To initiate running, we expend stored energy to facilitate movement upwards and forwards, similar to an airplane taking off. This begins with a leading leg extending forwards and subsequently landing as contact is made between the foot and the ground. Some of the used (kinetic) energy is absorbed from landing, and stored in elastic muscle tissues. Since our body has moved forward, the muscles in our back leg have stretched out like springs. The energy stored in the spring-load leg muscles then recoil, pulling our back leg forward until it becomes the leading leg. This cycle is repeated as we run. Our arms follow is similar cycle of swinging back and forth, but in opposition of our legs. This is a very simplified explanation of running biomechanics.
Rather than having to generate considerable energy to initiate movement forward or “take off” with each step, much of the kinetic energy we have already invested to start moving is recycled in our muscles. We do, however, have to expend additional energy to continue running. This is similar to how an airplane burns an significant quantity of fuel to take off, and then much less is needed to maintain course during flight. If an airplane were to be constantly veering side to side, while gaining and losing altitude, rather than maintaining a constant bearing and altitude to their destination, fuel would be burned in an inefficient manner. The same is true with running, in that veering all over the sidewalk, excessively swinging our arms and legs, and gaining too much height with each step, will result in inefficient biomechanics. The more efficient an individual’s running biomechanics are, the less energy they will need to expend to cover a given distance.
Striking refers to the part of the foot that lands or strikes the ground first when running. This is either the heal with rear-foot striking, or the mid to forefoot with forefoot striking. Many competitive runners alter their striking to gain speed and economy. However, after consulting the sports-medicine literature, the evidence to support forefoot vs rear-foot running is conflicting. While some articles support that the anatomy of the forefoot better accommodates the forces of striking than the heel, front and rear foot strikers appear equally efficient and at similar risk of injury. Importantly, many studies found that changing striking form too quickly puts runners at significant risk of injury. Barefoot running also remains controversial, with research advocating for running with supportive and cushioned footwear.
Stride and Cadence
To increase speed, a runner can increase either stride length (distance travelled per step) or cadence (steps per minute). Runners typically do not change their stride as this can throw off their balance and increase the impact of striking, resulting in greater risk of injury. Instead, runners typically increase their cadence towards 180 steps per minute. This allows for shorter but faster leg turnover, while promoting good posture and balance, running economy, and reducing the risk of injury.
Cadence = Foot Strikes per Minute
An easy way to calculate this is to count the number of times your left or right foot strikes the ground over 12 seconds, and multiply it by 10. This makes math easy when you may be mentally fatigued during a run.
Ex. 15 right foot strikes in 12 seconds = 150 steps/minute
As a runner’s legs swing back and forth like pendulums, runners should maintain an upright posture, stable core, with their head up, eyes forwards, and shoulders back and relaxed. This will promote balance and stability, while reducing the risk of injury. As the runner increases their speed, they should correspondingly increase how much they lean forward. This moves their centre of gravity forward, conserving momentum and reducing energy lost as each foot strikes the ground.
Despite conflicting evidence, it is important to realize that research studies compare groups of runners, rather than individuals. Furthermore, no two runners have identical form. Runners should find their own running style, while endeavouring to make gradual improvements to their biomechanics and form as necessary.