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Commentaries on Viewpoint: Time for a new metric for hypoxic dose?Commentaries on Viewpoint: Time for a new metric for hypoxic dose?Commentaries on Viewpoint: Time for a new metric for hypoxic dose?Commentaries on Viewpoint: Time for a new metric for hypoxic dose?Commentaries on Viewpoint: Time for a new metric for hypoxic dose?Commentaries on Viewpoint: Time for a new metric for hypoxic dose?Commentaries on Viewpoint: Time for a new metric for hypoxic dose?

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Gregoire P Millet at University of Lausanne
Gregoire P Millet
Jon Peter Wehrlin at Swiss Federal Institute of Sport Magglingen SFISM
Jon Peter Wehrlin
Juha E. Peltonen
Juha E. Peltonen
Juha E. Peltonen
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Keren Constantini at Sylvan Adams Sports Institute Tel Aviv University
Keren Constantini
  • Sylvan Adams Sports Institute Tel Aviv University
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Commentaries on Viewpoint: Time for a new metric for hypoxic dose?
NEW METRIC FOR THE HYPOXIC STIMULUS, NOT FOR THE
RESPONSE
TO THE EDITOR: The proposal by our well-respected colleagues
(2) to introduce a new metric—incorporating the altitude ele-
vation and the total exposure duration, termed “kilometer
hours”—for better describing the “hypoxic dose” is decidedly
a step forward. By only quantifying the “external” stress, this
metric presents several limitations: It suggests a linear rela-
tionship between altitude elevation and saturation decrease [but
the Fick curve is curvilinear (3)] or that it applies to all athletes
irrespectively of their training background [but elite endurance
athletes suffer the largest decrease in V
˙O
2max
(1)], altitude
experience [but elite athletes who have had previous hypoxic
exposure better adapt to hypoxic condition (4)], or type of
hypoxia [but hypobaric vs. normobaric hypoxia induces larger
desaturation (5)].
The large intersubject variability in the physiological re-
sponses to a given “hypoxic dose” implies that the magnitude
of the stimulus rather than the altitude elevation should instead
be considered. We therefore propose a new metric based on the
sustained duration at a given arterial saturation level. Hence,
desaturation levels in normoxia (exercise-induced arterial hy-
poxemia) or in hypoxia (3) predict the decrement in V
˙O
2max
in
hypoxia and therefore the ˙amplitude of the “hypoxic stimu-
lus.” This metric termed “saturation hours” is defined as %·h ⫽
(98/s - 1) ⫻h⫻100, where s is the saturation value (in %)
and h the time (in hours) sustained at any second level.
Practically, with the development of new sport gears incor-
porating the oximeter inside the textile, this metric will readily
be measured without any disturbances to individuals.
REFERENCES
1. Faiss R, von Orelli C, Dériaz O, Millet GP. Responses to exercise in
normobaric hypoxia: comparison of elite and recreational ski mountaineers.
Int J Sports Physiol Perform 9: 978 –984, 2014.
2. Garvican-Lewis LA, Sharpe K, Gore CJ. Viewpoint: Time for a new
metric for hypoxic dose? J Appl Physiol; doi:10.1152/japplphysiol.00579.2015.
3. Mollard P, Woorons X, Letournel M, Lamberto C, Favret F, Pichon A,
Beaudry M, Richalet JP. Determinants of maximal oxygen uptake in
moderate acute hypoxia in endurance athletes. Eur J Appl Physiol 100:
663–673, 2007.
4. Pugliese L, Serpiello FR, Millet GP, La Torre A. Training diaries during
altitude training camp in two olympic champions: an observational case
study. J Sports Sci Med 13: 666 –672, 2014.
5. Saugy JJ, Schmitt L, Cejuela R, Faiss R, Hauser A, Wehrlin JP, Rudaz
B, Delessert A, Robinson N, Millet GP. Comparison of “Live High-Train
Low” in normobaric versus hypobaric hypoxia. PLoS One 9: e114418,
2014.
Grégoire P. Millet
Franck Brocherie
Olivier Girard
Université de Lausanne
COMMENTARY ON VIEWPOINT: TIME FOR A NEW METRIC
HYPOXIC DOSE?
TO THE EDITOR: It is a very good idea of Garvican-Lewis, Sharpe,
and Gore (2) to initiate this discussion with a new metric
hypoxic dose by combining living altitude in kilometers with
hours spent at altitude (“kilometer hours”; km·h) in the field of
altitude training science. However, is the altitude component of
the dose really linear? Would exposure at lower altitudes
overestimate the hypoxic dose because some sort of “altitude-
threshold” exists? Physiological mechanisms behind a possible
“altitude-threshold” could be associated with the s-shape of the
oxyhemoglobin saturation curve: at altitudes above ⬃2,000 m
the desaturation of athletes would occur on the steeper part of
the curve resulting in more substantial increases in sEpo
(⬃90% at 2,400 m compared with ⬃30% at 1,800 m after 24 h)
(1). As the authors indicated, most recommendations for nat-
ural living altitudes are between 2,000 and 2,500 m (2, 5). Our
Swiss experiences are that only ⬃1/6 of the endurance athletes
living at 1,800 m (4) and 2/3 living at 2,200 m (3) have a
substantially increased hemoglobin mass after a 3-week alti-
tude training camp. Could the proposed method be “opti-
mized,” if “kilometer” is weighted in a way, that there is a
larger dose-difference for altitudes below and above an “alti-
tude-threshold”? For example, start counting kilometers above
1,300 m, with double hours at 1,800 m needed to reach the
same “dose” as compared with 2,300 m. Additionally, for elite
sport settings, one should also keep in mind that the hemoglo-
bin-mass-response to a given “dose” has been shown to be
largely idiosyncratic, thereby requiring individualized recom-
mendations (3, 4).
REFERENCES
1. Chapman RF, Karlsen T, Resaland GK, Ge RL, Harber MP, Wit-
kowski S, Stray-Gundersen J, Levine BD. Defining the “dose” of altitude
training: how high to live for optimal sea level performance enhancement.
J Appl Physiol (1985) 116: 595–603, 2014.
2. Garvican LA, Sharpe K, Gore CJ. Viewpoint: Time for a new metric
dose? J Appl Physiol; doi:10.1152/japplphysiol.00579.2015.
3. Hauser A, Schmitt L, Troesch S, Saugy JJ, Cejuela-Anta R, Faiss R,
Robinson N, Wehrlin JP, Millet GP. Similar hemoglobin mass response
in hypobaric and normobaric hypoxia in athletes. Med Sci Sports Exerc 48:
734 –741, 2016.
4. Troesch S, Hauser A, Steiner T, Gruenenfelder A, Heyer L, Gojanovic
B, Wehrlin JP. Individual hemoglobin mass response to altitude training at
1800m in elite endurance athletes. In: Abstract book: 20th Annual Congress
of the European College of Sport Science, edited by Radmann A, Heden-
borg S, and Tsolakidis E. Malmö: 2015.
5. Wilber RL, Stray-Gundersen J, Levine BD. Effect of hypoxic “dose” on
physiological responses and sea-level performance. Med Sci Sports Exerc
39: 1590 –1599, 2007.
Jon Peter Wehrlin
Severin Troesch
Anna Hauser
Thomas Steiner
Swiss Federal Institute of Sport
COMMENTARY ON VIEWPOINT: TIME FOR A NEW METRIC
FOR HYPOXIC DOSE?
TO THE EDITOR: Garvican-Lewis et al. (3) are to be congratulated
for their “kilometer hours” (km·h) approach predicting increas-
ing response along with increasing hypoxic dose during alti-
tude training. Previous literature has clearly shown that both
endurance training and hypoxic exposure as such can increase
hemoglobin mass (Hb
mass
), and the responses to their doses are
individual. Wehrlin et al. (5) with a 1,080 km·h (24 days
18 h/day, 2,500 m) showed an average 5.3% increase in Hb
mass
J Appl Physiol 121: 356 –358, 2016;
doi:10.1152/japplphysiol.00460.2016.Letter to the Editor
8750-7587/16 Copyright ©2016 the American Physiological Society http://www.jappl.org356
with all athletes showing a positive response. Siebenmann et al.
(4) reported no change in average Hb
mass
after 1,328 km·h
(4 wk, 16 h/day, 3,000 m). This greater dose was beneficial for
some athletes, but trivial or detrimental for others, leading to
no change on average. With an average 6% increase in red cell
mass volume, Chapman et al. (1) did not show any dose
response effect after 4 wk “living high, training high and low”
between 1,780, 2,085, 2,454, and 2,800 m. Their study sug-
gests that increasing the dose by increasing the altitude above
optimum may not provide any benefit (1). After more extreme
hypoxic dose, a 72-day self-supported Mt. Everest expedition
(⬎9,000 km·h), Cheung et al. (2) reported a wide scale of
positive, negative, and no change responses in Hb
mass
. Thus the
suggested model and the present literature, analogously with
our own unpublished data using the km·h approach, rather
highlight the need for careful evaluation of all factors influ-
encing athletes’ adaptation than solves the problem of how to
determine hypoxic dose in elite sports.
REFERENCES
1. Chapman RF, Karlsen T, Resaland GK, Ge RL, Harber MP, Wit-
kowski S, Stray-Gundersen J, Levine BD. Defining the “dose” of altitude
training: how high to live for optimal sea level performance enhancement.
J Appl Physiol (1985) 116: 595–603, 2014.
2. Cheung SS, Mutanen NE, Karinen HM, Koponen AS, Kyröläinen H,
Tikkanen HO, Peltonen JE. Ventilatory chemosensitivity, cerebral and
muscle oxygenation, and total hemoglobin mass before and after a 72-day
mt. Everest expedition. High Alt Med Biol 15: 331–340, 2014.
3. Garvican-Lewis LA, Sharpe K, Gore CJ. Viewpoint: Time for a new metric
for hypoxic dose? J Appl Physiol; doi:10.1152/japplphysiol.00579.2015.
4. Siebenmann C, Robach P, Jacobs RA, Rasmussen P, Nordsborg N,
Diaz V, Christ A, Olsen NV, Maggiorini M, Lundby C. “Live high-train
low” using normobaric hypoxia: a double-blinded, placebo-controlled
study. J Appl Physiol (1985) 112: 106 –117, 2012.
5. Wehrlin JP, Zuest P, Hallén J, Marti B. Live high-train low for 24 days
increases hemoglobin mass and red cell volume in elite endurance athletes.
J Appl Physiol (1985) 100: 1938 –1945, 2006.
Juha E. Peltonen
University of Helsinki
Heikki K. Rusko
University of Jyväskylä
COMMENTARY ON VIEWPOINT: TIME FOR A NEW METRIC
FOR HYPOXIC DOSE?
TO THE EDITOR: Although exposure to some effective dose of
hypobaric hypoxia provides a clear stimulus to increase hemo-
globin (Hb) mass (3), numerous physiological responses to
normobaric hypoxia have well documented differences to hy-
pobaric hypoxia (4). Because of these discrepancies, we be-
lieve the conditions should not be treated as equal, and other
meta-analyses (e.g., Ref. 1) have differentiated between “nat-
ural” and “artificial” hypoxic exposures. Additionally, given
that all but one of the included studies consisted of highly
trained subjects, the authors may wish to exclude the Sieben-
mann et al. study (5), which described subjects as “sedentary to
moderately trained individuals who were not involved in high-
level sport.” Finally, the model would benefit from a clear
establishment of a minimum threshold, both from an altitude
and a duration perspective, as the authors note both short
duration high/extreme altitude exposure and chronic residence
at mild altitude are each ineffective at increasing Hb mass.
We would be excited to see an expanded model that ac-
counts for the above concerns, thus addressing the sensitivity
in what is already a thin air of certainty in regards to hypoxic
training.
REFERENCES
1. Bonetti DL, Hopkins WG. Sea-level exercise performance following
adaptation to hypoxia: a meta-analysis. Sports Med 39: 107–127, 2009.
2. Garvican-Lewis LA, Sharpe K, Gore CJ. Viewpoint: Time for a new metric
for hypoxic dose? J Appl Physiol; doi:10.1152/japplphysiol.00579.2015.
3. Levine BD, Stray-Gundersen J. Dose-response of altitude training: how
much altitude is enough? in Hypoxia and Exercise. Springer, 2006, p.
233–247.
4. Millet GP, Faiss R, Pialoux V. Point:Counterpoint: Hypobaric hypoxia
induces/does not induce different responses from normobaric hypoxia. J
Appl Physiol 112: 1783–1784, 2012.
5. Siebenmann C, Cathomen A, Hug M, Keiser S, Lundby AKM, Hilty
MP, Goetze JP, Rasmussen P, Lundby C. Hemoglobin mass and intra-
vascular volume kinetics during and after exposure to 3,454 m altitude. J
Appl Physiol 119: 1194 –1201, 2015.
Keren Constantini
Timothy J. Fulton
Daniel G. Hursh
Tyler J. Noble
Hunter L. R. Paris
Chad C. Wiggins
Robert F. Chapman
Indiana University
Benjamin D. Levine
University of Texas Southwestern Medical Center
COMMENTARY ON VIEWPOINT: TIME FOR A NEW HYPOXIC
DOSE?
TO THE EDITOR: Guidelines for simulated altitude exposure
suggest athletes should spend around 14 h per day at 3,000 m
for 3 weeks (300 h of exposure) to observe a mean increase in
hemoglobin mass of 3–5% (3). Similarly, hypoxic exposure for
3– 4 weeks at ⬎2,200 m altitude will elicit a 3–5% increase in
hemoglobin mass (2), with 4 weeks exposure believed to
accelerate erythropoiesis (4). Hypoxia in both these occasions
is influenced by altitude and the duration of hypoxia. The new
metric of hypoxic dosing (1) addresses this problem, ensuring
standardization of the hypoxic dose at various altitudes and
hence will allow for comparing physiologic and nonphysi-
ologic effects on body systems. The hypoxic dose as per the
new metric for the studies mentioned above will be 882-1,478
km·h (2, 3). There have been questions regarding the minimum
altitude and the extent of duration that results in “hypoxic
dose” for physiologic changes to occur. The new metric is a
good starting point that combines altitude and duration to
measure outcomes across studies. The hypoxic dose per the
new metric is predominantly in the range of 600-1,500 km·h
that results in 3– 6% change in hemoglobin mass across mul-
tiple studies (1). As the relationship between altitude and
hypoxia is not exactly linear and various factors could influ-
ence physiologic adaptation or training performance, knowing
the baseline (“hypoxic dose”) will make interpretation more
well defined. The new metric may help to further characterize
the minimum “dose” required for optimal performance, percent
change in hemoglobin mass and other measures of physiologic
adaptation.
Letter to the Editor
357
J Appl Physiol •doi:10.1152/japplphysiol.00460.2016 •www.jappl.org
REFERENCES
1. Garvican-Lewis LA, Sharpe K, Gore CJ. Viewpoint: Time for a new metric
for hypoxic dose? J Appl Physiol; doi:10.1152/japplphysiol.00579.2015.
2. Rusko HK, Tikkanen HO, Peltonen JE. Altitude and endurance training.
J Sports Sci 22: 928 –944, 2004.
3. Saunders PU, Garvican-Lewis LA, Schmidt WF, Gore CJ. Relationship
between changes in haemoglobin mass and maximal oxygen uptake after
hypoxic exposure. Br J Sports Med 47, Suppl 1: i26 –i30, 2013.
4. Wilber RL, Stray-Gundersen J, Levine BD. Effect of hypoxic “dose” on
physiological responses and sea-level performance. Med Sci Sports Exerc
39: 1590 –1599, 2007.
Vasantha H. S. Kumar
University at Buffalo
COMMENTARY ON VIEWPOINT: TIME FOR A NEW METRIC
FOR HYPOXIC DOSE?
TO THE EDITOR: The actual model which includes the degree of
altitude as an equivalent parameter as the exposure time to
hypoxia (1) is a systematic further development of the former
model using just the exposure time (2), which was only valid
for athletes training at a relatively narrow range of altitude.
The authors correctly mention possible limitations concern-
ing the minimum hypoxic dose for altitude and hypoxic expo-
sure time. It seems to be also interesting if the new model is
applicable to athletes living permanently in hypoxia. Whenever
it is almost not possible to compare identical athletes under
normoxic and chronic hypoxic conditions cross-sectional stud-
ies on elite cyclists show bigger increases under chronic
altitude conditions (2,600 m) than calculated by the model [11
vs. 7.7% (4)]. For these cases a modification of the model
should be considered.
Following the idea of the authors that athletes who want to
increase their Hb-mass by altitude training may choose be-
tween a relatively long stay at lower or a shorter stay at higher
altitude for a fixed increase in Hb-mass they have to consider
if the hemoglobin gained at altitude can be transferred to low
altitude, where the competition takes place. As demonstrated
by Ryan et al. (3) a strong increase in Hb-mass after 16 days at
high altitude (5,260 m) is almost completely abolished after
some days at lower altitude. As the return from moderate
altitude is not associated with remarkable red cell destruction,
for practical reasons an altitude threshold for red cell cytolysis
has to be determined.
REFERENCES
1. Garvican-Lewis LA, Sharpe K, Gore CJ. Viewpoint: Time for a new metric
for hypoxic dose? J Appl Physiol; doi:10.1152/japplphysiol.00579.2015.
2. Gore CJ, Sharpe K, Garvican-Lewis LA, Saunders PU, Humberstone
CE, Robertson EY, Wachsmuth NB, Clark SA, McLean BD, Fried-
mann-Bette B, Neya M, Pottgiesser T, Schumacher YO, Schmidt WF.
Altitude training and haemoglobin mass from the optimised carbon mon-
oxide rebreathing method determined by a meta-analysis. Br J Sports Med
47, Suppl 1: i31–i39, 2013.
3. Ryan BJ, Wachsmuth NB, Schmidt WF, Byrnes WC, Julian CG,
Lovering AT, Subudhi AW, Roach RC. AltitudeOmics: rapid hemoglo-
bin mass alterations with early acclimatization to and de-acclimatization
from 5260 m in healthy humans. PLoS One 9: e108788, 2014.
4. Schmidt W, Heinicke K, Rojas J, Manuel Gomez J, Serrato M, Mora
M, Wolfarth B, Schmid A, Keul J. Blood volume and hemoglobin mass
in endurance athletes from moderate altitude. Med Sci Sports Exerc 34:
1934 –1940, 2002.
Walter F. J. Schmidt
University of Bayreuth, Germany
Letter to the Editor
358
J Appl Physiol •doi:10.1152/japplphysiol.00460.2016 •www.jappl.org
... In Fig. 3, individual values of hypoxic dose determined for two different methods, proposed by Garvican-Lewis et al. (2016), termed kilometers·hours (km h) and proposed by Millet et al. (2016) termed hypoxic hours (%·h). ...
... In this context, different guidelines on how to measure and what the minimum dose of exposure to hypoxia would have been published for beneficial effects to occur (Garvican-Lewis et al. 2016;Bejder et al. 2017). Indices that take into account external loads have already been proposed (Garvican-Lewis et al. 2016;Bejder et al. 2017); however, biological adaptations do not present a linear response with increasing altitude, in addition to ignoring the individual response to hypoxia, so more recently, another way has been proposed that takes into account individual adaptation to hypoxia (Garvican-Lewis et al. 2016;Millet et al. 2016;Bejder et al. 2017). ...
... Descriptive results and T test independent results of both groups LHTL live high training low group, CON control group, SpO 2MEAN peripheral oxygen saturation (%), SD standard deviation, hypoxia dose (km h) dose proposed byGarvican-Lewis et al. (2016), hypoxia dose (%·hours) dose proposed byMillet et al. (2016) ...
Four-week experimental plus 1-week taper period using live high train low does not alter muscle glycogen content
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This study aimed to investigate the effects of a 4-week live high train low (LHTL; FiO2 ~ 13.5%), intervention, followed by a tapering phase, on muscle glycogen concentration. Fourteen physically active males (28 ± 6 years, 81.6 ± 15.4 kg, 179 ± 5.2 cm) were divided into a control group (CON; n = 5), and the group that performed the LHTL, which was exposed to hypoxia (LHTL; n = 9). The subjects trained using a one-legged knee extension exercise, which enabled four experimental conditions: leg training in hypoxia (TLHYP); leg control in hypoxia (CLHYP, n = 9); leg trained in normoxia (TLNOR, n = 5), and leg control in normoxia (CLNOR, n = 5). All participants performed 18 training sessions lasting between 20 and 45 min [80–200% of intensity corresponding to the time to exhaustion (TTE) reached in the graded exercise test]. Additionally, participants spent approximately 10 h day⁻¹ in either a normobaric hypoxic environment (14.5% FiO2; ~ 3000 m) or a control condition (i.e., staying in similar tents on ~ 530 m). Thereafter, participants underwent a taper protocol consisting of six additional training sessions with a reduced training load. SpO2 was lower, and the hypoxic dose was higher in LHTL compared to CON (p < 0.001). After 4 weeks, glycogen had increased significantly only in the TLNOR and TLHYP groups and remained elevated after the taper (p < 0.016). Time to exhaustion in the LHTL increased after both the 4-week training period and the taper compared to the baseline (p < 0.001). Although the 4-week training promoted substantial increases in muscle glycogen content, TTE increased in LHTL condition.
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... En esta primera métrica del modelo que se plantea en este trabajo, TSS es adaptada como Puntuación de entrenamiento hipóxico (PEH) o Hypoxic Training Score (HTS) en inglés, donde las variables y segundos que comprenden la fórmula de Allen y Coggan (Allen et al., 2019) se presentan como el sumatorio de los segundos de desaturación de oxígeno en sangre del deportista multiplicados por el coeficiente numérico que pondera la severidad de la hipoxia a medida que va aumentando la zona de desaturación, obteniéndose como resultado final un valor significativo del estrés hipóxico al que ha estado sometido el organismo del deportista. Esta métrica también está inspirada en la métrica denominada "horas de saturación" definida como %·h= (98/s -1) x h x 100, donde s es el valor de saturación (en %) y h el tiempo (en horas) sostenido (Millet et al., 2016). ...
... El preacondicionamiento hipóxico a través de hipoxia normobárica intermitente (HNI) supone una oportunidad de intervención en la que la solicitación metabólica se eleva mientras que la carga mecánica puede ser baja, generando beneficios relevantes sobre el rendimiento y la salud (Girard et al. 2021). A pesar de los recientes intentos por cuantificar la carga hipóxica en relación al entrenamiento (Millet et al. 2016), este es el primer estudio que propone una cuantificación aguda y crónica, al igual que ya sucede en el entrenamiento deportivo (Gabbett et al. 2016), así como la integración de parámetros fisiológicos relevantes como la SpO2 y la FC en la monitorización del entrenamiento. La monitorización y acumulación de datos de un gran número de deportistas, desde olímpicos a recreacionales, ha permitido aplicar el presente modelo en la planificación deportiva de estos, convirtiéndose en una herramienta de gran utilidad para valorar de una forma visual, rápida y fiable la evolución y estado actual del entrenamiento en hipoxia intermitente de cada uno de ellos. ...
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... Modulating stimulus intensity will exclude the underexplored possibility of participants feeling demotivated during long-term training protocols (Bouten et al. 2020). Recently proposed for hypoxic acclimation erythropoietic gains and compatible to the progression principle (Millet et al. 2016), the controlled-desaturation technique implies individuals aiming for a standard oxygen desaturation/spleen contraction level and thus increase their efforts as training progresses. Even though spleen training remains a field in its infancy since it entails more questions than answers, there is ever-growing evidence to suggest adaptation of the spleen organ. ...
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... 2006) & (Harward J, 2009) The researchers also explain these indications also to the method of performance implemented to reduce the percentage of oxygen necessary for tissues and cells voluntarily from the normal level, and as a result of the great effort in muscle fibers, which consume large amounts of oxygen, which requires compensating them in larger quantities as a result of the shortage in their stores in order for the cell to carry out its functional duties and not be exposed to stresses, showing different vital reactions and work adaptations under exceptional circumstances, represented in metabolic efficiency and energy expenditure economy, Thus, muscle glycogen stores increase, and the number of red blood cells carrying oxygen-bound hemoglobin, which increases its percentage in the blood to enhance myoglobin stores of muscle cells and tissues for energy requirements, and this explanation was consistent with all previous studies, which confirmed that "the implementation of hypoxic training exposes muscle cells to oxygen deficiencies, which leads to vital reactions that in turn help in adapting them to work under hypoxic conditions, improve the level of performance of athletes and save energy." (Dale R. 2015) & (Walter F. 2016 and also "hypoxia training improves blood variables, including oxygen saturation, by increasing the number of red cells carrying it." (Czuba, 2014) & (Mackenzie, 2008) & (Carsten Lundby, 2011 and also "hypoxic training occurs responses and adaptations to the characteristics of the physiological state in the body, which have become many times the training without the hypoxic method." ...
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... Overall, the consideration of the actual physiological stress (resulting in a decrease inSpO 2 and eventually a shift in the hemoglobin-dissociation curve) to a given hypoxic stimulus (e.g., P I O 2 ) is required to better quantify the actual hypoxic dose(Soo et al., 2020). An evaluation of the hypoxic dose based on « saturation hours » as suggested byMillet et al. (2016) would likely align more closely with the physiological stress incurred during low altitude exposure. The latter, however, requires continuous monitoring of the SpO 2 which is impractical to record in athletes. ...
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Current guidelines for prolonged altitude exposure suggest altitude levels ranging from 2000 to 2500 m to optimize an increase in total hemoglobin mass (Hbmass). However, natural low altitude locations (<2000 m) remain popular, highlighting the interest to investigate any possible benefit of low altitude camps for endurance athletes. Ten elite racewalkers (4 women and 6 men) underwent a 4‐week “live high‐train high” (LHTH) camp at an altitude of 1720 m (PIO2 = 121 mmHg; 20.1°C; 67% relative humidity [RH]), followed by a 3‐week tapering phase (20 m; PIO2 = 150 mmHg; 28.3°C; 53% RH) in preparation for the World Athletics Championships (WC). Venous blood samples were withdrawn weekly during the entire observation period. In addition, blood volumes were determined weekly by carbon monoxide rebreathing during altitude exposure and 2 weeks after return to sea level. High‐level performances were achieved at the WC (five placings among the Top 10 WC races and three all‐time career personal bests). A slight but significant increase in absolute (+1.7%, p = 0.03) and relative Hbmass (+2.3%, p = 0.02) was observed after 4‐week LHTH. In addition, as usually observed during LHTH protocols, weekly training distance (+28%, p = 0.02) and duration (+30%, p = 0.04) significantly increased during altitude compared to the pre‐LHTH period. Therefore, although direct causation cannot be inferred, these results suggest that the combination of increased training load at low altitudes with a subsequent tapering period in a warm environment is a suitable competition‐preparation strategy for elite endurance athletes.
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... Hypoxic dose was calculated by multiplying the altitude in kilometers by the hypoxic exposure time in hours (km  h) (11). Hypoxic response was calculated as saturation hours: (31). A % h value for each hypoxic day was obtained by combining morning readings (representing night), rest samples during day, and a representative average during exercise. ...
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Article
  • Jul 2024
  • J APPL PHYSIOL
Athletes use hypoxic living and training to increase hemoglobin mass (Hb mass ), but Hb mass declines rapidly upon return to sea level. We investigated whether Intermittent Hypoxic Exposure (IHE) + Continuous Hypoxic Training (CHT) after return to sea level maintained elevated Hb mass , and if changes in Hb mass were transferred to changes in maximal oxygen uptake (V̇O 2max ) and exercise performance. Hb mass was measured in 58 endurance athletes before (PRE), after (POST1), and 30 days after (POST2) a 27 ± 4-day training camp in hypoxia (n=44, HYP) or at sea level (n=14, SL). After return to sea level, 22 athletes included IHE (2 h rest) + CHT (1 h training) into their training every third day for one month (HYP IHE+ CHT ), whereas the other 22 HYP athletes were not exposed to IHE or CHT (HYP SL ). Hb mass increased from PRE to POST1 in both HYP IHE+CHT (4.4 ± 0.7%, mean ± SEM) and HYP SL (4.1 ± 0.6%) (both p<0.001). Compared to PRE, Hb mass at POST2 remained 4.2 ± 0.8% higher in HYP IHE+CHT (p<0.001) and 1.9 ± 0.5% higher in HYP SL (p=0.023), indicating a significant difference between the groups (p=0.002). In SL, no significant changes were observed in Hb mass with mean alterations between -0.5% and 0.4%. V̇O 2max and time to exhaustion during an incremental treadmill test (n=35) were elevated from PRE to POST2 only in HYP IHE+ CHT (5.8 ± 1.2% and 5.4 ± 1.4%, respectively, both p<0.001). IHE+CHT possesses the potential to mitigate the typical decline in Hb mass commonly observed during the initial weeks after return to sea level.
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... Using a method for calculating the total hypoxic dose (Garvican-Lewis, Sharpe & Gore, 2016), which considers both the total time under hypoxia and the level of hypoxia (i.e., the kilometer hours, calculated as km.h = (elevation above sea level/1,000) × hours of exposure), the hypoxic dose received by the altitude training group in this study (~610 km.h) was relatively similar to doses implemented by others (e.g., 500-950 km.h; Robertson et al., 2010;Saugy et al., 2014;Brocherie et al., 2015). Although attractive, a metric based on the magnitude of the stimulus (i.e., SpO 2 as a reflection of the physiological demand), as opposed to altitude elevation (i.e., as an external load index), should perhaps be considered by practitioners (Millet, Brocherie & Girard, 2016). In this context, the SpO 2 to FiO 2 ratio could be used to assess an individual's response to hypoxia, offering a practical method to categorize athletes physiologically and customize FiO 2 levels accordingly during altitude training camps (Soo et al., 2020). ...
Effects of three weeks base training at moderate simulated altitude with or without hypoxic residence on exercise capacity and physiological adaptations in well-trained male runners
Article
Full-text available
  • Mar 2024
Objectives To test the hypothesis that ‘live high-base train high-interval train low’ (HiHiLo) altitude training, compared to ‘live low-train high’ (LoHi), yields greater benefits on performance and physiological adaptations. Methods Sixteen young male middle-distance runners (age, 17.0 ± 1.5 y; body mass, 58.8 ± 4.9 kg; body height, 176.3 ± 4.3 cm; training years, 3–5 y; training distance per week, 30–60 km.wk ⁻¹ ) with a peak oxygen uptake averaging ~65 ml.min ⁻¹ .kg ⁻¹ trained in a normobaric hypoxia chamber (simulated altitude of ~2,500 m, monitored by heart rate ~170 bpm; thrice weekly) for 3 weeks. During this period, the HiHiLo group ( n = 8) stayed in normobaric hypoxia (at ~2,800 m; 10 h.day ⁻¹ ), while the LoHi group ( n = 8) resided near sea level. Before and immediately after the intervention, peak oxygen uptake and exercise-induced arterial hypoxemia responses (incremental cycle test) as well as running performance and time-domain heart rate variability (5-km time trial) were assessed. Hematological variables were monitored at baseline and on days 1, 7, 14 and 21 during the intervention. Results Peak oxygen uptake and running performance did not differ before and after the intervention in either group (all P > 0.05). Exercise-induced arterial hypoxemia responses, measured both at submaximal (240 W) and maximal loads during the incremental test, and log-transformed root mean square of successive R-R intervals during the 4-min post-run recovery period, did not change (all P > 0.05). Hematocrit, mean reticulocyte absolute count and reticulocyte percentage increased above baseline levels on day 21 of the intervention (all P < 0.001), irrespective of group. Conclusions Well-trained runners undertaking base training at moderate simulated altitude for 3 weeks, with or without hypoxic residence, showed no performance improvement, also with unchanged time-domain heart rate variability and exercise-induced arterial hypoxemia responses.
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... hypobaric vs normobaric), hypoxic dose (i.e. duration and level of exposure) [120,[135][136][137][138] and possibly initial Hb mass level [139], iron deficiency, illness, inflammation or insufficient energy availability [140] are supposed to blunt the erythropoietic response to altitude exposure and consecutive haematological adaptation [141][142][143][144]. The cyclic variation in sex hormones [145,146] also plays a role in the regulation of EPO production in hypoxia [147]. ...
Recommendations for Women in Mountain Sports and Hypoxia Training/Conditioning
Article
Full-text available
  • Dec 2023
  • SPORTS MED
The (patho-)physiological responses to hypoxia are highly heterogeneous between individuals. In this review, we focused on the roles of sex differences, which emerge as important factors in the regulation of the body’s reaction to hypoxia. Several aspects should be considered for future research on hypoxia-related sex differences, particularly altitude training and clinical applications of hypoxia, as these will affect the selection of the optimal dose regarding safety and efficiency. There are several implications, but there are no practical recommendations if/how women should behave differently from men to optimise the benefits or minimise the risks of these hypoxia-related practices. Here, we evaluate the scarce scientific evidence of distinct (patho)physiological responses and adaptations to high altitude/hypoxia, biomechanical/anatomical differences in uphill/downhill locomotion, which is highly relevant for exercising in mountainous environments, and potentially differential effects of altitude training in women. Based on these factors, we derive sex-specific recommendations for mountain sports and intermittent hypoxia conditioning: (1) Although higher vulnerabilities of women to acute mountain sickness have not been unambiguously shown, sex-dependent physiological reactions to hypoxia may contribute to an increased acute mountain sickness vulnerability in some women. Adequate acclimatisation, slow ascent speed and/or preventive medication (e.g. acetazolamide) are solutions. (2) Targeted training of the respiratory musculature could be a valuable preparation for altitude training in women. (3) Sex hormones influence hypoxia responses and hormonal-cycle and/or menstrual-cycle phases therefore may be factors in acclimatisation to altitude and efficiency of altitude training. As many of the recommendations or observations of the present work remain partly speculative, we join previous calls for further quality research on female athletes in sports to be extended to the field of altitude and hypoxia.
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Apnoea as a novel method to improve exercise performance: A current state of the literature
Article
Full-text available
Acute breath‐holding (apnoea) induces a spleen contraction leading to a transient increase in haemoglobin concentration. Additionally, the apnoea‐induced hypoxia has been shown to lead to an increase in erythropoietin concentration up to 5 h after acute breath‐holding, suggesting long‐term haemoglobin enhancement. Given its potential to improve haemoglobin content, an important determinant for oxygen transport, apnoea has been suggested as a novel training method to improve aerobic performance. This review aims to provide an update on the current state of the literature on this topic. Although the apnoea‐induced spleen contraction appears to be effective in improving oxygen uptake kinetics, this does not seem to transfer into immediately improved aerobic performance when apnoea is integrated into a warm‐up. Furthermore, only long and intense apnoea protocols in individuals who are experienced in breath‐holding show increased erythropoietin and reticulocytes. So far, studies on inexperienced individuals have failed to induce acute changes in erythropoietin concentration following apnoea. As such, apnoea training protocols fail to demonstrate longitudinal changes in haemoglobin mass and aerobic performance. The low hypoxic dose, as evidenced by minor oxygen desaturation, is likely insufficient to elicit a strong erythropoietic response. Apnoea therefore does not seem to be useful for improving aerobic performance. However, variations in apnoea, such as hypoventilation training at low lung volume and repeated‐sprint training in hypoxia through short end‐expiratory breath‐holds, have been shown to induce metabolic adaptations and improve several physical qualities. This shows promise for application of dynamic apnoea in order to improve exercise performance.
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Intermittent Normobaric Hypoxia Alters Substrate Partitioning and Muscle Oxygenation in Obese Individuals: Implications for fat burning
Article
Full-text available
  • Dec 2023
  • AM J PHYSIOL-REG I
This single-blind, crossover study aimed to measure and evaluate the short-term metabolic responses to continuous and intermittent hypoxic patterns in individuals with obesity. Indirect calorimetry was used to quantify changes in resting metabolic rate (RMR), carbohydrate (CHO ox , %CHO) and fat oxidation (FAT ox , %FAT) in nine individuals with obesity pre- and post-: (i) breathing normoxic air [normoxic sham control (NS-control)]; (ii) breathing continuous hypoxia (CH); or (iii) breathing intermittent hypoxia (IH). A mean peripheral oxygen saturation (SpO 2 ) of 80-85% was achieved over a total of 45 minutes of hypoxia. Throughout each intervention pulmonary gas exchanges - oxygen consumption ( ), carbon dioxide production ( - and deoxyhaemoglobin concentration ( [HHb]) in the vastus lateralis were measured. Both RMR and CHO ox measured pre- and post-interventions were unchanged following each treatment: NS-control; CH; or IH (all p > 0.05). Conversely, a significant increase in FAT ox was evident between pre- and post-IH (+44%, p = 0.048). While the mean [HHb] values significantly increased during both IH and CH ( p<0.05), the greatest zenith of [HHb] was achieved in IH compared to CH ( p = 0.002). Furthermore, there was a positive correlation between ∆[HHb] and the shift in FAT ox measured pre- and post-intervention. It is suggested that during IH the increased bouts of muscle hypoxia, revealed by elevated ∆[HHb], coupled with cyclic periods of excess post-hypoxia oxygen consumption (EPHOC, inherent to the intermittent pattern) played a significant role in driving the increase in FAT ox post-IH.
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Relationship between changes in haemoglobin mass and maximal oxygen uptake after hypoxic exposure
Article
Full-text available
  • Nov 2013
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 (Hbmass) resulting in a greater maximal oxygen uptake (). Not all studies have shown a proportionate increase in as a result of increased Hbmass. 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 Hbmass and testing before and after intervention. Results For the pooled data, the correlation between per cent change in Hbmass 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 Hbmass, 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.
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Altitude training and haemoglobin mass from the optimised carbon monoxide rebreathing method determined by a meta-Analysis
Article
Full-text available
  • Nov 2013
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.
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Hemoglobin mass and intravascular volume kinetics during and after exposure to 3,454 m altitude
Article
Full-text available
  • Mar 2015
High altitude (HA) exposure facilitates a rapid contraction of plasma volume (PV) and a slower occurring expansion of hemoglobin mass (Hbmass). The kinetics of the Hbmass expansion has never been examined by multiple repeated measurements and this was our primary study aim. The second aim was to investigate the mechanisms mediating the PV contraction. Nine healthy, normally-trained sea-level (SL) residents (8 males, 1 female) sojourned for 28 days at 3,454 m. Hbmass was measured and PV estimated by carbon monoxide re-breathing at SL, on every fourth day at HA, and one and two weeks upon return to SL. Four weeks at HA increased Hbmass by 5.26 % (range 2.5 - 11.1 %; p<0.001). The individual Hbmass increases commenced with up to 12 days delay and reached a maximal rate of 4.04 ± 1.02 g.d(-1) after 14.9 ± 5.2 days. The probability for Hbmass to plateau increased steeply after 20-24 days. Upon return to SL Hbmass decayed by -2.46 ± 2.3 g.d(-1), reaching values similar to baseline after two weeks. PV, aldosterone concentration and renin activity were reduced at HA (p<0.001) while the total circulating protein mass remained unaffected. In summary the Hbmass response to HA exposure followed a sigmoidal pattern with a delayed onset and a plateau after ~3 weeks. The decay rate of Hbmass upon descent to SL did not indicate major changes in the rate of erythrolysis. Moreover, our data supports that PV contraction at HA is regulated by the renin-angiotensin-aldosterone axis and not by changes in oncotic pressure. Copyright © 2014, Journal of Applied Physiology.
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AltitudeOmics: Rapid Hemoglobin Mass Alterations with Early Acclimatization to and De-Acclimatization from 5260 m in Healthy Humans
Article
Full-text available
It is classically thought that increases in hemoglobin mass (Hbmass) take several weeks to develop upon ascent to high altitude and are lost gradually following descent. However, the early time course of these erythropoietic adaptations has not been thoroughly investigated and data are lacking at elevations greater than 5000 m, where the hypoxic stimulus is dramatically increased. As part of the AltitudeOmics project, we examined Hbmass in healthy men and women at sea level (SL) and 5260 m following 1, 7, and 16 days of high altitude exposure (ALT1/ALT7/ALT16). Subjects were also studied upon return to 5260 m following descent to 1525 m for either 7 or 21 days. Compared to SL, absolute Hbmass was not different at ALT1 but increased by 3.7±5.8% (mean ± SD; n = 20; p<0.01) at ALT7 and 7.6±6.6% (n = 21; p<0.001) at ALT16. Following descent to 1525 m, Hbmass was reduced compared to ALT16 (-6.0±3.7%; n = 20; p = 0.001) and not different compared to SL, with no difference in the loss in Hbmass between groups that descended for 7 (-6.3±3.0%; n = 13) versus 21 days (-5.7±5.0; n = 7). The loss in Hbmass following 7 days at 1525 m was correlated with an increase in serum ferritin (r = -0.64; n = 13; p<0.05), suggesting increased red blood cell destruction. Our novel findings demonstrate that Hbmass increases within 7 days of ascent to 5260 m but that the altitude-induced Hbmass adaptation is lost within 7 days of descent to 1525 m. The rapid time course of these adaptations contrasts with the classical dogma, suggesting the need to further examine mechanisms responsible for Hbmass adaptations in response to severe hypoxia.
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Ventilatory Chemosensitivity, Cerebral and Muscle Oxygenation, and Total Hemoglobin Mass Before and After a 72-Day Mt. Everest Expedition
Article
Full-text available
  • Sep 2014
  • HIGH ALT MED BIOL
Cheung, Stephen S, Niina E. Mutanen, Heikki M. Karinen, Anne S. Koponen, Heikki Kyröläinen, Heikki O. Tikkanen, and Juha E. Peltonen. Ventilatory chemosensitivity, cerebral and muscle oxygenation, and total hemoglobin mass before and after a 72-day Mt. Everest expedition. High Alt Med Biol. 15:000–000, 2014.—. doi:10.1089/ham.2013.1153. Sept. 11, 2014, epub ahead of print. Background: We investigated the effects of chronic hypobaric hypoxic acclimatization, performed over the course of a 72-day self-supported Everest expedition, on ventilatory chemosensitivity, arterial saturation, and tissue oxygenation adaptation along with total hemoglobin mass (tHb-mass) in nine experienced climbers (age 37±6 years, 55±7 mL·kg−1·min−1). Methods: Exercise-hypoxia tolerance was tested using a constant treadmill exercise of 5.5 km·h−1 at 3.8% grade (mimicking exertion at altitude) with 3-min steps of progressive normobaric poikilocapnic hypoxia. Breath-by-breath ventilatory responses, Spo2, and cerebral (frontal cortex) and active muscle (vastus lateralis) oxygenation were measured throughout. Acute hypoxic ventilatory response (AHVR) was determined by linear regression slope of ventilation vs. Spo2. PRE and POST (<15 days) expedition, tHb-mass was measured using carbon monoxide-rebreathing. Results: Post-expedition, exercise-hypoxia tolerance improved (11:32±3:57 to 16:30±2:09 min, p<0.01). AHVR was elevated (1.25±0.33 to 1.63±0.38 L·min−1.%−1 Spo2, p<0.05). Spo2 decreased throughout exercise-hypoxia in both trials, but was preserved at higher values at 4800 m post-expedition. Cerebral oxygenation decreased progressively with increasing exercise-hypoxia in both trials, with a lower level of deoxyhemoglobin POST at 2400, 3500 and 4800 m. Muscle oxygenation also decreased throughout exercise-hypoxia, with similar patterns PRE and POST. No relationship was observed between the slope of AHVR and cerebral or muscle oxygenation either PRE or POST. Absolute tHb-mass response exhibited great individual variation with a nonsignificant 5.4% increasing trend post-expedition (975±154 g PRE and 1025±124 g POST, p=0.17). Conclusions: We conclude that adaptation to chronic hypoxia during a climbing expedition to Mt. Everest will increase hypoxic tolerance, AHVR, and cerebral but not muscle oxygenation, as measured during simulated acute hypoxia at sea level. However, tHb-mass did not increase significantly and improvement in cerebral oxygenation was not associated with the change in AHVR.
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Training Diaries during Altitude Training Camp in Two Olympic Champions: An Observational Case Study
Article
Full-text available
  • Sep 2014
  • J SPORT SCI MED
Traditionally, Live High-Train High (LHTH) interventions were adopted when athletes trained and lived at altitude to try maximising the benefits offered by hypoxic exposure and improving sea level performance. Nevertheless, scientific research has proposed that the possible benefits of hypoxia would be offset by the inability to maintain high training intensity at altitude. However, elite athletes have been rarely recruited as an experimental sample, and training intensity has almost never been monitored during altitude research. This case study is an attempt to provide a practical example of successful LHTH interventions in two Olympic gold medal athletes. Training diaries were collected and total training volumes, volumes at different intensities, and sea level performance recorded before, during and after a 3-week LHTH camp. Both athletes successfully completed the LHTH camp (2090 m) maintaining similar absolute training intensity and training volume at high-intensity (> 91% of race pace) compared to sea level. After the LHTH intervention both athletes obtained enhancements in performance and they won an Olympic gold medal. In our opinion, LHTH interventions can be used as a simple, yet effective, method to maintain absolute, and improve relative training intensity in elite endurance athletes.
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Responses to Exercise in Normobaric Hypoxia: Comparison Between Elite and Recreational Ski-Mountaineers.
Article
Full-text available
  • Mar 2014
Hypoxia is known to reduce maximal oxygen uptake ( VO2max ) more in trained than in untrained subjects in several lowland sports. Ski mountaineering is practiced mainly at altitude. So elite ski-mountaineers spend significantly longer training duration at altitude than their lower level counterparts. Since acclimatization in hypobaric hypoxia is effective, we hypothesized that elite would exhibit a similar VO2max decrement in hypoxia than recreational ski-mountaineers. Eleven elite (E, Swiss national team) and twelve recreational (R) ski-mountaineers completed an incremental treadmill test to exhaustion in normobaric hypoxia (H, 3000 m, FIO2 14.6 ± 0.1%) and in normoxia (N, 485m, FIO2 20.9 ± 0.0%). Pulse oxygen saturation in blood (SpO2), VO2max, minute ventilation (VE) and heart rate (HR) were recorded. At rest, hypoxic ventilatory response was higher (p<0.05) in E than in R (1.58 ± 1.9 vs. 0.23 ± 0.49 l.min-1·%-1·kg-1). At maximal intensity, SpO2 was significantly lower (p<0.01) in E than in R, both in N (91.1 ± 3.3 vs. 94.3 ± 2.3%) and in H (76.4 ± 5.4 vs. 82.3 ± 3.5%). In both groups, SpO2 was lower (p<0.01) in H. Between N and H, VO2max decreased to a greater extent (p<0.05) in E than in R (-18% and -12%, p<0.01). In E only, VO2max decrement was significantly correlated with the SpO2 decrement (r=0.74, p<0.01) but also with VO2max measured in normoxia (r=0.64, p<0.05). Despite a probable better acclimatization to altitude, VO2max was more reduced in E than in R ski-mountaineers, confirming previous results observed in lowlander E athletes.
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Last Word on Viewpoint: Time for a new metric for hypoxic dose?
Article
  • Jul 2016
to the editor: The commentaries (see Ref. [3][1]) provided on our Viewpoint ([2][2]) is valuable and insightful. Our model is not without its limitations, as many have highlighted, particularly because we were unable to account for substantial variation in the response of hemoglobin mass (Hbmass) to
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Similar Hemoglobin Mass Response in Hypobaric and Normobaric Hypoxia in Athletes
Article
  • Apr 2016
PURPOSE: To compare hemoglobin mass (Hbmass) changes during an 18-d live high-train low (LHTL) altitude training camp in normobaric hypoxia (NH) and hypobaric hypoxia (HH). METHODS: Twenty-eight well-trained male triathletes were split into three groups (NH: n = 10, HH: n = 11, control [CON]: n = 7) and participated in an 18-d LHTL camp. NH and HH slept at 2250 m, whereas CON slept, and all groups trained at altitudes <1200 m. Hbmass was measured in duplicate with the optimized carbon monoxide rebreathing method before (pre-), immediately after (post-) (hypoxic dose: 316 vs 238 h for HH and NH), and at day 13 in HH (230 h, hypoxic dose matched to 18-d NH). Running (3-km run) and cycling (incremental cycling test) performances were measured pre and post. RESULTS: Hbmass increased similar in HH (+4.4%, P < 0.001 at day 13; +4.5%, P < 0.001 at day 18) and NH (+4.1%, P < 0.001) compared with CON (+1.9%, P = 0.08). There was a wide variability in individual Hbmass responses in HH (-0.1% to +10.6%) and NH (-1.4% to +7.7%). Postrunning time decreased in HH (-3.9%, P < 0.001), NH (-3.3%, P < 0.001), and CON (-2.1%, P = 0.03), whereas cycling performance changed nonsignificantly in HH and NH (+2.4%, P > 0.08) and remained unchanged in CON (+0.2%, P = 0.89). CONCLUSION: HH and NH evoked similar Hbmass increases for the same hypoxic dose and after 18-d LHTL. The wide variability in individual Hbmass responses in HH and NH emphasizes the importance of individual Hbmass evaluation of altitude training.
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Time for a new metric for hypoxic dose?
Article
  • Feb 2016
  • J APPL PHYSIOL
The overall "hypoxic dose" associated with altitude training for athletes is typically reported in the literature as hours of exposure. Current recommendations for altitude training are based around the need to acquire a given number of hours within a specific altitude range (typically 1800-3000 m); with the expected erythropoietic change proportional to the hours accumulated. We propose that elevation should also be incorporated when calculating the total dose of altitude exposure and introduce a new metric termed "kilometer hours" to define overall hypoxic dose.
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