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Sleeping in a hypoxic environment is becoming increasingly popular among athletes attempting to simulate a "live high, train low" training regime. The purpose of this study was to investigate the acute effects (one night) of sleeping in a normobaric hypoxic tent (NH) (PO(2) = 110 mm Hg approximately 2500 m) upon markers of sleep physiology and quality, compared with sleep in a normal ambient environment (BL) (PO(2) = 159 mm Hg approximately sea level) and sleep in a normobaric normoxic tent (NN) (PO(2) = 159 mm Hg). Eight male recreational athletes (age 34.5 +/- 6.9 yr; stature 169.1 +/- 8.7 cm; mass 69.3 +/- 8.2 kg; VO(2max) 56.4 +/- 8.3 participated in the study using a randomized, double-blind crossover design. Polysomnographic studies were undertaken to measure sleep stages, arterial oxygen saturation (SpO(2)), heart rate (HR), and the Respiratory Disturbance Index (RDI). The Leeds Sleep Evaluation Questionnaire (LSEQ) was used to measure subjective sleep quality. NH (89.9 +/- 4.8%) resulted in a significantly lower (P < 0.05) SpO(2) compared with both BL (95.7 +/- 1.5%) and NN (93.5 +/- 4.0%). Heart rate was significantly higher (P < 0.05) in NH (51.5 +/- 7.6 beats.min(-1)) compared with NN (48.3 +/- 6.9 beats.min(-1)) but was similar versus BL (50.3 +/- 4.3 beats.min(-1)). RDI (counts.h) and RDI (total counts) were lowest in BL (3.5 +/- 2.5; 18.1 +/- 7.9) and highest in NH (36.8 +/- 42.7; 221.9 +/- 254.5). The difference in RDI (counts.h(-1) and total counts) between NH and BL was significant (P < 0.05). The LSEQ revealed that subjects' "behavior following waking" score was significantly (P < 0.05) lower in NH (40.9 +/- 9.2) compared with BL (52.3 +/- 8.3). This study presents evidence that sleep in a normobaric hypoxic tent at a simulated altitude of 2500 m may affect sleep parameters in some individuals. This type of analysis may be useful in the early identification of poorly responding individuals to simulated altitude environments.
Acute Sleep Responses in a Normobaric
Hypoxic Tent
, and
English Institute of Sport, St. Mary’s College High Performance Centre, Twickenham, UNITED KINGDOM;
Medical Institute, Northwick Park Hospital, Harrow, UNITED KINGDOM;
HPRU Medical Research Centre, School of
Biomedical and Molecular Sciences University of Surrey, Guildford, UNITED KINGDOM; and
Sports Sciences, Brunel
University, Uxbridge, UNITED KINGDOM
PEDLAR, C., G. WHYTE, S. EMEGBO, N. STANLEY, I. HINDMARCH, and R. GODFREY. Acute Sleep Responses in a
Normobaric Hypoxic Tent. Med. Sci. Sports Exerc., Vol. 37, No. 6, pp. 1075–1079, 2005. Purpose: Sleeping in a hypoxic environment
is becoming increasingly popular among athletes attempting to simulate a “live high, train low” training regime. The purpose of this
study was to investigate the acute effects (one night) of sleeping in a normobaric hypoxic tent (NH) (PO
110 mm Hg 2500 m)
upon markers of sleep physiology and quality, compared with sleep in a normal ambient environment (BL) (PO
159 mm Hg sea
level) and sleep in a normobaric normoxic tent (NN) (PO
159 mm Hg). Methods: Eight male recreational athletes (age 34.5 6.9
yr; stature 169.1 8.7 cm; mass 69.3 8.2 kg; VO
56.4 8.3 mLkg
) participated in the study using a randomized,
double-blind crossover design. Polysomnographic studies were undertaken to measure sleep stages, arterial oxygen saturation (SpO2),
heart rate (HR), and the Respiratory Disturbance Index (RDI). The Leeds Sleep Evaluation Questionnaire (LSEQ) was used to measure
subjective sleep quality. Results: NH (89.9 4.8%) resulted in a significantly lower (P0.05) SpO
compared with both BL (95.7 1.5%)
and NN (93.5 4.0%). Heart rate was significantly higher (P0.05) in NH (51.5 7.6 beatsmin
) compared with NN (48.3 6.9
) but was similar versus BL (50.3 4.3 beatsmin
). RDI (countsh
) and RDI (total counts) were lowest in BL (3.5 2.5;
18.1 7.9) and highest in NH (36.8 42.7; 221.9 254.5). The difference in RDI (countsh
and total counts) between NH and BL was
significant (P0.05). The LSEQ revealed that subjects’ “behavior following waking” score was significantly (P0.05) lower in NH (40.9
9.2) compared with BL (52.3 8.3). Conclusion: This study presents evidence that sleep in a normobaric hypoxic tent at a simulated
altitude of 2500 m may affect sleep parameters in some individuals. This type of analysis may be useful in the early identification of poorly
responding individuals to simulated altitude environments. Key Words: RESPIRATORY DISTURBANCE INDEX, ALTITUDE TRAIN-
The physiological load placed on the human at altitude
results in physiological adaptations, primarily to the
oxygen transport system, that may be beneficial to
athletic performance (4). These adaptations are primarily
mediated by a reduced O
flux at moderate altitude (2000
3000 m). Maximal sustained exercise capacity is reduced,
however, and therefore training quantity and quality may be
hindered at moderate altitude (1,12). To combat this, ath-
letes often descend from altitude to perform training ses-
sions, returning to altitude at night to continue the acclima-
tization process. This concept of living high and training
low (HI-LO) has received considerable attention within the
literature. To date, no consensus on the efficacy of HI-LO
training has been reached with evidence supporting a physio-
logical and performance enhancement effect and evidence
doubting purported physiological gains (3,7,9,15,26). Never-
theless, athletic populations are increasingly using nocturnal
hypoxia in an attempt to gain some physiological benefit.
The principle methods used by athletes to achieve a
HI-LO training regime, without the complications of trav-
eling to and from true altitude (hypobaric hypoxia) include
sleeping in normobaric hypoxia while at sea level or breath-
ing a hyperoxic gas mixture while training at true altitude.
Living at sea level and sleeping in a normobaric hypoxic
environment artificially simulating an altitude of 2500 m is
a popular form of HI-LO training, with a number of facil-
ities ranging from hypoxic hotels to individual hypoxic tents
becoming increasingly popular (27).
In a recent study Kinsman and coworkers (14) attempted
to quantify the effect of normobaric hypoxia (2650 m) upon
markers of sleep quality. This study investigated respiratory
events in cyclists participating in a HI-LO program using a
nitrogen enriched facility, reporting a substantial increase in
respiratory events during sleep, present in nearly 25% of the
athletes studied. This study did not, however, investigate
sleep in a normobaric hypoxic tent, which is an alternative
method commonly used by athletes.
Address for correspondence: Charles Pedlar, English Institute of Sport, St.
Mary’s College High Performance Centre, Waldergrave Road, Twicken-
ham, TW1 4SX, United Kingdom; E-mail:
Submitted for publication September 2004.
Accepted for publication February 2005.
Copyright © 2005 by the American College of Sports Medicine
DOI: 10.1249/01.mss.0000171623.52757.0f
There remains a dearth of data evaluating sleep in nor-
mobaric hypoxic tents resulting in limited practical guid-
ance for the athlete and coach regarding HI-LO programs.
Accordingly, the aim of the present study was to examine
the effects of an acute exposure to normobaric hypoxia,
simulating an altitude of 2500 m upon sleep characteristics.
Participants. Eight healthy male nonsmoking recre-
ational athletes participated in the study (age 34.5 6.9 yr;
stature 169.1 8.7 cm; mass 69.3 8.2 kg; VO
8.3 mLkg
). All subjects were screened for a
period of 7 d before the study period using wristwatch
actigraphy (Cambridge Neurotechnologies, Cambridge,
UK). No subjects showed any evidence of sleep disruption
during this period. After approval by the local ethics com-
mittee, participants were fully informed of the study and
provided written informed consent.
Research design. All athletes undertook a progres-
sive cycle ergometry test to volitional exhaustion. Online
gas analysis and 12-lead electrocardiogram (Jaeger Oxycon-
Pro, Viasys Healthcare, UK) were employed to establish
and to perform a cardiovascular screening. Resting
maximal flow-volume loops were performed by each athlete
to record forced vital capacity (FVC) and forced expiratory
volume in 1 s (FEV
Subjects were subsequently investigated over three
nights. Between 2100 and 2200 h, subjects were prepared
for polysomnography, that is, placement of electrodes. All
subjects then remained in a lounge area and were free to go
to bed. All subjects were required to be in bed by 2300 h and
remain in the tent until 0700. Polysomnographic recordings
began upon going to bed in individual rooms (temperature
15.5 2°C) until a wake-up call at 0700 h. Night 1 (BL)
was a normalization night and allowed for the monitoring of
sleep in the ambient environment of the bedroom, thus
providing baseline data. A double-blind cross-over research
design was employed for nights 2 and 3, where subjects
were randomly assigned to either normobaric hypoxia (NH)
110 mm Hg) or normobaric normoxia (NN) (PO
159 mm Hg) conditions. The degree of hypoxia equal to a
true altitude of 2500 m was chosen because this is a typical
altitude chosen by athletes for HI-LO training (4). The
normobaric hypoxic environment was generated with a
commercially available tent and generator unit (Hypoxico
Inc., New York). The tent houses the subject and a standard
bed mattress within an enclosed environment constructed
predominantly from plastic. Gas is able to leak from the
enclosure through seams and zips. The hypoxic generator
units supply a nitrogen enriched gas mixture through a 4-m
plastic hose. The units were placed outside of the bedroom
to maintain silent conditions within the tent, delivering the
gas mixture through the hose provided with the unit. The
manufacturers report that the gas mixture flows at a rate of
100 Lmin
. Before each night, the gas mixture was
checked with a portable oxygen analyser (Teledyne Analyt-
ical Instruments, Los Angeles) placed in the stream of flow
to ensure the correct F
was delivered to the tent. No
further testing of the equipment was undertaken. Equipment
was set up precisely as described by the product manufac-
turers in order to closely mimic the practices of an athlete.
Sleep polysomnography (PSG). Recording of the
nocturnal polysomnogram (Nicholet Ultrasom 5 Worksta-
tion, Madison, U.S.) was performed in accordance with
standard criteria (10), using four electroencephalography
(EEG) channels (c4-a1, o2-a1, c3-a2, o1-a2), two elec-
trooculography (EOG) channels (LOC, ROC), electromyo-
graphy (EMG) channel, and two-lead electrocardiography
(ECG). Somatic measures of nocturnal physiology included
inductive plethysmography, body position measurements,
left and right leg EMG of anterior tibialis, finger pulse
oximetry (SpO
), oronasal airflow (airflow thermistor), and
the assessment of respiratory noise.
Sleep data were staged by an experienced sleep electro-
physiologist according to standard criteria (19). Sleep pa-
rameters in the analysis included stages of sleep and sleep
stage transitions. Time spent in sleep stages 1 and 2, and 3
and 4 (slow-wave sleep) and rapid eye movement (REM)
was recorded. Respiratory data were manually assessed by
a qualified sleep physiologist in accordance with American
Thoracic Society indications and standards for cardiopul-
monary sleep studies (2). A sleep apnea is defined as a
cessation of airflow for longer than 10 s. Sleep hypopnea is
defined as a 50% reduction in airflow for longer than 10 s
with a 3% reduction in SpO
. Respiratory disturbance index
(RDI) was used as a global measurement of respiratory
disturbance during sleep and is a sum of all apneas and
hypopneas (2). Data are presented in counts per hour
) and total counts (RDI
Oxygen saturation (SpO
) and heart rate (HR) were mea-
sured at 4-s intervals using a pulse oximeter (Ohmeda,
Herts, UK) attached to the index finger with medical tape.
Data were logged continuously for the whole night and an
arithmetical mean value was calculated. In addition, two-
lead ECG was used to confirm HR.
Subjective analysis of sleep quality was based on assess-
ment of the ease of getting to sleep (GTS), behavior fol-
lowing waking (BFW), and quality of sleep (QS). These
were measured using the Leeds Sleep Evaluation Question-
naire (18), where subjects are required to mark a series of
100-mm visuo-analog scales, indicating their present feeling
with regards to a midpoint, which represents their normal
state of mind before treatment began. Scores are represented
in millimeters.
Statistical analysis. Statistical analysis was per-
formed using the Wilcoxon signed ranks test for nonpara-
metric data with alpha set at 0.05. Additionally, simple
bivariate correlations were performed to assess the relation-
ship between SpO
and RDI
, and between RDI
height, weight, VO
, FVC, and FEV
NH resulted in a significant (P0.05) reduction in
oxygen saturation (89.9 4.8%) compared with both BL
Official Journal of the American College of Sports Medicine
(95.7 1.5%) and NN (93.5 4.0%) conditions. Heart rate
was elevated in NH (51.5 7.6 beatsmin
) compared
with BL (50.3 4.3 beatsmin
) and NN (48.3 6.9
); however, this was only statistically significant
(P0.05) between NH and NN.
No significant differences existed for sleep period total
(SPT) or sleep efficiency (SEff) between the three condi-
tions (P0.05). Duration of sleep stages 3 and 4 and REM
sleep was not significantly different between conditions (P
0.05); however, sleep stages 1 and 2 were significantly
different (P0.05) between NN (248.7 54.4 min) and
BL conditions (208.2 51.4 min).
Respiratory disturbance index counts per hour (RDIh
were lowest in BL conditions and highest in NH, and this
was significantly different between NH and BL conditions
(P0.05, see Table 1). Considerable interindividual dif-
ferences were apparent for RDI per hour. A similar finding
occurred for RDI
, where the mean value was lowest in
baseline conditions and highest in hypoxia, and this was
significant between hypoxic and baseline conditions (P
0.05, see Table 1). The composition of the respiratory dis-
turbance, that is, apneas and hypopneas, is displayed in
Table 1. The occurrence of sleep apneas was significantly
elevated in both NH and NN compared to BL conditions (P
0.05). Sleep hypopneas were significantly increased in
NH compared with BL (P0.05). The majority of apneas
and hypopneas were between 10 and 15 s in duration and
occurred during non-REM sleep stages.
Significant differences (P0.05) occurred between NH
and BL conditions for behavior following waking (see Table
2). No significant differences were found between conditions
for quality of sleep or getting to sleep parameters (P0.05).
No significant correlations were found between SpO
(r 0.09; P0.05). No significant correlations
were found between RDI
and height (r 0.02; P
0.05), weight (r ⫽⫺0.06), VO
(r 0.46; P0.05),
FVC (r 0.13; P0.05), or FEV
(r 0.51; P0.05).
The present study investigated the effect of acute normo-
baric hypoxia, specifically via the use of a commercially
available hypoxic tent, upon physiological and psychomet-
ric parameters of sleep in eight recreational athletes. Find-
ings suggest that some parameters of sleep were affected by
the hypoxic tent (NH) compared with placebo (NN) and
baseline conditions (BL).
NH resulted in a significant reduction in SpO
and a
significant increase in RDI compared with NN; however,
despite this respiratory disturbance, there was no significant
difference in stages 3 and 4 or REM sleep between condi-
tions. This indicates that slow-wave, restorative sleep is
maintained in the normobaric hypoxic tent. The duration of
sleep stages 1 and 2 was significantly shorter in BL com-
pared with NN conditions, which may be due to familiar-
ization with the new environment of the sleep laboratory.
The score for behavior following waking represents the
mean of the LSEQ visual analog scales for questions 8 –10,
which relate to ease of waking up and getting up, clumsi-
ness, and feelings of alertness versus tiredness. This score
was significantly reduced after sleep in NH, presumably
related to respiratory disturbance or other factors associated
with NH resulting in a feeling of residual tiredness. The
practical implications of this may be that early morning
performance may be impaired by NH. This could potentially
impact on an athletes’ ability to train or compete effectively;
however, to the knowledge of the researchers, this question-
naire has not been used to investigate the effects of sleep
upon performance in athletes.
TABLE 2. Subjective sleep quality data for baseline, hypoxia, and placebo conditions (mean SD, range in parentheses).
Hypoxia Significance
GTS (1–100 scale, mean SD) 55.6 12.6 50.4 10.2 46.4 10.6
(37.0–72.3) (37.5–70.5) (29.0–65.0)
BFW* (1–100 scale, mean SD) 52.3 8.3 47.4 5.7 40.9 9.2 H-B
(42.4–64.8) (36.0–52.1) (26.4–51.0)
QS (1–100 scale, mean SD) 56.5 19.2 54.1 13.8 41.9 14.0
(36.0–92.0) (41.6–84.3) (18.5–64.0)
*Denotes significant difference (P0.05); H-B denotes significant differences between hypoxic and baseline conditions; GTS, getting to sleep; BFW, behavior following waking; QS,
quality of sleep.
TABLE 1. Respiratory Disturbance Index (per hour and total counts), apneas, and hypopneas data for baseline, hypoxia, and placebo conditions (mean SD, range in
Hypoxia Significance
)3.5 2.5 8.0 12.2 36.8 42.7 H-B
(1.4–8.7) (0.4–37.3) (1.3–95.5)
*(counts) 18.1 7.9 49.1 66.9 221.9 254.5 H-B
(9–30) (3–208) (9–554)
APN* (counts) 1.9 1.6 19.9 36.3 91.3 112.9 H-B, P-B
(0–5) (0–108) (1–266)
HYP* (counts) 17.0 10.3 35.5 45.9 145.0 179.2 H-B
(0–35) (2–143) (8–459)
*Denotes significant difference (P0.05) (H-B denotes significant differences between hypoxic and baseline conditions, P-B denotes significant differences between placebo and
baseline conditions).
RDI, respiratory disturbance index; APN, apnea; HYP, hypopnea; SPT, sleep period total.
SLEEP IN A NORMOBARIC HYPOXIC TENT Medicine & Science in Sports & Exercise
Data in the present study demonstrated wide heterogene-
ity between individual athletes in the response to hypoxia,
and this is evidenced by wide ranges and large standard
deviations in the data, particularly for RDI (countsh
total counts). Other research involving athletes’ physiolog-
ical responses to hypoxia has repeatedly demonstrated wide
heterogeneity between individual data, and this is true of
sleep parameters (14,28), exercise capacity (6), and physi-
ological adaptation (11,22).
Previous studies have suggested a relationship between
anthropometrical measures and respiratory disturbance dur-
ing sleep in hypoxia. Ri-Li et al. (20) demonstrated a link
between body composition and symptoms of acute moun-
tain sickness (AMS) in men during a 24-h exposure to
hypobaric hypoxia (3658 m), showing that symptoms of
AMS were more common among obese men when com-
pared with normal controls. The present study, however,
found no relationship between the observed physiological
alterations during sleep and measurements of height and
weight, VO
, or lung function, which might help to
explain the findings.
Variations in sleep response have been observed at alti-
tude compared with sea level. Zielinski et al. (28) observed
increases in periodic breathing at an altitude of 3200 m with
wide individual variability in intensity. The number of
arousals and awakenings doubled at high altitude, and the
level of oxygen saturation (SpO
), was lower at high altitude
than at sea level. These findings concur with the findings of
the present study. We observed significant increases in
respiratory disturbance, particularly with increases in sleep
apneas in NH compared with BL. The cause of the rise in
sleep apneas and hypopneas in hypoxia is unclear but could
be related to the hypoxic environment of the tent. Others
have demonstrated respiratory disturbance during sleep in
normobaric hypoxia (14). Other factors relating to the tent
system could also have contributed to respiratory distur-
bance, because apneas were also raised in NN. Further
examination of the environment in the tent is warranted, for
example, temperature, humidity, and CO
The relationship between a reduced SpO
and respiratory
disturbance (periodic breathing) has been suggested by oth-
ers (16,23,14,17). Levine et al. (16) analyzed a model for
chemoreceptor mediated control of breathing. Although this
was a theoretical study, the author concluded that periodic
breathing may be a protective adaptation that serves to
improve oxygen delivery to the tissues. Salvaggio et al. (23),
investigating sleep at high altitude (5050 m), showed that
periodic breathing results in a slight improvement in SpO
In the present study, mean saturation levels dropped by
5.8% from baseline to hypoxia, and individual saturation
values fell below 88% in three of the eight subjects in
hypoxia, a level of desaturation considered clinically sig-
nificant in normal populations (SpO
88%, American
Thoracic Society). Mean level of desaturation, however,
showed no relationship to respiratory disturbance or subjec-
tive measures of sleep quality in the present study. This
finding concurs with the findings of Kinsman et al. (14),
who indicated that SpO
may not be sensitive enough to
predict respiratory events and therefore likely sleep distur-
bance. Significant oxygen desaturation during sleep in a
normal environment, particularly during REM sleep is often
seen in patients with COPD; however, it is uncommon in
normal individuals (17). To the knowledge of the authors,
there are no data available in the literature regarding the
prevalence of oxygen desaturation during sleep among ath-
letic populations; therefore, the long-term health implica-
tions are unknown.
In addition to the reduced SpO
observed in the present
study, heart rate was elevated during sleep (3.2 2.5
difference between hypoxia and placebo con-
ditions). These findings concur with those of Kinsman et al.
(14) reporting a drop in average oxygen saturation of 6
1% and an elevation in heart rate of 3 1 beatsmin
elite athletes sleeping in normobaric hypoxic dormitories
simulating 2650 m. It has been suggested that one role of the
increased heart rate is to compensate for the reduced SpO
in order to maintain oxygen delivery (14). In contrast, other
studies reporting a reduced SpO
at high altitude compared
with sea level, failed to report any alterations in heart rate
during a 4-wk sojourn gradually ascending to 5050 m (23).
Further study is warranted in a larger cohort to allow a more
detailed examination of this relationship in normobaric hy-
poxic environments simulating moderate altitude.
Sleep apneas are linked with hypertension and heart dis-
ease in diseased populations (8); however, the long-term
health implications of sleep apneas in athletes are not
known. It is widely believed that the quality of rest and
recovery of the athlete between training bouts is an essential
part of the adaptation process (the restorative hypothesis of
sleep; (24)). Inadequate recovery may lead to symptoms of
overtraining and ultimately underperformance. The findings
of the present study may have significant implications for an
individual wishing to commence a HI-LO program using a
normobaric hypoxic tent, to avoid the detrimental effects of
poor sleep upon training and recovery.
It has been suggested that short duration (90 min) of
exposure during the day may have an erythropoietic effect
comparable to nocturnal exposure (for a review, see (25)).
This would have the advantage of removing the possibility
of diminished sleep quality because the athlete can continue
to sleep in their normal environment; however, the data in
this area are limited. Rodriguez et al. (21) and Casas et al.
(5) demonstrated increased reticulocytes, hemoglobin, and
hematocrit after 9 and 17 d (3 and 5 hd
, 4000-m and
5500-m altitude); however, the quality of the data may be
confounded by the measurement techniques used. A further
method of intermittent hypoxic exposure during the day via
a portable breathing device supplying hypoxic gas (F
12% reducing to 10% over 4 wk, 5 d·wk
for intervals of
5 min, separated by 5 min of normoxia for a total of 70 min)
has also recently been investigated, but no physiological or
performance improvements were observed (13).
Data from the present study suggest that the use of indi-
vidual athlete assessment in hypoxia before embarking upon
a HI-LO program using a normobaric hypoxic tent system
may be useful for identifying those athletes at risk of poor
Official Journal of the American College of Sports Medicine
sleep quality. It must, however, be noted that this study is
limited to acute exposure to simulated moderate altitude via
a normobaric hypoxic tent, with a small subject group.
Further work is indicated to examine the effect of repeated
exposures to this environment and the subsequent impact
upon sleep disturbance. It is not known whether symptoms
of disrupted sleep in a normobaric hypoxic tent would
diminish over a number of days of acclimatization.
The present study provides evidence that selected parame-
ters of sleep may be significantly affected by a normobaric
hypoxic tent unit and that there is a wide variation in the
individual response in recreational athletes. The evaluation of
sleep quality may be useful in identifying individuals who are
vulnerable to sleep disruption in a normobaric hypoxic tent.
Effects of equivalentsea-level and altitude training on VO
running performance. J.Appl. Physiol. 39:262–266, 1975.
2. AMERICAN THORACIC SOCIETY. Indications and standards for car-
diopulmonary sleep studies. Am. Rev. Resp. Dis. 139:559–568,
3. ASHENDEN, M. J., C. J. GORE,G.P.DOBSON, and A. G. HAHN.Live
high, train lowdoes not change the total haemoglobin mass of
male endurance athletes sleeping at a simulated altitude of 3000 m
for 3 nights. Eur. J. Appl. Physiol. 80:479– 484, 1999.
4. BAILEY, D. M., and B. DAVIES. Physiological implications of alti-
tude training for endurance performance at sea level: a review.
Br. J. Sports Med. 31:183–190, 1997.
5. CASAS, M., H. CASAS,T.PAGES. Intermittent hypobaric hypoxia
induces altitude acclimation and improves the lactate threshold.
Aviat. Space. Environ. Med. 71:125–130, 2000.
6. CHAPMAN, R. F., M. EMERY, and J. M. STAGER. Degree of arterial
desaturation in normoxia influences VO
decline in moderate
hypoxia. Med. Sci. Sports Exerc. 31:658–663, 1999.
7. CHAPMAN, R. F., J. STRAY-GUNDERSEN, and B. D. LEVINE. Individual
variation in response to altitude training. J. Appl. Physiol. 85:
1448–1456, 1998.
8. CHERNIACK, N. S. Highlighted topic: oxygen sensing: applications
in humans. J. Appl. Physiol. 96:352–358, 2004.
9. HAHN, A. G., and C. J. GORE. The effect of altitude on cycling
performance: a challenge to traditional concepts. Sports Med.
31:533–557, 2001.
10. JASPER, H. H. The ten-twenty electrode system of the International
Federation. Electroencephalogr. Clin. Neurophysiol. 10:371–375,
11. JEDLICKOVA, K., D. W. STOCKTON,H.CHEN. Search for genetic
determinants of individual variability of the erythropoietin re-
sponse to high altitude. Blood Cells Mol. Dis. 31 175–182, 2003.
CHRISTENSEN, and N. H. SECHAR. High-altitude training does not
increase maximal oxygen uptake or work capacity at sea level in
rowers. Scand. J. Med. Sci. Sports. 3:256–262, 1993.
13. JULIAN, C. G., C. J. GORE,R.L.WILBER. Intermittent normobaric
hypoxia does not alter performance or erythropoietic markers in
highly trained distance runners. J. Appl. Physiol. 96:1800–1807,
MARTIN, and C. CHOW. -M. Respiratory events and periodic breath-
ing in cyclists sleeping at 2,650 m simulated altitude. J. Appl.
Physiol. 92:2114–2118, 2002.
15. LEVINE, B. D., and J. STRAY-GUNDERSEN, “Living high–training
low”: effect of moderate-altitude acclimatization with low-altitude
training on performance. J. Appl. Physiol. 83:102–112, 1997.
16. LEVINE, M., J. P. CLEAVE, and C. DODDS. Can periodic breathing
have advantages for oxygenation? J. Theor. Biol. 172:355–368,
17. O’DONOHUE, W. J., JR., and T. J. BOWMAN. Hypoxemia during
sleep in patients with chronic obstructive pulmonary disease:
significance, detection and effects of therapy. Respir. Care 45:
188–191, 2000.
18. PARROT, A. C., and I. HINDMARCH, The Leeds Sleep Evaluation
Questionnaire in psychopharmacological investigations: a review.
Psychophamacology (Berl.) 71:173–179, 1980.
19. RECHTSCHAFFEN, A., and A. KALES.A Manual of Standardized
Terminology, Techniques and Scoring System for Sleep Stages of
Human Subjects. NIH Publication 204. Washington, DC: U.S.
Government Printing Office, Department of Health Education and
Welfare, 1968, pp. 1–13.
20. RI-LI, G., P. J. CHASE,S.WITKOWSKI. Obesity: associations with
acute mountain sickness. Ann. Intern. Med. 139:253–257, 2003.
21. RODRIGUEZ, F. A., H. CASAS,M.CASAS. Intermittent hypobaric
hypoxia stimulates erythropoiesis and improves aerobic capacity.
Med. Sci. Sports. Exerc. 31:264–268, 1999.
transport in blood at high altitude: role of the haemoglobin-oxygen
affinity and impact of the phenomena related to haemoglobin
allosterism and red cell function. Eur. J. Appl. Physiol. 90:351–
359, 2003.
23. SALVAGGIO, A., G. INSALACO,O.MARRONE. Effects of high-altitude
periodic breathing on sleep and arterial oxyhaemoglobin satura-
tion. Eur. Resp. J. 12:651– 657, 1998.
24. SHAPIRO, C. M. Sleep and the athlete. Br. J. Sports Med. 15:51–55,
25. SCHMIDT, W. Effects of intermittent hypoxic exposure to high
altitude on blood volume and erythropoietic activity. High Alt.
Med. Biol. 3:166–167, 2002.
high and training low” altitude training improves sea level per-
formance in male and female elite runners. J. Appl. Physiol.
91:1113–1120, 2001.
27. WILBER, R. L. Current trends in altitude training. Sports Med.
41:249–265, 2001.
28. ZIELINSKI, J., M. KOZIEJ,M.MAVKOWSKI. The quality of sleep and
periodic breathing in healthy subjects at an altitude of 3200 m.
High Alt. Med. Biol. 1:331–336, 2000.
SLEEP IN A NORMOBARIC HYPOXIC TENT Medicine & Science in Sports & Exercise
... The most likely explanation relates to an accumulated influence of negative factors. In particular, the use of the (commercially available) normobaric hypoxic tent could have contributed to respiratory disturbance, with increases in sleep apneas (Pedlar et al. 2005), via an accumulation of expired carbon dioxide (CO 2 ), as well as a rise in temperature and humidity inside the tent. Alone or in combination with the hypoxic stress, hypercapnia might have induced neurocognitive deficits (i.e., acute changes in cerebral blood flow, pH, catecholamine, and neuronal excitability) and depression in cortical electrical activity, related to endocrine and cardiovascular alterations (see viewpoint and comments from Wang et al. 2016). ...
... Therefore, when using such low air volume material, CO 2 monitoring must be encouraged (in addition to desaturation-level control, which was not the case in Bejder et al. 2017). While the long-term health implications of sleep apneas in athletes remain unknown, inadequate restorative process between training sessions may lead to symptoms of overreaching or overtraining (Pedlar et al. 2005). ...
... Some accounts of changes in athletes' sleep patterns from near sea level to altitude have been reported in the scientific literature, [14][15][16][17][18]34,35 but these studies have been conducted at altitudes of 2000-3600 m. In the present study an altitude of 1800 m was used for its relevance to the Beijing 2022 Olympic Winter Games. ...
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Objectives: To observe changes in sleep from baseline and during an altitude training camp in elite endurance athletes. Design: Prospective, observational. Setting: Baseline monitoring at <500 m for 2 weeks and altitude monitoring at 1800 m for 17-22 days. Participants: Thirty-three senior national-team endurance athletes (mean age 25.8 ± S.D. 2.8 years, 16 women). Measurements: Daily measurements of sleep (using a microwave Doppler radar at baseline and altitude), oxygen saturation (SpO2), training load and subjective recovery (at altitude). Results: At altitude vs. baseline, sleep duration (P = .036) and light sleep (P < .001) decreased, while deep sleep (P < .001) and respiration rate (P = .020) increased. During the first altitude week vs. baseline, deep sleep increased (P = .001). During the first vs. the second and third altitude weeks, time in bed (P = .005), sleep duration (P = .001), and light sleep (P < .001) decreased. Generally, increased SpO2 was associated with increased deep sleep while increased training load was associated with increased respiration rate. Conclusion: This is the first study to document changes in sleep from near-sea-level baseline and during a training camp at 1800 m in elite endurance athletes. Ascending to altitude reduced total sleep time and light sleep, while deep sleep and respiration rate increased. SpO2 and training load at altitude were associated with these responses. This research informs our understanding of the changes in sleep occurring in elite endurance athletes attending training camps at competition altitudes.
... 63 92 93 Nevertheless, the reported magnitude of these sleep alterations with over-reaching/overtraining is quite modest in terms of both the reduction in sleep efficiency (<5%) and sleep duration (<30 min), particularly when compared with that observed in sleep disorder patients 94 or even in athletes in response to jet lag 95 or hypoxia. 96 Of note, a case study reported larger sleep deficiency (<6 hours per night compared with 8-10 hours per night following full recovery) in a talented female sprint cyclist who developed signs of overtraining (ie, persistent fatigue and underperforming over months). This case indicates that more severe sleep impairments could be associated with overtraining syndrome, but more research is needed to confirm this hypothesis. ...
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ABSTRACT Elite athletes are particularly susceptible to sleep inadequacies, characterised by habitual short sleep (<7 hours/night) and poor sleep quality (eg, sleep fragmentation). Athletic performance is reduced by a night or more without sleep, but the influence on performance of partial sleep restriction over 1–3 nights, a more real-world scenario, remains unclear. Studies investigating sleep in athletes often suffer from inadequate experimental control, a lack of females and questions concerning the validity of the chosen sleep assessment tools. Research only scratches the surface on how sleep influences athlete health. Studies in the wider population show that habitually sleeping <7 hours/night increases susceptibility to respiratory infection. Fortunately, much is known about the salient risk factors for sleep inadequacy in athletes, enabling targeted interventions. For example, athlete sleep is influenced by sport-specific factors (relating to training, travel and competition) and non-sport factors (eg, female gender, stress and anxiety). This expert consensus culminates with a sleep toolbox for practitioners (eg, covering sleep education and screening) to mitigate these risk factors and optimise athlete sleep. A one-size-fits-all approach to athlete sleep recommendations (eg, 7–9 hours/night) is unlikely ideal for health and performance. We recommend an individualised approach that should consider the athlete’s perceived sleep needs. Research is needed into the benefits of napping and sleep extension (eg, banking sleep).
... Nitrogen tents have been designed for high altitude train-ing of athletes (Pedlar et al., 2005). The tents are not air tight to prevent suffocation. ...
Herbaria are libraries of dried mounted plants used for plant identification, research vouchers and teaching. Herbarium specimens are subject to damage from insects, fungi and bacteria, and must be protected by treatments that kill damaging organisms. Naphthalene, the most common chemical currently used in herbaria, is a class C carcinogen and potential allergen. The aim was to develop an affordable alternative to treatment with persistent hazardous toxins for maintaining dried herbarium specimens. The new method uses ambient temperature nitrogen gas and widely available, valved, nylon, oxygen barrier bags. Nitrogen gas treatment has been shown to be less expensive than freezer storage and safer than treatment with naphthalene and other toxins. The lower hazard of nitrogen treatment compared to naphthalene offers a practical option for K-12 and institutions of higher education to initiate, reinstate or strengthen herbarium collections for teaching and/or research. This is the first report of the use of inexpensive valved oxygen barrier bags for herbarium pest control.
... S leep-disordered AU3 c breathing and fluctuations in arterial oxygen saturation (SaO 2 ) are common and linked to sleep arousals among lowlanders ascending to high altitude (Reite et al., 1975;Bärtsch and Saltin, 2008;Insalaco et al., 2012;Ainslie et al., 2013). Hypocapnia and respiratory alkalosis augment and propagate ventilatory instabilities such as periodic breathing (Eichenberger et al., 1996) and sleep apneas (Pedlar et al., 2005), both of which are associated with SaO 2 desaturations. It is difficult to determine whether SaO 2 desaturations, per se, contribute to the development of acute mountain sickness (Burgess et al., 2004;Erba et al., 2004). ...
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Patrician, Alexander, Harald Engan, David Lundsten, Ludger Grote, Helena Vigetun-Haughey, and Erika Schagatay. The effect of dietary nitrate on nocturnal sleep-disordered breathing and arterial oxygen desaturation at high altitude. High Alt Med Biol 00:000-000, 2017.-Sleep-disordered breathing and fluctuations in arterial oxygen saturation (SaO2) are common during sleep among lowlanders ascending to high altitude. Dietary nitrate (NO3-) supplementation has been shown to lower the O2 consumption in various conditions. Our objective was to investigate whether dietary NO3- could reduce sleep-disordered breathing and SaO2 desaturation during sleep at altitude. Cardiorespiratory responses during sleep were measured in 10 healthy lowlanders at 330 m and then again in the Himalayas at 3700-4900 m. Each subject received two 70 mL shots of either beetroot juice (BR; ∼5.0 mmol NO3- per shot) or placebo (PL: ∼0.003 mmol NO3- per shot) in a single-blinded, weighted order over two consecutive nights at altitude. At 2.5-4.5 hours into sleep at altitude, BR increased the SaO2 desaturation drop (4.2 [0.1]% with PL vs. 5.3 [0.4]% with BR; p = 0.024) and decreased the SaO2 desaturation duration (14.1 [0.9] seconds with PL to 11.1 [0.9] seconds with BR; p = 0.0.041). There was a reduction in breaths with flow limitation (p = 0.025), but no changes in Apnea-Hypopnea Index (AHI), mean and minimum SaO2. The study suggests BR supplementation does not improve AHI or oxygenation, but may increase fluctuations in arterial O2 saturation during sleep at altitude in native lowlanders.
... The Leeds Sleep Evaluation Questionnaire (Parrott and Hindmarch 1980) was also used to evaluate sleep quality in athletes in a number of studies (Montmayeur et al. 1994;Pedlar et al. 2005). This questionnaire comprises ten self-rating 100-mm-line analog questions concerned with aspects of sleep and early morning behavior (Parrott and Hindmarch 1980). ...
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During Ramadan, dehydration and disturbed sleep patterns are common, so accurate reliable methods for the assessment of hydration and sleep of athletes are necessary to maintain performance. The purpose of this review is: (1) to identify appropriate tools/methods for monitoring hydration status and sleep in sports people; (2) to discuss which of these tools/methods can be confidently used by sport scientists and trainers during Ramadan; and (3) to discuss the possible link that may exist between sleep and hydration status. Several markers of hydration status are currently used and include body mass, plasma/serum osmolality, dilution techniques, and neutron activation analysis. Used in an appropriate context, all can be indicative of the hydration status in the laboratory. In the field, monitoring hydration status in physically active individuals and athletes may be performed using a combination of body mass with some measure of urine concentration (e.g. urine osmolality, urine-specific gravity, urine color) and sensation of thirst. During Ramadan, appropriate timing of sample collection and the use of reference methods in future studies are warranted. In the field, careful use of body mass in conjunction with urine indices may be used to monitor the hydration status of subjects practicing physical activity during Ramadan. There is a need for the use of polysomnography or actigraphy for sleep assessment during Ramadan in future laboratory-based studies of athletes. However, in the field, monitoring sleep–wake patterns may be performed using actigraphy and/or the PSQI questionnaire.
... One investigation at 2,438 m found that, although subjects displayed moderately severe hypoxemia, there were no observed changes or reductions in sleep quality (21). In contrast, a sleep study using the same mode and severity of hypoxic delivery as our study found that overnight sleep in a normobaric hypoxic tent at 2,500 m resulted in a significantly greater index of respiratory disturbances and significantly lower scores on subjective measures quality of sleep vs. normoxic baseline sleep (22). However, subjects in this study showed no changes in stages 3 and 4 or in REM sleep. ...
For sea level-based endurance athletes who compete at moderate and high altitudes, many are not logistically able to arrive at altitude weeks prior to the event to fully acclimatize. For those who can only arrive at altitude the night before competition, we asked if there is a physiological and performance advantage in reducing altitude exposure time to two hours prior to competition. On three separate visits, ten cyclists completed overnight laboratory exposures of: 1) a 14-hour exposure to normobaric hypoxia (16.2% O2, simulating 2500m; 14H), 2) a 12-hour exposure to normoxia, then a 2-hour hypoxic exposure (2H), and 3) a 14-hour exposure to normoxia (CON). Immediately following each exposure, subjects completed a 20-km cycle ergometry time trial in normoxia (CON) or 16.2% O2 (14H and 2H). Measures of plasma volume changes, sleep quality, ventilatory acclimatization, perceived exertion, oxygen uptake, and 20-km time were collected. No significant differences were observed in performance measures or perceived exertion between hypoxic trials. Plasma volume loss was significantly greater during 14H than 2H and CON. No differences in ventilatory acclimatization or sleep quality were observed between trials. Although some divergent 20-km performance responses were observed between 14H and 2H, they were not explained by the physiological measures completed. The data suggest that endurance athletes who are logistically restricted from arriving at altitude more than the evening prior to competition would not gain an advantage by delaying their arrival until a few hours before the competition, although unique individual responses may ultimately influence optimal arrival strategy.
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The occupational demands of law enforcement increase the risk of poor-quality sleep, putting officers at risk of adverse physical and mental health. This cross-sectional study aimed to characterise sleep quality in day workers, 8 and 12 h rotating shift pattern workers. One hundred eighty-six officers volunteered for the study (37 female, age: 41 ± 7). Sleep quality was assessed using the Pittsburgh sleep quality index, actigraphy and the Leeds sleep evaluation questionnaire. The maximal aerobic capacity (VO2max ) was measured on a treadmill via breath-by-breath analysis. There was a 70% overall prevalence of poor sleepers based on Pittsburgh sleep quality index scores, where 8 h shifts exhibited the worst prevalence (92%, p = 0.029), however, there was no difference between age, gender, or role. In contrast, 12 h shifts exhibited the poorest short-term measures, including awakening from sleep (p = 0.039) and behaviour following wakefulness (p = 0.033) from subjective measures, and poorer total sleep time (p = 0.024) and sleep efficiency (p = 0.024) from the actigraphy. High VO2max predicted poorer wake after sleep onset (Rsq = 0.07, p = 0.05) and poorer sleep latency (p = 0.028). There was no relationship between the Pittsburgh sleep quality index scores and any of the short-term measures. The prevalence of poor sleepers in this cohort was substantially higher than in the general population, regardless of shift pattern. The results obtained from the long- and short-term measures of sleep quality yielded opposing results, where long-term perceptions favoured the 12 h pattern, but short-term subjective and objective measures both favoured the 8 h pattern.
Although scientific conclusions remain equivocal, there is evidence-based research, as well as anecdotal support, suggesting that altitude training can enhance performance among Olympic level athletes, particularly in endurance sport. This appears to be due primarily to hypoxia-induced increases in total hemoglobin mass and subsequent improvements in maximal oxygen uptake and other factors contributing to aerobic performance. Although less clear, it is possible that non-hematological adaptations may contribute secondarily to improvements in post-altitude performance. These physiological effects are most likely realized when the altitude exposure is of sufficient “hypoxic dose” to provide the necessary stimuli for performance-affecting changes to occur via hypoxia-inducible factor 1α (HIF-1α) and hypoxia-inducible factor 2α (HIF-2α) pathways and their downstream molecular signaling. Team USA has made a strong commitment over the past 20 years to utilizing altitude training for the enhancement of performance in elite athletes in preparation for the Olympic Games and World Championships. Team USA’s strongest medal-producing Olympic sports—USA Swimming and USA Track and Field—embraced altitude training several years ago, and they continue to be leaders within Team USA in the practical and successful application of altitude training. Whereas USA Swimming utilizes traditional “live high and train high” (LH + TH) altitude training, USA Track and Field tends more toward the use of the altitude training strategy whereby athletes live high (and potentially sleep higher, either naturally or via simulated altitude), while training high during moderate-intensity (< lactate threshold 2) training sessions, and train low during high-intensity (> lactate threshold 2) training sessions (LH + TH[LT]). Although USA Swimming and USA Track and Field have taken different approaches to altitude training, they have been equally successful at the Olympic Games and World Championships, both teams being ranked first in the world based on medals earned in these major international competitions. In addition to USA Swimming and USA Track and Field, several other Team USA sports have had consistently competitive performance results in conjunction with regular and systematic altitude training blocks. The purpose of this paper was to describe select altitude training strategies used by Team USA athletes, and the impact of those strategies on podium performance at major international competitions, specifically the Olympic Games and World Championships.
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Purpose This systematic review aims to describe objective sleep parameters for athletes under different conditions and address potential sleep issues in this specific population. Methods PubMed and Scopus were searched from inception to April, 2019. Included studies measured sleep only via objective evaluation tools such as polysomnography or actigraphy. The modified version of the Newcastle-Ottawa Scale was used for the quality assessment of the studies. Results Eighty-one studies were included, of which 56 were classified as medium quality, 5 as low, and 20 as high quality. A total of 1830 athletes were monitored over 18,958 nights. Average values for sleep-related parameters were calculated for all athletes according to sex, age, athletic expertise level, training season, and type of sport. Athletes slept on average 7.2 ± 1.1 h/night, with 86.3% ± 6.8% sleep efficiency (SE). In all datasets, the athletes’ mean total sleep time was <8 h. SE was low for young athletes (80.3% ± 8.8%). Reduced SE was attributed to high wake after sleep onset rather than sleep onset latency. During heavy training periods, sleep duration and SE were on average 36 min and 0.8% less compared to pre-season and 42 min and 3.0% less compared to in-season training periods, respectively. Conclusion Athletes’ sleep duration was found to be short with low SE, in comparison to the general consensus for non-athlete healthy adults. Notable sleep issues were revealed in young athletes. Sleep quality and architecture tend to change across different training periods.
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The Leeds Sleep Evaluation Questionnaire comprises ten self-rating 100-mm-line analogue questions concerned with aspects of sleep and early morning behaviour. The questionnaire has been used to monitor subjectively perceived changes in sleep during psychopharmacological investigations involving a variety of psychoactive agents, including sedative-hypnotics, antidepressants, anxiolytics, CNS stimulants, and antihistamines. Dose-related improvements in the self-reported ratings of getting to sleep and perceived quality of sleep were generally associated with reductions in the self-reported levels of alertness and behavioural integrity the morning following the nocturnal administration of sedative hypnotic and anti-anxiety agents. Psychostimulants, on the other hand, impaired subjective ratings of sleep and produced increases in early morning assessments of alertness. Certain antidepressant and antihistaminic agents produced effects similar to the sedative-hypnotics, while others did not affect self-reported aspects of sleep and early morning behaviour.
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Sleep is generally considered to be restorative and the notion of exercise being associated with the changes in subsequent sleep is popular but has only recently been demonstrated. There are several facets of exercise performed that have an influence on sleep. These include the intensity and duration of the exercise, and the interval between the cessation of exercise and sleep onset. Other factors that may alter sleep after exercise are the age and fitness of the subject, and his lean body mass. Most studies on the effect of exercise on sleep can be interpreted as being partially or totally supportive of the restorative theory of sleep function.
Acute exposure to moderate altitude is likely to enhance cycling performance on flat terrain because the benefit of reduced aerodynamic drag outweighs the decrease in maximum aerobic power [maximal oxygen uptake (V̇O2max)]. In contrast, when the course is mountainous, cycling performance will be reduced at moderate altitude. Living and training at altitude, or living in an hypoxic environment (~2500m) but training near sea level, are popular practices among elite cyclists seeking enhanced performance at sea level. In an attempt to confirm or refute the efficacy of these practices, we reviewed studies conducted on highly-trained athletes and, where possible, on elite cyclists. To ensure relevance of the information to the conditions likely to be encountered by cyclists, we concentrated our literature survey on studies that have used 2- to 4-week exposures to moderate altitude (1500 to 3000m). With acclimatisation there is strong evidence of decreased production or increased clearance of lactate in the muscle, moderate evidence of enhanced muscle buffering capacity (βm) and tenuous evidence of improved mechanical efficiency (ME) of cycling. Our analysis of the relevant literature indicates that, in contrast to the existing paradigm, adaptation to natural or simulated moderate altitude does not stimulate red cell production sufficiently to increase red cell volume (RCV) and haemoglobin mass (Hbmass). Hypoxia does increase serum erthyropoietin levels but the next step in the erythropoietic cascade is not clearly established; there is only weak evidence of an increase in young red blood cells (reticulocytes).Moreover, the collective evidence from studies of highly-trained athletes indicates that adaptation to hypoxia is unlikely to enhance sea level V̇O2max. Such enhancement would be expected if RCV and Hbmass were elevated. The accumulated results of 5 different research groups that have used controlled study designs indicate that continuous living and training at moderate altitude does not improve sea level performance of high level athletes. However, recent studies from 3 independent laboratories have consistently shown small improvements after living in hypoxia and training near sea level. While other research groups have attributed the improved performance to increased RCV and V̇O2max, we cite evidence that changes at the muscle level (βm and ME) could be the fundamental mechanism. While living at altitude but training near sea level may be optimal for enhancing the performance of competitive cyclists, much further research is required to confirm its benefit. If this benefit does exist, it probably varies between individuals and averages little more than 1%.
Purpose: Elite endurance athletes display varying degrees of pulmonary gas exchange limitations during maximal normoxic exercise and many demonstrate reduced arterial O-2 saturations (SaO(2)) at (V) over dot O-2max-a condition referred to as exercise induced arterial hypoxemia (EIH). We asked whether mild hypoxia would cause significant declines in SaO(2) and (V) over dot O-2max in EIH athletes while non-EIH athletes would be unaffected. Methods: Nineteen highly trained males were divided into EIH (N = 8) or Non-ELH (N = 6) groups based on SaO(2) at (V) over dot O-2max (EIH < 90%, Non-EIH > 92%). Athletes with intermediate SaO(2) values (N = 5) were only included in correlational analyses. Two randomized incremental treadmill tests to exhaustion were completed-one in normoxia, one in mild hypoxia (FIO2 = 0.187: similar to 1,000m). Results: EIH subjects demonstrated a significant decline in (V) over dot O-2max from normoxia to mild hypoxia(71.1 +/- 5.3 vs 68.1 +/- 5.0, P < 0.01), whereas the non-EIH group did not show a significant Delta(V) over dot O-2max (67.2 +/- 7.6 vs 66.2 +/- 8.4 For all 19 athletes, SaO(2) during maximal exercise in normoxia correlated with the change in (V) over dot O-2max from normoxia to mild hypoxia (r = -0.54, P < 0.05). However, the change in SaO(2) and arterial O-2 content from normoxia to mild hypoxia was equal for both EIH and Non-EIH (Delta SaO(2) = 5.2% for both groups), bringing into question the mechanism by which changes in SaO(2) affect (V) over dot O-2max in mild hypoxia. Conclusions: We conclude that athletes who display reduced measures of SaO(2) during maximal exercise in normoxia are more susceptible to declines in (V) over dot O-2max in mild hypoxia compared with normoxemic athletes.
Maximal oxygen uptake (Vo2max was evaluated after high-altitude training in rowers. Nine rowers trained in a camp at 1822 m for 3 weeks with no change in Vo2max or 6-min work capacity on a rowing ergometer at sea level. In contrast, 9 control rowers training at sea level increased Vo2max by 4 (0-8)% and work capacity by 3 (0-11)% (median and range). In rowers emphasizing endurance training during a summer of competitive rowing (n=9), Vo2max and work capacity increased by 6 (0-13)% and 3 (-1-6)%, respectively and no significant changes were noted in rowers performing interval training (n= 9). Exhaustive rowing on an ergometer was characterized by elevated plasma adrenaline, noradrenaline (n=13) and lactate (n=14) (to 19 (11-31), 74 (50-109) nmol l1 and 15 (11-22) mmol-I1, respectively). In heavyweight rowers (n=11), blood volume was 7.0 (5.9-8.3) litres, left ventricular wall thickness 13 (11-15) mm and end-diastolic diameter 57 (54-66) mm (n=11). This study demonstrated an elevated blood volume in rowers as well as myocardial hypertrophy and large internal heart diameters. In well-trained rowers, endurance training is superior to interval training for elevating Vo2max and work capacity, but high-altitude training does not contribute to increasing Vo2max or work capacity at sea level.
Twelve middle-distance runners, each having recently completed a competitive track season, were divided into two groups matched for maximal oxygen uptake (VO2max), 2-mile run time and age. Group 1 trained for 3 wk at Davis, PB = 760 mmHg, running 19.3 km/day at 75% of sea-level (SL) VO2max, while group 2 trained an equivalent distance at the same relative intensity at the US Air Force Academy (AFA), PB = 586 mmHg. The groups then exchanged sites and followed a training program of similar intensity to the group preceding it for an additional 3 wk. Periodic near exhaustive VO2max treadmill tests and 2-mile competitive time trials were completed. Initial 2-mile times at the AFA were 7.2% slower than SL control. Both groups demonstrated improved performance in the second trial at the AFA (chi = 2.0%), but mean postaltitude performance was unchanged from SL control. VO2max at the AFA was reduced initially 17.4% from SL control, but increased 2.6% after 20 days. However, postaltitude VO2max was 2.8% below SL control. It is concluded that there is no potentiating effect of hard endurance training at 2,300-m over equivalently severe SL training on SL VO2max or 2-mile performance time in already well conditioned middle-distance runners.