Plantar Flexor Mechanics during Rearfoot Striking and Forefoot Striking Running

Running is thought to be efficient largely due to elastic energy storage in muscles and tendons, particularly the plantar flexor muscles and the Achilles tendon. Although plantar flexor muscle mechanics have been explored during rearfoot striking, little is known about how converting to a forefoot striking running pattern affects energy storage in the Achilles tendon or alters demands placed on the plantar flexor muscles. This study examines how plantar flexor muscle-tendon mechanics during running differ between rearfoot and forefoot striking. Plantar flexor mechanics were estimated using musculoskeletal simulations driven by joint angles and electromyography recorded from runners using both rearfoot and forefoot striking running patterns. The simulations revealed that foot strike pattern affected the gastrocnemius and the soleus differently. For the gastrocnemius, forefoot striking resulted in greater force generation ability (i.e. the force generated per unit of activation) and increased negative fiber work compared to rearfoot striking. For the soleus, forefoot striking resulted in decreased energy storage in the tendon and decreased positive fiber work compared to rearfoot striking. Forefoot striking appears to place greater demands on the gastrocnemius and take advantage of its improved force generation ability. Based on increased activation and negative fiber work during early stance, runners interested in altering their foot strike pattern should be mindful of the increased demands on the gastrocnemius when converting to forefoot striking. <br/><br/>This project includes the following software/data packages: <br/> <ul> <li> <a href="https://simtk.org/frs?group_id=1611#pack_2048">simulation_data </a> : Simulations of medial and lateral gastrocnemius and soleus mechanics for 16 runners using a rearfoot striking and forefoot striking running pattern. Simulations were generated in OpenSim 3.3. </li> </ul>

奔跑被认为是一种高效的运动方式，其主要得益于肌肉和肌腱中的弹性能量储存，尤其是足底屈肌和跟腱。尽管在足跟触地阶段对足底屈肌的力学特性已有所研究，但对于转变为前足触地跑步模式如何影响跟腱中的能量储存或改变对足底屈肌的负荷需求，了解甚少。本研究旨在探讨在跑步过程中，足底屈肌-肌腱的力学特性在足跟触地和前足触地之间有何差异。通过利用来自采用足跟触地和前足触地跑步模式的跑者的关节角度和肌电图记录驱动的肌骨模拟，估计了足底屈肌的力学特性。模拟结果显示，足部触地模式对腓肠肌和比目鱼肌的影响不同。对于腓肠肌，与前足触地相比，足跟触地产生了更高的力生成能力（即单位激活产生的力）和增加的负纤维功。对于比目鱼肌，与前足触地相比，足跟触地导致跟腱中的能量储存减少和正纤维功的降低。前足触地似乎对腓肠肌提出了更高的要求，并充分利用了其改进的力生成能力。基于早期站立阶段激活程度的增加和负纤维功的增加，对于想要改变足部触地模式的跑者来说，应注意在转变为前足触地时对腓肠肌需求的增加。<br/><br/>本项目包括以下软件/数据包：<br/> <ul> <li> <a href="https://simtk.org/frs?group_id=1611#pack_2048">simulation_data </a> : 使用OpenSim 3.3模拟了16名跑者采用足跟触地和前足触地跑步模式时的内侧腓肠肌、外侧腓肠肌和比目鱼肌的力学特性。</li> </ul>