Heel needs to be able to go past the block. Provides a greater stretch on the achilles and more powerful start. One of the reasons to why a lot of athletes have been putting their feet high on the blocks. The blocks are now taller and in order to get the stretch-reflex, the heel must be able to go beyond.
The higher block limits the achilles’ ability to full stretch when the foot is in full contact.
Also, the head should hang down between the arms and come up to neutral by the second step and the body should have a slight forward lean while resting in the blocks. Shins parallel.
Kind of getting off topic here, but when do we ever stay on topic haha.