best core work for sprinters

When do you stop…
I don’t mind doing them from time to time,
i would rather like John says, do a large variety every 20-30sec or so than just doing Crunches, or bridges or one style. Do a lot of style, work them all, Work all forms of abs and you’ll be fine.

haha, speaking of bridges, the amount of people i see in the gym doing them completely wrong, their lower back is swaying under, their abs not even contracted…