Sit-ups tighten and tone the abdominal muscles that run from beneath the sternum to above the pelvis. This results in a flatter stomach and, if practised along with plenty of aerobic exercise ...

Sit-ups require you to lift all the way up ... like your triceps and shoulders, while you hold the pose. Still, all of these ab exercises can be part of a healthy, effective workout regimen.

Place your hands by your temples, with your elbows pointing out to the side. Lift your left knee, and at the same time, bend ...

Also known as a jackknife, the bodyweight move recruits the entire core and provides a stability challenge that sit-ups and crunches just can't get ya. And while it's a challenging pose on its own ...