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Purpose: There is debate as to which environmental intervention produces the most benefit for team sport athletes, particularly comparing heat and altitude. This quasi-experimental study aimed to compare blood volume (BV) responses with heat and altitude training camps in Australian footballers., Methods: The BV of 7 professional Australian footballers (91.8 [10.5] kg, 191.8 [10.1] cm) was measured throughout 3 consecutive spring/summer preseasons. During each preseason, players participated in altitude (year 1 and year 2) and heat (year 3) environmental training camps. Year 1 and year 2 altitude camps were in November/December in the United States, whereas the year 3 heat camp was in February/March in Australia after a full exposure to summer heat. BV, red cell volume, and plasma volume (PV) were measured at least 3 times during each preseason., Results: Red cell volume increased substantially following altitude in both year 1 (d = 0.67) and year 2 (d = 1.03), before returning to baseline 4 weeks postaltitude. Immediately following altitude, concurrent decreases in PV were observed during year 1 (d = -0.40) and year 2 (d = -0.98). With spring/summer training in year 3, BV and PV were substantially higher in January than temporally matched postaltitude measurements during year 1 (BV: d = -0.93, PV: d = -1.07) and year 2 (BV: d = -1.99, PV: d = -2.25), with year 3 total BV, red cell volume, and PV not changing further despite the 6-day heat intervention., Conclusions: We found greater BV after training throughout spring/summer conditions, compared with interrupting spring/summer exposure to train at altitude in the cold, with no additional benefits observed from a heat camp following spring/summer training.

Purpose: Determine if a series of trials with fraction of inspired oxygen (FiO2) content deception could improve 4000-m cycling time-trial (TT) performance., Methods: Fifteen trained male cyclists (mean ± SD: body mass 74.2 ± 8.0 kg; peak oxygen uptake 62 ± 6 mL.kg-1.min-1) completed six, 4000-m cycling TTs in a semi-randomised order. After a familiarisation TT, cyclists were informed in two initial trials they were inspiring normoxic air (NORM, FiO2: 0.21), however in one trial (deception condition) they inspired hyperoxic air (NORM-DEC, FiO2: 0.36). During two subsequent TTs, cyclists were informed they were inspiring hyperoxic air (HYPER, FiO2: 0.36), but in one trial normoxic air was inspired (HYPER-DEC). In the final TT (NORM-INFORM) the deception was revealed, and cyclists were asked to reproduce their best TT performance while inspiring normoxic air., Results: Greater power output and faster performances occurred when cyclists inspired hyperoxic air in both truthful (HYPER) and deceptive (NORM-DEC) trials compared to NORM (P < 0.001). However, performance only improved in NORM-INFORM (377 W [95% CI 325, 429]) vs NORM (352 W [299, 404]), P < 0.001) when participants (n = 4) completed the trials in the following order: NORM-DEC, NORM, HYPER-DEC, HYPER., Conclusions: Cycling performance improved with acute exposure to hyperoxia. Mechanisms for the improvement were likely physiological, however improvement in a deception trial suggests an additional placebo effect may be present. Finally, a particular sequence of oxygen deception trials may have built psycho-physiological belief in cyclists such that performance improved in a subsequent normoxic trial.

Purpose: To compare the effects of natural altitude training (NAT) and simulated (SIM) live high:train low altitude training on road-race walking performance (min), as well as treadmill threshold walking speed (km·h -1 ) at 4 mmol·L -1 and maximal oxygen consumption, at 1380 m., Methods: Twenty-two elite-level male (n = 15) and female (n = 7) race walkers completed 14 d of NAT at 1380 m (n = 7), SIM live high:train low at 3000:600 m (n = 7), or control conditions (600-m altitude; CON, n = 8). All preintervention and postintervention testing procedures were conducted at 1380 m and consisted of an incremental treadmill test, completed prior to a 5 × 2-km road-race walking performance test. Differences between groups were analyzed via mixed-model analysis of variance and magnitude-based inferences, with a substantial change detected with >75% likelihood of exceeding the smallest worthwhile change., Results: The improvement in total performance time for the 5 × 2-km test in NAT was not substantially different from SIM but was substantially greater (85% likely) than CON. The improvement in percentage decrement in the 5 × 2-km performance test in NAT was greater than in both SIM (93% likely) and CON (93% likely). The increase in maximal oxygen consumption was substantially greater (91% likely) in NAT than in SIM. Improvement in threshold walking speed was substantially greater than CON for both SIM (91% likely) and NAT (90% likely)., Conclusions: Both NAT and SIM may allow athletes to achieve reasonable acclimation prior to competition at low altitude.

Purpose: To determine the effect of altitude training at 1600 and 1800 m on sea-level (SL) performance in national-level runners., Methods: After 3 wk of SL training, 24 runners completed a 3-wk sojourn at 1600 m (ALT1600, n = 8), 1800 m (ALT1800, n = 9), or SL (CON, n = 7), followed by up to 11 wk of SL racing. Race performance was measured at SL during the lead-in period and repeatedly postintervention. Training volume (in kilometers) and load (session rating of perceived exertion) were calculated for all sessions. Hemoglobin mass was measured via CO rebreathing. Between-groups differences were evaluated using effect sizes (Hedges g)., Results: Performance improved in both ALT1600 (mean [SD] 1.5% [0.9%]) and ALT1800 (1.6% [1.3%]) compared with CON (0.4% [1.7%]); g = 0.83 (90% confidence limits -0.10, 1.66) and 0.81 (-0.09, 1.62), respectively. Season-best performances occurred 5 to 71 d postaltitude in ALT1600/1800. There were large increases in training load from lead-in to intervention in ALT1600 (48% [32%]) and ALT1800 (60% [31%]) compared with CON (18% [20%]); g = 1.24 (0.24, 2.08) and 1.69 (0.65, 2.55), respectively. Hemoglobin mass increased in ALT1600 and ALT1800 (∼4%) but not CON., Conclusions: Larger improvements in performance after altitude training may be due to the greater overall load of training in hypoxia compared with normoxia, combined with a hypoxia-mediated increase in hemoglobin mass. A wide time frame for peak performances suggests that the optimal window to race postaltitude is individual, and factors other than altitude exposure per se may be important.

New Findings: What is the central question of this study? Does 14 days of live-high, train-low simulated altitude alter an individual's metabolomic/metabolic profile? What is the main finding and its importance? This study demonstrated that ∼200 h of moderate simulated altitude exposure resulted in greater variance in measured metabolites between subject than within subject, which indicates individual variability during the adaptive phase to altitude exposure. In addition, metabolomics results indicate that altitude alters multiple metabolic pathways, and the time course of these pathways is different over 14 days of altitude exposure. These findings support previous literature and provide new information on the acute adaptation response to altitude., Abstract: The purpose of this study was to determine the influence of 14 days of normobaric hypoxic simulated altitude exposure at 3000 m on the human plasma metabolomic profile. For 14 days, 10 well-trained endurance runners (six men and four women; 29 ± 7 years of age) lived at 3000 m simulated altitude, accumulating 196.4 ± 25.6 h of hypoxic exposure, and trained at ∼600 m. Resting plasma samples were collected at baseline and on days 3 and 14 of altitude exposure and stored at -80°C. Plasma samples were analysed using liquid chromatography-high-resolution mass spectrometry to construct a metabolite profile of altitude exposure. Mass spectrometry of plasma identified 36 metabolites, of which eight were statistically significant (false discovery rate probability 0.1) from baseline to either day 3 or day 14. Specifically, changes in plasma metabolites relating to amino acid metabolism (tyrosine and proline), glycolysis (adenosine) and purine metabolism (adenosine) were observed during altitude exposure. Principal component canonical variate analysis showed significant discrimination between group means (P < 0.05), with canonical variate 1 describing a non-linear recovery trajectory from baseline to day 3 and then back to baseline by day 14. Conversely, canonical variate 2 described a weaker non-recovery trajectory and increase from baseline to day 3, with a further increase from day 3 to 14. The present study demonstrates that metabolomics can be a useful tool to monitor metabolic changes associated with altitude exposure. Furthermore, it is apparent that altitude exposure alters multiple metabolic pathways, and the time course of these changes is different over 14 days of altitude exposure., (© 2018 The Authors. Experimental Physiology © 2018 The Physiological Society.)

Introduction: We sought to determine the effect of low and moderate normobaric hypoxia on oxygen consumption and anaerobic contribution during interval running at different exercise intensities., Methods: Eight runners (age, 25 ± 7 yr, V˙O2max: 72.1 ± 5.6 mL·kg·min) completed three separate interval sessions at threshold (4 × 5 min, 2-min recovery), V˙O2max (8 × 90 s, 90-s recovery), and race pace (10 × 45 s, 1 min 45 s recovery) in each of; normoxia (elevation: 580 m, FiO2: 0.21), low (1400 m, 0.195) or moderate (2100 m, 0.18) normobaric hypoxia. The absolute running speed for each intensity was kept the same at each altitude to evaluate the effect of FiO2 on physiological responses. Expired gas was collected throughout each session, with total V˙O2 and accumulated oxygen deficit calculated. Data were compared using repeated-measures ANOVA., Results: There were significant differences between training sessions for peak and total V˙O2, and anaerobic contribution (P < 0.001, P = 0.01 respectively), with race pace sessions eliciting the lowest and highest responses respectively. Compared to 580 m, total V˙O2 at 2100 m was significantly lower (P < 0.05), and anaerobic contribution significantly higher (P < 0.05) during both threshold and V˙O2max sessions. No significant differences were observed between altitudes for race pace sessions., Conclusions: To maintain oxygen flux, completing acute exercise at threshold and V˙O2max intensity at 1400 m simulated altitude appears more beneficial compared with 2100 m. However, remaining at moderate altitude is a suitable when increasing the anaerobic contribution to exercise is a targeted response to training.

The questionable efficacy of Live High Train High altitude training (LHTH) is compounded by minimal training quantification in many studies. We sought to quantify the training load (TL) periodization in a cohort of elite runners completing LHTH immediately prior to competition. Eight elite runners (6 males, 2 females) with a V̇O 2peak of 70 ± 4 mL·kg -1 ·min -1 were monitored during 4 weeks of sea-level training, then 3-4 weeks LHTH in preparation for sea-level races following descent to sea-level. TL was calculated using the session rating of perceived exertion (sRPE) method, whereby duration of each training session was multiplied by its sRPE, then summated to give weekly TL. Performance was assessed in competition at sea-level before, and within 8 days of completing LHTH, with runners competing in 800 m (n = 1, 1500 m/mile (n = 6) and half-marathon (n = 1). Haemoglobin mass (Hb mass ) via CO rebreathing and running economy (RE) were assessed pre and post LHTH. Weekly TL during the first 2 weeks at altitude increased by 75% from preceding sea-level training (p = 0.0004, d = 1.65). During the final week at altitude, TL was reduced by 43% compared to the previous weeks (p = 0.002; d = 1.85). The ratio of weekly TL to weekly training volume increased by 17% at altitude (p = 0.009; d = 0.91) compared to prior sea-level training. Hb mass increased by 5% from pre- to post-LHTH (p = 0.006, d = 0.20). Seven athletes achieved lifetime personal best performances within 8 days post-altitude (overall improvement 1.1 ± 0.7%, p = 0.2, d = 0.05). S pecific periodization of training, including large increases in training load upon arrival to altitude (due to increased training volume and greater stress of training in hypoxia) and tapering, were observed during LHTH in elite runners prior to personal best performances. Periodization should be individualized and align with timing of competition post-altitude.

Purpose: Iron is integral for erythropoietic adaptation to hypoxia, yet the importance of supplementary iron compared with existing stores is poorly understood. The aim of the present study was to compare the magnitude of the hemoglobin mass (Hbmass) in response to altitude in athletes with intravenous (IV), oral, or placebo iron supplementation., Methods: Thirty-four, nonanemic, endurance-trained athletes completed 3 wk of simulated altitude (3000 m, 14 h·d), receiving two to three bolus iron injections (ferric carboxymaltose), daily oral iron supplementation (ferrous sulfate), or a placebo, commencing 2 wk before and throughout altitude exposure. Hbmass and markers of iron regulation were assessed at baseline (day -14), immediately before (day 0), weekly during (days 8 and 15), and immediately, 1, 3, and 6 wk after (days 22, 28, 42, and 63) the completion of altitude exposure., Results: Hbmass significantly increased after altitude exposure in athletes with IV (mean % [90% confidence interval (CI)], 3.7% [2.8-4.7]) and oral (3.2% [2.2-4.2]) supplementation and remained elevated at 7 d postaltitude in oral (2.9% [1.5-4.3]) and 21 d after in IV (3.0% [1.5-4.6]) supplementation. Hbmass was not significantly higher than baseline at any time point in placebo., Conclusions: Iron supplementation appears necessary for optimal erythropoietic adaptation to altitude exposure. IV iron supplementation during 3 wk of simulated live high-train low altitude training offered no additional benefit in terms of the magnitude of the erythropoietic response for nonanemic endurance athletes compared with oral supplementation.

The integrity of the athlete biological passport (ABP) is underpinned by understanding normal fluctuations of its biomarkers to environmental or medical conditions, for example, altitude training or iron deficiency. The combined impact of altitude and iron supplementation on the ABP was evaluated in endurance-trained athletes (n = 34) undertaking 3 weeks of simulated live-high: train-low (14 h.d -1 , 3000 m). Athletes received either oral, intravenous (IV) or placebo iron supplementation, commencing 2 weeks prior and continuing throughout hypoxic exposure. Venous blood was sampled twice prior, weekly during, and up to 6 weeks after altitude. Individual ABP thresholds for haemoglobin concentration ([Hb]), reticulocyte percentage (%retic), and OFF score were calculated using the adaptive model and assessed at 99% and 99.9% specificity. Eleven athletes returned values outside of the calculated reference ranges at 99%, with 8 at 99.9%. The percentage of athletes exceeding the thresholds in each group was similar, but IV returned the most individual occurrences. A similar frequency of abnormalities occurred across the 3 biomarkers, with abnormal [Hb] and OFF score values arising mainly during-, and %retic values mainly post- altitude. Removing samples collected during altitude from the model resulted in 10 athletes returning abnormal values at 99% specificity, 2 of whom had not triggered the model previously. In summary, the abnormalities observed in response to iron supplementation and hypoxia were not systematic and mostly in line with expected physiological adaptations. They do not represent a uniform weakness in the ABP. Nevertheless, altitude training and iron supplementation should be carefully considered by experts evaluating abnormal ABP profiles., (Copyright © 2017 John Wiley & Sons, Ltd.)

Altitude is a confounding factor within the Athlete Biological Passport (ABP) due, in part, to the plasma volume (PV) response to hypoxia. Here, a newly developed PV blood test is applied to assess the possible efficacy of reducing the influence of PV on the volumetric ABP markers; haemoglobin concentration ([Hb]) and the OFF-score. Endurance athletes (n=34) completed a 21-night simulated live-high train-low (LHTL) protocol (14 h.d -1 at 3000 m). Bloods were collected twice pre-altitude; at days 3, 8, and 15 at altitude; and 1, 7, 21, and 42 days post-altitude. A full blood count was performed on the whole blood sample. Serum was analysed for transferrin, albumin, calcium, creatinine, total protein, and low-density lipoprotein. The PV blood test (consisting of the serum markers, [Hb] and platelets) was applied to the ABP adaptive model and new reference predictions were calculated for [Hb] and the OFF-score, thereby reducing the PV variance component. The PV correction refined the ABP reference predictions. The number of atypical passport findings (ATPFs) for [Hb] was reduced from 7 of 5 subjects to 6 of 3 subjects. The OFF-score ATPFs increased with the PV correction (from 9 to 13, 99% specificity); most likely the result of more specific reference limit predictions combined with the altitude-induced increase in red cell production. Importantly, all abnormal biomarker values were identified by a low confidence value. Although the multifaceted, individual physiological response to altitude confounded some results, the PV model appears capable of reducing the impact of PV fluctuations on [Hb]., (Copyright © 2018 John Wiley & Sons, Ltd.)

Altitude training is associated with changes in blood markers, which can confound results of the Athlete?s Biological Passport (ABP). This meta-analysis aims to describe the fluctuations during- and post-altitude in key ABP variables; hemoglobin concentration ([Hb]), square-root transformed reticulocyte percentage (sqrt(retic%)) and the OFF-score. Individual de-identified raw data were provided from 17 studies. Separate linear mixed effects analyses were performed for delta values from baseline for [Hb], sqrt(retic%) and OFF-score, by altitude phase (during and post). Mixed models were fitted with the hierarchical structure: study and subject within study as random effects. Delta values as response variables and altitude dose (in kilometer hours; km.hr = altitude (m) / 1000 x hours), sex, age, protocol and baseline values as fixed effects. Allowances were made for potential autocorrelation. Within two days at natural altitude [Hb] rapidly increased. Subsequent delta [Hb] values increased with altitude dose, reaching a plateau of 0.94 g/dL [95%CI (0.69, 1.20)] at ~1000 km.hr. Delta sqrt(retic%) and OFF-score were the first to identify an erythrocyte response, with respective increases and decreases observed within 100 to 200 km.hr. Post-altitude, [Hb] remained elevated for two weeks. Delta sqrt(retic%) declined below baseline, the magnitude of change was dependent on altitude dose. Baseline values were a significant covariate (p<0.05). The response to altitude is complex resulting in a wide range of individual responses, influenced primarily by altitude dose and baseline values. Improved knowledge of the plausible hematological variations during- and post-altitude provides fundamental information for both the ABP expert and sports physician., (© 2017 Wiley Periodicals, Inc.)

There is evidence to suggest athletes have adopted recombinant human erythropoietin (rHuEPO) dosing regimens that diminish the likelihood of being caught by direct detection techniques. However, the temporal response in physiology, performance, and Athlete Biological Passport (ABP) parameters to such regimens is not clearly understood. Participants were assigned to a high-dose only group (HIGH, n = 8, six rHuEPO doses of 250 IU/kg over two weeks), a combined high micro-dose group (COMB, n = 8, high-dose plus nine rHuEPO micro-doses over a further three weeks), or one of two placebo control groups who received saline in the same pattern as the HIGH (HIGH-PLACEBO, n = 4) or COMB (COMB-PLACEBO, n = 4) groups. Temporal changes in physiology and performance were tracked by graded exercise test (GXT) and haemoglobin mass assessment at baseline, after high dose, after micro-dose (COMB and COMB-PLACEBO only) and after a four-week washout. Venous blood samples were collected throughout the baseline, rHuEPO administration, and washout periods to determine the haematological and ABP response to each dosing regimen. Physiological adaptations induced by a two-week rHuEPO high-dose were maintained by rHuEPO micro-dosing for at least three weeks. However, all participants administered rHuEPO registered at least one suspicious ABP value during the administration or washout periods. These results indicate there is sufficient sensitivity in the ABP to detect use of high rHuEPO doping regimens in athletic populations and they provide important empirical examples for use by anti-doping experts. Copyright © 2017 John Wiley & Sons, Ltd., (Copyright © 2017 John Wiley & Sons, Ltd.)

Objectives: Actical ® actigraphy is commonly used to monitor athlete sleep. The proprietary software, called Actiware ® , processes data with three different sleep-wake thresholds (Low, Medium or High), but there is no standardisation regarding their use. The purpose of this study was to examine validity and bias of the sleep-wake thresholds for processing Actical ® sleep data in team sport athletes., Design: Validation study comparing actigraph against accepted gold standard polysomnography (PSG)., Methods: Sixty seven nights of sleep were recorded simultaneously with polysomnography and Actical ® devices. Individual night data was compared across five sleep measures for each sleep-wake threshold using Actiware ® software. Accuracy of each sleep-wake threshold compared with PSG was evaluated from mean bias with 95% confidence limits, Pearson moment-product correlation and associated standard error of estimate., Results: The Medium threshold generated the smallest mean bias compared with polysomnography for total sleep time (8.5min), sleep efficiency (1.8%) and wake after sleep onset (-4.1min); whereas the Low threshold had the smallest bias (7.5min) for wake bouts. Bias in sleep onset latency was the same across thresholds (-9.5min). The standard error of the estimate was similar across all thresholds; total sleep time ∼25min, sleep efficiency ∼4.5%, wake after sleep onset ∼21min, and wake bouts ∼8 counts., Conclusions: Sleep parameters measured by the Actical ® device are greatly influenced by the sleep-wake threshold applied. In the present study the Medium threshold produced the smallest bias for most parameters compared with PSG. Given the magnitude of measurement variability, confidence limits should be employed when interpreting changes in sleep parameters., (Copyright © 2017 Sports Medicine Australia. All rights reserved.)

Aim: The aim of this study was to examine the relationship between ventilatory adaptation and performance during altitude training at 2700 m., Methods: Seven elite cyclists (age: 21.2 ± 1.1 yr, body mass: 69.9 ± 5.6 kg, height 176.3 ± 4.9 cm) participated in this study. A hypoxic ventilatory response (HVR) test and a submaximal exercise test were performed at sea level prior to the training camp and again after 15 d at altitude (ALT15). Ventilation (VE), end-tidal carbon-dioxide partial pressure (PETCO2) and oxyhaemoglobin saturation via pulse oximetry (SpO2) were measured at rest and during submaximal cycling at 250 W. A hill climb (HC) performance test was conducted at sea level and after 14 d at altitude (ALT14) using a road of similar length (5.5-6 km) and gradient (4.8-5.3%). Power output was measured using SRM cranks. Average HC power at ALT14 was normalised to sea level power (HC%). Multiple regression was used to identify significant predictors of performance at altitude., Results: At ALT15, there was a significant increase in resting VE (10.3 ± 1.9 vs. 12.2 ± 2.4 L·min(-1)) and HVR (0.34 ± 0.24 vs. 0.71 ± 0.49 L·min(-1)·%(-1)), while PETCO2 (38.4 ± 2.3 vs. 32.1 ± 3.3 mmHg) and SpO2 (97.9 ± 0.7 vs. 94.0 ± 1.7%) were reduced (P < .05). Multiple regression revealed ΔHVR and exercise VE at altitude as significant predictors of HC% (adjusted r(2) = 0.913; P = 0.003)., Conclusions: Ventilatory acclimatisation occurred during a 2 wk altitude training camp in elite cyclists and a higher HVR was associated with better performance at altitude, relative to sea level. These results suggest that ventilatory acclimatisation is beneficial for cycling performance at altitude.

This investigation examined the oxidative stress (F2-Isoprostane; F2-IsoP) and inflammatory (interleukin-6; IL-6) responses to repeat-sprint training in hypoxia (RSH). Ten trained male team sport athletes performed 3(sets)*9(repetitions)*5 s cycling sprints in simulated altitude (3000 m) and sea-level conditions. Mean and peak sprint power output (MPO and PPO) were recorded, and blood samples were collected pre-exercise, and again at 8 and 60 min post-exercise. Both MPO and PPO were significantly reduced in hypoxia (compared to sea-level) in the second (MPO: 855 ± 89 vs. 739 ± 95 W, p = .006; PPO: 1024 ± 114 vs. 895 ± 112 W, p = .010) and third (MPO: 819 ± 105 vs. 686 ± 83 W, p = .008; PPO: 985 ± 125 vs. 834 ± 99 W, p = .008) sets, respectively. IL-6 was significantly increased from pre- to 1 h post-exercise in both hypoxia (0.7 ± 0.2 vs. 2.4 ± 1.4 pg/mL, p = .004) and sea-level conditions (0.7 ± 0.2 vs. 1.6 ± 0.3 pg/mL, p < .001), with a large effect (d = 0.80) suggesting higher IL-6 levels of post-hypoxia. F2-IsoP was significantly lower 1 h post-exercise in both the hypoxic (p = .005) and sea-level (p = .002) conditions, with no differences between trials. While hypoxia can impact on exercise intensity and may result in greater post-exercise inflammation, it appears to have little effect on oxidative stress. These results indicate that team sport organisations with ready access to hypoxic training facilities could confidently administer RSH without significantly increasing the post-exercise inflammatory or oxidative stress response.

The aim of this paper is to provide a Bayesian formulation of the so-called magnitude-based inference approach to quantifying and interpreting effects, and in a case study example provide accurate probabilistic statements that correspond to the intended magnitude-based inferences. The model is described in the context of a published small-scale athlete study which employed a magnitude-based inference approach to compare the effect of two altitude training regimens (live high-train low (LHTL), and intermittent hypoxic exposure (IHE)) on running performance and blood measurements of elite triathletes. The posterior distributions, and corresponding point and interval estimates, for the parameters and associated effects and comparisons of interest, were estimated using Markov chain Monte Carlo simulations. The Bayesian analysis was shown to provide more direct probabilistic comparisons of treatments and able to identify small effects of interest. The approach avoided asymptotic assumptions and overcame issues such as multiple testing. Bayesian analysis of unscaled effects showed a probability of 0.96 that LHTL yields a substantially greater increase in hemoglobin mass than IHE, a 0.93 probability of a substantially greater improvement in running economy and a greater than 0.96 probability that both IHE and LHTL yield a substantially greater improvement in maximum blood lactate concentration compared to a Placebo. The conclusions are consistent with those obtained using a 'magnitude-based inference' approach that has been promoted in the field. The paper demonstrates that a fully Bayesian analysis is a simple and effective way of analysing small effects, providing a rich set of results that are straightforward to interpret in terms of probabilistic statements.

Heat and hypoxia exacerbate central nervous system (CNS) fatigue. We therefore investigated whether essential amino acid (EAA) and caffeine ingestion attenuates CNS fatigue in a simulated team sport-specific running protocol in a hot, hypoxic environment. Subelite male team sport athletes (n = 8) performed a repeat sprint running protocol on a nonmotorized treadmill in an extreme environment on 4 separate occasions. Participants ingested one of four supplements: a double placebo, 3 mg.kg-1 body mass of caffeine + placebo, 2 x 7 g EAA (Musashi Create)+placebo, or caffeine + EAA before each exercise session using a randomized, double-blind crossover design. Electromyography (EMG) activity and quadriceps evoked responses to magnetic stimulation were assessed from the dominant leg at preexercise, halftime, and postexercise. Central activation ratio (CAR) was used to quantify completeness of quadriceps activation. Oxygenation of the prefrontal cortex was measured via near-infrared spectroscopy. Mean sprint work was higher (M = 174 J, 95% CI [23, 324], p < .05, d = 0.30; effect size, likely beneficial) in the caffeine + EAA condition versus EAAs alone. The decline in EMG activity was less (M = 13%, 95% CI [0, 26]; p < .01, d = 0.58, likely beneficial) in caffeine + EAA versus EAA alone. Similarly, the pre- to postexercise decrement in CAR was significantly less (M = -2.7%, 95% CI [0.4, 5.4]; p < .05, d = 0.50, likely beneficial) when caffeine + EAA were ingested compared with placebo. Cerebral oxygenation was lower (M = -5.6%, 95% CI [1.0, 10.1]; p < .01, d = 0.60, very likely beneficial) in the caffeine + EAA condition compared with LNAA alone. Co-ingestion of caffeine and EAA appears to maintain muscle activation and central drive, with a small improvement in running performance.

The Athlete Biological Passport (ABP) estimates individualized reference ranges for key blood markers, such as haemoglobin concentration ([Hb]), using predetermined population mean, between- and within-subject variances. Here, we aim to reassess previously published estimates for within-subject [Hb] variance and determine whether sex-, analyzer-, sport-, or season-specific values are required. Our reference population contains 7723 male (mean ± SD, 22.3 ± 4.6 years of age) and 6164 female (21.6 ± 4.3) athlete observations from 49 sports. [Hb] was calculated using one of three cytometers; Bayer-H3 (1997-1999, n = 4554), ADVIA-120 (1999-2010, n = 8636) and Sysmex XT-2000i (2010-2012, n = 697). The final model was a linear mixed model for [Hb] with analyzer (H3, ADVIA, Sysmex), sex (male, female), sport (power-endurance, endurance, skill, team, disabled and non-athletes), season (summer, winter), and the interaction between sex and sport as fixed effects and athlete as a random effect. The model included an exponential correlation structure to allow for within-subject autocorrelation, and allowed different within-subject variances for each sport. Within-subject [Hb] variance (g(2) /L(2) ) was significantly less for power endurance (35.09, 95% CI 33.50 to 36.76), disabled (25.82, 95% CI 21.71 to 35.28) and non-athletes (34.30, 95% CI 28.53 to 35.87) than for endurance (40.35, 95% CI 39.62 to 47.22) and team sports (38.70, 95% CI 37.68 to 39.76) athletes. No new evidence was found to justify adjusting the current within-subject [Hb] variance estimate., (Copyright © 2015 John Wiley & Sons, Ltd.)

Purpose: The purpose of this study was to quantify the effects of moderate-high altitude on power output, cadence, speed and heart rate during a multi-day cycling tour., Methods: Power output, heart rate, speed and cadence were collected from elite male road cyclists during maximal efforts of 5, 15, 30, 60, 240 and 600 s. The efforts were completed in a laboratory power-profile assessment, and spontaneously during a cycling race simulation near sea-level and an international cycling race at moderate-high altitude. Matched data from the laboratory power-profile and the highest maximal mean power output (MMP) and corresponding speed and heart rate recorded during the cycling race simulation and cycling race at moderate-high altitude were compared using paired t-tests. Additionally, all MMP and corresponding speeds and heart rates were binned per 1000 m (<1000 m, 1000-2000, 2000-3000 and >3000 m) according to the average altitude of each ride. Mixed linear modelling was used to compare cycling performance data from each altitude bin., Results: Power output was similar between the laboratory power-profile and the race simulation, however MMPs for 5-600 s and 15, 60, 240 and 600 s were lower (p ≤ 0.005) during the race at altitude compared with the laboratory power-profile and race simulation, respectively. Furthermore, peak power output and all MMPs were lower (≥ 11.7%, p ≤ 0.001) while racing >3000 m compared with rides completed near sea-level. However, speed associated with MMP 60 and 240 s was greater (p < 0.001) during racing at moderate-high altitude compared with the race simulation near sea-level., Conclusion: A reduction in oxygen availability as altitude increases leads to attenuation of cycling power output during competition. Decrement in cycling power output at altitude does not seem to affect speed which tended to be greater at higher altitudes.

This study examined effects of low altitude training and a live-high: train-low protocol (combining both natural and simulated modalities) on haemoglobin mass (Hbmass), maximum oxygen consumption (VO2max), time to exhaustion, and submaximal exercise measures. Eighteen elite-level race-walkers were assigned to one of two experimental groups; lowHH (low Hypobaric Hypoxia: continuous exposure to 1380 m for 21 consecutive days; n = 10) or a combined low altitude training and nightly Normobaric Hypoxia (lowHH+NHnight: living and training at 1380 m, plus 9 h.night(-1) at a simulated altitude of 3000 m using hypoxic tents; n = 8). A control group (CON; n = 10) lived and trained at 600 m. Measurement of Hbmass, time to exhaustion and VO2max was performed before and after the training intervention. Paired samples t-tests were used to assess absolute and percentage change pre and post-test differences within groups, and differences between groups were assessed using a one-way ANOVA with least significant difference post-hoc testing. Statistical significance was tested at p < 0.05. There was a 3.7% increase in Hbmass in lowHH+NHnight compared with CON (p = 0.02). In comparison to baseline, Hbmass increased by 1.2% (±1.4%) in the lowHH group, 2.6% (±1.8%) in lowHH+NHnight, and there was a decrease of 0.9% (±4.9%) in CON. VO2max increased by ~4% within both experimental conditions but was not significantly greater than the 1% increase in CON. There was a ~9% difference in pre and post-intervention values in time to exhaustion after lowHH+NH-night (p = 0.03) and a ~8% pre to post-intervention difference (p = 0.006) after lowHH only. We recommend low altitude (1380 m) combined with sleeping in altitude tents (3000 m) as one effective alternative to traditional altitude training methods, which can improve Hbmass. Key pointsIn some countries, it may not be possible to perform classical altitude training effectively, due to the low elevation at altitude training venues. An additional hypoxic stimulus can be provided by simulating higher altitudes overnight, using altitude tents.Three weeks of combined (living and training at 1380 m) and simulated altitude exposure (at 3000 m) can improve haemoglobin mass by over 3% in comparison to control values, and can also improve time to exhaustion by ~9% in comparison to baseline.We recommend that, in the context of an altitude training camp at low altitudes (~1400 m) the addition of a relatively short exposure to simulated altitudes of 3000 m can elicit physiological and performance benefits, without compromise to training intensity or competition preparation. However, the benefits will not be greater than conducting a traditional altitude training camp at low altitudes.

There is a paucity of data examining the impact of high-intensity interval hypoxic training (IHT) on intermittent running performance. This study assessed the effects of IHT on 17 amateur Australian Footballers, who completed 8 interval treadmill running sessions (IHT [FIO2 = 15.1%] or PLACEBO) over 4 weeks, in addition to normoxic football (2 per week) and resistance (2 per week) training sessions. To match relative training intensity, absolute IHT intensity reduced by 6% of normoxic vV[Combining Dot Above]O2peak compared with PLACEBO. Before and after the intervention, performance was assessed by Yo-Yo intermittent recovery test level 2 (Yo-Yo IR2) and a self-paced team sport running protocol. Standardized effect size statistics were calculated using Cohen's d to compare between the interventions. Compared with PLACEBO, IHT subjects experienced (a) smaller improvements in Yo-Yo IR2 performance (Cohen's d = -0.42 [-0.82 to -0.02; 90% confidence interval]); (b) similar increases in high-intensity running distance during the team sport protocol (d = 0.17 [-0.50 to 0.84]); and (c) greater improvements in total distance (d = 0.72 [0.33-1.10]) and distance covered during low-intensity activity (d = 0.59 [-0.07 to 1.11]) during the team sport protocol. The lower absolute training intensity of IHT may explain the smaller improvements in Yo-Yo IR2 performance in the hypoxic group. Conversely, the data from the self-paced protocol suggest that IHT may positively influence pacing strategies in team sport athletes. In conclusion, IHT alters pacing strategies in team sport athletes (i.e., increased distance covered during low-intensity activity). However, IHT leads to smaller improvements in externally paced high-intensity intermittent running performance (i.e., Yo-Yo IR2), which may be related to a reduced absolute training intensity during IHT sessions.

To assess the impact of 'top-up' normoxic or hypoxic repeat-sprint training on sea-level repeat-sprint ability, thirty team sport athletes were randomly split into three groups, which were matched in running repeat-sprint ability (RSA), cycling RSA and 20 m shuttle run performance. Two groups then performed 15 maximal cycling repeat-sprint training sessions over 5 weeks, in either normoxia (NORM) or hypoxia (HYP), while a third group acted as a control (CON). In the post-training cycling RSA test, both NORM (13.6%; p = 0.0001, and 8.6%; p = 0.001) and HYP (10.3%; p = 0.007, and 4.7%; p = 0.046) significantly improved overall mean and peak power output, respectively, whereas CON did not change (1.4%; p = 0.528, and -1.1%; p = 0.571, respectively); with only NORM demonstrating a moderate effect for improved mean and peak power output compared to CON. Running RSA demonstrated no significant between group differences; however, the mean sprint times improved significantly from pre- to post-training for CON (1.1%), NORM (1.8%), and HYP (2.3%). Finally, there were no group differences in 20 m shuttle run performance. In conclusion, 'top-up' training improved performance in a task-specific activity (i.e. cycling); however, there was no additional benefit of conducting this 'top-up' training in hypoxia, since cycle RSA improved similarly in both HYP and NORM conditions. Regardless, the 'top-up' training had no significant impact on running RSA, therefore the use of cycle repeat-sprint training should be discouraged for team sport athletes due to limitations in specificity. Key points'Top-up' repeat-sprint training performed on a cycle ergometer enhances cycle repeat-sprint ability compared to team sport training only in football players.The addition of moderate hypoxia to repeat-sprint training provides no additional performance benefits to sea-level repeat-sprint ability or endurance performance than normoxic repeat-sprint training.'Top-up' cycling repeat-sprint training provides no significant additional benefit to running RSA or endurance performance than team sport training only, and therefore running based repeat-sprint interventions are recommended for team sport athletes.

Purpose: To investigate the influence of daily oral iron supplementation on changes in hemoglobin mass (Hbmass) and iron parameters after 2-4 weeks of moderate altitude exposure., Methods: Hematological data collected from 178 athletes (98 males, 80 females) exposed to moderate altitude (1,350-3,000 m) were analysed using linear regression to determine how altitude exposure combined with oral iron supplementation influenced Hbmass, total iron incorporation (TII) and blood iron parameters [ferritin and transferrin saturation (TSAT)]., Results: Altitude exposure (mean ± s: 21 ± 3 days) increased Hbmass by 1.1% [-0.4, 2.6], 3.3% [1.7, 4.8], and 4.0% [2.0, 6.1] from pre-altitude levels in athletes who ingested nil, 105 mg and 210 mg respectively, of oral iron supplement daily. Serum ferritin levels decreased by -33.2% [-46.9, -15.9] and 13.8% [-32.2, 9.7] from pre-altitude levels in athletes who supplemented with nil and 105 mg of oral iron supplement daily, but increased by 36.8% [1.3, 84.8] in athletes supplemented with 210 mg of oral iron daily. Finally, athletes who ingested either 105 mg or 210 mg of oral iron supplement daily had a greater TII compared with non-supplemented athletes (0 versus 105 mg: effect size (d) = -1.88 [-2.56, -1.17]; 0 versus 210 mg: effect size (d) = -2.87 [-3.88, -1.66])., Conclusion: Oral iron supplementation during 2-4 weeks of moderate altitude exposure may enhance Hbmass production and assist the maintenance of iron balance in some athletes with low pre-altitude iron stores.

The influence of low natural altitudes (< 2000 m) on erythropoietic adaptation is currently unclear, with current recommendations indicating that such low altitudes may be insufficient to stimulate significant increases in haemoglobin mass (Hbmass). As such, the purpose of this study was to determine the influence of 3 weeks of live high, train high exposure (LHTH) at low natural altitude (i.e. 1800 m) on Hbmass, red blood cell count and iron profile. A total of 16 elite or well-trained runners were assigned into either a LHTH (n = 8) or CONTROL (n = 8) group. Venous blood samples were drawn prior to, at 2 weeks and at 3 weeks following exposure. Hbmass was measured in duplicate prior to exposure and at 2 weeks and at 3 weeks following exposure via carbon monoxide rebreathing. The percentage change in Hbmass from baseline was significantly greater in LHTH, when compared with the CONTROL group at 2 (3.1% vs 0.4%; p = 0.01;) and 3 weeks (3.0% vs -1.1%; p < 0.02, respectively) following exposure. Haematocrit was greater in LHTH than CONTROL at 2 (p = 0.01) and 3 weeks (p = 0.04) following exposure. No significant interaction effect was observed for haemoglobin concentration (p = 0.06), serum ferritin (p = 0.43), transferrin (p = 0.52) or reticulocyte percentage (p = 0.16). The results of this study indicate that three week of natural classic (i.e. LHTH) low altitude exposure (1800 m) results in a significant increase in Hbmass of elite distance runners, which is likely due to the continuous exposure to hypoxia. Key pointsTwo and three weeks of LHTH altitude exposure (1800 m) results in a significant increase in HbmassLHTH altitude exposure increased Hbmass by 3.1% after 2 weeks, and 3.0% after 3 weeks of exposureLHTH altitude exposure may be a practical method to increase Hbmass in well-trained athletes.

The reliability and accuracy of five portable blood lactate (BLa) analysers (Lactate Pro, Lactate Pro2, Lactate Scout+, Xpress™, and Edge) and one handheld point-of-care analyser (i-STAT) were compared to a criterion (Radiometer ABL90). Two devices of each brand of analyser were assessed using 22 x 6 mL blood samples taken from five subjects at rest and during exercise who generated lactate ranging ~1-23 mM. Each sample was measured simultaneously ~6 times on each device. Reliability was assessed as the within-sample standard deviation (wsSD) of the six replicates; accuracy as the bias compared with the ABL90; and overall error (the root mean squared error (√MSE)) was calculated as the square root of (wsSD(2) and bias(2)). The √MSE indicated that both the Edge and Xpress had low total error (~0-2 mM) for lactate concentrations <15 mM, whereas the Edge and Lactate Pro2 were the better of the portable analysers for concentrations >15 mM. In all cases, bias (negative) was the major contribution to the √MSE. In conclusion, in a clinical setting where BLa is generally <15 mM the Edge and Xpress devices are relevant, but for athlete testing where peak BLa is important for training prescription the Edge and Lactate Pro2 are preferred. Key pointsThe reliability of five common portable blood lactate analysers were generally <0.5 mM for concentrations in the range of ~1.0-10 mM.For all five portable analysers, the analytical error within a brand was much smaller than the biological variation in blood lactate (BLa).Compared with a criterion blood lactate analyser, there was a tendency for all portable analysers to under-read (i.e. a negative bias), which was particularly evident at the highest concentrations (BLa ~15-23 mM).The practical application of these negative biases would overestimate the ability of the athlete and prescribe a training intensity that would be too high.

To compare relative match intensities of sea-level versus high-altitude native soccer players during a 2-week camp at 3600 m, data from 7 sea-level (Australian U17 National team, AUS) and 6 high-altitude (a Bolivian U18 team, BOL) native soccer players were analysed. Two matches were played at sea-level and three at 3600 m on Days 1, 6 and 13. The Yo-Yo Intermittent recovery test (vYo-YoIR1) was performed at sea-level, and on Days 3 and 10. Match activity profiles were measured via 10-Hz GPS. Distance covered >14.4 km.h(-1) (D>14.4 km·h(-1)) and >80% of vYo-YoIR1 (D>80%vYo-YoIR1) were examined. Upon arrival at altitude, there was a greater decrement in vYo-YoIR1 (Cohen's d +1.0, 90%CL ± 0.8) and D>14.4 km·h(-1) (+0.5 ± 0.8) in AUS. D>14.4 km.h(-1) was similarly reduced relative to vYo-YoIR1 in both groups, so that D>80%vYo-YoIR1 remained similarly unchanged (-0.1 ± 0.8). Throughout the altitude sojourn, vYo-YoIR1 and D>14.4 km·h(-1) increased in parallel in AUS, so that D>80%vYo-YoIR1 remained stable in AUS (+6.0%/match, 90%CL ± 6.7); conversely D>80%vYo-YoIR1 decreased largely in BOL (-12.2%/match ± 6.2). In sea-level natives competing at high-altitude, changes in match running performance likely follow those in high-intensity running performance. Bolivian data confirm that increases in 'fitness' do not necessarily translate into greater match running performance, but rather in reduced relative exercise intensity. Key pointsWhen playing at high-altitude, players may alter their activities during matches in relation to their transient maximal physical capacities, possibly to maintain a 'tolerable' relative exercise intensity.While there is no doubt that running performance per se in not the main determinant of match outcomes (Carling, 2013), fitness levels influence relative match intensity (Buchheit et al., 2012, Mendez-Villanueva et al., 2013), which in-turn may impact on decision making and skill performance (Rampinini et al., 2008).In the context of high-altitude competitions, it is therefore recommended to arrive early enough (i.e., ~2 weeks) to allow (at least partial) acclimatisation, and in turn, allow sea-level native players to regulate their running activities in relation to both actual game demands and relative match intensity.

The Athlete Biological Passport (ABP) detects blood doping in athletes through longitudinal monitoring of erythropoietic markers. Mathematical algorithms are used to define individual reference ranges for these markers for each athlete. It is unclear if altitude and exercise can affect the variables included in these calculations in a way that the changes might be mistaken for blood manipulation. The aim of this study was to investigate the influence of the simultaneous strenuous exercise and low to high altitude exposure on the calculation algorithms of the ABP. 14 sea level (SL) and 11 altitude native (ALT) highly trained athletes participated in a 14-day cycling stage race taking place at an average altitude of 2496 m above sea level (min. 1014 m, max. 4120 m), race distances ranged between 96 and 227 km per day. ABP blood measures were taken on days -1,3,6,10,14 (SL) and -1,9,15 (ALT) of the race. Four results from three samples of two different SL athletes exceeded the individual limits at the 99% specificity threshold and one value at 99.9%. In ALT, three results from three samples of three different athletes were beyond the individual limits at 99%, one at 99.9%. The variations could be explained by the expected physiological reaction to exercise and altitude. In summary, the abnormalities observed in the haematological ABP´s of well-trained athletes during extensive exercise at altitude are limited and in line with expected physiological changes., (Copyright © 2014 John Wiley & Sons, Ltd.)

Purpose: This study measured the influence of acute hypoxic exercise on Interleukin-6 (IL-6), hepcidin, and iron biomarkers in athletes., Methods: In a repeated measures design, 13 moderately trained endurance athletes performed 5 × 4 min intervals at 90 % of their peak oxygen consumption velocity (vVO2peak) in both normoxic [NORM, fraction of inspired oxygen (F IO2) = 0.2093, 15.3 ± 1.7 km h(-1)] and simulated hypoxic (HYP, F IO2 = 0.1450, 13.2 ± 1.5 km h(-1)) conditions. Venous blood samples were obtained pre-, post-, and 3 h post-exercise, and analysed for serum hepcidin, IL-6, ferritin, iron, soluble transferrin receptor (sTfR), and transferrin saturation., Results: Peak heart rate was significantly lower in HYP compared with NORM (p = 0.01); however, the rating of perceived exertion was similar between trials (p = 0.24). Ferritin (p = 0.02), transferrin (p = 0.03), and IL-6 (p = 0.01) significantly increased immediately post-exercise in both conditions, but returned to baseline 3 h later. Hepcidin levels significantly increased in both conditions 3 h post-exercise (p = 0.05), with no significant differences between trials. A significant treatment effect was observed between trials for sTfR (p = 0.01), but not iron and transferrin saturation., Conclusion: Acute exercise in hypoxia did not influence post-exercise IL-6 production, hepcidin activity or iron metabolism compared with exercise at the same relative intensity in normoxia. Hence, acute exercise performed at the same relative intensity in hypoxia poses no further risk to an athlete's iron status, as compared with exercise in normoxia.

Purpose: To determine the effect of intravenous iron supplementation on performance, fatigue and overall mood in runners without clinical iron deficiency., Methods: Fourteen distance runners with serum ferritin 30-100 µg · L(-1) were randomly assigned to receive three blinded injections of intravenous ferric-carboxymaltose (2 ml, 100 mg, IRON) or normal saline (PLACEBO) over four weeks (weeks 0, 2, 4). Athletes performed a 3,000 m time trial and 10 × 400 m monitored training session on consecutive days at week 0 and again following each injection. Hemoglobin mass (Hbmass) was assessed via carbon monoxide rebreathing at weeks 0 and 6. Fatigue and mood were determined bi-weekly until week 6 via Total Fatigue Score (TFS) and Total Mood Disturbance (TMD) using the Brief Fatigue Inventory and Brunel Mood Scale. Data were analyzed using magnitude-based inferences, based on the unequal variances t-statistic and Cohen's Effect sizes (ES)., Results: Serum ferritin increased in IRON only (Week 0: 62.8 ± 21.9, Week 4: 128.1 ± 46.6 µg · L(-1); p = 0.002) and remained elevated two weeks after the final injection (127.0 ± 66.3 µg · L(-1), p = 0.01), without significant changes in Hbmass. Supplementation had a moderate effect on TMD of IRON (ES -0.77) with scores at week 6 lower than PLACEBO (ES -1.58, p = 0.02). Similarly, at week 6, TFS was significantly improved in IRON vs. PLACEBO (ES -1.54, p = 0.05). There were no significant improvements in 3,000 m time in either group (Week 0 vs. Week 4; Iron: 625.6 ± 55.5 s vs. 625.4 ± 52.7 s; PLACEBO: 624.8 ± 47.2 s vs. 639.1 ± 59.7 s); but IRON reduced their average time for the 10 × 400 m training session at week 2 (Week 0: 78.0 ± 6.6 s, Week 2: 77.2 ± 6.3; ES-0.20, p = 0.004)., Conclusion: During 6 weeks of training, intravenous iron supplementation improved perceived fatigue and mood of trained athletes with no clinical iron deficiency, without concurrent improvements in oxygen transport capacity or performance.

Purpose: This study aimed to assess the impact of 3 heights of simulated altitude exposure on repeat-sprint performance in team-sport athletes., Methods: Ten trained male team-sport athletes completed 3 sets of repeated sprints (9 × 4 s) on a nonmotorized treadmill at sea level and at simulated altitudes of 2000, 3000, and 4000 m. Participants completed 4 trials in a random order over 4 wk, with mean power output (MPO), peak power output (PPO), blood lactate concentration (Bla), and oxygen saturation (SaO2) recorded after each set., Results: Each increase in simulated altitude corresponded with a significant decrease in SaO2. Total work across all sets was highest at sea level and correspondingly lower at each successive altitude (P < .05; sea level < 2000 m < 3000 m < 4000 m). In the first set, MPO was reduced only at 4000 m, but for subsequent sets, decreases in MPO were observed at all altitudes (P < .05; 2000 m < 3000 m < 4000 m). PPO was maintained in all sets except for set 3 at 4000 m (P < .05; vs sea level and 2000 m). BLa levels were highest at 4000 m and significantly greater (P < .05) than at sea level after all sets., Conclusions: These results suggest that "higher may not be better," as a simulated altitude of 4000 m may potentially blunt absolute training quality. Therefore, it is recommended that a moderate simulated altitude (2000-3000 m) be employed when implementing intermittent hypoxic repeat-sprint training for team-sport athletes.

Plasma volume (PV) can be modulated by altitude exposure (decrease) and periods of intense exercise (increase). Cycle racing at altitude combines both stimuli, although presently no data exist to document which is dominant. Hemoglobin mass (Hbmass), hemoglobin concentration ([Hb]), and percent reticulocytes (%Retics) of altitude (ALT; n = 9) and sea-level (SL; n = 9) residents were measured during a 14-day cycling race, held at 1,146-4120 m, as well as during a simulated tour near sea level (SIM; n = 12). Hbmass was assessed before and on days 9 and 14 of racing. Venous blood was collected on days 0, 3, 6, 10, and 14. PV was calculated from Hbmass and [Hb]. A repeated-measures ANOVA was used to assess the impact of racing at altitude over time, within and between groups. [Hb] decreased significantly in all groups over time (P < 0.0001) with decreases evident on the third day of racing. %Retics increased significantly in SL only (P < 0.0001), with SL values elevated at day 6 compared with prerace (P = 0.02), but were suppressed by the end of the race (P = 0.0002). Hbmass significantly increased in SL after 9 (P = 0.0001) and 14 (P = 0.008) days of racing and was lower at the end of the race than midrace (P = 0.018). PV increased in all groups (P < 0.0001). Multiday cycle racing at altitude induces hemodilution of a similar magnitude to that observed during SL racing and occurs in nonacclimatized SL residents, despite an altitude-induced increase in Hbmass. Osmotic regulatory mechanisms associated with intense exercise appear to supersede acute enhancement of oxygen delivery at altitude., (Copyright © 2014 the American Physiological Society.)

Background and Objective: Hypoxic training techniques are increasingly used by athletes in an attempt to improve performance in normoxic environments. The 'live low-train high (LLTH)' model of hypoxic training may be of particular interest to athletes because LLTH protocols generally involve shorter hypoxic exposures (approximately two to five sessions per week of <3 h) than other traditional hypoxic training techniques (e.g., live high-train high or live high-train low). However, the methods employed in LLTH studies to date vary greatly with respect to exposure times, training intensities, training modalities, degrees of hypoxia and performance outcomes assessed. Whilst recent reviews provide some insight into how LLTH may be applied to enhance performance, little attention has been given to how training intensity/modality may specifically influence subsequent performance in normoxia. Therefore, this systematic review aims to evaluate the normoxic performance outcomes of the available LLTH literature, with a particular focus on training intensity and modality., Data Sources and Study Selection: A systematic search was conducted to capture all LLTH studies with a matched normoxic (control) training group and the assessment of performance under normoxic conditions. Studies were excluded if no training was completed during the hypoxic exposures, or if these exposures exceeded 3 h per day. Four electronic databases were searched (PubMed, SPORTDiscus, EMBASE and Web of Science) during August 2013, and these searches were supplemented by additional manual searches until December 2013., Results: After the electronic and manual searches, 40 papers were deemed to meet the inclusion criteria, representing 31 separate studies. Within these 31 studies, four types of LLTH were identified: (1) continuous low-intensity training in hypoxia (CHT, n = 16), (2) interval hypoxic training (IHT, n = 4), (3) repeated sprint training in hypoxia (RSH, n = 3) and (4) resistance training in hypoxia (RTH, n = 4). Four studies also used a combination of CHT and IHT. The majority of studies reported no difference in normoxic performance between the hypoxic and normoxic training groups (n = 19), while nine reported greater improvements in the hypoxic group and three reported poorer outcomes compared with the control group. Selection of training intensity (including matching relative or absolute intensity between normoxic and hypoxic groups) was identified as a key factor in mediating the subsequent normoxic performance outcomes. Five studies included some form of normoxic training for the hypoxic group and 14 studies assessed performance outcomes not specific to the training intensity/modality completed during the training intervention., Conclusion: Four modes of LLTH are identified in the current literature (CHT, IHT, RSH and RTH), with training mode and intensity appearing to be key factors in mediating subsequent performance responses in normoxia. Improvements in normoxic performance appear most likely following high-intensity, short-term and intermittent training (e.g., IHT, RSH). LLTH programmes should carefully apply the principles of training and testing specificity and include some high-intensity training in normoxia. For RTH, it is unclear whether the associated adaptations are greater than those of traditional (maximal) resistance training programmes.

Purpose: To assess the influence of a simulated altitude exposure (~2,900 m above sea level) for a 3 h recovery period following intense interval running on post-exercise inflammation, serum iron, ferritin, erythropoietin, and hepcidin response., Methods: In a cross-over design, ten well-trained male endurance athletes completed two 8 × 3 min interval running sessions at 85 % of their maximal aerobic velocity on a motorized treadmill, before being randomly assigned to either a hypoxic (HYP: F IO2 ~0.1513) or a normoxic (NORM: F IO2 0.2093) 3 h recovery period. Venous blood was collected pre- and immediately post-exercise, and after 3 and 24 h of recovery. Blood was analyzed for interleukin-6, serum iron, ferritin, erythropoietin, and hepcidin., Results: Interleukin-6 was significantly elevated (p < 0.01) immediately post-exercise compared to baseline (NORM: 1.08 ± 0.061 to 3.12 ± 1.80) (HYP: 1.32 ± 0.86 to 2.99 ± 2.02), but was not different between conditions. Hepcidin levels were significantly elevated (p < 0.01) at 3 h post-exercise for both conditions when compared to baseline (NORM: 3.25 ± 1.23 to 7.40 ± 4.00) (HYP: 3.24 ± 1.94 to 5.42 ± 3.20), but were significantly lower (p < 0.05) in the HYP trial compared to NORM. No significant differences existed between HYP and NORM for erythropoietin, serum iron, or ferritin., Conclusion: Simulated altitude exposure (~2,900 m) for 3 h following intense interval running attenuates the peak hepcidin levels recorded at 3 h post-exercise. Consequently, a hypoxic recovery after exercise may be useful for athletes with compromised iron status to potentially increase acute dietary iron absorption.

Purpose: This study investigated the decrement in running performance of elite soccer players competing at low altitude and time course for abatement of these decrements., Methods: Twenty elite youth soccer players had their activity profile, in a sea-level (SL) and 2 altitude (Alt, 1600 m, d 4, and d 6) matches, measured with a global positioning system. Measures expressed in meters per minute of match time were total distance, low- and high-velocity running (LoVR, 0.01-4.16 m/s; HiVR, 4.17-10.0 m/s), and frequency of maximal accelerations (>2.78 m/s2). The peak and subsequent stanza for each measure were identified and a transient fatigue index calculated. Mean heart rate (HR) during the final minute of a submaximal running task (5 min, 11 km/h) was recorded at SL and for 10 d at Alt. Differences were determined between SL and Alt using percentage change and effect-size (ES) statistic with 90% confidence intervals., Results: Mean HR almost certainly increased on d 1 (5.4%, ES 1.01 ± 0.35) and remained probably elevated on both d 2 (ES 0.42 ± 0.31) and d3 (ES 0.30 ± 0.25), returning to baseline at d 5. Total distance was almost certainly lower than SL (ES -0.76 ± 0.37) at d 4 and remained probably reduced on d 6 (ES -0.42 ± 0.36). HiVR probably decreased at d 4 vs SL (-0.47 ± 0.59), with no clear effect of altitude at d 6 (-0.08 ± 0.41). Transient fatigue in matches was evident at SL and Alt, with a possibly greater decrement at Alt., Conclusion: Despite some physiological adaptation, match running performance of youth soccer players is compromised for at least 6 d at low altitude.

Purpose: Iron deficiency is prevalent in distance runners and may impair endurance performance. The current practice of oral supplementation is slow and often not well tolerated. The aim of this study was to assess the efficacy of intravenous (IV) iron supplementation (ferric carboxymaltose) compared with oral supplementation (ferrous sulfate) on iron status, hemoglobin mass (Hbmass), and physiological indices of running performance in distance runners., Methods: Twenty-seven highly trained distance runners with low (LOW) (ferritin <35 μg·L(-1) and transferrin saturation <20%, or ferritin <15 μg·L(-1)) or suboptimal (SUB) iron status (ferritin <65 μg·L(-1)) were supplemented with either IV iron (Ferinject®) or oral (ORAL) supplements (Ferrogradumet) for 6 wk. Iron status and Hbmass were assessed before supplementation and at 1, 2, 4, 6, and 8 wk in the four groups (IV LOW, IV SUB, ORAL LOW, and ORAL SUB). In addition, athletes completed a treadmill running test for running economy, lactate threshold, and V˙O2max before and after supplementation., Results: Both forms of supplementation substantially increased ferritin levels in all four groups. IV supplementation resulted in higher ferritin in both IV groups compared with both ORAL groups from week 1 onward. Hemoglobin concentration did not change substantially in any group. Hbmass increased in IV LOW (mean = +4.9%, 90% confidence interval [CI] = 1.1%-8.9%) and was accompanied by an increase in V˙O2max (mean = +3.3%, 90% CI = 0.4%-6.3%) and run time to exhaustion (mean = +9.3%, 90% CI = 0.9%-18.3%., Conclusions: IV supplementation can effectively increase iron stores in iron-deficient runners within 6 wk and, if Hbmass is compromised, may enhance endurance capacity by facilitating erythropoiesis. Hbmass appears a more sensitive tool for measuring changes in whole body hemoglobin than hemoglobin concentration and may be useful in the diagnosis and follow-up for iron deficiency.

Objectives: To examine the time course of wellness, fatigue and performance during an altitude training camp (La Paz, 3600 m) in two groups of either sea-level (Australian) or altitude (Bolivian) native young soccer players., Methods: Wellness and fatigue were assessed using questionnaires and resting heart rate (HR) and HR variability. Physical performance was assessed using HR responses to a submaximal run, a Yo-Yo Intermittent recovery test level 1 (Yo-YoIR1) and a 20 m sprint. Most measures were performed daily, with the exception of Yo-YoIR1 and 20 m sprints, which were performed near sea level and on days 3 and 10 at altitude., Results: Compared with near sea level, Australians had moderate-to-large impairments in wellness and Yo-YoIR1 relative to the Bolivians on arrival at altitude. The acclimatisation of most measures to altitude was substantially slower in Australians than Bolivians, with only Bolivians reaching near sea-level baseline high-intensity running by the end of the camp. Both teams had moderately impaired 20 m sprinting at the end of the camp. Exercise HR had large associations (r>0.5-0.7) with changes in Yo-YoIR1 in both groups., Conclusions: Despite partial physiological and perceptual acclimatisation, 2 weeks is insufficient for restoration of physical performance in young sea-level native soccer players. Because of the possible decrement in 20 m sprint time, a greater emphasis on speed training may be required during and after altitude training. The specific time course of restoration for each variable suggests that they measure different aspects of acclimatisation to 3600 m; they should therefore be used in combination to assess adaptation to altitude.

The question of whether altitude training can enhance subsequent sea-level performance has been well investigated over many decades. However, research on this topic has focused on athletes from individual or endurance sports, with scant number of studies on team-sport athletes. Questions that need to be answered include whether this type of training may enhance team-sport athlete performance, when success in team-sport is often more based on technical and tactical ability rather than physical capacity per se. This review will contrast and compare athletes from two sports representative of endurance (cycling) and team-sports (soccer). Specifically, we draw on the respective competition schedules, physiological capacities, activity profiles and energetics of each sport to compare the similarities between athletes from these sports and discuss the relative merits of altitude training for these athletes. The application of conventional live-high, train-high; live-high, train-low; and intermittent hypoxic training for team-sport athletes in the context of the above will be presented. When the above points are considered, we will conclude that dependent on resources and training objectives, altitude training can be seen as an attractive proposition to enhance the physical performance of team-sport athletes without the need for an obvious increase in training load.

Objectives: To examine the time course of changes in wellness and health status markers before and after episodes of sickness in young soccer players during a high-altitude training camp (La Paz, 3600 m)., Methods: Wellness and fatigue were assessed daily on awakening using specifically-designed questionnaires and resting measures of heart rate and heart rate variability. The rating of perceived exertion and heart rate responses to a submaximal run (9 km/h) were also collected during each training session. Players who missed the morning screening for at least two consecutive days were considered as sick., Results: Four players met the inclusion criteria. With the exception of submaximal exercise heart rate, which showed an almost certain and large increase before the day of sickness (4%; 90% confidence interval 3 to 6), there was no clear change in any of the other psychometric or physiological variables. There was a very likely moderate increase (79%, 22 to 64) in self-reported training load the day before the heart rate increase in sick players (4 of the 4 players, 100%). In contrast, training load was likely and slightly decreased (-24%, -78 to -11) in players who also showed an increased heart rate but remained healthy., Conclusions: A >4% increased heart rate during submaximal exercise in response to a moderate increase in perceived training load the previous day may be an indicator of sickness the next day. All other variables, that is, resting heart rate, heart rate variability and psychometric questionnaires may be less powerful at predicting sickness.

Aim: To quantify the year-to-year variability of altitude-induced changes in haemoglobin mass (Hb(mass)) in elite team-sport athletes., Methods: 12 Australian-Footballers completed a 19-day (ALT1) and 18-day (ALT2) moderate altitude (∼2100 m), training camp separated by 12 months. An additional 20 participants completed only one of the two training camps (ALT1 additional n=9, ALT2 additional n=11). Total Hb(mass) was assessed using carbon monoxide rebreathing before (PRE), after (POST₁) and 4 weeks after each camp. The typical error of Hb(mass) for the pooled data of all 32 participants was 2.6%. A contemporary statistics analysis was used with the smallest worthwhile change set to 2% for Hb(mass)., Results: POST₁ Hb(mass) was very likely increased in ALT1 (3.6 ± 1.6%, n=19; mean ± ∼90 CL) as well as ALT2 (4.4 ± 1.3%, n=23) with an individual responsiveness of 1.3% and 2.2%, respectively. There was a small correlation between ALT1 and ALT2 (R=0.21, p=0.59) for a change in Hb(mass), but a moderately inverse relationship between the change in Hb(mass) and initial relative Hb(mass) (g/kg (R=-0.51, p=0.04))., Conclusions: Two preseason moderate altitude camps 1 year apart yielded a similar (4%) mean increase in Hb(mass) of elite footballers, with an individual responsiveness of approximately half the group mean effect, indicating that most players gained benefit. Nevertheless, the same individuals generally did not change their Hb(mass) consistently from year to year. Thus, a 'responder' or 'non-responder' to altitude for Hb(mass) does not appear to be a fixed trait.

Background: We describe here the 3-year process underpinning a multinational collaboration to investigate soccer played at high altitude--La Paz, Bolivia (3600 m). There were two main aims: first, to quantify the extent to which running performance would be altered at 3600 m compared with near sea level; and second, to characterise the time course of acclimatisation of running performance and underlying physiology to training and playing at 3600 m. In addition, this project was able to measure the physiological changes and the effect on running performance of altitude-adapted soccer players from 3600 m playing at low altitude., Methods: A U20 Bolivian team ('The Strongest' from La Paz, n=19) played a series of five games against a U17 team from sea level in Australia (The Joeys, n=20). 2 games were played near sea level (Santa Cruz 430 m) over 5 days and then three games were played in La Paz over the next 12 days. Measures were (1) game and training running performance--including global positioning system (GPS) data on distance travelled and velocity of movement; (2) blood--including haemoglobin mass, blood volume, blood gases and acid-base status; (3) acclimatisation--including resting heart rate variability, perceived altitude sickness, as well as heart rate and perceived exertion responses to a submaximal running test; and (4) sleep patterns., Conclusions: Pivotal to the success of the project were the strong professional networks of the collaborators, with most exceeding 10 years, the links of several of the researchers to soccer federations, as well as the interest and support of the two head coaches.

Objective: To characterise the time course of changes in haemoglobin mass (Hbmass) in response to altitude exposure., Methods: This meta-analysis uses raw data from 17 studies that used carbon monoxide rebreathing to determine Hbmass prealtitude, during altitude and postaltitude. Seven studies were classic altitude training, eight were live high train low (LHTL) and two mixed classic and LHTL. Separate linear-mixed models were fitted to the data from the 17 studies and the resultant estimates of the effects of altitude used in a random effects meta-analysis to obtain an overall estimate of the effect of altitude, with separate analyses during altitude and postaltitude. In addition, within-subject differences from the prealtitude phase for altitude participant and all the data on control participants were used to estimate the analytical SD. The 'true' between-subject response to altitude was estimated from the within-subject differences on altitude participants, between the prealtitude and during-altitude phases, together with the estimated analytical SD., Results: During-altitude Hbmass was estimated to increase by ∼1.1%/100 h for LHTL and classic altitude. Postaltitude Hbmass was estimated to be 3.3% higher than prealtitude values for up to 20 days. The within-subject SD was constant at ∼2% for up to 7 days between observations, indicative of analytical error. A 95% prediction interval for the 'true' response of an athlete exposed to 300 h of altitude was estimated to be 1.1-6%., Conclusions: Camps as short as 2 weeks of classic and LHTL altitude will quite likely increase Hbmass and most athletes can expect benefit.

Despite the limited research on the effects of altitude (or hypoxic) training interventions on team-sport performance, players from all around the world engaged in these sports are now using altitude training more than ever before. In March 2013, an Altitude Training and Team Sports conference was held in Doha, Qatar, to establish a forum of research and practical insights into this rapidly growing field. A round-table meeting in which the panellists engaged in focused discussions concluded this conference. This has resulted in the present position statement, designed to highlight some key issues raised during the debates and to integrate the ideas into a shared conceptual framework. The present signposting document has been developed for use by support teams (coaches, performance scientists, physicians, strength and conditioning staff) and other professionals who have an interest in the practical application of altitude training for team sports. After more than four decades of research, there is still no consensus on the optimal strategies to elicit the best results from altitude training in a team-sport population. However, there are some recommended strategies discussed in this position statement to adopt for improving the acclimatisation process when training/competing at altitude and for potentially enhancing sea-level performance. It is our hope that this information will be intriguing, balanced and, more importantly, stimulating to the point that it promotes constructive discussion and serves as a guide for future research aimed at advancing the bourgeoning body of knowledge in the area of altitude training for team sports.

Objectives: The optimal strategy for soccer teams playing at altitude is not known, that is, 'fly-in, fly-out' versus short-term acclimatisation. Here, we document changes in blood gas and vascular volumes of sea-level (Australian, n=20) and altitude (Bolivian, n=19) native soccer players at 3600 m., Methods: Haemoglobin-oxygen saturation (Hb-sO₂), arterial oxygen content (CaO₂), haemoglobin mass (Hbmass), blood volume (BV) and blood gas concentrations were measured before descent (Bolivians only), together with aerobic fitness (via Yo-YoIR1), near sea-level, after ascent and during 13 days at 3600 m., Results: At baseline, haemoglobin concentration [Hb] and Hbmass were higher in Bolivians (mean ± SD; 18.2 ± 1.0 g/dL, 12.8 ± 0.8 g/kg) than Australians (15.0 ± 0.9 g/dL, 11.6 ± 0.7 g/kg; both p ≤ 0.001). Near sea-level, [Hb] of Bolivians decreased to 16.6 ± 0.9 g/dL, but normalised upon return to 3600 m; Hbmass was constant regardless of altitude. In Australians, [Hb] increased after 12 days at 3600 m to 17.3 ± 1.0 g/dL; Hbmass increased by 3.0 ± 2.7% (p ≤ 0.01). BV decreased in both teams at altitude by ∼400 mL. Arterial partial pressure for oxygen (PaO₂), Hb-sO₂ and CaO₂ of both teams decreased within 2 h of arrival at 3600 m (p ≤ 0.001) but increased over the following days, with CaO₂ overcompensated in Australians (+1.7 ± 1.2 mL/100 mL; p ≤ 0.001). Yo-YoIR1 was lower on the 3rd versus 10th day at altitude and was significantly related to CaO₂., Conclusions: The marked drop in PaO₂ and CaO₂ observed after ascent does not support the 'fly-in, fly-out' approach for soccer teams to play immediately after arrival at altitude. Although short-term acclimatisation was sufficient for Australians to stabilise their CaO₂ (mostly due to loss of plasma volume), 12 days appears insufficient to reach chronic levels of adaption.

Background: Endurance athletes have been using altitude training for decades to improve near sea-level performance. The predominant mechanism is thought to be accelerated erythropoiesis increasing haemoglobin mass (Hb(mass)) resulting in a greater maximal oxygen uptake (VO₂(max)). Not all studies have shown a proportionate increase in VO₂(max) as a result of increased Hb(mass). The aim of this study was to determine the relationship between the two parameters in a large group of endurance athletes after altitude training., Methods: 145 elite endurance athletes (94 male and 51 female) who participated in various altitude studies as altitude or control participants were used for the analysis. Participants performed Hb(mass) and VO₂(max) testing before and after intervention., Results: For the pooled data, the correlation between per cent change in Hb(mass) and per cent change in VO₂(max) was significant (p<0.0001, r(2)=0.15), with a slope (95% CI) of 0.48 (0.30 to 0.67) intercept free to vary and 0.62 (0.46 to 0.77) when constrained through the origin. When separated, the correlations were significant for the altitude and control groups, with the correlation being stronger for the altitude group (slope of 0.57 to 0.72)., Conclusions: With high statistical power, we conclude that altitude training of endurance athletes will result in an increase in VO₂(max) of more than half the magnitude of the increase in Hb(mass), which supports the use of altitude training by athletes. But race performance is not perfectly related to relative VO₂(max), and other non-haematological factors altered from altitude training, such as running economy and lactate threshold, may also be beneficial to performance.

Objectives: Water polo requires high aerobic power to meet the demands of match play. Live high:train low (LHTL) may enhance aerobic capacity at sea level. Before the Olympics, the Australian women's water polo team utilised LHTL in an attempt to enhance aerobic fitness., Methods: Over 6 months, 11 players completed three normobaric LHTL exposures (block 1:11 days at 3000 m; block 2+3:9 days at 2500 m, 11 days normoxia, 10 days at 2800 m). Haemoglobin mass (Hbmass) was measured through carbon monoxide-rebreathing. Before each block, the relationship between Hbmass and water polo-specific aerobic fitness was investigated using the Multistage Shuttle Swim Test (MSST). Effect size statistics were adopted with likely, highly likely and almost certainly results being >75%, >95%, >99%, respectively. A Pearson product moment correlation was used to characterise the association between pooled data of Hbmass and MSST., Results: Hbmass (mean ± SD, pre 721 ± 66 g) likely increased after block 1 and almost certainly after block 2+3 (% change; 90% confidence limits: block 1: 3.7%; 1.3-6.2%, block 2+3: 4.5%; 3.8-5.1%) and the net effect was almost certainly higher after block 2+3 than before block 1 (pre) by 8.5%; 7.3-9.7%. There was a very large correlation between Hbmass (g/kg) and MSST score (r=0.73)., Conclusions: LHTL exposures of <2 weeks induced approximately 4% increase in Hbmass of water polo players. Extra Hbmass may increase aerobic power, but since match performance is nuanced by many factors it is impossible to ascertain whether the increased Hbmass contributed to Australia's Bronze medal.