[NO-dependent effects
during adaptation of rats to intermittent hypoxia]
[Article in Ukrainian]
Kurhaliuk NM,
Kotsiuruba AV,
Bukhanevych OM,
Kosiakova HV.
In experiments on Wistar rats processes nitric oxide production on concentration
of anions (NO2-, NO3-), carbamide and polyamines contents were investigated
in processes of rats adaptation to acute hypoxia (7% O2 in N2, 30 min) and
intermittent hypoxia training (10% O2 in N2, 15 min, 5 cycles daily) during
14 days. NO production by oxygen-dependent and oxygen-independent metabolites
paths has been investigated. It is concluded that the disturbances in nitric
oxide system induced by acute hypoxia by L-arginine injections may result
in acute hypoxia.
Short-term altitude mountain
living improves glycemic control.
Lee WC, Chen JJ, Ho HY, Hou CW, Liang MP, Shen YW, Kuo CH.
The aim of this study was to investigate the effect of mountain living conditions
and high altitude hiking activities on glucose tolerance. In study I, we performed
an oral glucose tolerance test on nine untrained subjects before and after
3 days of mountain living. In study II, the same measurement was used to determine
the effect of high altitude hiking in two distinct geographic environments;
participants included 19 professionally trained mountaineers. We found that
trained mountaineers displayed significantly better sea-level glucose tolerance
than sedentary subjects of a similar age (p < 0.05). This result suggests
that mountaineering training could produce a beneficial effect on glucose
tolerance. More importantly, in study I we demonstrated that 3 days of high
altitude living (altitude approximately 2400 m) was sufficient to improve
glucose tolerance. Furthermore, hiking in a relatively flat plateau area (Pamirs
highland area, China, altitude approximately 4000 m) generated significantly
better improvement in glucose tolerance than hiking in a mountain that contained
many rough hills at a similar altitude (Mountain Snow, Taiwan, altitude approximately
3800 m). In conclusion, we found that living at a high altitude for the short
term can significantly improve glucose tolerance. Additionally, the improving
effect of hiking at high altitudes on glucose tolerance appears to be influenced
by the geographic environment. These preliminary results suggest that high
altitude living conditions and activities may possibly be developed as potential
natural medicines for the prevention and treatment of type II diabetes in
the future.
The
response of trained athletes to six weeks of endurance training in hypoxia
or normoxia.
Ventura N, Hoppeler H, Seiler R, Binggeli A, Mullis P, Vogt M.
Department of Anatomy,
This study was performed to investigate the effect of training under simulated
hypoxic conditions. Hypoxia training was integrated into the normal training
schedule of 12 endurance trained cyclists. Athletes were randomly assigned
to two groups and performed three additional training bouts per week for six
weeks on a bicycle ergometer. One group (HG) trained at the anaerobic threshold
under hypoxic conditions (corresponding to an altitude of 3200 m) while the
control group (NG) trained at the same relative intensity at 560 m. Preceding
and following the six training weeks, performance tests were performed under
normoxic and hypoxic conditions. Normoxic and hypoxic .VO2max, maximal power
output as well as hypoxic work-capacity were not improved after the training
period. Testing under hypoxic conditions revealed a significant increase in
oxygen saturation (SpO 2, from 67.1 +/- 2.3 % to 70.0 +/- 1.7 %) and in maximal
blood lactate concentration (from 7.0 to 9.1 mM) in HG only. Ferritin levels
were decreased from 67.4 +/- 16.3 to 42.2 +/- 9.5 microg/l (p < 0.05) in
the HG and from 54.3 +/- 6.9 to 31.4+/- 8.0 microg/l (p = 0.17) in the NG.
Reticulocytes were significantly increased in both groups by a factor of two.
In conclusion, the integration of six weeks of high intensity endurance training
did not lead to improved performance in endurance trained athletes whether
this training was carried out in hypoxic or normoxic conditions.
Publication Types:
· Clinical Trial
· Randomized Controlled Trial
Effects of exercise training
on acclimatization to hypoxia: systemic O2 transport during maximal exercise.
Favret F, Henderson KK,
Richalet JP,
Gonzalez NC.
Dept. of Molecular and Integrative Physiology,
Acclimatization to hypoxia has minimal effect on maximal O2 uptake (Vo2 max).
Prolonged hypoxia shows reductions in cardiac output (Q), maximal heart rate
(HR-max), myocardial beta-adrenoceptor (beta-AR) density, and chronotropic
response to isoproterenol. This study tested the hypothesis that exercise
training (ET), which attenuates beta-AR downregulation, would increase HRmax
and Q of acclimatization and result in higher Vo2 max. After 3 wk of ET, rats
lived at an inspired Po2 of 70 Torr for 10 days (acclimatized trained rats)
or remained in normoxia, while both groups continued to train in normoxia.
Controls were sedentary acclimatized and nonacclimatized rats. All rats exercised
maximally in normoxia and hypoxia (inspired Po2 of 70 Torr). Myocardial beta-AR
density and the chronotropic response to isoproterenol were reduced, and myocardial
cholinergic receptor density was increased after acclimatization; all of these
receptor changes were reversed by ET. Normoxic Vo2 max (in ml.min-1.kg-1)
was 95.8 +/- 1.0 in acclimatized trained (n = 6), 87.7 +/- 1.7 in nonacclimatized
trained (P < 0.05, n = 6), 74.2 +/- 1.4 in acclimatized sedentary (n =
6, P < 0.05), and 72.5 +/- 1.2 in nonacclimatized sedentary (n = 8; P >
0.05 acclimatized sedentary vs. nonacclimatized sedentary). A similar distribution
of Vo2 max values occurred in hypoxic exercise. Q was highest in trained acclimatized
and nonacclimatized, intermediate in nonacclimatized sedentary, and lowest
in acclimatized sedentary groups. ET preserved Q in acclimatized rats thanks
to maintenance of HRmax as well as of maximal stroke volume. Q preservation,
coupled with a higher arterial O2 content, resulted in the acclimatized trained
rats having the highest convective O2 transport and Vo2 max. These results
show that ET attenuates beta-AR downregulation and preserves Q and Vo2 max
after acclimatization, and support the idea that beta-AR downregulation partially
contributes to the limitation of Vo2 max after acclimatization in rats.
Intermittent hypoxia improves
endurance performance and submaximal exercise efficiency.
Katayama K, Matsuo H, Ishida K, Mori S, Miyamura M.
The purpose of the present study was to elucidate
the influence of intermittent hypobaric hypoxia at rest on endurance performance
and cardiorespiratory and hematological adaptations in trained endurance athletes.
Twelve trained male endurance runners were assigned to either a hypoxic group
(n = 6) or a control group (n = 6). The subjects in the hypoxic group were
exposed to a simulated altitude of 4500 m for 90 min, three times a week for
3 weeks. The measurements of 3000 m running time, running time to exhaustion,
and cardiorespiratory parameters during maximal exercise test and resting
hematological status were performed before (Pre) and after 3 weeks of intermittent
hypoxic exposure (Post). These measurements were repeated after the cessation
of intermittent hypoxia for 3 weeks (Re). In the control group, the same parameters
were determined at Pre, Post, and Re for the subjects not exposed to intermittent
hypoxia. The athletes in both groups continued their normal training together
at sea level throughout the experiment. In the hypoxic group, the 3000 m running
time and running time to exhaustion during maximal exercise test improved.
Neither cardiorespiratory parameters to maximal exercise nor resting hematological
parameters were changed in either group at Post, whereas oxygen uptake (.V(O2))
during submaximal exercise decreased significantly in the hypoxic group. After
cessation of intermittent hypoxia for 3 weeks, the improved 3000 m running
time and running time to exhaustion tended to decline, and the decreased .V(O2)
during submaximal exercise returned to Pre level. These results suggest that
intermittent hypoxia at rest could improve endurance performance and submaximal
exercise efficiency at sea level in trained endurance athletes, but these
improvements are not maintained after the cessation of intermittent hypoxia
for 3 weeks.
Publication Types:
· Clinical Trial
· Controlled Clinical Trial
[Physical activity and
training at high altitude]
[Article in Hebrew]
Navot-Mintzer
D, Epstein M, Constantini N.
In recent years there has been a growing interest in the effects of high altitudes
on the human body. High altitudes are being frequented by more and more people
for sport and leisure pursuits, and are increasingly being used both as a
training environment and for investigating the healthy body in hypoxic conditions.
During the ascent from sea level, atmospheric pressure and partial oxygen
pressure decrease, humidity and temperature decrease, and radiation is elevated.
The altitudes at which physiological changes and clinical symptoms occur are
not constant, but variations may usually appear above 2300-2800 meters. There
is a wide variability of reactions to low oxygen in the air inhaled. The physiological
parameters during both rest and physical activity at high altitudes are different
from those at sea level, and the differences are reflected in concomitant
changes in attitude and behavior. Research into altitude as a training environment
that could improve athletic endurance and performance has grown in the last
decade, with the development of a number of new training methods, such as
"Living High--Training Low" and "Training High--Living Low".
These have contributed to an improvement of performance in a significant number
of athletes. This article will demonstrate the impact and possible dangers
of physical activity at high altitude, and will present the current knowledge
and methods of altitude training. This article reviews the influence of low
air and oxygen pressure on athletic performance. Recommendations are presented
regarding physical activity at high altitude and nutritional support.
Publication Types:
· Review
· Review, Tutorial
A closed-loop reduced
oxygen breathing device for inducing hypoxia in humans.
Sausen KP, Bower EA, Stiney ME, Feigl C, Wartman R, Clark JB.
Naval Aerospace Medical Research Laboratory,
BACKGROUND: Hypoxia poses a documented threat to aerospace and diving operations
in healthy people and is a component of many clinical conditions. Practical
training for aircrew, and research on clinically
relevant hypoxic conditions frequently rely exclusively on large, expensive
hypobaric chambers. PURPOSE: Here we describe and report the efficacy of a
compact, economical, closed-loop rebreather-type reduced-oxygen breathing
device (ROBD) for hypoxia induction in humans. METHODS: Subjects were four
healthy student Naval flight surgeons. During baseline,
subjects breathed normoxic air (21% O2, equivalent to sea-level). Baseline
was followed by an altitude period, during which participants were exposed
to hypoxic air (about 10% O2, approximating 5,486 m [18,000 ft mean sea-level])
for 30 min followed by a normoxic recovery period. Subjects' peripheral arterial
oxygen saturation (SpO2), BP, impedance cardiography, cardiac output, and
systemic vascular resistance served as dependent measures along with the fraction
of inspired oxygen (FiO2). RESULTS: Circuit FiO2 and subjects' SpO2 were significantly
lower during the altitude period than the baseline and recovery periods. HR
and cardiac output were significantly higher, and systemic vascular resistance
was significantly lower, during hypoxic air exposure than during baseline
or recovery. CONCLUSIONS: These data support the closed-loop ROBD as a potentially
useful device for training and research involving acute hypoxia in healthy
and clinical populations
[Mechanisms of human adaptation
to hypoxia]
[Article in Russian]
Baranova TI,
Kovalenko RI,
Molchanov AA,
Sviridenko MV,
Ianvareva IN,
Zhekalov AN.
The effects of adaptation to cold-and-hypoxic exposure on the cardiovascular
system, lipid peroxidation and concentrations of adaptogenesis involved hormones
were studied in male students. The two weeks cold- and hypoxic training was
shown to be accompanied by a significant increase of apnea duration, reduced
velocity of bradycardia development and a more rapid ECG post-cold and- hypoxic
exposure normalization, as well as by inhibition of activation of adrenal
cortex and thyroid gland after stress of different nature. The changes of
the character of influences between the indices under study, were demonstrated. The correlation analysis showed an
increase of the human's adaptive potential and a decrease of its dependence
on the adrenal cortex hormones.
Oxygen
saturation response to exercise VO2 at 2100 m and 4350 m in women mountaineering
trainees.
Bhaumik G, Purkayastha SS,
Selvamurthy W,
Banerjee PK.
Defence Institute of Physiology and Allied Sciences,
Human work performances decreases at high altitude
(HA). This decrement does not appear to be similar for every individual, may
be due to variety of factors like elevation, mode of induction, work intensity,
physical condition and specificity of the subjects. The purpose of the study
was to evaluate the effects of alteration in responses of oxygen saturation
(SaO2) and oxygen consumption (VO2) to a standard exercise in women mountaineering
trainees under hypobaric hypoxia. Experiments were conducted in 2 groups (10
each) of females and compared the difference in responses of native women
of moderate altitude with those of the plains/low altitude. A standard exercise
test (Modified Harvard Step-Test for women) was performed on a 30 cm stool
with 24 cycles/min for 5 min, initially at 2100 m and then at 4350 m. The
exercise VO2 values for plains dwelling women achieved apparently VO2max level
at both altitude locations with significant reduction in SaO2 during standard
exercise. Exercise VO2 values decreased on exposure to 4350 m with further
reduction in SaO2. Whereas with same work intensity, under same situation
the exercise VO2 values of the moderate altitude women did not appear to have
reached VO2max. They also maintained comparatively higher level of SaO2. It
may be concluded that hypoxic exposure along with mountaineering training,
the moderate altitude women maintained a higher level of SaO2 during standard
exercise at both altitude locations, compared to low altitude women who might
have lost a compensatory reserve to defend the hypoxic stress to exercise.
Thus, moderate altitude women are proved to be better fit for hypoxic tolerance/HA
performance.
[Hypoxic training of high
qualification sportsmen]
[Article in Ukrainian]
Radziievs'kii PO,
Radziievs'ka MP.
National Univercity of Physical Education and Sports of
Normobaric intermittent hypoxic training (IHT) is an effective method for
improving of of the functional respiration system (FRS) state, increase of
aerobic productivity, general and special capacity for work in sportsmen of
high qualification. The advantage of the use of intermittent hypoxic training
during the preparation of high qualification sportsmen is so that hypoxic
hypoxia and hypoxia of load influence on the sportsman organism in different
time (IHT is doing during the rest, out of the planned sport training without
the influence on it). This is a difference with the hypoxic training in mountain
conditions where two types of hypoxia influence on the sportsman organism
simultaneously and permanently--hypoxia of load and hypoxic hypoxia, and additive
destructive action of the both types of hypoxia may be revealed. High efficacy
of intermittent hypoxic training in improving of all parts of sportsmen FRS
is a result alternating of hypoxic influences and normoxic intervals between
them during which the level of plastic processes remains increased, oxygen
tension in arterial blood and tissues increases to normoxic values. After
IHT course, the state of respiration organs improves, the respiration volume,
part of alveolar ventilation in the minute volume of respiration, saturation
of arterial blood by oxygen, haemoglobin content in blood--increase as well
as increase economy and efficacy of oxygen regimes of organism, general and
special (especially important) physical capacity for work increase too.
| Eur
J Appl Physiol. 2003 Jan;88(4-5):390-5. Epub 2002 Nov 7. |
Changes in performance,
maximal oxygen uptake and maximal accumulated oxygen deficit after 5, 10 and
15 days of live high:train low altitude exposure.
Roberts AD, Clark SA, Townsend NE,
Anderson ME,
Gore CJ, Hahn AG.
Centre for Sports Studies,
Nineteen well-trained cyclists (14 males and 5 females, mean initial .VO(2max)
62.3 ml kg(-1 )min(-1)) completed a multistage cycle ergometer test to determine
maximal mean power output in 4 min (MMPO(4min)), maximal oxygen uptake (.VO(2max))
and maximal accumulated oxygen deficit (MAOD). The athletes were divided into
three groups, each of which completed 5, 10 or 15 days of both a control condition
(C) and live high:train low altitude exposure (LHTL).
The C groups lived and trained at the ambient altitude of 610 m. The LHTL
groups spent 8-10 h night(-1) in normobaric hypoxia
at a simulated altitude of 2,650 m, and trained at the ambient altitude of
610 m. The changes to MMPO(4min), .VO(2max) and MAOD in response to LHTL altitude
exposure were not significantly different for the 5-, 10- and 15-day treatment
periods. For the pooled data from all three treatment periods, there were
significant increases in MMPO(4min) [mean (SD) 5.15
(0.83) W kg(-1) vs 5.34 (0.78) W kg(-1)] and MAOD [50.1 (14.2) ml kg(-1) vs
54.9 (13.1) ml kg(-1)] in the LHTL athletes between pre- and post-altitude
exposure. There were no significant changes in MMPO(4min)
[5.09 (0.76) W kg(-1) vs 5.16 (0.86) W kg(-1)] or MAOD [50.5 (14.1) ml kg(-1)
vs 49.1 (13.0) ml kg(-1)] in the C athletes over the corresponding period.
There were significant increases in .VO(2max) in the athletes during both
the LHTL [63.2 (9.0) ml kg(-1 )min(-1) vs 64.1 (9.0) ml kg(-1 )min(-1)] and
C [62.0 (8.6) ml kg(-1 )min(-1) vs 63.4 (9.2) ml kg(-1 )min(-1)] conditions.
In these athletes, there was no difference in the impact of 5, 10 or 15 days
of LHTL on the increases observed in MMPO(4min),
.VO(2max) or MAOD; and LHTL increased MMPO(4min) and MAOD more than training
at low altitude alone.
Incidence
of decompression sickness in hypoxia training with and without 30-min O2 prebreathe.
Rice GM, Vacchiano CA,
Moore JL Jr,
Anderson DW.
Department of Biomedical Sciences, Naval Aerospace Medical
Research Laboratory,
BACKGROUND: All naval aviators, navigators, and aircrewmen are required to
participate in hypoxia familiarization training. This training is performed
in a hypobaric chamber and is considered high risk due to the potential for
barotrauma and/or decompression sickness (DCS). Prior analysis of the DCS
in U.S. Navy hypobaric chambers revealed a significantly higher incidence
among inside observers (IOs) compared with students. In response to these
reports, all IOs are required to denitrogenate by breathing 100% oxygen for
30 min prior to altitude exposure (prebreathing). Although the Army, Navy,
and Air Force prebreathe for 30 min prior to most hypobaric training exposures,
there have been no reports validating the efficacy of this measure. This study
examined the incidence of altitude DCS during training exposures to simulated
altitudes of 25,000 ft (25k) and 35,000 ft (35k) in IOs and students, some
of whom prebreathed and some of whom did not. METHODS: Exposures and DCS cases
for a period of 9 yr were tabulated from training reports maintained at the
Naval Operational Medicine Institute in Pensacola, FL. Chi-square or Fisher's
Exact test was used to compare the data sets and p < or = 0.05 was considered
significant. RESULTS: The overall DCS incidence for students and IOs for all
chamber profiles was 0.25%. The incidence for 25k was 0.29% for students who
did not prebreathe and 0.15% for IOs who did (p = 0.10). Within the student
group there was a 0.44% DCS incidence for 25k with no prebreathe and a 0.17%
DCS incidence for 35k with prebreathe (p = 0.004). CONCLUSIONS: A 30-min prebreathe prior to altitude exposure appears to contribute
to a reduction in the risk of DCS during hypobaric chamber training.
Publication Types:
· Validation Studies
Anaerobic energy provision
does not limit Wingate exercise performance in endurance-trained cyclists.
Calbet JA, De Paz JA, Garatachea N,
Cabeza de Vaca S,
Chavarren J.
Department of Physical Education, University of Las Palmas
de Gran Canaria,
The aim of this study was to evaluate the effects
of severe acute hypoxia on exercise performance and metabolism during 30-s
Wingate tests. Five endurance- (E) and five sprint- (S) trained track cyclists
from the Spanish National Team performed 30-s Wingate tests in normoxia and
hypoxia (inspired O(2) fraction = 0.10). Oxygen deficit was estimated from
submaximal cycling economy tests by use of a nonlinear model. E cyclists showed
higher maximal O(2) uptake than S (72 +/- 1 and 62 +/- 2 ml x kg(-1) x min(-1),
P < 0.05). S cyclists achieved higher peak and mean power output, and 33%
larger oxygen deficit than E (P < 0.05). During the Wingate test in normoxia,
S relied more on anaerobic energy sources than E (P < 0.05); however, S
showed a larger fatigue index in both conditions (P < 0.05). Compared with
normoxia, hypoxia lowered O(2) uptake by 16% in E
and S (P < 0.05). Peak power output, fatigue index, and exercise femoral
vein blood lactate concentration were not altered by hypoxia in any group.
Endurance cyclists, unlike S, maintained their mean power output in hypoxia
by increasing their anaerobic energy production, as shown by 7% greater oxygen
deficit and 11% higher postexercise lactate concentration. In conclusion,
performance during 30-s Wingate tests in severe acute hypoxia is maintained
or barely reduced owing to the enhancement of the anaerobic energy release.
The effect of severe acute hypoxia on supramaximal exercise performance depends
on training background.
Publication Types:
· Clinical Trial
· Randomized Controlled Trial
Effect
of high-intensity hypoxic training on sea-level swimming performances.
Truijens MJ,
Toussaint HM,
Dow J, Levine BD.
Institute for Exercise and Environmental Medicine, Presbyterian Hospital of
Dallas and University of Texas Southwestern Medical Center at Dallas, 75231,
USA.
The objective of this study was to test the hypothesis that high-intensity
hypoxic training improves sea-level performances more than equivalent training
in normoxia. Sixteen well-trained collegiate and Masters swimmers (10 women,
6 men) completed a 5-wk training program, consisting of three high-intensity
training sessions in a flume and supplemental low- or moderate-intensity sessions
in a pool each week. Subjects were matched for gender, performance level,
and training history, and they were assigned to either hypoxic [Hypo; inspired
O2 fraction (Fi(O(2))) = 15.3%, equivalent to a simulated
altitude of 2,500 m] or normoxic (Norm; Fi(O(2)) = 20.9%) interval training
in a randomized, double-blind, placebo-controlled design. All pool training
occurred under Norm conditions. The primary performance measures were 100-
and 400-m freestyle time trials. Laboratory outcomes included maximal O(2) uptake (Vo(2 max)), anaerobic capacity (accumulated O(2)
deficit), and swimming economy. Significant (P = 0.02 and <0.001 for 100-
and 400-m trials, respectively) improvements were found in performance on
both the 100- [Norm: -0.7 s (95% confidence limits: +0.2 to -1.7 s), -1.2%;
Hypo: -0.8 s (95% confidence limits: -0.1 to -1.5 s), -1.1%] and 400-m freestyle
[Norm: -3.6 s (-1.8 to -5.5 s), -1.2%; Hypo: -5.3 s (-2.3 to -8.3 s), -1.7%].
There was no significant difference between groups for either distance (ANOVA
interaction, P = 0.91 and 0.36 for 100- and 400-m trials, respectively). Vo(2
max) was improved significantly (Norm: 0.16 +/- 0.23 l/min, 6.4 +/-8.1%; Hypo:
0.11 +/- 0.18 l/min, 4.2 +/- 7.0%). There was no significant difference between
groups (P = 0.58). We conclude that 5 wk of high-intensity training in a flume
improves sea-level swimming performances and Vo(2
max) in well-trained swimmers, with no additive effect of hypoxic training.
Publication Types:
· Clinical Trial
· Randomized Controlled Trial
In-flight hypoxia incidents
in military aircraft: causes and implications for training.
Cable GG.
Royal Australian Air Force Institute of Aviation Medicine,
RAAF Base
BACKGROUND: Hypoxia has long been recognized as a significant physiological
threat at altitude. Aircrew have traditionally been trained to recognize the
symptoms of hypoxia using hypobaric chamber training at simulated altitudes
of 25,000 ft or more. The aim of this study was to analyze incidents of hypoxia
reported to the Directorate of Flying Safety of the Australian Defence Force
(DFS-ADF) for the period 1990-2001, as no previous analysis of these incidents
has been undertaken. The data will be useful in planning future training strategies
for aircrew in aviation physiology. METHOD: A search was requested of the
DFS-ADF database, for all Aircraft Safety Occurrence Reports (ASOR) listing
hypoxia as a factor. These cases were reviewed and the following data analyzed:
aircraft type, number of persons on board (POB), number of hypoxic POB, any
fatalities, whether the victims were trained or untrained as aircrew, if the
symptoms were recognized as hypoxia, symptoms experienced, the altitude at
which the incident occurred, and the likely cause. RESULTS: During the period
studied. 27 reports of hypoxia were filed, involving 29
aircrew. In only two cases was consciousness lost, and one of these
resulted in a fatality. Most incidents (85.1%) occurred in fighter or training
aircraft with aircrew who use oxygen equipment routinely.
The majority of symptoms occurred between 10,000 and 19,000 ft. The most common
cause of hypoxia (63%) in these aircraft was the failure of the mask or regulator,
or a mask leak. Rapid accidental decompression did not feature as a cause
of hypoxia. Symptoms were subtle and often involved cognitive impairment or
light-headedness. The vast majority (75.8%) of these episodes were recognized
by the aircrew themselves, reinforcing the importance and benefit of hypoxia
training. CONCLUSION: This study confirms the importance and effectiveness
of hypoxia training for aircrew. Hypoxia incidents occur most commonly at
altitudes less than 19,000 ft. This should be emphasized to aircrew, whose
expectation may be that it is only a problem of high altitude. Proper fitting
of masks, leak checks, and equipment checks should be taught to all aircrew
and reinforced regularly. Current hypobaric chamber training methods should
be reviewed for relevance to the most at-risk aircrew population. Methods
that can simulate subtle incapacitation while wearing oxygen equipment should
be explored. Hypoxia in flight still remains a serious threat to aviators,
and can result in fatalities
The
response of trained athletes to six weeks of endurance training in hypoxia
or normoxia.
Ventura N, Hoppeler H, Seiler R, Binggeli A, Mullis P, Vogt M.
Department of Anatomy,
This study was performed to investigate the effect of training under simulated
hypoxic conditions. Hypoxia training was integrated into the normal training
schedule of 12 endurance trained cyclists. Athletes were randomly assigned
to two groups and performed three additional training bouts per week for six
weeks on a bicycle ergometer. One group (HG) trained at the anaerobic threshold
under hypoxic conditions (corresponding to an altitude of 3200 m) while the
control group (NG) trained at the same relative intensity at 560 m. Preceding
and following the six training weeks, performance tests were performed under
normoxic and hypoxic conditions. Normoxic and hypoxic .VO2max, maximal power
output as well as hypoxic work-capacity were not improved after the training
period. Testing under hypoxic conditions revealed a significant increase in
oxygen saturation (SpO 2, from 67.1 +/- 2.3 % to 70.0 +/- 1.7 %) and in maximal
blood lactate concentration (from 7.0 to 9.1 mM) in HG only. Ferritin levels
were decreased from 67.4 +/- 16.3 to 42.2 +/- 9.5 microg/l (p < 0.05) in
the HG and from 54.3 +/- 6.9 to 31.4+/- 8.0 microg/l (p = 0.17) in the NG.
Reticulocytes were significantly increased in both groups by a factor of two.
In conclusion, the integration of six weeks of high intensity endurance training
did not lead to improved performance in endurance trained athletes whether
this training was carried out in hypoxic or normoxic conditions.
Publication Types: