Changes in Muscle Tension During Stretching
Tension in a muscle decreases as the stretch is held. Note that the majority of the decrease occurs in the first 15 seconds. Note also that muscle tension is reduced with subsequent stretching. This is why stretches should be held for 15-30 seconds and why multiple sets are recommended.
This slide provides graphic representations of the typical responses to a stretched muscle. Muscle tension decreases as the stretch is held but the majority of the decrease occurs in the first 15-30 seconds.
Source: Knudsen, D. (1998). Stretching: From Science to Practice. JOPERD, 69(3), 38-42