Wrist flexor and extensor tendon stiffness during functional grip: A pilot study

The purpose of this study was to quantify differences between resting and submaximal gripping stiffness of the common wrist flexor (CWFT) and common wrist extensor tendons (CWET). Secondly, we aimed to compare tendon stiffness values between the flexor and extensor tendons both at rest and during submaximal grip.

The shear wave modulus, measured in kilopascals (kPa), was obtained during rest and 25 % of the maximum grip strength on the CWET and CWFT using 2D SWE ultrasound imaging (GE Logiq S8, 9L, linear transducer). Within examiner intraclass correlation coefficients (ICC) with 95 % confidence intervals were calculated. A two-way univariate analysis of variance was run with stiffness as the dependent variable, while tendon (flexor, extensor) and condition (rest, grip) were used as the independent variables.

Twenty healthy participants (mean age = 23.7 ± 1.8 years) were recruited. The within day intra-rater reliability for all measures were good (ICCs 0.80-0.93). There was a main effect for tendon (p < .001) as stiffness values were higher for the extensors, and there was a main effect for condition (p < .001) as stiffness values were higher during grip. However, there was a significant interaction between condition and tendon (p < .001) with post hoc tests revealing that the increase in stiffness from rest to contraction was significant for the CWET.

CWET tendon stiffness increases significantly from rest during grip. Compared to the CWFT, there were greater levels of CWET stiffness both at rest and during contraction in healthy young adults.