12.
ACUTE ALTITUDE SICKNESS - CAN BUBBLES BE INVOLVED?. Alf O. Brubakk
1
, Ulrik
Wisloff
1
. ISB, Norwegian University of Science and Technology, Trondheim, Norway
1
.
Traditionally, acute mountain sickness is considered to be a disease caused by exposure to
hypoxia. The likelihood and severity of altitude illness is greater with increasing rate of ascent,
higher altitude attained, and higher levels of exertion. Decompression sickness (DCS) is caused
by bubble growth when gas comes out of solution following reduction in pressure. There is
experimental evidence that bubbles in the vascular system can occur at any supersaturation and
gas bubbles have been observed at a pressure of 70 kPa, that is equivalent to approximately 3000
m altitude. Bubbles grow from nuclei, which probably are stable gas-filled spheres. We have
demonstrated experimentally that such nuclei probably are attached to the endothelial surface and
that exercise may influence their size and attachment to the wall. Both duration and timing of the
exercise influences this; we have shown that exercise 24 hours before a dive reduces bubble
formation in man (Duijc etl al J Physiol 2004;15:637-42) and that exercise shortly before
decompression promotes bubble formation. We have also shown that blocking NO production
will promote bubble production (Wisloff et al J Physiol 2003;15:577-82). Hypoxia reduces nitric
oxide (NO) production and high altitude pulmonary edema is linked to a reduction in NOS
activity. Some symptoms observed could be explained by bubble formation. Bubble growth is
slow if the pressure gradients are small; we have shown that bubbles reduce endothelial function
with a time lag of hours (Nossum et al Eur J Appl Physiol 2003;89:243-48). Bubbles lead to
extravasation of fluids and inflammatory changes. Dry cough on exertion is a symptom that is
related to bubble formation. If bubble formation is involved in the development of acute
mountain sickness, this could have implications both for prophylaxis and treatment of the disease.
Altitude decompression procedures will have to be reevaluated if bubble growth already has
occurred on ascent..
13.
LIVING HIGH-TRAINING LOW: EFFECT ON RED CELL MASS AND AEROBIC
PERFORMANCE IN ELITE MIDDLE-DISTANCE RUNNERS. Julien V BRUGNIAUX
1
, Paul
ROBACH
2
, Laurent SCHMITT
3
, Gérard NICOLET
3
, Jean-Pierre FOUILLOT
1
, Niels V OLSEN
4
,
Jean-Paul RICHALET
1
. EA
23
6
3
, ARPE, Université Paris
13
, Bobigny, France
1
, ENSA, Chamonix,
France
2
, CNSN, ID Jacobeys, Prémanon, France
3
, Department of Pharmacology, The Panum
Institute, University of Copenhagen, Copenhagen, Denmark
4
.
This study verified whether the "living high-training low" method improves red cell mass
and/or aerobic performance and if this increase persists 15 days after the training session. Twelve
male athletes performed a 18-day stage of living hightraining low at 1100m, by sleeping either
in ambient air (CON, n=6) or in hypoxic rooms (HYP, n=6, with 3 nights at 2500m and 15 nights
at 3000m, mean daily exposure = 14h/24h). The measurements (performed at 1100m, before
(PRE), during (H3000, i.e. after the 2nd night at 3000m), and 1 (POST1) and 15 days (POST2)
after training) were VO2max (treadmill), submaximal test (10-min run at 19.5 km/h), red cell
volume (RCV), and hemoglobin (Hb) and hematocrit (Hct) concentrations. VO2max increased
from PRE to POST1 in HYP (+9%, P<0.05) but not in CON (+4%) and tended to remain higher
at POST2 for HYP (5.8%, P=0.08). Heart rate (HR) during submaximal test progressively
decreased for HYP (-2.2% at POST1 and 3.3%, P<0.05 at POST2) whereas HR remained
unchanged in CON. Training did not significantly modify Hb and Hct in either group. RCV
tended to increase from PRE to POST1 (+ 5.1%) for HYP. The present study indicates that 18
days of living high training low induced a net increase of 5% in aerobic performance, which
tended to persist 15 days after the end of training. Erythropoiesis was only slightly stimulated by
hypoxia. The present data therefore suggest that, besides hematological changes, living high-
training low may also enhance aerobic performance through other processes. This study was
supported by grants from the International Olympic Committee and the French Ministry of
Sports.
