Technology & development
Measuring muscle mechanics
How a movement exerciser helps us to better understand muscle behaviour
Jakob Tiebel
Health Business Consultant
What happens to our muscles when they move – without us consciously contracting them? A new study shows how passive training can help to objectively capture muscular changes. In neurological rehabilitation – such as after a stroke or with multiple sclerosis – muscle tone often changes. Spasticity, increased muscle stiffness or passive movement restrictions may be the outcome. But how can these changes be reliably tracked? And how can we tell if a therapy – such as physical treatments or passive movement training – is working effectively?
A research team at Kawasaki University of Medical Welfare tested an innovative and promising approach: passive leg movement with the THERA-Trainer mobi 540, combined with special sensor technology to detect muscle movement – a technique known as Displacement Mechanomyography (DMMG).
A research team at Kawasaki University of Medical Welfare tested an innovative and promising approach: passive leg movement with the THERA-Trainer mobi 540, combined with special sensor technology to detect muscle movement – a technique known as Displacement Mechanomyography (DMMG).
What was investigated?
the THERA-Trainer movement exerciser – the device powered the pedals with its motor while the participants passively followed the cyclical movement. Sensors measured the slightest deformations of the thigh muscles. These arise solely through external movement – similar to a patient with severe paralysis or spasticity.
Particularly interesting was the time delay between the actual joint movement (pedal rotation) and the muscle reaction (visible in the DMMG signals). This phase behaviour can indicate the tissue properties of muscles – such as increased muscle stiffness, which may be caused by spasticity, immobility or inflammatory processes.
Particularly interesting was the time delay between the actual joint movement (pedal rotation) and the muscle reaction (visible in the DMMG signals). This phase behaviour can indicate the tissue properties of muscles – such as increased muscle stiffness, which may be caused by spasticity, immobility or inflammatory processes.
What did the study reveal?
During faster passive movement, the phase behaviour of the musculature changed markedly. The muscle reacted to the movement with a delay – a possible sign of increased intramuscular inertia.
If the muscle was treated with heat before training, the delay was reduced. This suggests that thermal applications reduce passive resistance in the muscle – allowing for a short-term decrease in tone or improved extensibility.
The magnitude of the muscle movement itself remained constant. The “quality” of the reaction, i.e. its timing, provided more revealing insights than the extent of the movement.
If the muscle was treated with heat before training, the delay was reduced. This suggests that thermal applications reduce passive resistance in the muscle – allowing for a short-term decrease in tone or improved extensibility.
The magnitude of the muscle movement itself remained constant. The “quality” of the reaction, i.e. its timing, provided more revealing insights than the extent of the movement.
Why is this relevant for clinical practice?
In neurological rehabilitation, it is often difficult to distinguish between active spasticity, structural tissue changes and adaptively increased muscle tone. This study shows that valuable information can be obtained through passive training with the THERA-Trainer and accompanying measurement of phase behaviour:
• Objective assessment of passive muscle resistance
• Differentiation between tonic reactions and structural shortenings
• Progress assessment following heat application or passive training
Of particular interest is the fact that since measurements are taken during passive movement, this method is effective even for individuals who cannot actively participate – offering a distinct advantage particularly for early rehabilitation applications or when working with severely affected patients.
• Objective assessment of passive muscle resistance
• Differentiation between tonic reactions and structural shortenings
• Progress assessment following heat application or passive training
Of particular interest is the fact that since measurements are taken during passive movement, this method is effective even for individuals who cannot actively participate – offering a distinct advantage particularly for early rehabilitation applications or when working with severely affected patients.
Conclusion
The THERA-Trainer was not used as a training device in the traditional sense in this study, but rather as a measuring instrument for muscular reactions. In combination with DMMG sensors, this creates a new pathway to understand and precisely target adaptive muscle behaviour, spasticity and passive resistance with greater precision – using simple technology that integrates seamlessly into daily clinical practice.
Differentiated assessment of muscle behaviour in spasticity, immobility or increased tone
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Jakob Tiebel
Health Business Consultant
Jakob Tiebel is OT and studied applied psychology with a focus on health economics. He has clinical expertise from his previous therapeutic work in neurorehabilitation. He conducts research and publishes on the theory-practice transfer in neurorehabilitation and is the owner of an agency for digital health marketing.
References:
- Fukuhara, S., Oka, H. Displacement MMG-based estimation of dynamic muscle viscoelasticity in the quadriceps during passive pedaling. Sci Rep 15, 3538 (2025). https://doi.org/10.1038/s41598-025-87842-7
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