title: Achilles tendon stiffness is unchanged one hour after a marathon.
abstract: Overuse-induced injuries have been proposed as a predisposing factor for Achilles tendon (AT) ruptures. If tendons can be overloaded, their mechanical properties should change during exercise. Because there data are lacking on the effects of a single bout of long-lasting exercise on AT mechanical properties, the present study measured AT stiffness before and after a marathon. AT stiffness was determined as the slope of the force-elongation curve between 10 and 80% of maximum voluntary force. AT force-elongation characteristics were measured in an ankle dynamometer using simultaneous motion-capture-assisted ultrasonography. Oxygen consumption and ankle kinematics were also measured on a treadmill at the marathon pace. All measurements were performed before and after the marathon. AT stiffness did not change significantly from the pre-race value of 197±62 N mm(-1) (mean ± s.d.) to the post-race value of 206±59 N mm(-1) (N=12, P=0.312). Oxygen consumption increased after the race by 7±10% (P<0.05) and ankle kinematic data revealed that in nine out of 12 subjects, the marathon induced a change in their foot strike technique. The AT of the physically active individuals seems to be able to resist mechanical changes under physiological stress. We therefore suggest that natural loading, like in running, may not overstress the AT or predispose it to injury. In addition, decreased running economy, as well as altered foot strike technique, was probably attributable to muscle fatigue.
authors.affiliation: Neuromuscular Research Center, Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä 40014, Finland. jussi.t.peltonen@jyu.fi
authors.forename: Jussi
authors.initials: J
authors.lastname: Peltonen
authors.forename: Neil J
authors.initials: NJ
authors.lastname: Cronin
authors.forename: Lauri
authors.initials: L
authors.lastname: Stenroth
authors.forename: Taija
authors.initials: T
authors.lastname: Finni
authors.forename: Janne
authors.initials: J
authors.lastname: Avela
mesh_terms: D000125:Achilles Tendon / Q000000981:diagnostic imaging / Q000293:injuries / Q000502:physiology*; D000328:Adult; D000842:Ankle / Q000000981:diagnostic imaging / Q000502:physiology*; D000843:Ankle Joint / Q000000981:diagnostic imaging / Q000502:physiology*; D001696:Biomechanical Phenomena; D012090:Cumulative Trauma Disorders; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D018763:Muscle Fatigue; D018482:Muscle, Skeletal / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology; D012420:Running / Q000293:injuries / Q000502:physiology*; D014463:Ultrasonography; D055815:Young Adult