Specificity of muscle-tendon properties in predicting postural stability: A preliminary investigation

The muscle-tendon complex is crucial in transmitting force from soft tissue to bones, supporting locomotion and postural stability. Mechanical properties of the Achilles tendon have exhibited region-specific variation fundamental to the control necessary for efficient human performance in an upright stance. Assessment of tendon mechanics has relied on isokinetic devices and diagnostic imaging technologies, such as ultrasound and magnetic resonance imaging. However, such equipment's high cost and complexity create barriers to widespread evaluation, limiting access for many clinicians. More accessible tools, like the MyotonPRO, offer promising solutions for evaluating muscle-tendon mechanics in diverse healthcare settings. Thus, this project aimed to investigate region-specific associations between passive mechanical properties of the low-leg muscle-tendon complex and single-leg stability performance while exploring the clinical usefulness of a myotonometry device for objectively assessing soft tissue mechanics. The initial investigation consisted of 10 healthy adult males of traditional college age, and the primary measured outcomes, including muscle-tendon complex passive mechanical properties of creep, elasticity, frequency, time-to-relax, and stiffness, were collected from the medial gastrocnemius (MG) and the Achilles tendon at the musculotendinous junction (MTJ) and free tendon (FT). Postural stability measures were the overall stability index (OSI), anterior-posterior index (API), and medial-lateral index (MLI). Data show neither MG nor MTJ passive mechanical properties were significantly correlated or predictive of single-leg balance performance (P>0.05), while select passive mechanical properties of the FT demonstrated a significant relationship and predictability of single-leg balance performance. These findings underscore the region-specific influence of tendon properties on postural stability control, highlighting the potential of myotonometry as a valuable tool for assessing tissue mechanics that are relevant to balance performance.