Abstract
Achilles tendinopathy and patellofemoral pain are common running injuries associated with increased Achilles tendon (AT) forces and patellofemoral joint (PFJ) stresses. This study examined AT forces and PFJ stresses at different running speeds in high-performing endurance runners. Twenty runners ran overground at four running speeds (3.3, 3.9, 4.8, and 5.6m/s). AT forces and PFJ stresses were estimated from kinematic and kinetic data. Repeated measures ANOVA with partial eta squared effect sizes was conducted to assess differences between running speeds. Increased peak AT forces (19.5%; p<0.001) and loading rates (57.3%; p<0.001) from 3.3m/s to 5.6m/s were observed. Cumulative AT loading was greater in the faster speeds compared to the slower speeds. Faster running speeds resulted in increased peak plantar flexor moments, increased peak plantar flexion angles, and a more flexed knee and an anterior center of pressure position at touchdown. Peak PFJ stress was lower in the slowest speed (3.3m/s) compared to the faster running speeds (3.9-5.6m/s; p=0.005). PFJ stress loading rate significantly increased (43.6%; p<0.001). Greater AT loading observed could be associated with strategies such as increased plantar flexor moments and altered lower body position at touchdown which are commonly employed to generate greater ground contact forces. Greater AT and PFJ loading rates were likely due to shorter ground contact times and therefore less time available to reach the peak. Running at faster speeds could increase the risk of developing Achilles tendinopathy and patellofemoral pain or limit recovery from these injuries without sufficient recovery.
Highlights
Injuries to the lower extremities are common in runners.[1]
Increased running speed resulted in greater peak Achilles tendon forces
While patellofemoral joint stress initially increased when the high-p erforming endurance runners increased speed from the slowest speed but did not increase beyond 3.9 m/s, the differences observed with Achilles tendon forces and with the initial increase in patellofemoral joint stress are likely to be a result of the strategies commonly employed by runners when running at faster running speeds
Summary
Injuries to the lower extremities are common in runners.[1]. In particular, Achilles tendinopathy and patellofemoral pain are among the most common running-related injuries accounting for 6.2–10% and 5.5–17% of all running-related injuries, respectively.[1,2]The Achilles tendon largely comprises of collagen and elastin fibers and contributes significantly to the mechanical work done by the plantar flexors.3-5 During running, the Achilles tendon experiences considerable repetitive loads.[5]. . High Achilles tendon forces and loading rates may inhibit recovery from Achilles tendinopathy owing to the associated diminished mechanical and material properties.[3] In addition to high prevalence, Achilles tendinopathy has considerably higher reinjury rates with 35% of marathon runners who developed Achilles tendinopathy reporting a previous Achilles tendinopathy 12 months prior to their injury.[7] When running at faster speeds, the contribution from Achilles tendon increases to support efficient mechanical work done by the plantar flexors.[4] Greater cumulative loading of the Achilles tendon has been associated with faster running speeds in recreational runners.[8] With increasing levels of tendon fatigue, morphological changes have been observed.[9] Without sufficient recovery, running at faster speeds could lead to increased degeneration of the tendon. Understanding factors such as running speed and the consequential potential changes in loading in high-performing runners can support the development of appropriate training and competition programs to minimize the risk of developing Achilles tendinopathy
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