Build strong core muscles without weights, just using these three crunch variations from a functional training coach.

Side bends and plate dips can only go so far ... challenges you to work a different way than you would doing situps or crunches. This isn't only working your obliques—but your whole core will ...

since bicycle crunches engage three major core muscle groups at once – including your external obliques (the pair of muscles either side of your abdomen), transverse abdominis (known as your ...