Landing heel-first when running was not only proven to be a major risk factor for shin splints, it also dramatically increases the risk of shin fracture as compared with forefoot running, (see here what a proper forefoot strike looks like) which was found to be far more effective at reducing net impacts off the shins than any other approach!
Heel strike running has unfortunately demonstrated a long track record of causing excessive impacts that the muscles can’t absorb, and at faster running speeds, these excessive impacts, such as a burst in collisional impact, is poorly absorbed by the heel pad, even in a cushioned heeled running shoe. As a consequence, a heel strike runner becomes more vulnerable to a shin fracture, and of course, heel injury.
Most evidence (references below article) to date suggests there are at least two main factors that cause stress fractures of the shin in runners who use a heel strike, and not in runners who use a forefoot strike.
High Acceleration and Loading
To quantify ground reaction forces in heel strike running, researchers measure tibia (shin) peak acceleration and loading rates, and found:
- heel strike running generates the highest tibial peak acceleration and the highest loading rates which are the top risk factors for shin fracture.
Heel Pad Breaks-Down
Another way heel strike running contributes to shin splints and fracture is that the pronounced downward force at heel strike directly damages the foot’s heel pad to such an extent where it loses all of its shock absorbing properties, which causes more impact to ripple out from the heel to the lower leg, even in a cushioned shoe:
- The human heel pad contains a venous plexus which acts as a shock absorber. The venous plexus was found to be very capable and effective at absorbing impact when walking with a heel strike, but was found to quickly deform when running with a heel strike.
For example, one investigation found that the venous plexus failed to dampen the ground reaction force in heel strike runners, and here was the consequences:
- impact forces penetrated through the heel pad, up the skeleton
- the heel pad lost most of its shock absorption properties during running, but not during walking
The scientists concluded that the shock absorbing properties of the heel pad works best for heel strike walking, but not for heel strike running.
Other work has found that the human heel pad operates close to its pain threshold at fast walking speeds while barefoot, which is why when running barefoot runners prefer a forefoot strike.
Its for all these reasons that many researchers believe forefoot running is highly encouraging as a preventive strategy for lower leg stress fractures since it eliminates the high burst in the ground reaction force at touchdown, while impact remains lowest at the heel, which is also why heel injuries are extremely rare in forefoot runners.
Moreover, the reasons forefoot running alone is a major slam dunk for preventing shin fracture is by aligning the shin in a better position at landing, allowing it to be more vertically aligned closer to your center mass (torso), rather than aligning the shin more horizontally farther away from the body, like in heel strike running, shown below:
A shin bone aligned more vertically at landing, which is what happens when you land forefoot-first, when running is the only way to reduce the amount of compressive forces and torsional stress on the shin. This is why forefoot running remains critically important to preventing injuries to the shin, but also the knees, hips and lower back! Read more here on that!
References:
Crowell, HP and Davis, SI. (2011). Gait retraining to reduce lower extremity in loading in runners. Clin Biomech, 2011; 26(1):78-83
Friesenbichler, B. (2011). Tissue vibration in prolong running. J Biomech, 2011; 44(1):116-20.
Wiejers, RE. (2005). The dampening properties of the venus plexus of the heel region of the foot simulated at heel strike. J Biomech, 2005;38(12):2423-30.
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