The exercise of running backwards helps the runner fix quite a few of the most common biomechanical problems, such as lateral knee pain, certain kinds of lower back pain, and plantar fasciitis. It does this by correcting the location of your center of gravity (CoG).

The CoG is importantly related to the body’s “mechanical solution,” the algorithm of muscle contractions that maintains the body erect and stable throughout the course of activity. Because the CoG is defined as the place where there are no forces acting on the body, any shifts or changes in the muscle firings that the body interacts with mechanical energy—any change in the mechanical solution—will necessarily alter the location of the center of gravity.

Strengthening a muscle that was previously too weak to be used in strenuous exercise will change the body’s mechanical solution: for any particular action, employing more muscles instead of less facilitates the body’s movement through space, since the brain is better able to correct for a center of gravity that moves due to change of direction, change of speed, or variable terrain.

Most of the time, lateral knee pain has to do with “simple muscle imbalance,” that is, having one particular muscle (usually on the hip or thigh, but also on the calf), pull with more force than its opposing muscle. Even though the leg only seems to travel straight back, there are a multitude of forces acting on the leg, including torque (rotational force). This is because, during the optimal running stride, the leg rotates outwards as it swings forwards, and rotates inwards during the landing phase, as it swings back. When the muscles that create this rotational motion are impaired, the torque does not become neutralized. Because the knee mostly works as a hinge (moving primarily forwards and back), whereas the ankle, the hips, and the back can rotate much more effectively, rotational forces are much more likely to damage the knee than any other joint.

Strengthening the weak muscles—or, in more real terms, strengthening the relationship between strong and weak muscles—removes the conditions that caused knee pain in the first place.

Things to keep in mind:

1. Use a flat, predictable surface, such as a track. Running on a variable surface can make you tense up and develop compensation patterns to maintain balance
2. If you must look behind you, alternate the ratio of right-to-left looks; make sure that both sides of your body are getting tired at the same time.
3. The point of this exercise is not speed or power, but mobility and comfort. The skills gained during backwards running are not meant to increase backwards running speed or endurance per se, but rather to be transferred to our normal running to increase forwards speed and reduce the incidence of injury.

The best way to go about a training plan that includes running backwards is by designing a slow progression for this exercise, tailored to the specific athlete’s skill and endurance level. If used as a part of a larger workout, the running-backwards session should serve as a strenuous warm-up at the beginning of the workout, so that the frontal muscles (and movement patterns used) become reinforced throughout the exercise session.

Remember that running backwards is a corrective exercise (to achieve and maintain proper CoG-related biomechanics). The body’s mechanical paradigm doesn’t support backwards travel as the predominant way of locomotion, especially at high speeds. This exercise is meant to solve mechanical problems by teaching the frontal and rear muscles of the body to work together, and allow the CoG to move along the correct axis: starting from the centerpoint of the hips towards the front and directly parallel to the horizon.