ABC of Stretching - The basics
Stretching is an eccentric contraction (Lengthening) of a muscle(s) that is performed/achieved by reversing the action of that particular muscle(s). There are different types of streching and there is a necessity to hold each stretch for an prescribed timline to achieve the maximum benefit out of it especially if it is a static stretch (later expalined).
Image Courtesy: Harish Uthaman
Science behind the Stretch
The Basic Science behind the streching is