PATRICK CONWAY, MS, EMT, FF-1, CSCS,*D
SAUNA SUITS AND WEIGHT LOSS
A common problem faced by the military is that many soldiers
are required to meet specific bodyweight requirements as part of
their physical and fitness standards. Unlike civilian counterparts,
the inability to make bodyweight standards for soldiers can lead
to disciplinary action such as reductions in rank or even discharge
from the service. Due to these adverse actions, many different
tactics are used by soldiers to help maintain or lower bodyweight.
While some soldiers will increase their exercise and watch their
diet, others may try fad diets or equipment touted to help people
lose weight quickly.
One such approach to facilitate rapid weight loss is the wearing
of outfits designed to make the soldier sweat excessively. Many
soldiers do not see the act of losing large amounts of water weight
quickly or raising internal body temperature to high levels as
risky. A possible reason for this misconception may be due to the
approach taken by the companies selling these devices who claim
their products are “therapeutic,” “healthy,” and “help you safely
lose weight fast.” Before donning a sauna suit and putting the
body through the risks that come with these approaches, it would
be useful to take a look at how the body cools itself and what
happens when substantial amounts of water and minerals are lost.
Four external mechanisms that can affect body temperature are
radiation, conduction, convection, and evaporation. Radiation is
the transfer of heat between objects through electromagnetic
waves with the hotter object passing heat to the cooler object.
An example of radiation would be the heat transferred from a
hot road to an individual. Temperature can also be influenced by
conduction, which is when an outside substance transfers heat
during physical contact of the objects. Water provides a good
example as cold water draws heat away from the body while hot
water transfers heat to the body. Convection is defined as the
transfer of heat from one place to another by the motion of a
heated substance and can be explained by wind blowing across
an object to cool or heat it up depending on the temperature of
the wind. Evaporation occurs when water, which is cooler than the
object it is in contact with, draws heat away from the object. When
the water gains enough heat it is converted from a liquid to a gas.
The human body uses different ways to regulate internal
temperature for heat buildup. Circulation and respiration provide
two examples. As the internal temperature of the body increases,
circulating blood is shunted outward to superficial blood vessels.
Considering this, during exercise the primary means of heat
loss is through evaporation, whereby internal water is excreted
through millions of sweat glands located in the skin. By sweating
water to the surface of the skin, evaporation can occur which
will bring temperature down through evaporation. Respiration
provides another means of heat transfer through evaporation by
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dispelling heated air when breathing out. When all of these ways
are combined, the human body can be efficient at reducing rising
internal heat (11).
By controlling heat through circulation, and respiration, humans
are able to sustain high levels of physical activity for long
durations. Other mammals can only perform short bursts of heavy
physical activity before resting because they primarily reduce heat
through respiration alone. Humans discovered long ago that if they
kept chasing animals that were much faster at a steady pace, the
long distance would not allow the animals to rest enough to cool
off though panting alone. Eventually the animal would develop
heat exhaustion and be unable to continue running. Once heat
exhaustion occurred, the human was then able to catch the faster
animal. This begs the question: why wear a suit that is designed to
stop one of our greatest assets during physical performance?
Research has shown that uniforms worn by football players (e.g.,
football pads, a helmet, jersey uniform, and a tee-shirt) can greatly
influence core temperatures as they block the surface area used
to dissipate internal heat (2,12). Because deaths from overheating
have occurred to football players, many modifications have been
made to make their uniforms as porous as possible in order to help
reduce this hazard (2,12). While these studies used football players
as examples, the same dangers of overheating could be applied to
tactical athletes wearing outfits, such as body armor or protective
vests, which are specifically designed not to let any air in or out
(3,4).
It is estimated that most people lose 1 – 2 L of water in sweat in
one hour of heavy exercise (about 2% of bodyweight), but the
body can only absorb 1 L an hour of water consumed (8,11). So,
to wear gear which forces the body to sweat even more water
than normal is a recipe for disaster as an individual cannot
ingest sufficient water to replace what is lost in such a scenario.
Furthermore, as water is excreted sodium, chloride, potassium,
and magnesium, are also lost. These minerals are needed to
ensure the muscles work properly. As the body overheats and
loses water, it also loses sodium and potassium which can result
in hypernatremia whereby muscles begin to fail. It is worth
reiterating the fact that the human heart is a muscle. With water
weight losses of 4 – 5% of bodyweight, significant impairment of
physical and psychological functions can lead to heart palpitations
or worse (1,9,15).
For each 1 L of fluid lost the heart will increase its beats by
approximately 8 beats per min, but in the process it will lose 1 L of
cardiac output (oxygen getting to tissue) (11). In other words, as
water is lost, the heart tries to work harder by beating faster while
it loses its ability to transport oxygenated blood to the tissue.
As mentioned above, 1 – 2 L is a normal loss of fluid for an hour
NSCA’S TSAC REPORT | ISSUE 32