By Jordana Bieze Foster
Running a marathon does not significantly affect Achilles tendon stiffness, suggesting that overuse may not explain Achilles ruptures in runners, according to a Finnish study published in the October issue of the Journal of Experimental Biology.
Researchers from the University of Jyvaskyla in Finland analyzed 12 participants who ran a marathon-length distance on a treadmill and found that Achilles tendon stiffness one hour after the run was not significantly different from before the run. Achilles tendon force-elongation was characterized using an ankle dynamometer and simultaneous motion-capture-assisted ultrasonography; stiffness was defined as the slope of the force-elongation curve between 10% and 80% of maximum voluntary force.
Oxygen consumption was 7% higher after the run than at baseline, and three-quarters of the runners changed their foot strike pattern during the run, which suggests that the activity did result in physiological stress but that the mechanical properties of the Achilles tendon were not affected. The authors hypothesize that because running involves natural loading, even extended running does not overload the Achilles tendon.
Peltonen J, Cronin NJ, Stenroth L, et al. Achilles tendon stiffness is unchanged one hour after a marathon. J Exp Biol 2012;215(Pt 20):3665-3671.