When
your muscle fibres contract, they get their energy for the process by splitting an organic compound called adenosine triphosphate (ATP).
As more
muscle fibres contract, your strength increases.
Not exact matches
You can't see it, but when you hold a plank or other isometric pose,
muscle fibres are pulled from both ends of the
contracting muscle — not just one section — meaning your body recruits more
muscle fibres than if you were changing the joint angle.
This causes the two main protein molecules (Aktin und Myosin) inside the
muscle fibres to move relative to each other resulting in shortening (
contracting) and lengthening (relaxing)
muscle movement.