Does stretching actually make your muscles longer?
Why Stretching Works: It's Mostly Your Nervous System, Not Longer Muscles
· By Anthony Falcone
Verdict: Keep it. Stretching works, just not the way most people think. Over weeks, you mainly get better at tolerating the stretch, and the muscle gets a bit less stiff. Muscle fibres didn't get longer.
What the researchers asked
Everyone agrees static stretching improves range of motion. The question was why: do muscles get structurally longer, mechanically less stiff, or do you simply tolerate more stretch?
What they found
One session of stretching slightly reduced stiffness, more so when people stretched to the point of discomfort rather than staying gentle.
Weeks of stretching also slightly reduced stiffness and moderately increased stretch tolerance — how much tension you can accept before you stop. Both were linked to the long-term gains in range of motion.
Muscle fascicle length (how long the fibres are) didn't change, even in programmes up to 24 weeks.
The authors suggest that if you play a sport built on springiness — sprinting, jumping — static stretching fits better after training than right before it.
What this means for you
- Stretch to mild discomfort, not pain-free and not to pain. Gentle stretching barely changed stiffness.
- Be consistent: the tolerance effect builds over weeks.
- Before explosive work, prefer a dynamic warm-up; do long static holds after.
- If you actually want longer muscle fibres, the authors point to eccentric strength training, not stretching.
How much to trust it
- The authors rate the certainty of the evidence as low to very low.
- Most studies tested hamstrings or calves in young men; few looked at women or other muscles.
- Stretch "intensity" was based on how each study described discomfort, not a standard measure.
The study
Ingram LA, Tomkinson GR, d'Unienville NMA, Gower B, et al. Mechanisms Underlying Range of Motion Improvements Following Acute and Chronic Static Stretching: A Systematic Review, Meta-analysis and Multivariate Meta-regression. Sports Medicine, 2025. doi.org/10.1007/s40279-025-02204-7
Our Mobility & Flexibility Protocol combines loaded stretching, joint control work and a daily 15-minute flow, so you gain range you can actually use. See the protocol