title: The Achilles tendon is mechanosensitive in older adults: adaptations following 14 weeks versus 1.5 years of cyclic strain exercise.
abstract: The aging musculoskeletal system experiences a general decline in structure and function, characterized by a reduced adaptability to environmental stress. We investigated whether the older human Achilles tendon (AT) demonstrates mechanosensitivity (via biomechanical and morphological adaptations) in response to long-term mechanical loading. Thirty-four female adults (60-75 years) were allocated to either a medium-term (14 weeks;N=21) high AT strain cyclic loading exercise intervention or a control group (N=13), with 12 participants continuing with the intervention for 1.5 years. AT biomechanical properties were assessed using ultrasonography and dynamometry. Tendon cross-sectional area (CSA) was investigated by means of magnetic resonance imaging. A 22% exercise-related increment in ankle plantarflexion joint moment, along with increased AT stiffness (598.2±141.2 versus 488.4±136.9 N mm-1at baseline), Young's modulus (1.63±0.46 versus 1.37±0.39 GPa at baseline) and about 6% hypertrophy along the entire free AT were identified after 14 weeks of strength training, with no further improvement after 1.5 years of intervention. The aging AT appears to be capable of increasing its stiffness in response to 14 weeks of mechanical loading exercise by changing both its material and dimensional properties. Continuing exercise seems to maintain, but not cause further adaptive changes in tendons, suggesting that the adaptive time-response relationship of aging tendons subjected to mechanical loading is nonlinear.
authors.affiliation: Institute of Movement and Sport Gerontology, German Sport University Cologne, 50933 Cologne, Germany g.epro@dshs-koeln.de.|Institute of Biomechanics and Orthopaedics, German Sport University Cologne, 50933 Cologne, Germany.|Sport and Exercise Science Research Centre, School of Applied Sciences, London South Bank University, London SE1 0AA, UK.
authors.forename: Gaspar
authors.identifier: 0000-0002-7241-1533
authors.initials: G
authors.lastname: Epro
authors.affiliation: Institute of Movement and Neurosciences, German Sport University Cologne, 50933 Cologne, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Mierau
authors.affiliation: Department of Radiology, University of Bonn, 53127 Bonn, Germany.
authors.forename: Jonas
authors.initials: J
authors.lastname: Doerner
authors.affiliation: Department of Radiology, University of Bonn, 53127 Bonn, Germany.
authors.forename: Julian A
authors.initials: JA
authors.lastname: Luetkens
authors.affiliation: Department of Radiology, University of Bonn, 53127 Bonn, Germany.
authors.forename: Lukas
authors.initials: L
authors.lastname: Scheef
authors.affiliation: Department of Radiology, University of Bonn, 53127 Bonn, Germany.
authors.forename: Guido M
authors.initials: GM
authors.lastname: Kukuk
authors.affiliation: Department of Radiology, University of Bonn, 53127 Bonn, Germany.
authors.forename: Henning
authors.initials: H
authors.lastname: Boecker
authors.affiliation: Research Institute for Sport and Exercise Sciences, Faculty of Science, Liverpool John Moores University, Liverpool L3 3AF, UK.
authors.forename: Constantinos N
authors.initials: CN
authors.lastname: Maganaris
authors.affiliation: Institute of Biomechanics and Orthopaedics, German Sport University Cologne, 50933 Cologne, Germany.|Cologne Center for Musculoskeletal Biomechanics, Medical Faculty, University of Cologne, 50931 Cologne, Germany.
authors.forename: Gert-Peter
authors.initials: GP
authors.lastname: Brüggemann
authors.affiliation: Sport and Exercise Science Research Centre, School of Applied Sciences, London South Bank University, London SE1 0AA, UK.
authors.forename: Kiros
authors.initials: K
authors.lastname: Karamanidis
mesh_terms: D000125:Achilles Tendon / Q000000981:diagnostic imaging / Q000502:physiology*; D000222:Adaptation, Physiological; D000368:Aged; D000375:Aging; D001696:Biomechanical Phenomena; D055119:Elastic Modulus; D015444:Exercise; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000502:physiology
keywords: Aging; Strength training; Tendon Young's modulus; Tendon cross-sectional area; Tendon stiffness