14 Overview of Physical Fitness
Figure 1-4. An Example for Determining Your Target
Training Heart Rate for SwimmingEnergy Systems Used by Exercising Muscle
Before describing the methods used for physical training, it is important to
understand the three systems that provide energy to the exercising muscle. All three
systems are important. Depending on the activity, there may be a greater reliance on one
system over the others.ATP-CP System for Speed Work
Adenosine triphosphate (ATP) is the immediate source of energy within all cells of
our body for activities such as sprinting. There are small stores of ATP within skeletal
muscle, and these energy stores provide immediate energy to sustain physical activities for
a short time. Once the ATP is used, it breaks down into adenosine diphosphate (ADP). For
regeneration of ADP into ATP for more energy, creatine phosphate (CP) is needed. It is the
CP that regenerates the ATP. Without CP, ATP could provide energy for only a few
seconds. With CP, the ATP-PC system can provide energy for about 30 seconds before
other energy systems must take over. Thus, this ATP-CP system, sometimes referred to as
the phosphate pool or reservoir, provides immediate anaerobic energy for muscle
contraction.A 22 year old SEAL wants to swim at 70% of Max HR
Then his Max HR = 220 - 22 = 198 -13 = 185 bpm
70% of Max HR = 0.7 X 185 = 130 bpm
ATP ADP + Phosphate + Energy
ADP + CP ATP + Creatine