Measure at rest if you plan to track the patient over time. Stiffness readings rise during voluntary contraction, and reliability drops in the same moment. Published reference values are built on resting muscle. Mixing the two states across visits produces a trend line that reflects effort, not tissue change.
Why does contraction change the reading?
Because active muscle is mechanically a different tissue. A quantitative analysis in Diagnostics comparing shear wave elastography and myotonometry found stiffness significantly higher during voluntary contraction than at rest across the major muscles tested. Both methods agreed on the direction of that shift.
That is not a device flaw. It is the muscle doing its job. The problem is clinical, not technical. If a patient braces on visit one and relaxes on visit four, the drop you see may reflect nothing more than how comfortable they got with the procedure.
How much reliability do you lose during contraction?
Enough to matter for a progress report. The same analysis reported lower intra-rater reliability during contraction than at rest. A review of myotonometry in the Journal of Athletic Training places typical reliability in the good to excellent range under standardized resting conditions, which is the condition most of the supporting literature was built on.
You are choosing between a measurement you can repeat and a measurement you cannot. For tracking a patient across six weeks, that decision is already made.
| Factor | Resting measurement | Contracted measurement |
|---|---|---|
| Typical stiffness value | Lower baseline | Significantly higher |
| Intra-rater reliability | Higher | Lower |
| Comparable to published reference values | Yes | No |
| Sensitive to patient guarding | Yes, and detectable | Yes, and hidden inside the effort |
| Best use | Tracking change over weeks | Research on tissue behavior under load |
What do published reference values assume?
They assume rest. A 2025 pilot study in the Journal of Manual and Manipulative Therapy established preliminary reference values for resting muscle stiffness and bilateral asymmetry in healthy young adults. Sex was the only significant predictor of resting stiffness in that sample, and bilateral asymmetry ran roughly 10% to 14%.
A 2026 paper on methodological considerations for reference values makes the same point from the other direction. Reference data is only usable when the protocol behind it is reproduced. A contracted reading compared against resting norms is a category error, not a finding.
What if the patient cannot relax?
Treat guarding as information, not as a number to record. Shorten and support the muscle. Let the limb rest on the table rather than being held. Wait, talk about something else, and re-measure. Most bracing settles within a minute.
If it does not settle, write that down. A note that the patient could not relax the upper trapezius may reflect protective tone or apprehension, and it is more honest than logging an inflated resting value you will later compare against.
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 told their stiffness was still elevated.
How do you standardize a resting protocol?
Fix everything you can control and write it into the chart. Same patient position, same marked site, same limb support, same rough time of day. Take the measurement before manual work rather than after, so the reading is not capturing the last five minutes instead of the last two weeks.
The payoff is not precision for its own sake. It is that a stable protocol makes a small change believable when you show it to the patient. A patient who felt better and is thinking about stopping cares whether the number moved. They will not care if you have to explain why the number is noisy.
Frequently Asked Questions
Should you measure muscle stiffness at rest or during contraction?
Measure at rest if the goal is tracking a patient over time. Stiffness readings rise during voluntary contraction and reliability drops, and published reference values are built on resting muscle.
How much higher are stiffness readings during contraction?
A quantitative analysis comparing shear wave elastography and myotonometry found stiffness significantly higher during voluntary contraction than at rest in every major muscle tested. The size of the shift varies by muscle and by contraction intensity, which is part of why it is hard to standardize.
What do I do if the patient cannot relax the muscle?
Reposition to shorten and support the muscle, wait, and re-measure. If guarding persists, note it in the record rather than treating the elevated number as a resting value.
Can I compare a resting reading to a contracted reading?
No. They are different measurements. Comparing across states can produce an apparent change that reflects only the patient's muscle activity that day.
Do published reference values assume a resting protocol?
Yes. A 2025 pilot study establishing reference values for muscle stiffness and bilateral asymmetry measured healthy young adults at rest. Comparing a contracted reading to those values is not a valid comparison.
Is measuring during contraction ever useful?
It has research uses in performance and activation work, where the question is how tissue behaves under load. For routine clinical tracking of change over weeks, the added variability usually outweighs the information.
What else has to stay constant between visits?
Patient position, the marked measurement site, limb support, and roughly the same time of day. Protocol drift is the most common reason a stiffness trend looks noisy.
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.