The Science Behind Stretching: What Happens to Your Body and Why It Matters

By Dr. Hanna Sattler, PT, DPT

Stretching is one of the most commonly recommended practices in fitness and physical therapy — but how often do we really stop to think about what stretching actually does to our bodies? Whether you're an athlete, a weekend warrior, or someone recovering from an injury, understanding the science behind stretching can help you make more informed decisions about your movement routine.

In this post, we’ll break down the physiological process of stretching, its benefits, when to stretch, and debunk a few common myths.

What Happens to Your Body When You Stretch?

Stretching may seem simple, but underneath the surface, your body is undergoing a complex set of physiological events:

1. Muscle Fiber Elongation

When you stretch, your muscles are pulled to an extended position causing your muscle fibers to lengthen. Initially, this lengthening is temporary. With consistent stretching, your muscles can adapt and lengthen over time, increasing flexibility.

2. Nervous System Modulation

Your nervous system plays a crucial role in stretching. When you begin to stretch, sensors called muscle spindles detect the change in length and trigger a protective reflex to prevent overstretching (the “stretch reflex”). Over time and with consistent practice, the body becomes more tolerant, allowing a greater range of motion. This is why it is important NOT to stretch into pain!

3. Connective Tissue Adaptation

Beyond muscles, stretching affects tendons and fascia (the connective tissues around muscles). While these tissues are less elastic, regular stretching can improve their flexibility and hydration, making movements smoother and less injury-prone.

4. Circulation Boost

Stretching increases blood flow to the muscles, bringing in oxygen and nutrients while removing waste products like lactic acid. This can reduce soreness and enhance recovery.

The Benefits of Stretching

Stretching offers a wide range of benefits, especially when done correctly and consistently:

• Increased Flexibility & Range of Motion More mobile joints and flexible muscles lead to better movement efficiency and reduced risk of injury.

• Improved Posture Stretching tight muscles (like hip flexors, chest, and hamstrings) can relieve postural imbalances, especially in people who sit often.

• Injury Prevention Flexible muscles and tendons are less likely to tear when placed under sudden stress.

• Reduced Muscle Tension & Pain Stretching can alleviate muscle tightness and reduce the sensation of pain, especially for those with chronic conditions or after a workout.

• Enhanced Recovery Post-exercise stretching supports circulation and helps return muscles to their resting length.

When Is the Best Time to Stretch?

Timing your stretching properly can maximize its benefits:

✅ Dynamic Stretching Before Exercise

Dynamic stretches are active movements that mimic the activity you’re about to do. These are ideal before workouts because they:

• Increase heart rate and body temperature

• Prepare muscles and joints for movement

• Improve neuromuscular readiness

Examples: scoops, butt kickers, high knees, leg swings, open books, arm circles, etc.

✅ Static Stretching After Exercise

Static stretches involve holding a position for at least 30–60 seconds. These are best done when muscles are warm:

• Helps reduce muscle stiffness

• Aids recovery and flexibility

• Encourages relaxation

Examples: seated hamstring stretch, calf stretch, couch stretch

🕓 Other Ideal Times to Stretch (static or dynamic)

• After a warm shower – when muscles are warm and pliable

• Mid-day or during work breaks – to counteract sitting-related tension

• Before bed – to promote relaxation and better sleep

Common Myths About Stretching — Debunked

❌ Myth 1: Stretching prevents all injuries.

Truth: While stretching can reduce the risk of injury, it's not a guarantee. Injury prevention is best achieved with a well-rounded program that includes strength training, mobility work, and proper technique.

❌ Myth 2: You should always stretch before working out.

Truth: Static stretching before intense activity can temporarily reduce muscle strength and power. Opt for dynamic warm-ups instead.

❌ Myth 3: Stretching should hurt to be effective.

Truth: Stretching should never be painful. A gentle pulling sensation is normal, but sharp or intense pain is a sign to stop.

❌ Myth 4: If you're not flexible, stretching won't help.

Truth: Everyone starts somewhere. With consistent practice, even the least flexible individuals can see improvements.

Final Thoughts

Stretching is more than a pre- or post-workout ritual — it's a powerful tool that supports your overall musculoskeletal health. By understanding the science behind it, you can tailor your routine to fit your body’s needs, prevent injury, and improve how you move and feel every day.

If you're dealing with stiffness, limited range of motion, or recovering from an injury, working with a physical therapist can help you develop a personalized stretching program that's safe and effective. 

It’s imperative that you establish an individualized routine for YOU. Having an appropriate movement prescription for where you are at in your journey is in my opinion, the most important part of this post. Doing a stretch correctly in the wrong phase of your plan of care, or doing the right stretch but incorrectly, are both going to do more harm than good. In the age of social media and fitness influencers, you may find so many mobility challenges, workouts, and routines that seem fun or interesting, but they may not be right for you RIGHT NOW. Consult with your movement specialist to make sure you’re performing the proper movements. 

Looking to improve your flexibility or recover safely? Contact OTB to schedule a personalized assessment with one of our licensed physical therapists.