Achilles Tendon Strain In Runners With Achilles Tendinopathy During Running

PURPOSE: Achilles tendinopathy (AT) is one of the most common running-related injuries.1 Previous studies investigating biomechanical risk factors during running mainly focused on kinematic and kinetic factors2. These are, however, surrogate measures for Achilles tendon loading. A more direct measure is Achilles tendon strain. This strain has been examined during isometric plantar flexion in runners with AT,3 however not during running in runners with AT. The purpose is to compare Achilles tendon strain between runners with AT and injury-free runners during running. METHODS: To date, 15 of the planned 24 long-distance runners (seven AT, eight injury-free) were included. 3D marker positions, ground reaction forces and displacement of the Achilles tendon origin were recorded during running at 3.33 m/s on an instrumented treadmill. The Achilles tendon origin was defined as the myotendinous junction with the gastrocnemius medialis, which was tracked using an ultrasound transducer attached to the lower leg.4 Tendon length was represented by the distance between its insertion on the calcaneus and the myotendinous junction. Achilles tendon strain was defined as the percentage change in tendon length during running relative to the static standing Achilles tendon length.4 Independent t-tests were conducted to compare time-normalized waveforms and peak and average values of tendon strain between groups. RESULTS: AT runners showed significantly higher Achilles tendon strain values at initial contact and a higher peak (5.4 ± 2.8%) and average (1.9 ± 2.1%) strain during the stance phase, compared to injury-free runners (2.3 ± 1.7% and -0.7 ± 1.7%, respectively). CONCLUSIONS:An increased Achilles tendon strain during running in AT runners may potentially be associated with AT. Hence, Achilles tendon strain may prove to be a factor to consider in better understanding the biomechanical mechanisms underlying AT in runners. Further studies on Achilles tendon strain may be larger and prospective to deepen our knowledge of AT mechanisms in runners, and is essential to improve treatment and injury prevention. References: [1] Lagas et al., J Sci Med Sport (2020)[2] Willwachter et al., Sports Med (2022)[3] Child et al., Am J Sports Med (2010)[4] Farris et al., Eur J Appl Physiol (2012)