EXERCISE ECG
E
of the cardiovascular and respiratory
systems;
some
forms improve
flexi-
bility; some increase muscular strength;
and some improve physical endurance.
During
aerobic
exercise,
such
as
jogging or swimming, the heart and
lungs work faster and more efficiently
to meet the muscles’ increased demand
for oxygen. Regular aerobic exercise
improves the condition of both the
cardiovascular and respiratory systems.
Exercises
such
as
weight
training
increase muscle strength and endurance.
Activities
such
as
yoga
and
pilates
improve flexibility For further informa-
tion on the effects of exercise, see the
illustrated box below.
BENEFITS OF EXERCISE
There is an association between high
levels of aerobic exercise and a low inci-
dence of
coronary artery disease
.
Regular
aerobic exercise usually leads to reduced
blood pressure. It also increases levels of
high density lipoprotein
(HDL)
in the
blood, w hich is thought to help protect
against
atherosclerosis
(the accumulation
of fatty deposits on artery walls) and
myocardial infarction
(heart attack).
Exercise can help to relieve the symp-
toms of
peripheral vascular disease
as
well as
of some
psychological
dis-
orders, particularly
depression
.
Regular
weight-bearing exercise (such as run-
ning) increases bone density, making
the bones stronger; hence
osteoporosis
is
less common in people who have exer-
cised throughout their adult lives. Such
exercise also increases muscle mass and
strengthens the muscles and ligaments.
It can therefore help to prevent or ease
lower back pain and can make the liga-
ments less susceptible to strains.
THE EFFECTS OF EXERCISE
Exercise produces many changes
in different body organs. Muscles
receive an increased blood flow
because of their greater energy
requirements, and the heart
and lungs work faster and more
efficiently to keep the body
tissues well supplied with blood.
These changes are controlled
by the release of the chemicals
adrenaline and noradrenaline from
the sympathetic nervous system.
The lungs
The rate and depth of breathing
increase to ensure a sufficient
flow of oxygen from the lungs
into the blood. This increase in
breathing also helps to remove
additional carbon dioxide
produced bythe muscle cells
during exercise.
Bones
Regular exercise helps to maintain the
strength and density of the bones and
so prevents or slows the development
ofthe bone disease osteoporosis.
The muscles
As the muscles flex and relax,
there is a rise in the chemical
activity within muscle cells. The
rate at which the cells consume
oxygen and glucose increases.
R e l a x e d m u s c l e
ECG printout showing heart
rate at rest
Heart rate during exercise
The heart and
circulation
The heart beats
faster and more
powerfully to
increase the blood
flow to the working
muscles. Blood
vessels in the
intestines, liver,
stomach, and
kidneys narrow so
that more blood is
directed away from
these areas and to
the muscles.
COMMON TYPES OF EXERCISE
Aerobic
Isometric
^
Isotonic
Isokinetic
Aerobic exercise is activityin
which the body continuously
needs to take in additional
oxygen to meetthe muscles’
increased demands. Regular
aerobic exercise improves
the performance ofthe
cardiovascular and respiratory
systems. Jogging, swimming,
and cycling are examples of
aerobic exercise.
Isometric exercise is exercise
without movement, in which
one group of muscles exerts
steady pressure against either
an immovable object or an
opposing group of muscles.
It is an effective means of
increasing muscle strength,
but does not exercise the
cardiovascular system or help
in muscular endurance.
Isotonic exercise is exercise with
movement, in which muscle
tension is more or less constant
and the bodyworks against its
own weight or external weights.
Isotonic exercise includes weight
training and calisthenics
(repetitious movementswith little
or no equipment). It increases
muscle strength, size, and
endurance.
Isokinetic exercise involves
both isotonic and isometric
exercise. The muscles move
reasonably heavy loads, but
are also put through their
full range of movement.
Isokinetics combines strength
training with some aerobic
exercise, but requires
specialist equipment.
286
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