Phantom material testing indicates that the mechanical properties, geometrical dimensions, and tensional state of tendons affect oscillation-based measurements

Abstract

Objective: There is an increasing interest in the application of oscillation-based measurement techniques to evaluate the mechanical stiffness of healthy and diseased tendons. These techniques measure the stiffness of a tendon indirectly by registering the oscillation response of a tendon to an external mechanical impulse. Although these measurement techniques seem to be comparatively easy and time-saving, their applicability is implicitly limited by their indirect measurement principle. Approach: In this study, we aim to find evidence that the oscillation response of a tendon to an external mechanical impulse is not only affected by the stiffness of a tendon but also by the tendons’ cross-sectional area (CSA), length, and tension. Therefore, we reviewed the current literature on oscillation-based techniques that measure in vivo tendon properties. Further, a phantom material was used to mimic the nature of tendons and to test the impact of four factors on oscillation-based measurements. Main results: Our results indicate that the mechanical properties, geometrical dimensions (length and CSA), and tensional state affect oscillation-based measures. Surprisingly, most studies on tendon behavior often exclusively associate their oscillation-based measurements with the mechanical stiffness of a tendon. Significance: While this narrow perspective bears the risk of misinterpretation or false implications, a broader understanding of oscillation-based measurements has the potential to shed new light on the interaction of muscles and tendons in vivo.

Myotonometry and extended field-of-view ultrasound imaging allow reliable quantification of patellar tendon stiffness and length at rest and during maximal load, whereas several restrictions exist for the Achilles tendon

“…With this in mind, our study showed good estimated ICCs for the intra- and interrater reliabilities, but these results should be interpreted with caution due to the measurement error-related dropouts for a few data pairs, resulting in a smaller than the calculated sample size, and the 95% CIs indicated a large range from poor to excellent reliability. It should also be noted that myotonometry-based measurements record the transversal stiffness at the local measurement site of the tendon and could be affected by numerous tendon-related parameters ( 33 ). Therefore, it should be emphasized that stiffness measurements using myotonometry at loading conditions cannot be considered interchangeable with traditional procedures using synchronized force and ultrasound diagnostics ( 6 ).…”

The Myometric Assessment of Achilles Tendon and Soleus Muscle Stiffness before and after a Standardized Exercise Test in Elite Female Volleyball and Handball Athletes—A Quasi-Experimental Study

“…Especially in sports with high vertical forces like jumping and sprinting, or those with high static contraction like hammer throw, muscles and tendons are exposed to a multiple of the individual’s bodyweight [ 34 ]. Due to repetitive training, tissue adaptions such as an increased tendon cross-sectional area and higher values of Young’s modulus can be observed [ 35 , 36 ]. Regular examinations with ultrasound and shear wave elastography are often still reserved for male athletes with better medical infrastructure.…”

An Identical Twin Study on Human Achilles Tendon Adaptation: Regular Recreational Exercise at Comparatively Low Intensities Can Increase Tendon Stiffness

“…Consequently, the amplitude and frequency of the sinusoidal curve are used as a surrogate measure of tendon stiffness ( Schneider et al, 2015 ). The easily accessible and cost-effective device has already been used in previous studies to test its validity and reliability and to detect changes in Achilles tendon stiffness non-invasively (for review see Sichting and Kram, 2020 ). Regarding the quality of stiffness assessment, several studies have demonstrated that the use of the handheld device produces valid ( Pruyn et al, 2016 ; Feng et al, 2018 ) and reliable results.…”