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Achilles Tendinopathy Modulates Force Frequency Characteristics of Eccentric Exercise


Medicine & Science in Sports & Exercise: March 2013 - Volume 45 - Issue 3 - p 520–526
doi: 10.1249/MSS.0b013e31827795a7
Applied Sciences

Introduction Previous research has demonstrated that ground reaction force (GRF) recorded during eccentric ankle exercise is characterized by greater power in the 8- to 12-Hz bandwidth when compared with that recorded during concentric ankle exercise. Subsequently, it was suggested that vibrations in this bandwidth may underpin the beneficial effect of eccentric loading in tendon repair. However, this observation has been made only in individuals without Achilles tendinopathy. This research compared the force frequency characteristics of eccentric and concentric exercises in individuals with and without Achilles tendinopathy.

Methods Eleven male adults with unilateral midportion Achilles tendinopathy and nine control male adults without tendinopathy participated in the research. Kinematics and GRF were recorded while the participants performed a common eccentric rehabilitation exercise protocol and a concentric equivalent. Ankle joint kinematics and the frequency power spectrum of the resultant GRF were calculated.

Results Eccentric exercise was characterized by a significantly greater proportion of spectral power between 4.5 and 11.5 Hz when compared with concentric exercise. There were no significant differences between limbs in the force frequency characteristics of concentric exercise. Eccentric exercise, in contrast, was defined by a shift in the power spectrum of the symptomatic limb, resulting in a second spectral peak at 9 Hz, rather than 10 Hz in the control limb.

Conclusions Compared with healthy tendon, Achilles tendinopathy was characterized by lower frequency vibrations during eccentric rehabilitation exercises. This finding may be associated with changes in neuromuscular activation and tendon stiffness that have been shown to occur with tendinopathy and provides a possible rationale for the previous observation of a different biochemical response to eccentric exercise in healthy and injured Achilles tendons.

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1Institute of Health and Biomedical Innovation, Queensland University of Technology, Kelvin Grove, Queensland, AUSTRALIA; 2Faculty of Health Sciences and Medicine, Bond University, Gold Coast, Queensland, AUSTRALIA, 3Center of Excellence for Applied Sport Science Research, Queensland Academy of Sport, Sunny Bank, Queensland, AUSTRALIA; and 4DeustoTech, University of Deusto, Bilbao, SPAIN

Address for correspondence: Nicole L. Grigg, Ph.D. Center for Musculoskeletal Research, Griffith University Gold Coast, Queensland 4222, Australia; E-mail:

Submitted for publication April 2012.

Accepted for publication October 2012.

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© 2013 American College of Sports Medicine