What Physical Therapists Say About How Stretching Changes Muscles

Regular stretching improves flexibility primarily by altering how your nervous system responds to tension rather than by physically lengthening muscle tissue. According to physical therapists, early gains stem from increased stretch tolerance, as the nervous system becomes more comfortable with resistance and allows a greater range of motion.

Sticking with a stretching habit often leads to reaching farther than before, which makes it easy to assume that muscles have physically grown longer. However, the reality behind flexibility is more nuanced.

How the Nervous System Controls Flexibility

When individuals stretch regularly, the primary shift occurs in stretch tolerance and neural feedback loops. Most early flexibility gains appear to come from increased stretch tolerance and changes in how the nervous system responds, explains Alex McRobbie, PT, D.P.T., OCS, noting that the nervous system becomes less likely to inhibit muscle elongation under tension.

As people move deeper into a stretch, sensory signals register rising tension and discomfort in the surrounding tissues. According to Kaylee LeCavalier, PT, D.P.T., SCS, CSCS, CAPS, some of the increase in range of motion comes from a change in how the nervous system perceives and responds to the stretch rather than the muscle simply becoming longer. Dhara Shah, PT, D.P.T., adds that while regular stretching helps maintain flexibility and mobility, the underlying mechanics involve more than simple muscle lengthening.

Static Versus Dynamic Stretching Routines

Different stretching methods serve distinct purposes within a workout plan. Static stretching involves holding a lengthened position for a set duration, whereas dynamic stretching uses active movement through a range of motion, such as arm circles, walking lunges, or leg swings.

Physical therapists generally recommend using dynamic stretching before exercise and static stretching afterward. While static stretching before a workout is not strictly forbidden, holding positions for longer than 60 seconds can temporarily impair lifting performance. LeCavalier cautions that prolonged static stretching immediately before activities requiring maximal strength, power or speed can temporarily reduce performance.

What Physical Therapists Say About How Stretching Changes Muscles

Experts Recommend Beginner Stretching Routines and Safety Tips

Experts recommend performing a beginner-friendly routine two to three times per week, either independently or following a workout, after a brief warmup like brisk walking or marching in place. Static stretches should be held for 15 to 30 seconds and repeated two to three times per side.

Supine Hamstring Stretch: Lying on the back and bringing one leg inward while straightening the knee until a comfortable stretch occurs along the back of the thigh.
Half-Kneeling Hip Flexor Stretch: Kneeling on one knee with the opposite foot forward and shifting weight forward while keeping the torso upright.
Standing Calf Stretch: Facing a wall with one foot back to target the upper calf, or slightly bending the back knee to target the soleus lower calf.
Open-Book Rotation: A dynamic movement involving side-lying rotations of the top arm and upper back for 5 to 10 slow, controlled repetitions per side.

Physical therapists advise against bouncing during static stretches, recommending steady breathing and relaxation into the position instead. Practitioners also emphasize consistency over occasional intense sessions and suggest combining stretching with resistance training through full ranges of motion. Anyone experiencing persistent pain, numbness, tingling, weakness, sudden loss of mobility, or recovering from recent injuries or surgeries should consult a healthcare professional.