Build strong core muscles without weights, just using these three crunch variations from a functional training coach.
You don't need sit-ups to build a strong core, just try this five-move dumbbell abs workout designed by a Hyrox age group ...
A prime example of this fitness savvy is his nighttime ab routine, which consists of one exercise, one weight (or not), and takes less than 10 minutes to complete. If you need proof of concept ...