Foot strike pattern during running alters muscle-tendon dynamics of the gastrocnemius and the soleus

Jennifer R Yong,Christopher L Dembia,Amy Silder,Scott L Delp,Michael Fredericson,Rachel W Jackson

doi:10.1038/s41598-020-62464-3

Abstract

Running is thought to be an efficient gait due, in part, to the behavior of the plantar flexor muscles and elastic energy storage in the Achilles tendon. Although plantar flexor muscle mechanics and Achilles tendon energy storage have been explored during rearfoot striking, they have not been fully characterized during forefoot striking. This study examined how plantar flexor muscle-tendon mechanics during running differs between rearfoot and forefoot striking. We used musculoskeletal simulations, driven by joint angles and electromyography recorded from runners using both rearfoot and forefoot striking running patterns, to characterize plantar flexor muscle-tendon mechanics. The simulations revealed that foot strike pattern affected the soleus and gastrocnemius differently. For the soleus, forefoot striking decreased tendon energy storage and fiber work done while the muscle fibers were shortening compared to rearfoot striking. For the gastrocnemius, forefoot striking increased muscle activation and fiber work done while the muscle fibers were lengthening compared to rearfoot striking. These changes in gastrocnemius mechanics suggest that runners planning to convert to forefoot striking might benefit from a progressive eccentric gastrocnemius strengthening program to avoid injury.

Highlights

Running is thought to be an efficient gait due, in part, to the behavior of the plantar flexor muscles and elastic energy storage in the Achilles tendon
The plantar flexors are crucial to body weight support and forward propulsion during running[25]; it is critical to understand the effects of foot strike pattern on tendon energy storage, the force generation ability of the plantar flexors, and the work done while muscle fibers are shortening and lengthening
Foot strike pattern affected tendon energy storage differently for the components of the Achilles tendon associated with the gastrocnemii and the soleus

Summary

Introduction

Running is thought to be an efficient gait due, in part, to the behavior of the plantar flexor muscles and elastic energy storage in the Achilles tendon. The plantar flexor muscles and Achilles tendon span the ankle joint, suggesting that their mechanics would be affected by foot strike pattern. Forefoot striking is associated with a more plantarflexed ankle[9] and flexed knee[20] at foot contact compared to rearfoot striking These kinematic differences cause shorter plantar flexor muscle-tendon lengths and likely shorter muscle fiber lengths, which can affect these muscles’ ability to generate force during forefoot striking. The plantar flexors are crucial to body weight support and forward propulsion during running[25]; it is critical to understand the effects of foot strike pattern on tendon energy storage, the force generation ability of the plantar flexors, and the work done while muscle fibers are shortening and lengthening

Objectives

Methods

Results

Conclusion