Physiological Effects of Stretching

Stretching:

- Lengthens the sarcomeres

As a muscle stretches, the actin-myosin overlap decreases (increasing the overall sarcomere length) allowing the muscle fibre to elongate.

- Stretches the collagen within the tendons (via plastic deformation)

Once the fibre has reached it maximum length, additional stretching places force on the surrounding connective tissue. As the tension increases, collagen fibres align themselves along the same line of force as the tension (helps realign any disorganised fibres in the direction of the tension). The realignment is what helps to rehabilitate scarred tissue back to their previous length.

- Can help to train the stretch reflex (muscle spindles)

Muscle spindles are sensorimotor organs located within skeletal muscle. Each muscle spindle is made up of three to five specialized muscle cells known as intrafusal fibres. These cells, bundled together by a sheath of connective tissue, lay alongside the rest of the skeletal muscle fibres. When intrafusal fibres detect a change in muscle length, they reflexively stimulate a muscle contraction to prevent over-stretching and muscle fibre damage (stretch reflex).

It is important to hold a stretch for prolonged period of time because as you hold the muscle in a stretched position, the muscle spindle habituates (becomes accustomed to the new length) and reduces its signaling.