An attempt to quantify the placebo effect from a three-week simulated altitude training camp in elite race walkers

Physiological and performance effects of live high train low altitude training for elite endurance athletes: A narrative review

Altitude training has become an important training application for athletes due its potential for altering physiology and enhancing performance. This practice is commonly used by athletes, with a popular choice being the live high - train low approach. This model recommends that athletes live at high altitude (1250-3000 m), but train at low altitude or sea-level (0-1200 m). Exposure to altitude often leads to hypoxic stress and in turn stimulates changes in total haemoglobin mass, erythropoietin, and soluble transferrin receptors, which alter further underlying physiology. Through enhanced physiology, improved exercise performance may arise through enhancement of the oxygen transport system which is important for endurance events. Previous investigations into the effects of altitude training on exercise performance have been completed in a range of contexts, including running, cycling, swimming, and triathlon. Often following a LHTL altitude intervention, athletes realise improvements in maximal oxygen consumption capacity, time trial performance and peak power outputs. Although heterogeneity exists among LHTL methodologies, i.e., exposure durations and altitude ranges, we synthesised this data into kilometre hours, and found that the most common hypoxic doses used in LHTL interventions ranged from ∼578-687 km h. As this narrative review demonstrates, there are potential advantages to using altitude training to enhance physiology and improve performance for endurance athletes.

"Living High-Training Low" for Olympic Medal Performance: What Have We Learned 25 Years After Implementation?

BACKGROUND

Altitude training is often regarded as an indispensable tool for the success of elite endurance athletes. Historically, altitude training emerged as a key strategy to prepare for the 1968 Olympics, held at 2300 m in Mexico City, and was limited to the "Live High-Train High" method for endurance athletes aiming for performance gains through improved oxygen transport. This "classical" intervention was modified in 1997 by the "Live High-Train Low" (LHTL) model wherein athletes supplemented acclimatization to chronic hypoxia with high-intensity training at low altitude.

PURPOSE

This review discusses important considerations for successful implementation of LHTL camps in elite athletes based on experiences, both published and unpublished, of the authors.

APPROACH

The originality of our approach is to discuss 10 key "lessons learned," since the seminal work by Levine and Stray-Gundersen was published in 1997, and focusing on (1) optimal dose, (2) individual responses, (3) iron status, (4) training-load monitoring, (5) wellness and well-being monitoring, (6) timing of the intervention, (7) use of natural versus simulated hypoxia, (8) robustness of adaptative mechanisms versus performance benefits, (9) application for a broad range of athletes, and (10) combination of methods. Successful LHTL strategies implemented by Team USA athletes for podium performance at Olympic Games and/or World Championships are presented.

CONCLUSIONS

The evolution of the LHTL model represents an essential framework for sport science, in which field-driven questions about performance led to critical scientific investigation and subsequent practical implementation of a unique approach to altitude training.

Living high - training low model applied to C57BL/6J mice: Effects on physiological parameters related to aerobic fitness and acid-base balance

There is a scarcity of data regarding the acclimation to high altitude (hypoxic environment) accompanied by training at low altitude (normoxic conditions), the so-called "living high-training low" (LHTL) model in rodents. We aimed to investigate the effects of aerobic training on C57BL/6J mice living in normoxic (NOR) or hypoxic (HYP) environments on several parameters, including critical velocity (CV), a parameter regarded as a measure of aerobic capacity, on monocarboxylate transporters (MCTs) in muscles and hypothalamus, as well as on hematological parameters and body temperature. In each environment, mice were divided into non-trained (N) and trained (T). Forty rodents were distributed into the following experimental groups (N-NOR; T-NOR; N-HYP and T-HYP). HYP groups were in a normobaric tent where oxygen-depleted air was pumped from a hypoxia generator set an inspired oxygen fraction [FiO₂] of 14.5 %. The HYP-groups were kept (18 h per day) in a normobaric tent for consecutive 8-weeks. Training sessions were conducted in normoxic conditions ([FiO₂] = 19.5 %), 5 times per week (40 min per session) at intensity equivalent to 80 % of CV. In summary, eight weeks of LHTL did not promote a greater improvement in the CV, protein expression of MCTs in different tissues when compared to the application of training alone. The LHTL model increased red blood cells count, but reduced hemoglobin per erythrocyte was found in mice exposed to LHTL. Although the LHTL did not have a major effect on thermographic records, exercise-induced hyperthermia (in the head) was attenuated in HYP groups when compared to NOR groups.

Adaptation to a low carbohydrate high fat diet is rapid but impairs endurance exercise metabolism and performance despite enhanced glycogen availability

KEY POINTS

Brief (5-6 days) adaptation to a low carbohydrate high fat diet in elite athletes increased exercise fat oxidation to rates previously observed with medium (3-4 weeks) or chronic (>12 months) adherence to this diet, with metabolic changes being washed out in a similar time frame. Increased fat utilisation during exercise was associated with a 5-8% increase in oxygen cost at speeds related to Olympic Programme races. Acute restoration of endogenous carbohydrate (CHO) availability (24 h high CHO diet, pre-race CHO) only partially restored substrate utilisation during a race warm-up. Fat oxidation continued to be elevated above baseline values although it was lower than achieved by 5-6 days' keto adaptation; CHO oxidation only reached 61% and 78% of values previously seen at exercise intensities related to race events. Acute restoration of CHO availability failed to overturn the impairment of high-intensity endurance performance previously associated with low carbohydrate high fat adaptation, potentially due to the blunted capacity for CHO oxidation.

ABSTRACT

We investigated substrate utilisation during exercise after brief (5-6 days) adaptation to a ketogenic low-carbohydrate (CHO), high-fat (LCHF) diet and similar washout period. Thirteen world-class male race walkers completed economy testing, 25 km training and a 10,000 m race (Baseline), with high CHO availability (HCHO), repeating this (Adaptation) after 5-6 days' LCHF (n = 7; CHO: <50 g day^-1 , protein: 2.2 g kg^-1 day^-1 ; 80% fat) or HCHO (n = 6; CHO: 9.7 g kg^-1 day^-1 ; protein: 2.2 g kg^-1 day^-1 ) diet. An Adaptation race was undertaken after 24 h HCHO and pre-race CHO (2 g kg^-1 ) diet, identical to the Baseline race. Substantial (>200%) increases in exercise fat oxidation occurred in the LCHF Adaptation economy and 25 km tests, reaching mean rates of ∼1.43 g min^-1 . However, relative V ̇ O 2 (ml min^-1  kg^-1 ) was higher (P < 0.0001), by ∼8% and 5% at speeds related to 50 km and 20 km events. During Adaptation race warm-up in the LCHF group, rates of fat and CHO oxidation at these speeds were decreased and increased, respectively (P < 0.001), compared with the previous day, but were not restored to Baseline values. Performance changes differed between groups (P = 0.009), with all HCHO athletes improving in the Adaptation race (5.7 (5.6)%), while 6/7 LCHF athletes were slower (2.2 (3.4)%). Substrate utilisation returned to Baseline values after 5-6 days of HCHO diet. In summary, robust changes in exercise substrate use occurred in 5-6 days of extreme changes in CHO intake. However, adaptation to a LCHF diet plus acute restoration of endogenous CHO availability failed to restore high-intensity endurance performance, with CHO oxidation rates remaining blunted.

Crisis of confidence averted: Impairment of exercise economy and performance in elite race walkers by ketogenic low carbohydrate, high fat (LCHF) diet is reproducible

INTRODUCTION

We repeated our study of intensified training on a ketogenic low-carbohydrate (CHO), high-fat diet (LCHF) in world-class endurance athletes, with further investigation of a "carryover" effect on performance after restoring CHO availability in comparison to high or periodised CHO diets.

METHODS

After Baseline testing (10,000 m IAAF-sanctioned race, aerobic capacity and submaximal walking economy) elite male and female race walkers undertook 25 d supervised training and repeat testing (Adapt) on energy-matched diets: High CHO availability (8.6 g∙kg-1∙d-1 CHO, 2.1 g∙kg-1∙d-1 protein; 1.2 g∙kg-1∙d-1 fat) including CHO before/during/after workouts (HCHO, n = 8): similar macronutrient intake periodised within/between days to manipulate low and high CHO availability at various workouts (PCHO, n = 8); and LCHF (<50 g∙d-1 CHO; 78% energy as fat; 2.1 g∙kg-1∙d-1 protein; n = 10). After Adapt, all athletes resumed HCHO for 2.5 wk before a cohort (n = 19) completed a 20 km race.

RESULTS

All groups increased VO2peak (ml∙kg-1∙min-1) at Adapt (p = 0.02, 95%CI: [0.35-2.74]). LCHF markedly increased whole-body fat oxidation (from 0.6 g∙min-1 to 1.3 g∙min-1), but also the oxygen cost of walking at race-relevant velocities. Differences in 10,000 m performance were clear and meaningful: HCHO improved by 4.8% or 134 s (95% CI: [207 to 62 s]; p < 0.001), with a trend for a faster time (2.2%, 61 s [-18 to +144 s]; p = 0.09) in PCHO. LCHF were slower by 2.3%, -86 s ([-18 to -144 s]; p < 0.001), with no evidence of superior "rebound" performance over 20 km after 2.5 wk of HCHO restoration and taper.

CONCLUSION

Our previous findings of impaired exercise economy and performance of sustained high-intensity race walking following keto-adaptation in elite competitors were repeated. Furthermore, there was no detectable benefit from undertaking an LCHF intervention as a periodised strategy before a 2.5-wk race preparation/taper with high CHO availability.

TRIAL REGISTRATION

Australia New Zealand Clinical Trial Registry: ACTRN12619000794101.

Hematological status and endurance performance predictors after low altitude training supported by normobaric hypoxia: a double-blind, placebo controlled study

The benefits of altitude/hypoxic training for sea level performance are still under debate. This study examined the effects of low altitude training supported by normobaric hypoxia on hematological status and endurance performance predictors in elite female cyclists. Twenty-two female cyclists trained for 3 weeks at low altitude (<1100 m) and 2 weeks near sea level. During the first 3 weeks, 15 subjects stayed in hypoxic rooms simulating an altitude of 2200 m (+NH group, n = 8) or 1000 m (placebo group, n = 7), and 7 (control group) stayed in regular rooms. Significant increases in total hemoglobin mass (tHb-mass: p = 0.008, p = 0.025), power at 4 mmol·l^-1 lactate (PAT4: p = 0.004, p = 0.005) (in absolute and relative values, respectively) and maximal power (PF: p = 0.034) (in absolute values) were observed. However, these effects were not associated with normobaric hypoxia. Changes in tHb-mass were not associated with initial concentrations of ferritin or transferrin receptor, whereas changes in relative tHb-mass (r = -0.53, p = 0.012), PF (r = -0.53, p = 0.01) and PAT4 (r = -0.65, p = 0.001) were inversely correlated with initial values. Changes in tHb-mass and PAT4 were positively correlated (r = 0.50, p = 0.017; r = 0.47, p = 0.028). Regardless of normobaric hypoxia application, low altitude training followed by sea-level training might improve hematological status in elite female cyclists, especially with relatively low initial values of tHb-mass, which could translate into enhanced endurance performance.

Training to Compete at Altitude:Natural Altitude or Simulated Live High:Train Low?

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.

Applying the Optimized CO Rebreathing Method for Measuring Blood Volumes and Hemoglobin Mass in Heart Failure Patients

Introduction: Determination of blood volume, red cell volume, and plasma volume contributes to the understanding of the pathophysiology in heart failure, especially concerning anemia and volume load. The optimized carbon monoxide (CO)-rebreathing method (oCORM) is used to determine these parameters and hemoglobin mass (Hbmass) in exercise physiology. The applicability of oCORM to determine the intravascular volumes and Hbmass in heart failure patients is currently undetermined because assumptions concerning CO kinetics with oCORM rely on healthy subjects with a normal ejection fraction. Therefore, the aim of the present study is to determine the applicability and the systematic error of oCORM arising from a reduced EF when oCORM is used for measurement of intravascular volumes and Hbmass in heart failure patients. Methods: oCORM was performed in 21 patients with heart failure and a reduced ejection fraction (EF) of < 30% (EFsev) and 25 controls (CONT). CO kinetics in capillary blood was studied 3-15 min after commencement of CO rebreathing. Differences in CO kinetics between the groups were assessed using a generalized linear model. The systematic error for determination of Hbmass with oCORM arising from differences in CO kinetics was assessed using the Monte Carlo method. Results: The CO kinetics was significantly different between EFsev and CONT. In both groups, exposure to CO led to a COHb increase to 6.0 ± 1.0% 3 min after CO rebreathing. There were no CO related side effects or any clinical symptoms. Monte Carlo simulation quantifies the systematic error for determination of Hbmass arising from an impaired ejection fraction to be -0.88%. Conclusion: Our results indicate an impaired vascular mixing of CO when EF is severely reduced. When Hbmass is determined using the original oCORM protocol in heart failure patients with a reduced EF, the systematic underestimation of about 1% should be considered. However, the error arising from this impaired vascular mixing appears small and clinically negligible. Furthermore, application of oCORM was safe and not related to any side effects resulting from CO exposure. In conclusion, oCORM can be used for assessing intravascular volumes and Hbmass in patients with a reduced EF.

The impact of chronic carbohydrate manipulation on mucosal immunity in elite endurance athletes

Carbohydrate (CHO) availability could alter mucosal immune responses to exercise. This study compared the effect of three dietary approaches to CHO availability on resting and post-exercise s-IgA levels. Elite race walkers (n = 26) adhered to a high CHO diet (HCHO), periodised CHO availability (PCHO) or a low CHO/high fat diet (LCHF) for 3 weeks while completing an intensified training program. HCHO and PCHO groups consumed 8.0-8.5 g.kg^-1 CHO daily, with timing of ingestion manipulated to alter CHO availability around key training sessions. The LCHF diet comprised 80% fat and restricted CHO to < 50 g.day^-1. A race walk test protocol (19 km females, 25 km males) was completed at baseline, after adaptation, and following CHO restoration. On each occasion, saliva samples were obtained pre- and post-exercise to quantify s-IgA levels. Resting s-IgA secretion rate substantially increased ~ two-fold post-intervention in all groups (HCHO: 2.2 ± 2.2, PCHO: 2.8 ± 3.2, LCHF: 1.6 ± 1.6; fold-change± 95% confidence limits), however, no substantial differences between dietary treatments were evident. Post-exercise, substantial 20-130% increases in s-IgA concentration and 43-64% reductions in flow rate occurred in all dietary treatments, with trivial differences evident between groups. It appears that high volume training overrides any effect of manipulating CHO availability on mucosal immunity in elite athletes.

The athlete's hematological response to hypoxia: A meta-analysis on the influence of altitude exposure on key biomarkers of erythropoiesis

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.

Resistance Training Using Different Hypoxic Training Strategies: a Basis for Hypertrophy and Muscle Power Development

The possible muscular strength, hypertrophy, and muscle power benefits of resistance training under environmental conditions of hypoxia are currently being investigated.Nowadays, resistance training in hypoxia constitutes a promising new training strategy for strength and muscle gains. The main mechanisms responsible for these effects seem to be related to increased metabolite accumulation due to hypoxia. However, no data are reported in the literature to describe and compare the efficacy of the different hypertrophic resistance training strategies in hypoxia.Moreover, improvements in sprinting, jumping, or throwing performance have also been described at terrestrial altitude, encouraging research into the speed of explosive movements at altitude. It has been suggested that the reduction in the aerodynamic resistance and/or the increase in the anaerobic metabolism at higher altitudes can influence the metabolic cost, increase the take-off velocities, or improve the motor unit recruitment patterns, which may explain these improvements. Despite these findings, the applicability of altitude conditions in improving muscle power by resistance training remains to be clarified.This review examines current knowledge regarding resistance training in different types of hypoxia, focusing on strategies designed to improve muscle hypertrophy as well as power for explosive movements.

Adding heat to the live-high train-low altitude model: a practical insight from professional football

Objectives

To examine with a parallel group study design the performance and physiological responses to a 14-day off-season ‘live high-train low in the heat’ training camp in elite football players.

Methods

Seventeen professional Australian Rules Football players participated in outdoor football-specific skills (32±1°C, 11.5 h) and indoor strength (23±1°C, 9.3 h) sessions and slept (12 nights) and cycled indoors (4.3 h) in either normal air (NORM, n=8) or normobaric hypoxia (14±1 h/day, FiO₂ 15.2–14.3%, corresponding to a simulated altitude of 2500–3000 m, hypoxic (HYP), n=9). They completed the Yo-Yo Intermittent Recovery level 2 (Yo-YoIR2) in temperate conditions (23±1°C, normal air) precamp (Pre) and postcamp (Post). Plasma volume (PV) and haemoglobin mass (Hb_mass) were measured at similar times and 4 weeks postcamp (4WPost). Sweat sodium concentration ((Na⁺)_sweat) was measured Pre and Post during a heat-response test (44°C).

Results

Both groups showed very large improvements in Yo-YoIR2 at Post (+44%; 90% CL 38, 50), with no between-group differences in the changes (−1%; −9, 9). Postcamp, large changes in PV (+5.6%; −1.8, 5.6) and (Na⁺)_sweat (−29%; −37, −19) were observed in both groups, while Hb_mass only moderately increased in HYP (+2.6%; 0.5, 4.5). At 4WPost, there was a likely slightly greater increase in Hb_mass (+4.6%; 0.0, 9.3) and PV (+6%; −5, 18, unclear) in HYP than in NORM.

Conclusions

The combination of heat and hypoxic exposure during sleep/training might offer a promising ‘conditioning cocktail’ in team sports.

Relationship between changes in haemoglobin mass and maximal oxygen uptake after hypoxic exposure

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 (). Not all studies have shown a proportionate increase in 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 testing before and after intervention.

Results

For the pooled data, the correlation between per cent change in Hb_mass and per cent change in was significant (p<0.0001, r²=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 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 , and other non-haematological factors altered from altitude training, such as running economy and lactate threshold, may also be beneficial to performance.

Effect of different simulated altitudes on repeat-sprint performance in team-sport athletes

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.

Application of the optimized CO-rebreathing method for determination of hemoglobin mass in patients with polycythemia vera

Determination of red cell volume (RCV) might contribute to establishing the diagnosis of polycythemia vera (PV). A novel simplified method to detect RCV through CO rebreathing is nowadays applied in healthy young individuals but was not tested in a clinical or PV setting. The aim of the present study is to evaluate whether this spirometric approach is applicable in older subjects and contributes to PV diagnosis in a proof-of-concept approach. At first, RCV was determined by the optimized CO-rebreathing method in healthy subjects >50 years of age (n = 81, age 66 ± 9 years). Failure rate and age distribution of subjects who failed with CO rebreathing were analyzed. Then, RCV was measured in male PV patients (n = 7) and compared to healthy male controls (n = 35). RCV values in relation to several anthropometric references (body weight, body surface area (BSA), lean body mass (LBM)) were calculated to determine the sensitivity and specificity of established RCV thresholds when using optimized CO rebreathing. In healthy subjects, test failure rate was 9.9 %, but failure was not associated with age. Sensitivity and specificity (sens/spec) to detect PV was 100 %/83 % using the criteria of the PV study group. Using criteria based on BSA, sens/spec was 14 %/100 %. An arbitrary threshold of 50 ml/kg LBM yielded sens/spec of 100 %/97 %. In conclusion, this proof-of-concept indicates that optimized CO rebreathing is applicable in older subjects and allows determining RCV for the diagnosis of PV. Normalized values for RCV measures obtained from CO rebreathing are needed to grant sufficient sensitivity and/or specificity.

Altitude training and haemoglobin mass from the optimised carbon monoxide rebreathing method determined by a meta-analysis

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.

Four weeks of normobaric "live high-train low" do not alter muscular or systemic capacity for maintaining pH and K⁺ homeostasis during intense exercise

It was investigated if athletes subjected to 4 wk of living in normobaric hypoxia (3,000 m; 16 h/day) while training at 800-1,300 m ["live high-train low" (LHTL)] increase muscular and systemic capacity for maintaining pH and K(+) homeostasis as well as intense exercise performance. The design was double-blind and placebo controlled. Mean power during 30-s all-out cycling was similar before and immediately after LHTL (650 ± 31 vs. 628 ± 32 W; n = 10) and placebo exposure (658 ± 22 vs. 660 ± 23 W; n = 6). Supporting the performance data, arterial plasma pH, lactate, and K(+) during submaximal and maximal exercise were also unaffected by the intervention in both groups. In addition, muscle buffer capacity (in mmol H(+)·kg dry wt(-1)·pH(-1)) was similar before and after in both the LHTL (140 ± 12 vs. 140 ± 16) and placebo group (145 ± 2 vs. 140 ± 3). The expression of sarcolemmal H(+) transporters (Na(+)/H(+) exchanger 1, monocarboxylate transporters 1 and 4), as well as expression of Na(+)-K(+) pump subunits-α(1), -α(2), and -β(1) was also similar before and after the intervention. In conclusion, muscular and systemic capacity for maintaining pH and K(+) balance during exercise is similar before and after 4 wk of placebo-controlled normobaric LHTL. In accordance, 30-s all-out sprint ability was similar before and after LHTL.