Recovering the leg
If you do a couple of small jumps in place, you will notice how important the extension of the ankle is – in even a very small jump, the whole leg is engaged. This is the bi-articular muscle system at work. (The Biarticular Muscles in Running) Every stride can be considered a small jump, an extension of the whole body from a fixed point.
At the end of this extension, in running, the leg will recover itself as the other leg extends. There is no good reason for emphasizing leg recovery, and, indeed, there are several good reasons for not working on leg recovery.
The first among these is that focusing on recovery will tend work against a proper complete extension. If the leg completes its extension (depending on the desired speed, the leg will be more or less straightened), then the stretch applied to the iliopsoas and psoas muscles will lead to an easy recovery. If this is done, the leg will not be contracted towards the trunk, and will move easily to the ground underneath the trunk, arriving before the weight of the body falls.
If, on the other hand, one focuses on leg recovery (driving the knees forward, for example, which is often recommended), on will tend to lift the leg, contracting it towards the trunk. This is where we will often see the ankle flexed, and the toes lifted. This contracted state will tend to persist, leaving the leg lifted in front of the running body. The leg will then hang there until the weight of the body falls upon it, leading to excess compression, interference with the natural spring that the muscles of the biarticular system create, and braking forwards movement. Simply put, if you lift your leg, you will then need to put it down, whereas, if you work on extension, the recovery will take care of itself, and you will eliminate “landing” on the foot.
The recovery of the leg is linked to the arc of the running stride. When the standing leg is underneath the body the joints of the legs are bent such that the body is at the lowest point in the stride. As the body has come over the foot, it has descended – this descent helps to swing the leg down to go forward. By the time the body has reached its lowest point, the recovering leg has come alongside of the standing leg. Then, when the body begins to extend off of the driving leg, the recovering leg is carried both forward and upward with the body. Remember, in order to recover, the leg is moving faster than the forward speed of the body. Accelerating the body also accelerates the leg swing. The lower leg, if nicely free, simply follows the movement of the thigh rotating forward at the hip. However, when the knee reaches the extent of its forward swing, and begins to descend, the lower leg continues forward, hinging at the knee, which gives the body extra impetus in both forward and upward direction. The extension of the lower leg allows the body to remain airborne for an instant longer, allowing the foot to reach the ground before the body falls upon it. Arm swing further assists the body in stretching the arc of the running stride – if a long-jumper does not swing body legs and arms forward, he will not be able to jump as far. However, while forward swing of the arm accompanies the extension of the body off of the driving leg, the forward swing of leg comes after the extension and, thus, lengthens the arc of the stride.
There is absolutely no reason that a foot that lands in front of the body should slow the forward movement of the body. In fact, if the joints are free, putting the weight of the leg on the ground helps maintain forward momentum through the descent phase of the arc of the running stride.