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Faculty Advisor(s)

Harold Merriman, PT, PhD; Joseph Day, PT, PhD, OCS


Purpose/Hypothesis: Ultrasound shear wave elastography (SWE) quantifies muscle stiffness, a mechanical muscle property that is known to influence muscle function. Gripping is an important functional task and relies on the synergistic actions of the wrist flexors and extensors. To date, there are no studies to quantify tendon stiffness as measured by SWE during a functional task like gripping. The purpose of this study was to quantify differences between resting and submaximal gripping stiffness of the common wrist flexor (CFT) and common wrist extensor tendons (CET). Secondly, we aimed to compare tendon stiffness values between the flexor tendon and extensor tendons both at rest and during submaximal gripping.

Subjects: Forty upper limbs (20 participants)

Materials/Methods: Using previously established procedures, the participants maximal grip strength was taken bilaterally using a handheld dynamometer. The shear wave modulus, measured in kilopascals (kPa), was obtained during rest and 25% of the maximum grip strength on the dominant and non-dominant CET and CFT using 2D SWE ultrasound imaging (GE Logiq S8,9L, linear transducer). For each condition, four measures were taken and averaged for a single data point. Within examiner intraclass correlation coefficients (ICC (3, 1)) with 95% confidence intervals were calculated using a two-way mixed model single measure for absolute agreement. Paired t-test were used to determine difference in tendon stiffness between the dominated and non-dominate limbs. A two-way univariate analysis of variance was run with stiffness as the dependent variable, while tendon (flexor, extensor) and state (rest, grip) were used as the independent variables.

Results: The 20 participants (9 male/11 female, mean age = 23.7± 1.8 yr, 80% right-handed) had an average BMI of 26.10 +/-2.96 kg/m2. The within day intra-rater reliability for all conditions and both tendons were good (ICCs .80 - .93). MDC ranged from 5.53-29.54 kPa. There were no differences between the dominant and non-dominant arms across both tendons and during both conditions (rest and grip) p>.095. There was a significant main effect for condition (p < .001) as stiffness values were higher for the gripping task, mean difference = 29.36 ± 6.92 kPa. There was also a main effect for tendon (p

Conclusion: Both CET and CFT stiffness measures can be consistently measured during rest and grip within the same day. CET and CFT tendon stiffness increase significantly during functional grip, while the CET is generally stiffer during both rest and grip when compared to the CFT.

Clinical Relevance: Obtaining stiffness values during rest and functional grip is a viable option of data collection for the CFT and CET. Compared to the CFT, clinicians should expect significantly greater CET stiffness both at rest and during contraction. Higher CET stiffness may support its functionality as a wrist stabilizer during grip.

Publication Date



Physical Therapy | Rehabilitation and Therapy

Wrist Flexor and Extensor Tendon Stiffness During Functional Grip: A Pilot Study