Measurement of Achilles tendon loading using shear wave tensiometry: a reliability study

BACKGROUND: Shear wave tensiometry is a recent promising technology which can be used to evaluate tendon loading. Knowing the clinimetric features (e.g., reliability) of this technology is important for use in clinical and research settings.

OBJECTIVES: To evaluate the inter-session reliability of a novel shear wave tensiometer for the assessment of Achilles tendon loading. A further aim was to test the construct validity of this device by evaluating its precision in detecting Achilles tendon loading changes induced by a plantar flexor isometric contraction of increasing intensity.

METHOD: Ten healthy participants were recruited. Five measurements were performed at different time points to evaluate inter-session reliability. Shear wave speed along the Achilles tendon was evaluated during different isometric contractions using a shear wave tensiometer composed of an array of four accelerometers fixed on the tendon, ranging from 4 to 8.5 cm from the calcaneal insertion of the tendon. Test-retest, intra- and inter-session reliability were determined using intraclass correlation coefficient (ICC 3.1). Absolute reliability was calculated using the standard error of measurement and minimal detectable change.

RESULTS: Test-retest reliability was good to excellent (ICC 3.1 0.87-0.99) for each of the contraction levels examined. Intra-session reliability was good to excellent (ICC 3.1 0.85-0.96) and inter-session reliability was also good to excellent (ICC 3.1 0.75-0.93) for each of the contraction levels.

CONCLUSIONS: This study confirms the reliability of this novel device. Future studies analyzing participants with Achilles tendinopathy are needed to evaluate the capability of shear wave tensiometry to detect transient changes in loading due to pathology.