2. When a swimmer first pushes off the
wall or dives into the pool to
commence their race/laps they will
be using what’s called the ATP-PC
system which lasts for about 10
seconds at maximal intensity
exercise. After this initial bout of
energy expenditure they will
continue to use the ATP-PC system
for the next few strokes and then the
Lactic Acid system will take over.

3. Now that the Lactic Acid system or
the Anaerobic Glycolysis system has
taken over, the swimmer continues
to be able to push through the
exercise for around the next 30
seconds to a minute depending on
how high the intensity is, after this
time frame the Lactic Acid system
will have also been used until it gets
replenished. The aerobic system
then takes over as the dominate
energy source.

4. The aerobic system never really
fully takes over as the swimmer
is under water for most of the
exercise and only comes up for a
quick breath not very often.
While the other systems have
been exhausted this system is
still able to pick up some of the
slack through these small
breaths, this limited amount of
oxygen will usually suffice for
the duration of the exercise until
recovery can take place.

5. For both preparation and the
recovery the aerobic system
would be major source of
energy.

6. The replenishing of the ATP-PC system takes on
average 2-3 day to completely recover after
being completely used up. The Lactic Acid
system takes about a hour to a day to fully
recover, the aerobic system takes around 10
minutes to fully replenish itself.