Ė A HEARTY ISSUE
exercise, the heart muscle improves in at least three ways. The
muscle itself grows thicker and stronger much the way skeletal
muscles are changed by weight lifting. Secondly, the size of the
chamber (or ventricle) inside the heart enlarges so that more
blood is pumped with each heartbeat. In the past, some physicians
made the error of diagnosing as pathological the heart enlarged
by exercise Ė confusing it with enlargement due to heart failure.
The third improvement involves the capillaries that feed the heart
muscle its own supply of blood. With increased aerobic exercise,
existing capillaries that branch off the heartís coronary arteries
dilate Ė allowing blood to pass through heart muscles more freely
so that remote areas of the heart receive blood more easily. Itís
as if small towns and villages suddenly had more roads coming
to them from other towns. It isnít the size of the roads (or capillaries)
thatís significant; itís the number because they provide alternate
routes. Applied to villages, we might call this phenomenon encroaching
civilization; in our heart we call it increased vascularity decreasing
the possibility of heart attack and speeding recovery if you do
of heart attack during exercise is so rare that when one does
occur it hits the newspapers. In contrast, the number of heart
attacks in sedentary individuals is so common as to be a national
disgrace. It becomes obvious that a sedentary life is far more
dangerous than an athletic life. To insist on a stress elector-cardiogram
before undertaking an exercise program misses the point. Instead,
perhaps we should take stress elector-cardiograms if we plan not
to exercise because we know that if we are not in perfect physical
condition a sedentary lifestyle will kill us.
also increases the number of capillaries in the muscles so that
oxygen and fuel are delivered more easily to the individual muscle
cells which in turn decreases the work load of the heart and lungs.
Most people feel that their lungs are what limit them when they
run. It is a natural reaction to blame your lungs when your chest
is heaving during a run but the lungs are only trying to compensate
for poor oxygen uptake in the muscles. Oxygen rich blood is red
when it enters the muscles. As the blood passes through the muscles,
oxygen is removed so that the blood is blue when it flows into
the veins. Increased vascularity of fit muscles brings more muscle
cells into contact with capillaries allowing for rapid oxygen
absorption. In other words, it isnít necessary for oxygen to profuse
among cells to reach remote cells.
in capillaries in the body as the result of aerobic exercise has
far reaching effects:
- The heart
doesnít have to work as hard during exercise.
- The lungs
donít puff so hard.
- Every individual
muscle cell is more likely to get immediate oxygen when needed.