Where practical, yes. But it is a preference, not a requirement. Same-examiner reliability is the highest figure reported in the myotonometry literature, and different-examiner reliability is close behind. A written protocol closes most of the remaining gap, which matters in a real clinic where one person is not always available.
What do the reliability numbers actually say?
Both conditions perform well, with the same examiner slightly ahead. The gap is smaller than clinical intuition suggests.
A 2024 systematic review evaluating the reliability of the MyotonPro pooled dozens of studies and reported consistently high intra-rater and inter-rater reliability across muscle groups, with intra-rater values generally the higher of the two. A study of lower lumbar myofascial tissue in healthy adults reported intra-rater intraclass correlation coefficients in the range of 0.88 to 0.91 for stiffness, with a 24 hour interval between sessions.
That distinction has a specific meaning. Intra-rater reliability removes operator variability by definition, so it sets the ceiling. Inter-rater reliability includes it, so it tells you what you actually get when two people share the work.
| Condition | What varies | Reported reliability | Practical verdict |
|---|---|---|---|
| Same examiner, same session | Nothing but the tissue | Highest | Ideal |
| Same examiner, different day | Tissue and daily state | High, ICC around 0.88 to 0.91 in lumbar tissue | Standard for tracking change |
| Two trained examiners, same protocol | Placement and technique | High, slightly below intra-rater | Workable |
| Two examiners, no shared protocol | Placement, angle, positioning | Not established | Avoid |
| Two different devices | The measurement method itself | Systematic bias reported | Not comparable |
What actually causes two examiners to disagree?
Where the probe lands, not who is holding it. The instrument is the repeatable part of the setup.
Three inputs account for most of the divergence. Site placement comes first, because a centimetre of drift can move you off the muscle belly. Probe angle comes second, since published protocols specify perpendicular contact. Patient positioning comes third, and it is the one most often left undocumented. If two people measure the same upper trapezius with the patient seated in one case and prone in the other, the difference in the numbers is not an examiner problem.
Can a chiropractic assistant take the readings?
Yes, provided the protocol is written down rather than held in someone's head. This is the practical form of the question in most clinics.
The workable version looks like this. Mark each site against a bony landmark and record the landmark. Fix one patient position per site and write it in the chart. Take the same number of repeat readings each time and average within that examiner. Note who took the measurement. That last field costs nothing and lets you interpret an odd result later instead of guessing.
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.
How do you check that two people are measuring the same way?
Run a small in-house comparison rather than assuming. It takes one afternoon and settles the question for your clinic specifically.
Pick three or four willing patients. Have both examiners measure the same sites within a few minutes of each other, without seeing each other's numbers. Compare site by site. Where readings diverge by more than your usual repeat-measure spread, watch the second examiner take that site again and look at placement first. In most cases the fix is a marking habit, not a training problem.
Reference data supports doing this locally. Reference values for muscle stiffness and asymmetry using myotonometry are reported against specific protocols, and asymmetry thresholds in particular assume consistent bilateral placement. A left-right difference that comes from probe placement may look exactly like a clinical finding on the report.
What should you not do?
Do not average across examiners, and do not mix devices. Both moves destroy the thing that makes the number useful.
Averaging two examiners into one figure hides where a difference came from, so an unexpected result becomes uninterpretable. Published protocols average repeat readings within one examiner instead, which is a different operation with a different purpose. Switching devices mid-course is the more serious error, since methods report different units and show systematic bias against each other. Compared to that, a handover between two trained staff on a shared protocol is a minor issue.
Frequently Asked Questions
Should the same person take every muscle stiffness measurement?
Where practical, yes. Intra-rater reliability, meaning the same examiner repeating the measurement, is consistently reported as the highest figure in the literature. Inter-rater reliability is also good, so a second examiner is workable when the protocol is written down and followed.
How much reliability do you lose with a second examiner?
Less than most clinicians expect. Reliability studies report high values for both same-examiner and different-examiner conditions, with the same-examiner figure usually slightly higher because it removes operator variability.
Can a chiropractic assistant take the measurements?
Yes, if they are trained on the same protocol and the protocol is documented. The instrument is repeatable. The variable is where the probe goes and how the patient is positioned.
What creates most of the variation between examiners?
Site placement, probe angle, and patient positioning, in roughly that order. Marking the site against a bony landmark and recording the patient position addresses most of it.
Does it matter if the examiner changes mid-course?
Note the change in the chart so you can interpret an unexpected jump correctly. A protocol-following handover is far less disruptive than switching devices, which is not comparable at all.
How do you train a second person to measure consistently?
Have both examiners measure the same few patients on the same day and compare readings site by site. Where the numbers diverge, watch the placement rather than blaming the device.
Should you average readings from two examiners?
No. Averaging across examiners hides the source of any difference. Take repeat readings within one examiner and average those instead, which is what published protocols do.
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.