The sliding filament theory

What is the sliding filament theory?

Muscle contraction is explained by the sliding filament theory...

• This is where myosin and actin filaments slide over one another to make the sarcomeres contract - the myofilaments themselves don't contract.
• The simultaneous contraction of lots of sarcomeres means the myofibrils and muscle fibres contract.
• During contraction, the sarcomere gets shorter as the Z-lines get closer together. The I-band and H-zones get shorter, where as the A-band stays the same length. 
• Sarcomeres return to their original length as the muscle relaxes.