Sonographic evaluation of the immediate effects of eccentric heel drop exercise on Achilles tendon and gastrocnemius muscle stiffness using shear wave elastography

Abstract

BackgroundMechanical loading is crucial for muscle and tendon tissue remodeling. Eccentric heel drop exercise has been proven to be effective in the management of Achilles tendinopathy, yet its induced change in the mechanical property (i.e., stiffness) of the Achilles tendon (AT), medial and lateral gastrocnemius muscles (MG and LG) was unknown. Given that shear wave elastography has emerged as a powerful tool in assessing soft tissue stiffness with promising intra- and inter-operator reliability, the objective of this study was hence to characterize the stiffness of the AT, MG and LG in response to an acute bout of eccentric heel drop exercise.MethodsForty-five healthy young adults (36 males and nine females) performed 10 sets of 15-repetition heel drop exercise on their dominant leg with fully-extended knee, during which the AT and gastrocnemius muscles, but not soleus, were highly stretched. Before and immediately after the heel drop exercise, elastic moduli of the AT, MG and LG were measured by shear wave elastography.ResultsAfter the heel drop exercise, the stiffness of AT increased significantly by 41.8 + 33.5% (P < 0.001), whereas the increases in the MG and LG stiffness were found to be more drastic by 75 + 47.7% (P < 0.001) and 71.7 + 51.8% (P < 0.001), respectively. Regarding the AT, MG and LG stiffness measurements, the inter-operator reliability was 0.940, 0.987 and 0.986, and the intra-operator reliability was 0.916 to 0.978, 0.801 to 0.961 and 0.889 to 0.985, respectively.DiscussionThe gastrocnemius muscles were shown to bear larger mechanical loads than the AT during an acute bout of eccentric heel drop exercise. The findings from this pilot study shed some light on how and to what extent the AT and gastrocnemius muscles mechanically responds to an isolated set of heel drop exercise. Taken together, appropriate eccentric load might potentially benefit mechanical adaptations of the AT and gastrocnemius muscles in the rehabilitation of patients with Achilles tendinopathy.

Real-time sonoelastography: principles and clinical applications in tendon disorders.

“…After long term exercise, Achilles tendon stiffness was higher than that of infrequent exercisers on nondominant leg but not on dominant ankle 22 . Same results were confirmed after eccentric heel drop exercises 23 .…”

Shear Wave Elastography Measures of the Achilles Tendon: Influence of Time of Day, Leg Dominance and the Impact of an Acute 30-Minute Bout of Running

“…An increased level of stiffness detected immediately after an acute mechanical load, may allow for less extension of the tendon [50] which potentially may help reduce macro-trauma risk. Previous research demonstrated that in young healthy ATs, an acute bout of eccentric exercise resulted in a significant increase in AT stiffness as measured with SWE [51]. Other studies however show that a single 30-min bout of running did not impact the stiffness of the AT and concluded that the mechanical properties of tendons remain constant throughout locomotion [23].…”

Ultrasound elastography and ultrasound tissue characterisation for tendon evaluation

“…For nonruptured Achilles tendinopathy, UE has revealed increased tendon stiffness in response to long-term therapy [23] . These changes can be observed immediately after a therapy session [56] . Specifically, eccentric loading of the Achilles tendon has been shown to immediately induce increased tendon stiffness with SWE [56] .…”

“…These changes can be observed immediately after a therapy session [56] . Specifically, eccentric loading of the Achilles tendon has been shown to immediately induce increased tendon stiffness with SWE [56] .…”

“…SWE for the Achilles tendon has fair to excellent interobserver agreement (CC: 0.43–0.987) and excellent intraobserver agreement (CC: 0.870–0.978) [25] , [26] , [47] , [56] . At the patellar tendon, SWE has been shown to have excellent intraobserver (CC: 0.831–0.966) and interobserver (CC: 0.71–0.821) agreement [49] , [69] .…”