Have you decided that the time has finally come to make fitness a priority in your life? No more excuses. No more putting it off for another day. Because you
know doing so will only lead to further procrastination. And the truth is... once you start on an exercise
kick, you will actually begin to feel so much better that you'll wonder why on earth you put it off so long in
the first place.
When you exercise or
compete in sports, you notice several things about your body. You breathe heavier and faster, your heart
beats faster, your muscles hurt and you sweat. These are all normal responses to exercise whether you work
out regularly or only once in a while or whether you are a "weekend warrior" or a trained athlete. When you
watch world-class athletes compete, you see the same responses, only magnified.
The body has an incredibly complex set of processes to meet the demands of working
muscles. Every system in the body is involved. On this site, we will look at how your body responds to strenuous
exercise -- how muscles, blood circulation, breathing and body heat are affected. You will also see how these
responses can be enhanced by training.
Whether you are a novice or already have some experience, this site will offer you
a wealth of information on the various options available to you now that you have decided to...
Put Fitness First!
Physical exercise is activity performed in
order to develop or maintain physical fitness and overall health. Frequent and regular exercise is an
important component in the prevention of some of the diseases of affluence such as cancer, heart disease,
diabetes and obesity.
generally grouped into three types depending on the overall effect they have on the human
Flexibility exercises such as stretching improve the range of motion of muscles and
exercises such as walking and running focus on increasing cardiovascular
exercises such as weightlifting increase short-term muscle strength.
Exercise can be an important part of physical
therapy, weight loss or sports performance.
Exercise can be
fun, but be sure to do what you like and eat enough calories, so when you do exercise you are building up muscles,
not breaking them down for fuel. Carbohydrates are muscle-sparing; and if you don't get enough calories overall,
you burn muscles up with the fat to make up the deficit.
Common Fitness Myths
Many common myths
have arisen surrounding exercise, some of which have a basis in reality, and some which are completely
No Pain No Gain.
This is generally
false. Depending upon the type of exercise you are engaged in and the underlying cause of the pain, actual pain, as
opposed to discomfort, is generally a sign that you are causing more harm than good (eg tearing a muscle). It is
common to experience sore muscles the day after a workout following the start of an exercise program. This is due
many microscopic 'micro-tears' in the muscle and possibly metabolite build-up, and is known either as Post Exercise
Muscle Stiffness or Delayed Onset Muscle Soreness (DOMS).
You should NOT
feel pain during or immediately after a workout. Pain at these times can indicate a serious condition that requires
immediate medical attention. It is uncommon to experience pain the next day after you have been engaged in a
program for a month or more. If this is the case you should seek medical advice.
Only overweight people need a physical before beginning an
Absolutely false. Only a physician can determine your ability to engage in an exercise program.
Apparently healthy people can still have unknown medical conditions, such as a heart murmur, that can cause severe
injury or death not only to themselves, but also to others that are dependent upon them, such as someone they are
Your Body's Response to Exercise
Any type of exercise uses your muscles. Running, swimming,
weightlifting -- any sport you can imagine -- uses different muscle groups to generate motion. In running and
swimming, your muscles are working to accelerate your body and keep it moving. In weightlifting, your muscles are
working to move a weight. Exercise means muscle activity!
As you use your muscles, they begin to make demands on the rest of the body. In
strenuous exercise, just about every system in your body either focuses its efforts on helping the muscles do their
work, or it shuts down. For example, your heart beats faster during strenuous exercise so that it can pump more
blood to the muscles, and your stomach shuts down during strenuous exercise so that it does not waste energy that
the muscles can use.
When you exercise, your muscles act something like electric motors. Your muscles
take in a source of energy and they use it to generate force. An electric motor uses electricity to supply its
energy. Your muscles are biochemical motors, and they use a chemical called adenosine triphosphate (ATP) for their
energy source. During the process of "burning" ATP, your muscles need three things:
- They need oxygen, because chemical reactions require ATP and oxygen is
consumed to produce ATP.
- They need to eliminate metabolic wastes (carbon dioxide, lactic acid) that
the chemical reactions generate.
- They need to get rid of heat. Just like an electric motor, a working muscle
generates heat that it needs to get rid of.
In order to continue exercising, your muscles must continuously make ATP. To make
this happen, your body must supply oxygen to the muscles and eliminate the waste products and heat. The more
strenuous the exercise, the greater the demands of working muscle. If these needs are not met, then exercise will
cease -- that is, you become exhausted and you won't be able to keep going.
To meet the needs of working muscle, the body has an orchestrated response
involving the heart, blood vessels, nervous system, lungs, liver and skin. It really is an amazing
Let's examine each need and how it is met by the various systems of the
ATP is Energy!
For your muscles -- in fact, for every cell in your body -- the
source of energy that keeps everything going is called ATP. Adenosine
triphosphate (ATP) is the biochemical way to store and use
The entire reaction that turns ATP into energy is a bit complicated, but here is a
- Chemically, ATP is an adenine nucleotide bound to three
- There is a lot of energy stored in the bond between the second and third
phosphate groups that can be used to fuel chemical reactions.
- When a cell needs energy, it breaks this bond to
form adenosine diphosphate (ADP) and a free phosphate molecule.
- In some instances, the second phosphate group can also be broken to
form adenosine monophosphate (AMP).
- When the cell has excess energy, it stores this energy by forming ATP from
ADP and phosphate.
ATP is required for the biochemical reactions involved in any muscle contraction.
As the work of the muscle increases, more and more ATP gets consumed and must be replaced in order for the muscle
to keep moving.
Because ATP is so important, the body has several different systems to create ATP.
These systems work together in phases. The interesting thing is that different forms of exercise use different
systems, so a sprinter is getting ATP in a completely different way from a marathon runner!
ATP comes from three different biochemical systems in the muscle, in this
- phosphagen system
- glycogen-lactic acid system
- aerobic respiration
On the next
page we will examine each one of these ATP/energy creation systems in