Yes. On average, measured muscle stiffness tends to be higher in men than in women. A 2025 myotonometry pilot study reported mean global stiffness of about 236 N/m in males versus 196 N/m in females, a statistically significant difference, and found sex was the only significant predictor of resting stiffness. This is a group average, so individuals overlap and any single person can sit outside the pattern.
What Does the Evidence Show?
Men showed higher resting stiffness, and sex outweighed other factors. A 2025 pilot study in the Journal of Manual & Manipulative Therapy measured resting muscle stiffness with a handheld myotonometer in healthy young adults. Mean global stiffness was about 236 N/m in males and 196 N/m in females, with a large effect size. Sex was the only statistically significant predictor; age, body mass index, and weekly exercise were not significant within that cohort.
Why Would Sex Change a Stiffness Reading?
Differences in muscle mass, composition, and connective tissue likely play a role. The exact mechanism is not settled, and the study population was small, so the numbers are best treated as preliminary. The useful point for practice is not the mechanism but the consequence: a reading that looks high for one group may be entirely typical for another. Sex is a variable to account for before calling a reading abnormal.
How Should This Change What You Compare Against?
Use sex-specific reference intervals, not a single mixed-sex range. Comparing a woman's reading to a range built mostly from men, or the reverse, can make a normal value look abnormal. The 2025 study derived separate 95% reference intervals for males and females for exactly this reason. When you track a patient over time, their own baseline matters more than any population range, but the right reference group still frames the first reading.
| Factor | Effect on stiffness reading |
|---|---|
| Sex | Significant: males higher (~236 vs ~196 N/m) |
| Age | Not significant in this cohort |
| Body mass index | Not significant in this cohort |
| Weekly exercise | Not significant in this cohort |
| Side-to-side asymmetry | Small, ~10 to 14% (normal) |
Survey data: In a 2026 survey of 455 patients who stopped chiropractic care, 58% cited perception-based reasons: 36% felt no progress, and 22% felt better and stopped. Reading a patient's stiffness against the right reference group, and tracking their own baseline, gives you a number you can show instead of relying on impressions.
Frequently Asked Questions
Do men have stiffer muscles than women?
On average, measured resting stiffness tends to be higher in men. A 2025 myotonometry pilot study reported mean global stiffness of about 236 N/m in males versus 196 N/m in females, a statistically significant difference. This is a group average, so individuals overlap and any one person can fall outside the pattern.
Why does sex affect muscle stiffness readings?
The exact mechanism is not settled, but differences in muscle mass, composition, and connective tissue likely contribute. In the 2025 study, sex was the only significant predictor of stiffness, while age, body mass index, and weekly exercise were not significant within that cohort.
Should you compare a patient's reading to a mixed-sex normal range?
No. Because stiffness differs by sex, comparing a reading to a mixed reference range can be misleading. Sex-specific reference intervals give a more accurate sense of whether a reading is typical, which is why the 2025 study derived separate intervals for males and females.
Does a higher stiffness reading in men mean more pain or dysfunction?
No. A higher reading that reflects a normal sex difference is not a sign of pathology or pain. Stiffness and pain are independent, so interpret a reading against the right reference group rather than assuming higher means worse.
How much side-to-side asymmetry is normal?
In the 2025 pilot study, average bilateral asymmetry was small, roughly 10 to 14 percent, consistent with normal physiological side-to-side differences rather than pathology. A modest left-right gap on its own is usually not a red flag.
Does this mean stiffness readings are unreliable?
No. It means readings need the right context. Myotonometry shows good reliability in reviews, and a sex difference is a reason to compare against matched reference values, not a reason to distrust the measurement itself.
One approach is to add a second channel of objective data alongside subjective pain reports. Options include soft tissue stiffness measurement (such as MuscleMap), range-of-motion testing, and posture analysis. Each gives you something concrete to show the patient rather than asking them to take your word for it.