58

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2 Movement

Figure 2.2: The myosin head walks along the actin fiber, acting as a lever and thus creating the force in

muscle contraction (adapted from [5]).

muscle fibers get shorter. After that, the energy of the myosin head is spent. It will be

immediately recharged while the muscle is at rest.

What kind of energy are we talking about? In the body, energy comes from oxidiz-

ing the food molecules, sugar (glucose) and fat (Figure 1.31). Usually, oxidizing chemicals

results in heat (a fire is a rapid oxidation that can be prevented by blocking access to oxy-

gen). In the body oxidation results in specific controlled chemical reactions that generate

reducing agents (nicotinamide adenine dinucleotide, NADH) (Figure 1.30) and adenosine

triphosphate (ATP) (Figure 1.29) for future reactions. So essentially, NADH and ATP are