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go2altitude Newsletter: BLOOD TESTING AT
ALTITUDE
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NUTRITION AT ALTITUDE
Many climbers undergo
bloods to measure certain altitude-related parameters
within the body to assess how well the body is
adapting. The most commonly assessed parametres
includes:
FBC ...
(or Full Blood Count) which is a measure that includes
just about everything. However in particular the most
significant indicators tend to be red blood cell
counts, hematocrit and hemoglobin.
Red blood cells (RBC)
- It is these cells that carry oxygen and make up
between 35-50% of the total blood volume. To some
extent the more red blood cells you have, the greater
the body's ability to deliver oxygen to working
muscles. Altitude exposure increases red blood cell,
which in turn leads to a greater availability of
oxygen to working muscles allowing the athlete to work
harder (i.e. Go faster for longer).
Hematocrit (or [Hct])
- Is an expression of red cell volume as a percentage
of the total blood volume. In a normal adult it tends
to be between 40 to 45%. An optimum hematocrit is a
balance between maximising oxygen carrying capacity
and how thick (or viscose) the blood becomes - making
it harder and harder for the heart to pump. When Hct
increases above 50% there is an exponential rise in
this viscosity. With endurance training, however,
there is a decrease in viscosity (because the plasma
volume expands - which is the solution in which the
RBC float), as well as increase in the pliability of
the RBC, making the blood more fluid. Hct do become
dangerous 55% or above. It should be noted if you can
elevate your Hct by 25% (from say 40 to 50%) you'll be
making any additional 25% more oxygen available to
your working muscles. Short of cheating by injecting
an illicit substance, altitude simulation can help you
to achieve this.
Hemoglobin (or Hb) -
Is the protein that binds and carries oxygen on the
RBC. At high oxygen concentrations (in the lungs) Hb
binds oxygen. It then travels (to areas of low oxygen
concentrations (e.g. Working muscle cells) where the
Hb releases the oxygen. As a consequence of altitude,
the resultant greater circulating Hb increases the
oxygen-carrying capacity of the blood.
EPO...is a hormone
that regulates the growth and development of RBC and
Hb from stem cells of long bones. Measuring EPO
concentrations in the blood can be used to determine
the potential of the body to increase RBC production
and hence improve oxygen delivery to the tissues.
Within hours of
altitude exposure, EPO concentrations increase
significantly by as much as 40% hitting maximum levels
within 72 hours. The higher the altitude the greater
the EPO response. If the athlete stays at altitude
this response levels out within a week, but stays
elevated relative to sea-level conditions.
FERRITIN ... (or
Serum Ferritin) is a common indicator of iron stores,
which in turn are an indicator of Hb production. A low
ferritin can be indicative of iron deficiency - not an
uncommon occurrence for athletes traveling to altitude
for the first time and not being aware of the
increases in RBC production and hence the potential
for iron depletion which eventually results in
over-training syndromes, a lowering of athletic
performance and illness.
There are various
papers that indicated iron supplementation may be
beneficial to athletes training at altitude. However
iron supplementation should not be undertaken without
first consulting with a knowledgeable physician in the
area and discussing your intentions. If the doctor
agrees that you have a greater need for iron it is
suggested you start taking 200-300mg of iron/day 3-12
weeks before undertaking altitude exposure. Remember,
excess iron intake is toxic and in extreme cases
lethal - so take care.
NUTRITION AT ALTITUDE
To perform at your
best you have to be optimally fueled. At altitude this
becomes even more important because of the additional
physiological stress the body is placed under compared
to sea-level dwelling. When exposed to altitude, many
athletes actually have a lowered appetite as their
basal metabolic rate increases. This lowered
inclination to eat coupled with a higher energy output
can cause all sorts of micro-nutrient deficiencies as
well as significant weight loss. The greater the
different between energy intake and energy output the
more likely these problems become.
Dehydration is
another problem associated with actual and simulated
altitude. Since the relative humidity at altitude is
lower than at sea-level, the air that you ventilate
draws moisture out of the body (via the respiratory
tract). Given that you are initially breathing harder,
deeper and regularly at altitude the body loses vital
fluids even more rapidly. It is therefore important
that athletes consume considerably more fluid (ideally
water) than they otherwise would at sea level.
In relation to
specific dietary changes, there is no specific diet
that athletes should be prescribed when training at
altitude. There are however some useful guidelines to
consider.
Eat a wide variety of
foods early and often. Monitor your body weight and
try to maintain energy balance. Increase your
carbohydrate (and possibly protein) intakes. Diets
need to be tailored to individual athletes, however an
increase in carbohydrate and protein is pretty much
standard and for those athletes struggling to maintain
energy balance fat can be added back into the diet if
a stable body weight cannot be maintained. Drink early
and often. At altitude your fluid requirements may
exceed 5 liters per day. Using sports drinks can help
provide fluid as well as extra carbohydrate. Even
though there is some dispute over the necessity of
vitamin/mineral intake at altitude, there is certainly
no harm in adding a daily multi-vitamin/mineral
supplement to the diet to ensure adequate intakes of
these micro-nutrients. For example, a drop of as
little as 10% in Hb concentrations (due to inadequate
iron intake) can lower performance by a staggering
20-25%. So stay on top of your dietary practices when
traveling to altitude or using any altitude simulation
equipment - remember altitude is a physiological
stressor and your body is going to need all the
appropriate nutrition to deal with that.
References:
1. Ruud J, Lickteig
JA. The Height of Good Nutrition. Today's Dietician.
2002, 28-31.
2. Berglund, Bo. High-altitude training-aspects of
haemotological adaptation. Sports Medicine. 1992;
14(5):189-303.
3. Puranen AS, Rusko HK. On- and Off-response of EPO,
reticulocytes, 2,3-DPG, and plasma volume to living
high, training low. Medicine and Science in Sports and
Exercise. 1996;28:s159.
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