Gait (human) - Foot Strike

One variable aspect in different gaits is foot strike – how the foot contacts the ground, specifically which part of the foot first contacts the ground.

• forefoot strike – toe-heel: ball of foot lands first
• midfoot strike – heel and ball land simultaneously
• heel strike – heel-toe: heel of foot lands, then plantar flexes to ball

In sprinting, gait typically features a forefoot strike, but the heel does not contact the ground.

Some researchers classify foot strikes by the initial center of pressure; this is mostly applicable to shod running (running while wearing shoes). In this classification:

• a rearfoot strike (heel strike) has the initial center of pressure in the rear third of the shoe (0–33% of shoe length);
• a midfoot strike is in the middle third (34–67% of shoe length);
• a forefoot strike is in the front third (68–100% of shoe length).

Foot strike varies to some degree between strides, and between individuals. It varies significantly and notably between walking and running, and between wearing shoes (shod) and not wearing shoes (barefoot).

Typically, barefoot walking features heel or midfoot strike, while barefoot running features midfoot or forefoot strike. Barefoot running rarely features heel strike, because the impact is painful, the human heel pad not absorbing much of the force of impact. By contrast, 75% of runners wearing modern running shoes heel strike; running shoes being characterized by a padded sole, stiff soles and arch support, and sloping down from a more padded heel to a less padded forefoot.

The cause of this change in gait in shod running is unknown, but Liebermann notes that there is correlation between the foot-landing style and exposure to shoes. In some individuals, the gait is largely unchanged – the leg position and foot position are identical in barefoot and shod running – but the wedge shape of the padding moving the point of impact back from the forefoot to the midfoot. In other cases, it is conjectured that the padding of the heel softens the impact and resulting in runner modifying their gait to contact further back in the foot.

A 2012 study using Harvard University runners found that those who "habitually rearfoot strike had approximately twice the rate of repetitive stress injuries than individuals who habitually forefoot strike". This was the first study that investigated the link between foot strike and injury rates.