Three-dimensional morphology and strain of the Achilles free tendon immediately following eccentric heel drop exercise

Abstract

Our understanding of the immediate effects of exercise on Achilles free tendon transverse morphology is limited to single site measurements acquired at rest using 2D ultrasound. The purpose of this study was to provide a detailed 3D description of changes in Achilles free tendon morphology immediately following a single clinical bout of exercise. Freehand 3D ultrasound was used to measure Achilles free tendon length, and regional cross-sectional area (CSA), medio-lateral (ML) diameter and antero-posterior (AP) diameter in healthy young adults (N=14) at rest and during isometric muscle contraction, immediately before and after 3×15 eccentric heel drops. Post-exercise reductions in transverse strain were limited to CSA and AP diameter in the midproximal region of the Achilles free tendon during muscle contraction. The change in CSA strain during muscle contraction was significantly correlated to the change in longitudinal strain (r=−0.72) and the change in AP diameter strain (r=0.64). Overall findings suggest the Achilles free tendon experiences a complex change in 3D morphology following eccentric heel drop exercise that manifests under contractile but not rest conditions, is most pronounced in the mid-proximal tendon and is primarily driven by changes in AP diameter strain and not ML diameter strain.

Three‐dimensional morphology and volume of the free Achilles tendon at rest and under load in people with unilateral mid‐portion Achilles tendinopathy

“…The tendinopathic free tendon underwent a greater longitudinal strain, which was approximately two‐thirds greater than contralateral and healthy control tendons under the same tensile load (50% MVIC). The strains for the contralateral and healthy control tendons from the present study (∼6.5%) were in close agreement (∼5–6.8%) with earlier studies of normal tendon using the same approach (Nuri et al., ; Obst et al., , ). Two earlier studies reported 25% greater longitudinal whole AT strain in MAT compared with healthy control tendons at 100% MVIC (Arya & Kulig, ; Child et al ).…”

“…The larger negative CSA strain in MAT was primarily driven by a greater negative strain along the AP diameter in MAT (−15.9%) compared with the positive strain of AP diameter in contralateral (8.1%) and healthy control tendons (7.0%), with no differences in tendon negative strain along the ML diameter (∼−9%). Although the polarity AP strain for contralateral and healthy tendons was positive, indicating tendon bulging along the AP axis under tensile load so that the tendon CSA becomes more cylindrical under load (Obst et al., , ), the AP strain for MAT was negative, indicating thinning of the tendon along the AP axis as reported in earlier in vivo studies for tendinopathic tendon in response to an acute bout of exercise (Fahlström & Alfredson, ; Grigg et al., ; Wearing et al., ). The tendinopathic tendon also underwent a non‐uniform tendon transverse morphology strain along its length under load, with the tendon mid‐portion undergoing greater reduction in tendon CSA (−28.4%), AP diameter (−20.0%) and ML diameter (−12.0%) relative to the tendon distal and proximal portions.…”

“…tendon mid‐portion) or affect the entire tendon length. Furthermore, although the normal free AT is known to remain isovolumetric and experience a reduction in tendon CSA and mediolateral (ML) diameter, and an increase in AP diameter throughout the entire tendon length during tensile loading (Iwanuma et al., ; Nuri, Obst, Newsham‐West, & Barrett, ; Obst, Renault, Newsham‐West, & Barrett, , ), relatively little is currently known about how three‐dimensional (3‐D) tendon morphology during tensile loading is altered in MAT. Studies of the tendinopathic Achilles and patellar tendons have demonstrated an immediate decrease in AP diameter and water content after an acute bout of eccentric exercise (Grigg et al., ; Ho & Kulig, ; Wearing, Locke, Smeathers, & Hooper, ) and 1 h floor‐ball match (Fahlström & Alfredson, ), and an immediate reduction in tendon CSA and volume during repeated isometric loading (Nuri et al., ) and after long‐term eccentric exercise (Shalabi et al., ; Tsehaie et al., ).…”

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

“…Third, a randomized, controlled experimental setting in a larger sample of the trained and untrained should be considered. Fourth, the sample size of all outcome measures in the present study were not estimated by a power analysis, but the size of the experimental group ( n  = 45) was similar to or even much larger than that in other similar studies (Jeong et al, 2014; Mahieu et al, 2008; Obst, Newsham-West & Barrett, 2015; Weinert-Aplin, Bull & McGregor, 2015). Last but not least, the gender issue in tendinopathy should have further study under a better structured experimental design since the presence of female dominance predisposing to soft tissue injury during physical activity has been recently provoked (Astill et al, 2017).…”

“…Eccentric calf muscle exercise was demonstrated to induce acute changes on the transverse morphology and strain of the AT in healthy, recreationally active adults (Grigg, Wearing & Smeathers, 2009; Obst, Newsham-West & Barrett, 2015), and thickness alteration of the AT assessed by ultrasonography was conferred as a promising prognostic parameter for predicting Achilles tendinopathy within six to 12 months in asymptomatic and symptomatic patients (Bakkegaard et al, 2015; Fredberg & Bolvig, 2002). Eccentric heel drops involve maximal ankle dorsiflexion, eccentrically lengthened calf muscles and reduced ankle planter flexion moments (Alfredson et al, 1998; Maffulli et al, 2008; Jeong et al, 2014; Sayana & Maffulli, 2007).…”