Reliability of tensiomyography and myotonometry in detecting mechanical and contractile characteristics of the lumbar erector spinae in healthy volunteers

Tensiomyography™ (TMG) and MyotonPRO^® (MMT) are two non-invasive devices for monitoring muscle contractile and mechanical characteristics. This study aimed to evaluate the test–retest reliability of TMG and MMT parameters for measuring (TMG:) muscle displacement (D_m), contraction time (T_c), and velocity (V_c) and (MMT:) frequency (F), stiffness (S), and decrement (D) of the erector spinae muscles (ES) in healthy adults. A particular focus was set on the establishment of reliability measures for the previously barely evaluated secondary TMG parameter V_c.

Twenty-four subjects (13 female and 11 male, mean ± SD, 38.0 ± 12.0 years) were measured using TMG and MMT over 2 consecutive days. Absolute and relative reliability was calculated by standard error of measurement (SEM, SEM%), Minimum detectable change (MDC, MDC%), coefficient of variation (CV%) and intraclass correlation coefficient (ICC, 3.1) with a 95% confidence interval (CI).

The ICCs for all variables and test–retest intervals ranged from 0.75 to 0.99 indicating a good to excellent relative reliability for both TMG and MMT, demonstrating the lowest values for TMG T_c and between-day MMT D (ICC < 0.90). Absolute reliability was suitable for all parameters (CV 2–8%) except for D_m (10–12%). V_c demonstrated to be the most reliable and repeatable TMG parameter (ICC > 0.95, CV < 8%).

The reliability for TMG V_c could be established successfully. Its further applicability needs to be confirmed in future studies. MMT was found to be more reliable on repeated testing than the two other TMG parameters D_m and T_c.