Measure at the mid-belly of the sternocleidomastoid, with the patient relaxed and the head neutral, and take the same reading on the opposite side. Consistency of landmark and position matters more than any single number, because a contracted or rotated muscle can read dramatically stiffer than a resting one.
Where is the correct measurement site?
The mid-belly, roughly halfway between the mastoid process and the sternal head. The sternocleidomastoid is easy to find and easy to measure badly. Both ends of the muscle are tendinous, and tendon reads much stiffer than muscle. If your baseline lands near the sternal attachment and your six-week re-measure lands two centimetres higher on the belly, the change you record is a change in your hand, not in the patient.
Find the muscle by asking the patient to rotate the head slightly away from the side you are measuring. Mark the mid-belly. Then return the head to neutral and let the muscle go quiet before taking the reading. This matters more on the sternocleidomastoid than on most muscles, because it fires with even small head movements and with speaking.
How reliable is the reading?
Good to excellent, provided your protocol is consistent. A 2024 systematic review evaluating the reliability of the MyotonPRO reported strong intra-rater and inter-rater reliability for stiffness across muscle groups, with intraclass correlation coefficients commonly in the 0.75 to 0.95 range. Separate work on the reliability of neck and back muscle mechanical property measurement supports the same conclusion for cervical musculature specifically.
Reliability is a property of the protocol, not of the device. The variables that break it are the ones you control: landmark drift, head rotation, an unrelaxed patient, and measuring right after manual work when the tissue has not settled.
What does the protocol look like in a real visit?
| Step | What to do | Why it matters |
|---|---|---|
| 1. Position | Supine or seated, head neutral, shoulders down | A contracted sternocleidomastoid reads far stiffer than a resting one |
| 2. Landmark | Mid-belly, midway between mastoid and sternal head | Tendon ends read much higher and are not comparable |
| 3. Mark it | Note the site relative to a bony landmark | Lets you return to the same spot at re-examination |
| 4. Measure both sides | Same site, same order, every visit | Side-to-side comparison controls for the patient's own baseline |
| 5. Timing | Before manual treatment, not after | Post-treatment tissue has not settled and skews the trend |
| 6. Repeat interval | Baseline, then each re-examination | A trend is interpretable, a one-off reading is not |
What does the number actually tell you?
Less than you might hope, and more than a pain score alone. A stiffer sternocleidomastoid on the symptomatic side may reflect a difference in the tissue. It does not identify the source of the neck pain, and it does not predict what will happen next. Stiffness and pain are independent, and the painful side is not consistently the stiffer side.
Where the reading earns its place is over time. A 2025 study in the Journal of Musculoskeletal and Neuronal Interactions used myotonometry on the sternocleidomastoid in infants with congenital muscular torticollis and found the measured muscle properties changed significantly after a course of physiotherapy. The authors framed the technique as a follow-up tool rather than a diagnostic one, which is exactly the right frame for chairside use. For interpreting how far a reading sits from typical, the 2025 reference values pilot in the Journal of Manual and Manipulative Therapy is a useful anchor, though it also found sex to be a primary predictor of stiffness, so a population average is a weak comparator next to the patient's own baseline.
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. Neither group was shown that their soft tissue stiffness was still elevated.
That is the practical case for measuring a muscle like the sternocleidomastoid in a neck pain patient. Most of the people who leave care leave because of what they perceive, and perception follows symptoms. A repeatable reading gives you a second thing to put on the table when the symptom story runs out.
Frequently Asked Questions
Where exactly do you measure the sternocleidomastoid?
Measure at the mid-belly of the muscle, roughly halfway between the mastoid process and the sternal head. Avoid the tendinous ends at either attachment, because tendon readings run much higher than muscle readings and are not comparable visit to visit.
What position should the patient be in?
Supine or seated with the head neutral and the muscle fully relaxed. Rotate the head slightly away only long enough to find the muscle belly, then return to neutral before taking the reading. An actively contracting sternocleidomastoid reads far stiffer than a resting one.
Is myotonometry reliable on neck muscles?
Yes. A 2024 systematic review of MyotonPRO reliability reported good to excellent intra-rater and inter-rater reliability for stiffness across muscle groups including the neck. Reliability depends on consistent landmarking and consistent patient position.
Should you measure both sides?
Always. Side-to-side comparison is more informative than a single reading, because it controls for the patient's own baseline. Some asymmetry is normal in healthy people, so treat a difference as a starting point for a conversation rather than a finding.
Does a stiffer sternocleidomastoid mean that side hurts?
No. Stiffness and pain are independent measures and the painful side is not consistently the stiffer side. A reading may reflect a difference in the tissue, but it does not diagnose the source of the neck pain.
How often should you re-measure?
At baseline and at each re-examination, typically every two to four weeks or every six to twelve visits. Measuring at the same interval you already re-examine keeps the trend interpretable without adding a separate appointment.
Is there evidence that sternocleidomastoid readings change with treatment?
A 2025 study in the Journal of Musculoskeletal and Neuronal Interactions used myotonometry on the sternocleidomastoid in infants with congenital muscular torticollis and reported significant changes in muscle properties after physiotherapy. The authors described myotonometry as a practical follow-up tool.
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.