How does a muscle shorten during its contraction and return to its original form during relaxation ?

How does the muscle shorten during its contraction and lengthen during its relaxation?

Answer the following briefly : (a) How does the muscle shorten during its contraction and lengthen during its relaxation ? (b) What biological functions are served by the skeletal system ? (c ) What type of muscles will be antagonistic to pronators and abductors respectively, and why ? (d) Why a red muscle fibre can work for a prolonged period while a white muscle fibre suffers from fatigue after a shorter work? (e ) Where from the muscle gets energy for its contraction ?

During muscle contraction

During muscle contraction

During muscle contraction