1Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI; 2Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI; and 3Department of Orthopedics and Rehabilitation, University of Wisconsin-Madison, Madison, WI.
Med Sci Sports Exerc. 2014 Mar;46(3):557-64. doi: 10.1249/MSS.0b013e3182a78c3a.
Increasing step rate has been shown to elicit changes in joint kinematics and kinetics during running, and it has been suggested as a possible rehabilitation strategy for runners with patellofemoral pain. The purpose of this study was to determine how altering step rate affects internal muscle forces and patellofemoral joint loads, and then to determine what kinematic and kinetic factors best predict changes in joint loading.
We recorded whole body kinematics of 30 healthy adults running on an instrumented treadmill at three step rate conditions (90%, 100%, and 110% of preferred step rate). We then used a 3-D lower extremity musculoskeletal model to estimate muscle, patellar tendon, and patellofemoral joint forces throughout the running gait cycles. In addition, linear regression analysis allowed us to ascertain the relative influence of limb posture and external loads on patellofemoral joint force.
Increasing step rate to 110% of the preferred reduced peak patellofemoral joint force by 14%. Peak muscle forces were also altered as a result of the increased step rate with hip, knee, and ankle extensor forces, and hip abductor forces all reduced in midstance. Compared with the 90% step rate condition, there was a concomitant increase in peak rectus femoris and hamstring loads during early and late swing, respectively, at higher step rates. Peak stance phase knee flexion decreased with increasing step rate and was found to be the most important predictor of the reduction in patellofemoral joint loading.
Increasing step rate is an effective strategy to reduce patellofemoral joint forces and could be effective in modulating biomechanical factors that can contribute to patellofemoral pain.
增加步频已被证明会改变跑步时的关节运动学和动力学，并且它已被提议作为髌股疼痛患者的一种可能的康复策略。本研究的目的是确定改变步频如何影响内部肌肉力量和髌股关节负荷，然后确定哪些运动学和动力学因素可以最好地预测关节负荷的变化。
我们记录了 30 名健康成年人在仪器化跑步机上以三种步频条件（90%、100%和 110%的最佳步频）跑步时的全身运动学。然后，我们使用 3D 下肢肌肉骨骼模型来估计整个跑步步态周期中的肌肉、髌腱和髌股关节力。此外，线性回归分析使我们能够确定肢体姿势和外部负载对髌股关节力的相对影响。
将步频增加到 110%的最佳步频会使峰值髌股关节力降低 14%。由于步频增加，髋关节、膝关节和踝关节伸肌以及髋关节外展肌的力量也发生了变化，在中足期，这些肌肉的力量都减小了。与 90%的步频相比，在更高的步频下，股直肌和腘绳肌在早期和晚期摆动时的峰值负荷分别增加。随着步频的增加，峰值站立阶段膝关节屈曲减小，并且被发现是减少髌股关节负荷的最重要预测因素。
增加步频是一种有效降低髌股关节力的策略，可能有效调节导致髌股疼痛的生物力学因素。
