School · Shoes, explained · 45 s .
Stack height
How much shoe sits between your foot and the ground.
Stack height is the thickness of the sole under the heel and under the forefoot. Modern trainers range from under 25 mm to over 45 mm.
More stack means more protection and, with good foam, more energy return. It also means less ground feel and a higher, less stable platform.
For elite road racing, World Athletics caps sole thickness at 40 mm.
High stack for long and easy runs; lower stack for agility, track and technical trails.
Quick check .
What limit does World Athletics set on sole thickness for road racing?
In elite road racing, the sole can't be thicker than 40 mm.