What type of stretching involves an external force to lengthen a muscle?

What type of stretching involves an external force to lengthen a muscle? Passive stretching does.

In passive stretching, the target muscle stays relaxed while a partner, strap, towel, machine, gravity, or another body part supplies the force. A lying hamstring stretch assisted by a strap is a familiar example. The external assistance can move a joint farther than the person could reach using voluntary muscle action alone.

A common mix-up is treating “passive” and “static” as opposites of the same classification. They describe different features: passive refers to where the force comes from, while static means the position is held rather than moved through repeated motion. A stretch can therefore be static-passive. Dynamic stretching generally uses controlled movement, and ballistic stretching adds bouncing or swinging momentum.

PNF stretching can combine passive positioning with an isometric contraction, so it is more complex than ordinary relaxed passive stretching. Passive work is useful in flexibility training and rehabilitation, but excessive force can strain muscle-tendon tissue or irritate a joint.