The role of forearm muscle viscoelasticity in wrist kinematics: A quantitative analysis of tone, stiffness, decrement, and range of motion in healthy young adults

The aim of this study was to objectively determine the viscoelastic parameters (tone, stiffness, elasticity) of the flexor and extensor muscle groups of the forearm in healthy young adults and to examine the effect of these parameters on wrist range of motion (ROM). A total of 38 healthy volunteers aged 18-40 years were included in the study. The viscoelastic properties of the M. Flexor Carpi Radialis (FCR), M. Flexor Carpi Ulnaris (FCU), M. Palmaris Longus (PL), and M. Extensor Digitorum (ED) muscles in the dominant and non-dominant forearms of the participants were measured using a MyotonPro device. Wrist ROM values (flexion, extension, radial and ulnar deviation) were evaluated with an analog goniometer. Descriptive statistics, paired samples t-test, and Pearson correlation analysis were used in the analysis of the data. The decrement (loss of elasticity) value of the ED muscle on the dominant side was found to be significantly higher than on the non-dominant side (p=0.014). In terms of joint mobility, the radial deviation angle of the non-dominant side was found to be higher than that of the dominant side (p=0.020). Correlation analyses revealed significant positive correlations between FCU tone and wrist flexion (r=.367, p=.028) and FCR tone and wrist extension (r=.357, p=.033) on the dominant side. On the non-dominant side, significant positive correlations were found between PL (r=.407, p=.014) and FCU (r=.334, p=.046) tone and ulnar deviation. MyotonPro provides objective viscoelastic data to complement goniometric measurements, identifying the mechanical state of the muscle underlying joint movement. Flexor tone and ROM are positively correlated, suggesting optimal basal tension is essential for joint stability and mobility. This allows for more personalised rehabilitation, with clinicians using objective tone profiles to differentiate between structural stiffness and neuromuscular tone deficits, targeting the specific constraint to maximize recovery.