaustion (TTE) at VO2max power (PPO) for both X condition and C condition (randomized). Oxygen uptake (VO2) and heart rate were collected during steady state of sub-maximal intensity, TTEwas taken at the end of maximal aerobic intensity and rating of perceived exertion, thermal and sweating sensation were provided every 5 min during the test. All parameters were compared between X and C; no significantdifferences (p.05) were found, so the initial hypothesis was confirmed