The first part of your foot you should land on when running is your forefoot. Why? There’s a special relationship between this contact-point on the foot with the ground and injury prevention in running. More specifically, the precise part of your forefoot that should strike first is towards the outer-side (lateral) of the forefoot, just under the 4th and 5th toes. Landing on the lateral side of the forefoot has proved to be incredibly effective for dispersing bending strain over a larger area of the forefoot, thereby preventing peak pressures from exceeding normal on the foot. Read more here about the advantages and the mechanical relevance of making initial-ground contact towards under the 5th toe, not the big toe in forefoot running. 
What Part of Your Foot Should You Land on When Running?
