Not only will it challenge your balance and agility, but you'll also really work the hamstrings, glutes, abs, triceps, and shoulder muscles while doing it.
How to do this exercise:
Crab walks are done by first sitting on the ground, hands planted just behind your back and legs bent, feet on the floor.
Next, raise the hips up slightly so that only your hands and feet are now in contact with the ground. The higher you can raise your hips at this point, the more abdominal benefits you're going to see.
Once you're in this position, you then want to “walk” across the room as fast as you can. If you'd like, try creating an obstacle course to move through, as the extra turning will further work the upper body muscles.
Try to crab walk for a minute straight then rest and go at it again. Once you're really comfortable with the movement, if you want to challenge yourself further, try wearing a weight vest or belt while you do it to add extra resistance.