August 2022

Protocol and reference values for minimal detectable change of MyotonPRO and ultrasound imaging measurements of muscle and subcutaneous tissue

Authors: Paul E. Muckelt 1, 2, Martin B. Warner 1, 2, Tom Cheliotis‐James 1, Rachel Muckelt 3, Maria Hastermann 4, Britt Schoenrock 5, David Martin 6, Robert MacGregor 7, Dieter Blottner 5, 9, Maria Stokes 1, 2, 8


  1. School of Health Sciences, University of Southampton, Southampton, UK
  2. Centre for Sport, Exercise and Osteoarthritis Research Versus Arthritis, Southampton, UK
  3. University Centre Sparsholt, Winchester, UK
  4. Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Experimental and Clinical Research Center (ECRC) & NeuroCure Clinical Research Center (NCRC), Clinical Neuroimmunology, Charite-Universitätsmedizin Berlin, Lindenbergerweg 80, 13125 Berlin, Germany
  5. NeuroMuscular Group, Center of Space Medicine and Extreme Environments at Charite, Berlin, Germany
  6. KBR, Houston, TX, USA
  7. Airbus DS Space Systems, Inc, Houston, TX, USA
  8. Southampton NIHR Biomedical Research Centre, Southampton, UK
  9. Charite-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin Institute of Health, Institute of Integrative Neuroanatomy, Berlin, Germany

Journal: Nature - Scientific Reports - August 2022, Volume 12, Article no. 13654 (DOI: 10.1038/s41598-022-17507-2)

The assessment of muscle health is of paramount importance, as the loss of muscle mass and strength can affect performance. Two non-invasive tools that have been found to be useful in this are the MyotonPRO and rehabilitative ultrasound imaging, both have shown to be reliable in previous studies many of which conducted by the research team. This study aims to determine the reliability of previously unassessed local body structures and to determine their minimal detectable changes (MDC) to support both researchers and clinicians.

Twenty healthy participants were recruited to determine the reliability of seven skin positions out of a previously established protocol. Reliability was determined between three independent raters, and day to day reliability was assessed with one rater a week apart.

Intraclass Correlation Coefficients (ICC) between raters and between days for tissue stiffness, tone and elasticity range from moderate to excellent (ICC 0.52–0.97), with most good or excellent. ICCs for subcutaneous thickness between days was good or excellent (ICC 0.86–0.91) and moderate to excellent between raters (ICC 0.72–0.96), in muscles it was moderate to excellent between raters and days (ICC 0.71–0.95).

The protocol in this study is repeatable with overall good reliability, it also provides established MDC values for several measurement points.

A protocol for testing muscle biomechanical properties such as tone, stiffness and elasticity (using the MyotonPRO device) and subcutaneous and muscle thickness (using ultrasound imaging) has been described for measuring several sites of the healthy body (female and male) relevant for assessing the effects of inactivity and recovery in relatively young and healthy study participants. Reliability of both technologies was high. Intrarater reliability (same session) for the MyotonPRO was consistently excellent (all ICCs > 0.96) at all measurement points and for each of the three parameters, indicating that only one set of five mechanical impulses (5 × 0.4 N force) are necessary per measurement point.

Overall, interrater reliability of MyotonPRO measurements was excellent to good, with a small number of values moderate. This indicates that any Myoton operators within future protocols in many research laboratories and clinical settings will be able to collect reliable data.

The excellent to moderate intra-rater reliability (between-days) results indicate that the Myoton results for the operator studied (Rater 1) were repeatable.

The ultrasound scans from this study have been shown to be good to excellent except for three points which remained moderate: Intrarater reliability between days thickness of the Achilles tendon (ICC 0.71), Interrater reliability plantar fascia subcutaneous thickness and Achilles tendon thickness, (ICC 0.72 and 0.71 respectively).

Minimal detectable change (MDC) values have been documented for measurement points over particular muscles, tendons and the plantar fascia, for both Myoton and ultrasound measurements, providing a reference source for studies monitoring change over time. Values for MDC available in the literature from measurement points in the Myotones protocol but not included in the present study are also given in the present paper to provide a more complete reference for the protocol.