Objective: Several diagnostic methods have been used in the identification of mechanical properties of skeletal muscle, including myofascial trigger points (MTrPs), however, they are not suitable for daily clinical use. Myotonometry offers an easy noninvasive alternative to assess these muscle properties. Nevertheless, previous research has not yet studied the mechanical properties of MTrPs by myotonometry. The purposes of this study were (1) to analyze the differences in the mechanical properties between latent MTrPs and their taut bands by myotonometry, (2) to investigate the inter-rater reproducibility of myotonometric measurements, and (3) to examine the association between myotonometry and passive isokinetic dynamometry.
Approach: Fifty individuals (58% male; age 24.6 ± 7.9 years) with a latent medial MTrP of the right soleus muscle participated. The mechanical properties of this MTrP area of soleus muscle and its taut band area were measured using a myotonometer (MyotonPRO). Additionally, passive resistive torque and extensibility of triceps surae muscle were assessed using a Kin-Com dynamometer.
Main results: Statistical analysis indicated higher values for the stiffness parameter in the taut band with respect to the MTrP (P < 0.05). The inter-rater reliability of the myotonometric measurements was good for all variables (ICC3,1 > 0.75). The standard error of measurement (SEM) and minimal detectable difference (MDD) indicated a small measurement error for frequency and stiffness variables (SEM% < 10%; MDD95% < 20%). Significant fair correlations between myotonometric parameters and passive isokinetic parameters ranged from -0.29 to 0.48 (P < 0.05).
Significance: The myotonometer was demonstrated to be a reliable tool and was able to quantify differences in the mechanical properties of myofascial tissues. The potential of this method for the assessment of myofascial pain syndromes requires further investigation.