Repeated-sprint Training In Hypoxia Research Articles

Repeated-sprint training in hypoxia: A review with 10 years of perspective.

Over the past decade, numerous studies have investigated an innovative "live low-train high" approach based on the repetition of short (<30 s) "all-out" sprints with incomplete recoveries in hypoxia; the so-called Repeated-Sprint training in Hypoxia (RSH). The aims of the present review are therefore threefold. First, this study summarizes the available evidence on putative additional performance enhancement after RSH comparing to the same training in normoxia (RSN). Second, a critical analysis of underpinning mechanisms discusses how advantages can be obtained through RSH for sea-level performance enhancement. An enhanced microcirculatory vasodilation leading to improved muscle perfusion and/or oxygenation and an increase in muscular phosphocreatine content may help explain the superiority of RSH vs. RSN. Third, the present review aims to provide guidelines for coaches, athletes and scientists to apply RSH interventions with regard to the interval duration, exercise-to-rest ratio and training volume. In conclusion, this review supports repeated-sprint training in hypoxia as an efficient (but not magic) training intervention with 77% of the controlled studies reporting an additional benefit with added hypoxia, mainly for team-, combat- and racket-sports athletes but also for all other sports (e.g. endurance) that require repeated accelerations with lesser fatigue.

Apnoea as a novel method to improve exercise performance: A current state of the literature.

Acute breath-holding (apnoea) induces a spleen contraction leading to a transient increase in haemoglobin concentration. Additionally, the apnoea-induced hypoxia has been shown to lead to an increase in erythropoietin concentration up to 5h after acute breath-holding, suggesting long-term haemoglobin enhancement. Given its potential to improve haemoglobin content, an important determinant for oxygen transport, apnoea has been suggested as a novel training method to improve aerobic performance. This review aims to provide an update on the current state of the literature on this topic. Although the apnoea-induced spleen contraction appears to be effective in improving oxygen uptake kinetics, this does not seem to transfer into immediately improved aerobic performance when apnoea is integrated into a warm-up. Furthermore, only long and intense apnoea protocols in individuals who are experienced in breath-holding show increased erythropoietin and reticulocytes. So far, studies on inexperienced individuals have failed to induce acute changes in erythropoietin concentration following apnoea. As such, apnoea training protocols fail to demonstrate longitudinal changes in haemoglobin mass and aerobic performance. The low hypoxic dose, as evidenced by minor oxygen desaturation, is likely insufficient to elicit a strong erythropoietic response. Apnoea therefore does not seem to be useful for improving aerobic performance. However, variations in apnoea, such as hypoventilation training at low lung volume and repeated-sprint training in hypoxia through short end-expiratory breath-holds, have been shown to induce metabolic adaptations and improve several physical qualities. This shows promise for application of dynamic apnoea in order to improve exercise performance. HIGHLIGHTS: What is the topic of this review? Apnoea is considered as an innovative method to improve performance. This review discusses the effectiveness of apnoea (training) on performance. What advances does it highlight? Although the apnoea-induced spleen contraction and the increase in EPO observed in freedivers seem promising to improve haematological variables both acutely and on the long term, they do not improve exercise performance in an athletic population. However, performing repeated sprints on end-expiratory breath-holds seems promising to improve repeated-sprint capacity.

Acute Responses to Repeated-SprintTraining in Hypoxia Combined With Whole-Body Cryotherapy: A Preliminary Study.

This study aimed to investigate acute psychophysiological responses to repeated-sprint training in hypoxia (RSH) combined with whole-body cryotherapy (WBC). Sixteen trained cyclists performed 3 sessions in randomized order: RSH, WBC-RSH (WBC pre-RSH), and RSH-WBC (WBC post-RSH). RSH consisted of 3 sets of 5 × 10-second sprints with 20-second recovery at a simulated altitude of 3000m. Power output, muscle oxygenation (tissue saturation index), heart-rate variability, and recovery perception were analyzed. Sleep quality was assessed on the nights following test sessions and compared with a control night using nocturnal ActiGraphy and heart-rate variability. Power output did not differ between the conditions (P = .27), while the decrease in tissue saturation index was reduced for WBC-RSH compared to RSH-WBC in the last set. In both conditions with WBC, the recovery perception was higher compared to RSH (WBC-RSH: +15.4%, and RSH-WBC: +21.9%, P < .05). The number of movements during the RSH-WBC night was significantly lower than for the control night (-18.7%, P < .01) and WBC-RSH (-14.9%, P < .05). RSH led to a higher root mean square of the successive differences of R-R intervals and high-frequency band during the first hour of sleep compared to the control night (P < .05) and RSH-WBC (P < .01). Inclusion of WBC in an RSH session did not modify the power output but could improve prolonged performance in hypoxia by maintaining muscle oxygenation. A single RSH session did not deteriorate sleep quality. WBC, particularly when performed after RSH, positively influenced recovery perception and sleep.

Four Sessions of Repeated-Sprint Cycling Training With or Without Severe Hypoxia Do Not Modify Overground Running Sprint Force-Velocity Profile.

To investigate the effect of cycling-based repeated-sprint training in hypoxia versus in normoxia on single overground running sprint performance and associated force-velocity (F-V) profile in world-class female rugby sevens players. Eighteen world-class female rugby sevens players were randomly assigned to repeated-sprint cycling training in normobaric hypoxia (n = 9) or normoxia (n = 9) groups. Training consisted of 4 sessions ofrepeated-sprint cycling training in normobaric hypoxiaor in normoxia (4 × 5 × 5-s cycle sprints-25-s intersprint recovery performed in simulated altitude of ∼5000m or in normoxia with 3-min interset rest in normoxia for both groups) in addition to rugby sevens training and strength and conditioning sessions within a 9-day intervention period before an international competition. Before and 1day after the intervention, single 50-m overground running "all-out" sprint performance and associated F-V-related mechanical output were assessed. No interaction (group × time; all P > .088), time effect(before vs 1d after; all P > .296), or group effect(repeated-sprint cycling training in normobaric hypoxia vs in normoxia; all P > .325) was detected for 50-m overground running sprint performance and any derived F-V profiling variables. Four sessions ofrepeated-sprint training either in hypoxia or in normoxia performed over 9days had no influence on single 50-m overground running sprint performance and associated F-V profile. In world-class female rugby sevens players, the intervention (training camp before an international competition) might have been too short to induce measurable changes. It is also plausible that implementing a similar program in players with likely different F-V profile may result in negligible mechanical effect.

Well-being as a performance pillar: a holistic approach for monitoring tennis players.

This perspective article aims to discuss the usefulness of tools that can assist tennis professionals effectively manage the well-being of their players. This includes identifying and monitoring meaningful metrics (i.e., training load, training intensity, heart rate variability), as well as careful planning of training and competition schedules with appropriate recovery periods. The use of innovative training methods (i.e., repeated-sprint training in hypoxia and heat training), and proper dietary practices, along with biometric assessment for young players, represents should be considered. Adopting a holistic approach to decision-making about training and competition, balancing both health and performance considerations, is crucial for tennis players and their support teams. More research is needed to refine best practices for enhancing tennis performance while prioritizing the well-being of players.

Effects of 2 Different Protocols of Repeated-Sprint Training in Hypoxia in Elite Female Rugby Sevens Players During an Altitude Training Camp.

Repeated-sprint training in hypoxia (RSH) is an effective way of improving physical performance compared with similar training in normoxia. RSH efficiency relies on hypoxia severity, but also on the oxidative-glycolytic balance determined by both sprint duration and exercise-to-rest ratio. This study investigated the effect of 2 types of RSH sessions during a classic altitude camp in world-class female rugby sevens players. Sixteen players performed 5 RSH sessions on a cycle ergometer (simulated altitude: 3000m above sea level [asl]) during a 3-week natural altitude camp (1850m asl). Players were assigned to 2 different protocols with either a high (RSH1:3, sprint duration: 8-10s; exercise-to-rest ratios: 1:2-1:3; n = 7) or a low exercise-to-rest ratio (RSH1:5, sprint duration: 5-15s; exercise-to-rest ratios: 1:2-1:5; n = 9). Repeated-sprint performances (maximal and mean power outputs [PPOmax, and PPOmean]) were measured before and after the intervention, along with physiological responses. PPOmax (962 [100] to 1020 [143]W, P = .008, Cohen d = 0.47) and PPOmean (733 [71] to 773 [91]W, P = .008, d = 0.50) increased from before to after. A significant interaction effect (P = .048, d = 0.50) was observed for PPOmean, with a larger increase observed in RSH1:3 (P = .003). No interaction effects were observed (P > .05) for the other variables. A classic altitude camp with 5 RSH sessions superimposed on rugby-sevens-specific training led to an improved repeated-sprint performance, suggesting that RSH effects are not blunted by prolonged hypoxic exposure. Interestingly, using a higher exercise-to-rest ratio during RSH appears to be more effective than when applying a lower exercise-to-rest ratio.

The Anaerobic Speed Reserve Influences Speed And Power Improvements From Repeated-sprint Training In Hypoxia (RSH) In World-class Short-track Speed Skaters

The Anaerobic Speed Reserve Influences Speed And Power Improvements From Repeated-sprint Training In Hypoxia (RSH) In World-class Short-track Speed Skaters

Time Decay in the Performance Benefits From Repeated-Sprint Training in Hypoxia in World-Class Short-Track Speed Skaters.

In short-track speed skating, athletes need to possess specific physiological capabilities to perform explosive starts and to finish races with faster lap times than their opponents. Repeated-sprint training in hypoxia (RSH) can enhance repeated-sprint ability and high-intensity performance. This study aimed to evaluate the relationship between on- and off-ice performance indicators for training and testing purposes and how these are optimized with RSH in world-class short-track speed skaters including world and Olympic champions. RSH training was administered for 3 consecutive weeks, 3 times per week, at 3500m of simulated altitude. Testing sessions (on-ice: 3-lap, 27-lap; off-ice: cycling incremental test, 7-s and 30-s Wingate) were performed immediately before and 2 and 4weeks after RSH to determine the time course of decay. On-ice top speed showed a small and possibly beneficial change of ∼0.9% for the women and large and almost certain ∼0.7% improvement for the men 2weeks post-RSH. Cycling peak power showed a moderate and probable ∼5.4% improvement for the men 2weeks after RSH. These adaptations reverted to baseline 4weeks post-RSH. Wingate average power showed a small and possibly beneficial gain (∼3.4%) in performance 4weeks post-RSH. Although scientific controls could not be added due to the extremely high caliber of these athletes and low sample size of the national team, this study suggests that cycling RSH can be added immediately after on-ice training and can transfer into meaningful improvements on the ice in both male and female skaters.

Repeated-sprint training in hypoxia boosts up team-sport-specific repeated-sprint ability: 2-week vs 5-week training regimen.

To investigate (1) the boosting effects immediately and 4 weeks following 2-week, 6-session repeated-sprint training in hypoxia (RSH2-wk, n = 10) on the ability of team-sport players in performing repeated sprints (RSA) during a team-sport-specific intermittent exercise protocol (RSAIEP) by comparing with normoxic counterpart (CON2-wk, n = 12), and (2) the dose effects of the RSH by comparing the RSA alterations in RSH2-wk with those resulting from a 5-week, 15-session regimen (RSH5-wk, n = 10). Repeated-sprint training protocol consisted of 3 sets, 5 × 5-s all-out sprints on non-motorized treadmill interspersed with 25-s passive recovery under the hypoxia of 13.5% and normoxia, respectively. The within- (pre-, post-, 4-week post-intervention) and between- (RSH2-wk, RSH5-wk, CON2-wk) group differences in the performance of four sets of RSA tests held during the RSAIEP on the same treadmill were assessed. In comparison with pre-intervention, RSA variables, particularly the mean velocity, horizontal force, and power output during the RSAIEP enhanced significantly immediate post RSH in RSH2-wk (5.1-13.7%), while trivially in CON2-wk (2.1-6.2%). Nevertheless, the enhanced RSA in RSH2-wk diminished 4 weeks after the RSH (-3.17-0.37%). For the RSH5-wk, the enhancement of RSA immediately following the 5-week RSH (4.2-16.3%) did not differ from that of RSH2-wk, yet the enhanced RSA was well-maintained 4-week post-RSH (0.12-1.14%). Two-week and five-week RSH regimens could comparably boost up the effects of repeated-sprint training in normoxia, while dose effect detected on the RSA enhancement was minimal. Nevertheless, superior residual effects of the RSH on RSA appear to be associated with prolonged regimen.

Repeated-Sprint Training at 5000-m Simulated Altitude in Preparation for the World Rugby Women's Sevens Series: Too High?

The objective of this study is to investigate the effectiveness of novel repeated-sprint training in hypoxia (RSH) protocol, likely maximizing hypoxic stimulus (higher than commonly used) while preserving training quality (interset rest in normoxia). Twenty-three world-class female rugby sevens players performed four repeated-sprint training sessions (4 sets of 5 × 5-s cycle sprints-25-s intersprint recovery and 3-min interset rest) under normobaric hypoxia (RSH, exercise and interset rest at FiO 2 of 10.6% and 20.9%, respectively; n = 12) or normoxia (repeated-sprint training in normoxia; exercise and interset rest at FiO 2 of 20.9%; n = 11) during a 9-d training camp before international competition. Repeated-sprint ability (8 × 5-s treadmill sprints-25-s recovery), on-field aerobic capacity, and brachial endothelial function were assessed pre- and postintervention. Arterial oxygen saturation (pooled data: 87.0% ± 3.1% vs 96.7% ± 2.9%, P < 0.001) and peak and mean power outputs (sets 1 to 4 average decrease: -21.7% ± 7.2% vs -12.0% ± 3.8% and -24.9% ± 8.1% vs -14.9% ± 3.5%; both P < 0.001) were lower in RSH versus repeated-sprint training in normoxia. The cumulated repeated-sprint distance covered significantly increased from pre- to postintervention (+1.9% ± 3.0%, P = 0.019), irrespective of the condition ( P = 0.149). On-field aerobic capacity did not change (all P > 0.45). There was no significant interaction (all P > 0.240) or condition main effect (all P > 0.074) for any brachial artery endothelial function variable. Only peak diameter increased ( P = 0.026), whereas baseline and peak shear stress decreased ( P = 0.014 and 0.019, respectively), from pre- to postintervention. In world-class female rugby sevens players, only four additional repeated-sprint sessions before competition improve repeated-sprint ability and brachial endothelial function. However, adding severe hypoxic stress during sets of repeated sprints only did not provide supplementary benefits.

Long recovery induced by short exercise-to-rest ratio and effort duration determine the influence of hypoxia during repeated cycling sprints to exhaustion

Introduction&#x0D; Repeated sprints exercise (RSE) performed in hypoxia (RSH) induce greater performance improvement than in normoxia (Brocherie et al., 2017). It has been previously argued that RSH efficiency depend on the oxidative-glycolytic balance which is influenced by sprint duration and exercise-to-rest-ratio (E:R). Indeed, we recently showed that long sprint duration (e.g. 20 s vs 10 s or 5 s) blunts the additional impact of hypoxia on RSH with a constant large E:R of 1:22. However, E:R also influence acute response to RSH. Therefore, this study aims to compare acute responses during RSE to exhaustion with a short E:R (1:6) in normoxia (RSN) and hypoxia (FiO2 = 0.13) and the same sprint durations (5, 10 or 20 s) previously used.&#x0D; Methods&#x0D; On separate visits, 10 active participants completed in random order three RSH and three RSN sessions to exhaustion on a cycle-ergometer (Excalibur Sport, Lode) with three sprint durations and a constant short E:R of 1:6 (5:30; 10:60 and 20:120). Vastus lateralis muscle de-reoxygenation (Oxymon, Artinis Medical Systems) and power output were continuously recorded. Lower limb and breathing discomfort, blood lactate, and ratings of perceived exertion were evaluated immediately after exhaustion.&#x0D; Results&#x0D; Number of sprints and peak power output were higher while blood lactate was lower (all p &lt; 0.001) during 5:30 compared to 10:60 or 20:120. No condition or interaction effects were reported for blood lactate and exercise-related sensation. Blood lactate and muscle deoxyhemoglobin increase (p &lt; 0.001) and total hemoglobin decrease (p = 0.002) during sprint were more pronounced when sprint duration increased (no hypoxia effect).&#x0D; Discussion&#x0D; Similar deoxygenation changes during recovery were reported in hypoxia compared to normoxia suggesting that 1:6 ratio and the associated long recovery period seemed to allow myoglobin O2 store restauration, even with a FiO2 = 13%. Sprint effort should be interspersed by incomplete recovery making impossible the full O2 reloading myoglobin and PCr resynthesis. The increase in blood lactate and the concomitant decrease in muscle oxygenation during sprint with longer duration confirmed a switch in the oxidative-glycolytic balance for energy supply. Since short exercise-to-rest ratio blunt hypoxic effect during RSH due to too long recovery period, hypoxia did not participate to the switch from oxidative to glycolytic energy supply.&#x0D; Conclusion&#x0D; During RSE to exhaustion, a short exercise-to-rest ratio (i.e., 1:6) blunts the specific psychophysiological responses induced by hypoxia, probably due to too long of recovery period. Manipulating effort duration rather than hypoxic exposure is preferable to alter both anaerobic energy system solicitation and power produced during repeated cycling sprints to exhaustion using a short exercise-to-rest ratio.&#x0D; References&#x0D; Brocherie, F., Girard, O., Faiss, R., &amp; Millet, G. P. (2017). Effects of repeated-sprint training in hypoxia on sea-level performance: A meta-analysis. Sports Medicine, 47, 1651-1660. https://doi.org/10.1007/s40279-017-0685-3

Adding heat stress to repeated-sprint training in hypoxia does not enhance performance improvements in canoe/kayak athletes.

The present study investigated the effects of adding heat stress to repeated-sprint training in hypoxia on performance and physiological adaptations in well-trained athletes. Sixteen canoe/kayak sprinters conducted 2weeks of repeated-sprint training consisting of three sets of 5 × 10s sprints with 20s active recovery periods under conditions of either normobaric hypoxia (RSH, FiO2: 14.5%, ambient temperature: 18 ℃, n = 8) or combined heat and normobaric hypoxia (RSHH, FiO2: 14.5%, ambient temperature: 38 ℃, n = 8). Before and after training, the 10 × 10s repeated-sprint ability (RSA) test and 500m time trial were performed on a canoe/kayak ergometer. Peak and average power outputs during the RSA test were significantly improved after training in both RSH (peak power: + 21.5 ± 4.6%, P < 0.001; average power: + 12.5 ± 1.9%, P < 0.001) and RSHH groups (peak power: + 18.8 ± 6.6%, P = 0.005; average power: + 10.9 ± 6.8%, P = 0.030). Indirect variables of skeletal muscle oxygen extraction (deoxygenated hemoglobin) and blood perfusion (total hemoglobin) during the RSA test were significantly increased after training in the RSH group (P = 0.041 and P = 0.034, respectively) but not in the RSHH group. In addition, finish time during the 500m time trial was significantly shortened after the training only in the RSH group (RSH: -3.9 ± 0.8%, P = 0.005; RSHH: -3.1 ± 1.4%, P = 0.078). Adding heat stress to RSH does not enhance performance improvement and may partially mask muscle tissue adaptation.

Maximizing anaerobic performance with repeated-sprint training in hypoxia: In search of an optimal altitude based on pulse oxygen saturation monitoring.

Purpose: Repeated-sprint training in hypoxia (RSH) leads to great improvements in anaerobic performance. However, there is no consensus about the optimal level of hypoxia that should be used during training to maximize subsequent performances. This study aimed to establish whether such an optimal altitude can be determined and whether pulse oxygen saturation during RSH is correlated with training-induced improvement in performance. Methods: Peak and mean power outputs of healthy young males [age (mean ± SD) 21.7 ± 1.4 years] were measured during a Wingate (30 s) and a repeated-sprint ability (RSA; 10 x 6-s sprint with 24-s recovery) test before and after RSH. Participants performed six cycling sessions comprising three sets of 8 x 6-s sprint with 24-s recovery in normobaric hypoxia at a simulated altitude of either 1,500 m, 2,100 m, or 3,200 m (n = 7 per group). Heart rate variability was assessed at rest and during recovery from Wingate test before and after RSH. Results: The subjective rating of perceived exertion and the relative exercise intensity during training sessions did not differ between the three groups, contrary to pulse oxygen saturation (p < 0.001 between each group). Mean and peak power outputs were significantly increased in all groups after training, except for the mean power in the RSA test for the 3200 m group. Change in mean power on RSA test (+8.1 ± 6.6%) was the only performance parameter significantly correlated with pulse oxygen saturation during hypoxic training (p < 0.05, r = 0.44). The increase in LnRMSSD during recovery from the Wingate test was enhanced after training in the 1,500 m (+22%) but not in the two other groups (≈– 6%). Moreover, the increase in resting heart rate with standing after training was negatively correlated with SpO2 (p < 0.01, r =–0.63) suggesting that hypoxemia level during training differentially altered autonomic nervous system activity. Conclusion: These data indicate that RSH performed as early as 1,500 m of altitude is effective in improving anaerobic performance in moderately trained subjects without strong association with pulse oxygen saturation monitoring during training.

Taking the plunge: When is best for hot water immersion to complement exercise in heat and hypoxia

ABSTRACT This investigation assessed the psycho-physiological and performance effects of hot water immersion (HWI) implemented either before or after a repeated-sprint training in hypoxia (RSH) session conducted in the heat. Ten participants completed three RSH trials (3 × 10 × 5-s sprints), conducted at 40°C and simulated altitude of 3000 m. A 30-min monitoring period preceded and followed all exercise sessions. In PRE, the pre-exercise period was HWI, and the post-exercise period was seated rest in temperate conditions. This combination was reversed in POST. In CON, participants were seated in temperate conditions for both periods. Compared to CON, PRE elicited a reduction in power output during each repeated-sprint set (14.8–16.2%, all p < 0.001), and a significantly higher core temperature (Tc) during the pre-exercise period and throughout the exercise session (p < 0.001 and p = 0.025, respectively). In POST, power output and Tc until the end of exercise were similar to CON, with Tc higher at the conclusion of the post-exercise period (p < 0.001). Time across the entire protocol spent ≥38.5°C Tc was significantly longer in PRE (48.1 ± 22.5 min) than POST (31.0 ± 11.3 min, p = 0.05) and CON (15.8 ± 16.3 min, p < 0.001). Employing HWI following RSH conducted in the heat provides effective outcomes regarding physiological strain and cycling performance when compared to pre-exercise or no HWI.

Effects of repeated-sprint training in hypoxia induced by voluntary hypoventilation on performance during ice hockey off-season

This study aimed to assess the effects of an off-season period of repeated-sprint training in hypoxia induced by voluntary hypoventilation at low lung volume (RSH-VHL) on off-ice repeated-sprint ability (RSA) in ice hockey players. Thirty-five high-level youth ice hockey players completed 10 sessions of running repeated sprints over a 5-week period, either with RSH-VHL (n = 16) or with unrestricted breathing (RSN, n = 19). Before (Pre) and after (Post) the training period, subjects performed two 40-m single sprints (to obtain the reference velocity (Vref)) followed by a running RSA test (12 × 40 m all-out sprints with departure every 30 s). From Pre to Post, there was no change in Vref or in the maximal velocity reached in the RSA test in both groups. In RSH-VHL, the mean velocity of the RSA test was higher (88.9 ± 5.4 vs. 92.9 ± 3.2% of Vref; p &lt; 0.01) and the percentage decrement score lower (11.1 ± 5.2 vs. 7.1 ± 3.3; p &lt; 0.01) at Post than at Pre whereas no significant change occurred in the RSN group (89.6 ± 3.3 vs. 91.3 ± 1.9% of Vref, p = 0.11; 10.4 ± 3.2 vs. 8.7 ± 2.3%; p = 0.13). In conclusion, five weeks of off-ice RSH-VHL intervention led to a significant 4% improvement in off-ice RSA performance. Based on previous findings showing larger effects after shorter intervention time, the dose-response dependent effect of this innovative approach remains to be investigated.

Increased air temperature during repeated-sprint training in hypoxia amplifies changes in muscle oxygenation without decreasing cycling performance

ABSTRACT The present study aims to investigate the acute performance and physiological responses, with specific reference to muscle oxygenation, to ambient air temperature manipulation during repeated-sprint training in hypoxia (RSH). Thirteen male team-sport players completed one familiarisation and three experimental sessions at a simulated altitude of ∼3000 m (FIO2 0.144). Air temperatures utilised across the three experimental sessions were: 20°C, 35°C and 40°C (all 50% relative humidity). Participants performed 3 × 5 × 10-s maximal cycle sprints, with 20-s passive recovery between sprints, and 5 min active recovery between sets. There were no differences between conditions for cycling peak power, mean power, and total work (p>0.05). Peak core temperature (Tc) was not different between conditions (38.11 ± 0.36°C). Vastus lateralis muscle deoxygenation during exercise and reoxygenation during recovery was of greater magnitude in 35°C and 40°C than 20°C (p<0.001 for all). There was no condition × time interaction for Tc, skin temperature, pulse oxygen saturation, heart rate, rating of perceived exertion and thermal sensation (P>0.05). Exercise-induced increases in blood lactate concentration were higher in 35°C and 40°C than 20°C (p=0.010 and p=0.001, respectively). Integrating ambient temperatures up to 40°C into a typical RSH session had no detrimental effect on performance. Additionally, the augmented muscle oxygenation changes experienced during exercise and recovery in temperatures ≥35°C may indicate that the potency of RSH training is increased with additional heat. However, alterations to the training session may be required to generate a sufficient rise in Tc for heat training purposes. Highlights Heat exposure (35-40°C) did not affect mechanical performance during a typical RSH session. This indicates hot ambient temperature can be implemented during RSH, without negative consequence to training output. Hotter ambient conditions (35-40°C) likely result in greater muscle oxygenation changes during both exercise and recovery compared to temperate conditions. Although hotter sessions were perceived as more difficult and more thermally challenging, they did not further elevate Tc beyond that of temperate conditions. Accordingly, if intended to be used for heat acclimation purposes, alterations to the session may be required to increase heat load.

Increased air temperature during repeated-sprint training in hypoxia amplifies muscle oxygenation flux without decreasing cycling performance

Introduction: Training under environmental stress is a popular approach to enhance athlete adaptation. Although the advantages repeated-sprint training in hypoxia (RSH) and heat exposure are well established, the benefits of a session combining these two stimuli are not yet understood. As such, the purpose of this study was to investigate the acute performance and physiological responses, with specific reference to muscle oxygenation, to ambient air temperature manipulation during RSH.

Heat Added to Repeated-Sprint Training in Hypoxia Does Not Affect Cycling Performance.

This study aimed to assess the influence of graded air temperatures during repeated-sprint training in hypoxia (RSH) on performance and physiological responses. Ten well-trained athletes completed one familiarization and 4 experimental sessions at a simulated altitude of 3000m (0.144FIO2) above sea level. Air temperatures utilized across the 4 experimental sessions were 20°C, 25°C, 30°C, and 35°C (all 50% relative humidity). The participants performed 3 sets of 5 × 10 seconds "all-out" cycle sprints, with 20 seconds of active recovery between sprints and 5 minutes of active recovery between sets (recovery intensity = 120W). Core temperature, skin temperature, pulse oxygen saturation, heart rate, rating of perceived exertion, and thermal sensation were collected. There were no differences between conditions for peak power, mean power, and total work in each set (P > .05). There were no condition × time interaction effects for any variables tested. The peak core temperature was highest at 30°C (38.06°C [0.31°C]). Overall, the pulse oxygen saturation was higher at 35°C than at 20°C (P < .001; d < 0.8), 25°C (P < .001; d = 1.12 ± 0.54, large), and 30°C (P < .001; d = 0.84 ± 0.53, large). Manipulating air temperature between 20°C and 35°C had no effect on performance or core temperature during a typical RSH session. However, the pulse oxygen saturation was preserved at 35°C, which may not be a desirable outcome for RSH interventions. The application of increased levels of ambient heat may require a different approach if augmenting the RSH stimulus is the desired outcome.

Haematological responses to repeated sprints in hypoxia across different sporting modalities

ABSTRACT The aim was to determine the effects of repeated-sprint training in hypoxia on haematocrit and haemoglobin in different sporting modalities. Seventy-two participants were randomly allocated to Active-Repeated sprint in hypoxia (A-RSH, n= 8); Active-Repeated sprint in normoxia (A-RSN, n= 8); Active-Control (A-CON, n= 8); Team Sports-RSH (T-RSH, n= 8); Team Sports-RSN (T-RSN, n= 8); Team Sports-Control (T-CON, n= 8); Endurance-RSH (E-RSH, n= 8); Endurance-RSN (E-RSN, n= 8); Endurance-Control (E-CON, n= 8). Sessions consisted of two sets of five sprints of 10 swith recovery of 20 sbetween sprints and 10 min between sets. Blood samples for haematocrit and haemoglobin concentrations were obtained before and after, and 2 weeks after cessation. Haematocrit and haemoglobin were lower for the E-RSN group following 2 weeks of cessation of protocol compared with E-RSH (p = 0.035) and E-CON (p = 0.045). Haematocrit of the A-RSH group was higher compared with baseline (p = 0.05) and Post (p = 0.05). Similarly, the T-RSH group demonstrated increases in haematocrit following 2 weeks of cessation compared with Post (p = 0.04). Repeated Sprint Training in Hypoxia had different haematological effects depending on sporting modality.

Acute performance responses to repeated treadmill sprints in hypoxia with varying inspired oxygen fractions, exercise-to-recovery ratios and recovery modalities.

For optimizing the quality of repeated-sprint training in hypoxia, the differences in the acute performance responses to a single session of repeated-sprint exercise with various (i) inspired oxygen fractions; (ii) exercise-to-recovery (E:R) ratios and (iii) recovery modalities were examined. Ten male participants performed three sets, 5 × 5-s all-out treadmill sprints, E:R ratio of 1:5, passive recovery, in seven trials randomly. In four of the seven trials, hypoxic levels were set corresponding to sea level (SL1:5P), 1500 (1.5K1:5P), 2500 (2.5K1:5P), and 3500m (3.5K1:5P), respectively. In a further two trials, the hypoxic level of 3.5K1:5P was maintained, while the E:R ratio was reduced to 1:4 (3.5K1:4P) and 1:3 (3.5K1:3P), respectively. In the last trial, the passive recovery mode of 3.5K1:5P was changed to active (3.5K1:5A). In comparison to SL1:5P, the averaged peak velocity (P-Vel), mean velocity (M-Vel), and velocity decrement score (Sdec) of the sprints, and the cumulative HR-based training impulse (cTRIMP) in 1.5K1:5P and 2.5K1:5P were well maintained. Minor decrement in the M-Vel was found in 3.5K1:5P. Conversely, lowered E:R ratio in 3.5K1:4P and 3.5K1:3P significantly reduced the P-Vel (≥ -2.3%, Cohen's d ≥ 0.43) and M-Vel (≥ -2.4%, ≥ 0.49), and in 3.5K1:3P altered the Sdec (107%, ≥ 0.96), and cTRIMP (-16%, 1.39), when compared to 3.5K1:5P. Furthermore, mild reductions in M-Vel (-2.6%, 0.5) was observed in 3.5K1:5A using the active recovery mode. Other variables did not change. The findings suggest that a 3.5K1:5P marginally maintained sea-level training loads, and as a result, could maximally optimize the training stress of hypoxia.