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Thus, it is clear that a person has the capability of extreme power surges for short periods of time, such as during a 100-meter dash that is completed entirely within 10 seconds, whereas for long-term endurance events, the power output of the muscles is only one fourth as great as during the initial power surge.

This does not mean that one's athletic performance is four times as great during the initial power surge as it

Adenosine Triphosphate. The source of energy actually used to cause muscle contraction is adenosine triphos-phate (ATP), which has the following basic formula:

The bonds attaching the last two phosphate radicals to the molecule, designated by the symbol are high-energy phosphate bonds. Each of these bonds stores 7300 calories of energy per mole of ATP under standard conditions (and even slightly more than this under the physical conditions in the body, which is discussed in detail in Chapter 67). Therefore, when one phosphate radical is removed, more than 7300 calories of energy are released to energize the muscle contractile process. Then, when the second phosphate radical is removed,

Figure 84-1

Important metabolic systems that supply energy for muscle contraction.

I. Phosphocreatine

Creatine + PO.

. Glycogen

Lactic acid

. Glucose J

Amino acids J +


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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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