the decrease of NO and NO/ET-1 and elevation of ET-1 may be a marker of maladaptation to
high altitude in emigrated rats.
47.
SHORT-TERM INTERMITTENT HYPOBARIC HYPOXIA EXPOSURE DOES NOT ALTER
HEMODYNAMICS AND BAROREFLEX FUNCTION IN YOUNG ATHLETES. Qi Fu
1
,
Nathan Townsend
2
, Martin Truijens
3
, Emily Martini
4
, Dean Palmer
4
, James Stray-Gundersen
1
,
Ferran Rodríguez
5
, Christopher Gore
2
, Benjamin Levine
1
. IEEM, Presbyterian Hospital of Dallas
and UT Southwestern Medical Center at Dallas
1
, Australian Institute of Sport, Canberra,
Australia
2
, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
3
, IEEM, Presbyterian
Hospital of Dallas
4
, INEFC, Universitat de Barcelona, Spain
5
.
Intermittent hypoxia (IH) is the discontinuous use of hypoxia to reproduce some key features
of altitude acclimatization. It is commonly used in athletes to improve performance, and also used
as a model for sleep apnea causing, sustained sympathoexcitation and hypertension in animals.
The PURPOSE of this study was to test the hypothesis that short-term IH exposure affects
hemodynamics and baroreflex function in healthy trained individuals. METHODS: 22 young elite
athletes (11 males and 11 females) were randomly assigned to either hypobaric hypoxia (HYPO:
simulated altitude of 4000-5500m) or normoxia (NORM: 0-5000m) in a randomized, double
blind, placebo controlled design. Both groups rested in a hypobaric chamber 3h/d, 5d/wk for 4
wks. Hemodynamics including blood pressure (BP, automated cuff), heart rate (HR, ECG),
cardiac output (Qc, C2H2 rebreathing), total peripheral resistance (TPR=BP/Qc) and stroke
volume (SV=Qc/HR), and baroreflex function evaluated by the Valsalva maneuver (early phase
II) were measured twice before (Pre1 and Pre2) and 3 days after (Post) the last chamber exposure
in the sitting position. RESULTS: No significant changes in hemodynamics or baroreflex
sensitivity (BRS) were observed for either group after this exposure (Table 1, values are
means±SD). CONCLUSION: Short-term intermittent hypobaric hypoxia exposure does not alter
hemodynamics or baroreflex function in young athletes. In contrast to animal studies, we found
no evidence for sustained physiologically significant sympathoexcitation in this model. Table 1
Normoxia
(n=12)
Hypoxia
(n=10)
Variable
Pre1
Pre2
Post
Pre1
Pre2
Post
SBP (mmHg)
125±9
124±11
121±8
125±10
120±11
120±11
DBP (mmHg)
74±9
71±9
69±6
72±6
68±5
69±6
HR (bpm)
67±15
71±19
69±18
71±11
68±11
72±15
Qc (L/min)
7.76±2.33
7.53±1.70
7.93±2.05
7.61±2.06
7.23±1.69
7.31±2.12
SV (ml)
118±28
112±32
125±32
111±23
108±28
106±36
TPR
(dyne.s.cm-5)
1034±367
990±240
916±195
985±214
991±228
1014±309
BRS
(ms/mmHg)
5.50±3.26
6.45±3.38
5.37±2.57
5.55±3.47
6.51±2.59
5.27±3.58
48.
HYPOXIC PRECONDITIONING AND EXERCISE IMPROVES PHYSICAL FITNESS
ASCENDING TO HIGH ALTITUDE BY AIRPLANE . Yuqi Gao. Institute of High Altitude
Medicine, The Third Military Medical University, Chongqing, China.
Objective: To evaluate the effects of hypoxic preconditioning combined with exercise on
physical fitness for rapid ascent to high altitude. Methods: 120 male youth aged 19±1 years were
divided into four groups. I: control group, II: mask-wearing group, III: exercise group and IV:
hypoxia combined-exercise group. At first, the PWC170 was tested and then the training of
hypoxia combined-exercise (wearing hypoxic respirator, walking for 10min, then rest for 5min
for 4 cycles, twice per day, 7 days) was done at sea level. Subjects of IV group wore a hypoxic
respirator and walked rapidly. III group only took the hypoxic respirator but breathed outside air.
II group did like the IV group but sat quietly instead of exercise. Seven days later, the four groups
