Effect of Fatigue Loading on Tendon Fascicle Extension Mechanisms

Tendon injury is common, probably occurring due to accumulation of microdamage within the tendon matrix as a result of repetitive loading rather than as a sudden onset condition ¹. The human Achilles tendon is highly susceptible to injury; this tendon functions as an energy store and experiences high stresses and strains during normal use ². The equine superficial digital flexor (SDFT) is also an energy storing tendon and is highly injury prone, therefore it is often used as a model to study structure function relationships within this type of tendon ³. Our previous work has characterized the microstructural response of SDFT fascicles to applied strain, with results indicating the presence of a helical component to the fascicle which may facilitate extension by unwinding of the coil ⁴. The aim of this study was to assess the effect of cyclic fatigue loading (creep) on the microstructural strain response of the equine SDFT to test the hypothesis that fatigue loading would result in altered fascicle extension mechanisms.