Running

Every day, I go for a run. Running involves many joint and muscle actions. When broken down to a single leg working, there are three basic phases: initial swing, terminal swing, and stance.

During the initial swing, the foot plantarflexes to push off the ground. The knee swings from extension into flexion. The hip goes into slight extension in order to get the leg behind the torso.  Plantarflexion of the ankle, flexion of the knee, and extension of the hip move in the sagittal plane about the frontal axis. While the knee flexes, the hamstrings act as the agonist to concentrically contract, and the quadriceps act as the antagonist. The osteokinematics of the knee is extension to flexion in an open kinematic chain. In terms of arthrokinematics, the concave tibial plateau rolls and glides posteriorly on the stable convex femur.

In order to get to the terminal swing, the hip must flex in the sagittal plane about the frontal axis. The hip swings from behind the torso to in front of the torso.

Terminal swing begins with the knee flexed in the air and the hip slightly flexed. The knee extends from flexion, and the foot dorsiflexes to plant the foot on the ground. Knee and hip flexion, ankle dorsiflexion, and knee extension act in the sagittal plane about the frontal axis in an open kinematic chain. (The distal foot is lowering to the ground) Once the foot is on the ground, the leg is in the stance phase. The foot then pushes off the ground again to begin the initial swing.