It is a well-known fact that smoking reduces fitness. It does this
in a number of ways, chiefly by reducing the amount of oxygen
available in the body. Since oxygen plays a major role in energy
production, even a minor depletion has an impact on physical
performance.
MAJOR EFFECTS OF SMOKING ON FITNESS
David Pyne, an Australian sports physiologist, lists the major
effects of smoking on the body's respiratory and circulatory system as
follows:
- High levels of carbon monoxide from smoking reduce the amount of
oxygen absorbed into the blood from the lungs.
- Carbon monoxide in the blood also reduces the amount of oxygen
that is released from the blood into the muscles.
- Smoke inhalation has an immediate effect on respiration,
increasing airways resistance and therefore reducing the amount of
oxygen absorbed into the blood.
- Smoking causes chronic (or long-term) swelling of mucous
membranes, which also leads to increased airways resistance.
- Smoking increases the heart rate for a given level of exercise.
CARBON MONOXIDE - THE MAIN OFFENDER
Carbon monoxide, the same lethal gas which is released by motor
vehicle exhausts, is present in cigarette smoke and is absorbed
rapidly into the bloodstream. The mechanisms by which it does this are
as follows:
- Once it leaves the lungs, oxygen is transported in the blood by
attaching to the haemoglobin within red blood cells. Oxygen has a
great affinity for haemoglobin. However, carbon monoxide has a much
greater affinity (200 to 300 times greater than oxygen) and so binds
preferentially to haemoglobin.
- Therefore, as the level of carbon monoxide in the blood
increases, the level of oxygen decreases.
- Raised levels of carbon monoxide in the blood also impair the
release of oxygen from the blood into the cells. This has a
significant effect on heart and other muscle cells where there is a
high demand for oxygen.
- Blood levels of carbon monoxide from smoking can also produce
distortions of time perception, psychomotor and visual impairment
and negative effects on cognitive skill.
- Oxygen is important for the functioning of all energy systems in
the body, so any mechanism which interferes with oxygen transport
and uptake interferes with energy production and therefore sports
performance.
AIRWAYS RESISTANCE
Inhaling cigarette smoke results in airways resistance (narrowing
of air passages) in a number of ways:
- Inhalation of smoke from a cigarette can, within seconds, cause
a two to three-fold increase in airways resistance, the rate at
which air moves in and out of the lungs.
- Smoking also causes chronic swelling of the mucous membranes of
the airways, which adds to airways resistance.
- When demand for oxygen is elevated, such as during exercise,
this increased resistance is more noticeable. Reduced lung capacity
can cause a smaller volume of oxygen to reach the alveoli, resulting
in impaired gas exchange and less oxygen in the blood.
- The tar in cigarette smoke adds to airways resistance. This tar
coats the lungs, reducing the elasticity of the air sacs and
resulting in the absorption of less oxygen into the bloodstream.
- Tar also affects the cleansing mechanism of the lungs, allowing
pollutants to remain in the bronchial tubes and lungs. Increased
phlegm and coughing, and damage to the cilia (the hair-like
projections which "sweep" pollutants out of the airways) are the
result.
EFFECTS ON THE HEART
The combined effect of carbon monoxide and increased airways
resistance is to cause the heart to work harder in an attempt to
compensate for the lack of oxygen reaching the muscles.
The nicotine in cigarette smoke also acts as a stimulant,
increasing the heart rate and blood pressure, and decreasing the flow
of blood through the blood vessels.
EFFECTS ON ENDURANCE
Smoking reduces physical endurance and impedes the improvement in
physical performance in smokers compared with non-smokers. It also
increases fatigue during and after exercise. David Pyne noted the
following:
- While exercise training can increase maximal oxygen uptake by up
to 20%, smoking can reduce this effect by up to 10%.
- In a recent study adolescents who had smoked for five days had
an 8% reduction in endurance time compared to controls.
- Individuals who smoke are less likely to continue in exercise
programs.
- A US study of more than 3,000 naval personnel found smoking was
detrimental to physical fitness even among relatively young, fit
individuals. The study also found smokers have lower physical
endurance than non or ex-smokers.
- The same study found those who smoked undertook less physical
exercise sessions each week than non or ex-smokers. They also
exercised less time per session.
- An earlier US study found that smokers had higher levels of
fatigue during both exercise and recovery. The authors believed this
increased fatigue may explain why smokers are less likely to
participate in regular exercise.
PASSIVE SMOKING
Exposure to environmental tobacco smoke either before or during an
event also impairs athletic performance.
