Sliding filament theory shows a reasonable explanation on how the muscles produce force and eventually show physical manifestation such as muscle contraction and relaxation. This shows the cycle of the steps that causes the filament to produce force within the muscle fibers.
The force that was created is due to the complex biochemical reaction of combination of actin, myosin and ATP (adenosine triphosphate) in order to produce energy (or force), ADP (adenosine diphosphate) and an inorganic phosphate. These are the general steps in the theory:
1. The muscle action potential is generated due to the release of calcium ions to the sarcoplasm
2. The released calcium ions bind to troponin (a regulatory protein) that allows the binding site to be exposed to the myosin head.
3. Myosin binds with actin which forms the cross bridge. Consequently, ATP is split into ADP and an inorganic phosphate.
4. The myosin pivots and bends thus making the power stroke.
5. As the new ATP enters, the cross bridge is disconnected to the actin and relaxation occurs.