EFFECTS OF SEX AND FATIGUE ON ULTRASOUND-BASED MEASURES OF TENDON STIFFNESS
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Date
2024
Authors
Shlesinger, Daniel
Journal Title
Journal ISSN
Volume Title
Publisher
University of Oregon
Abstract
Tendons transmit skeletal muscle force to produce joint torque. Insight into tendon stiffness could help better understand the limits of musculotendinous performance and may help predict the risk of soft tissue injuries in response to extreme load. Clinical ultrasound imaging, both traditional B-mode and more recently, shear wave elastography (SWE) have been used to assess muscle and tendon stiffness. Recent studies using SWE have illustrated that acute fatigue can decrease stiffness in skeletal muscle. Others have demonstrated the effects biological sex and age on tendon stiffness using multiple ultrasound-based approaches. However, no studies have used SWE to assess the effect of acute fatigue on tendon stiffness, nor have any studies compared these measures with those produced using B-mode ultrasound. While SWE has shown promise in assessing muscle stiffness, we aimed to evaluate its correlation with more traditional modes of assessing tendon stiffness. Purpose: the purpose of the study was to investigate the effects of fatigue and sex on tendon stiffness measured by two ultrasound-based techniques: B-mode and SWE (SWE). Methods: In this study, young healthy males (n=15) and females (n=21) were recruited. Subjects performed 3 maximum voluntary isometric contractions (MVIC) of the knee extensors to evaluate maximal torque and rate of torque development (RTD) using an isokinetic dynamometer (Biodex Medical Systems, Shirley, NY). During ramped isometric contractions a linear array ultrasound transducer was used to measure elongation of the patellar tendon (PT). In a subset of participants (n=5) Shear wave velocity (SWV) measurements were observed during passive measurements. Participants were then instructed to fatigue their muscles by performing a bout of repeated maximum voluntary knee extensions with isotonic load set to 30% MVIC until task failure (inability to complete more than ~50% range of motion or maintain pace of contractions). Results: As measured by B-mode ultrasound, fatigue did not reduce active stiffness in the PT (p = .101) or have a fatigue by sex interaction (p = .075). Active and passive SWV was not reduced by fatigue (p = .157). Conclusion: Our data suggest that a dynamic fatiguing exercise of the knee extensors does not alter PT stiffness under active and passive conditions. While B-mode ultrasound demonstrated an increase in stiffness relative to the %MVIC, SWE showed no difference in stiffness as %MVIC increased. Both modalities illustrated an unaltered stiffness response to acute fatigue, suggesting a degree of consistency between both ultrasound methods.
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Keywords
Physiology, Stiffness, Tendon, Muscle, Biology