Yes, and by more than most measurement error. A 2026 randomized crossover trial found myotonometry stiffness rose roughly 20% after a bout of calf raises, and the effect was still detectable 10 minutes later. If a patient does their home exercises in your waiting room, you are not measuring the same tissue state you measured at baseline.
What did the 2026 study test?
Four activity conditions against a control, in the same participants. Warneke and colleagues, publishing in BMC Medical Imaging in 2026, put 30 healthy adults through cycling, jogging, calf raises, or rest, then measured muscle thickness and stiffness by shear wave elastography and myotonometry immediately before, immediately after, and 10 minutes after.
Muscle thickness increased significantly after calf raises and after jogging. Cycling and the control condition produced no thickness effect. Stiffness moved too, and the size of the shift was large enough that the authors recommended standardizing or at minimum documenting pre-measurement activity.
Why did the two devices disagree?
Because they interrogate the tissue differently. After calf raises, shear wave elastography showed stiffness decreasing about 17% while myotonometry showed it increasing about 20%. Both were measuring the same limbs at the same time.
The authors pointed to acute changes in muscle perfusion and blood inflow as a plausible source of bias. Whatever the mechanism, the practical implication is clean: readings from different measurement technologies should not be treated as interchangeable, and a clinic should track a patient with one method rather than switching.
| Pre-measurement activity | Effect on muscle thickness | Still present at 10 minutes? |
|---|---|---|
| Calf raises | Significant increase (about 10%) | Yes |
| Jogging | Significant increase (about 3%) | Yes |
| Cycling | No significant effect | Not applicable |
| Rest (control) | No significant effect | Not applicable |
Does this mean stiffness measurement is unreliable?
No, and the same paper is the evidence against that reading. Reliability within the study was good to excellent, with myotonometry intraclass correlation coefficients running from 0.77 to 0.98 for muscle. That is consistent with a 2024 systematic review of MyotonPRO reliability across 48 studies, which reported similar ranges.
The finding is about protocol, not about the instrument. A device can be highly reliable and still return a different number if you change the conditions between readings. That is true of blood pressure cuffs and it is true here.
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.
What should you change in the clinic?
Measure first, treat second. If the stiffness reading happens after traction, soft tissue work, or a set of in-office exercises, the comparison against baseline is no longer clean. Taking the reading at the top of the visit removes the largest source of avoidable variation at zero cost.
Two smaller habits help. Keep the patient in the same position for every reading, since posture is a known confounder. And note in the chart if the patient came straight from the gym, so a reading that looks anomalous later has an explanation attached to it.
How much change matters after accounting for this?
Enough to exceed both device error and activity-driven shift. A 20% swing from a set of calf raises sets a floor. If you want to tell a patient their reading meaningfully improved, the change should be comfortably larger than what a warm-up could have produced, and it should come from a measurement taken under the same conditions as the baseline.
This is the unglamorous half of objective measurement. The number is only worth showing a patient if the protocol behind it was consistent, and consistency is a scheduling decision more than a clinical one.
Frequently Asked Questions
Does recent exercise affect a muscle stiffness measurement?
Yes. A 2026 randomized four-arm crossover study in BMC Medical Imaging measured 30 healthy adults before and after cycling, jogging, calf raises, or rest. Myotonometry stiffness rose about 20% after calf raises, and effects were still present at the 10-minute retention measurement.
How long should a patient rest before a stiffness measurement?
The 2026 crossover study found that more than 10 minutes of rest was needed to diminish the bias after some activities, specifically calf raises. In a clinic, the practical version is to measure before any in-office exercise, traction, or manual therapy rather than after.
Does walking in from the parking lot change the reading?
Light activity had the smallest effect in the 2026 study. Cycling produced no significant change in muscle thickness, while jogging and calf raises did. Ordinary walking sits closer to the low end, though the honest answer is that it was not tested directly.
Why did myotonometry and elastography move in opposite directions?
In the 2026 study, shear wave elastography showed stiffness decreasing about 17% after calf raises while myotonometry showed it increasing about 20%. The two methods interrogate tissue differently, and the authors attributed the divergence partly to acute changes in muscle perfusion. Readings from different devices should not be pooled.
Does this make stiffness measurement unreliable?
No. Reliability in the same 2026 study was good to excellent for myotonometry, with intraclass correlation coefficients from 0.77 to 0.98 for muscle. The finding is about standardization, not about the instrument. An unstandardized protocol adds noise that a standardized one avoids.
How does this compare to other measurement confounders?
Recent activity belongs to the same family as time of day, patient positioning, and measurement site. Each adds variability that is controllable by protocol. The practical response is to fix the conditions and record what they were, so a later reading is comparable.
What should a chiropractic clinic actually change?
Measure at the start of the visit before any treatment, keep the patient in the same position each time, and note if they arrived directly from a workout. Consistency between a patient's own visits matters more than matching any external standard.
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.