Trainer tips: Keep your elbows pointing directly behind you throughout the exercise. Don’t allow your shoulders to shrug ...

A. Get in plank position with hands shoulder-width apart on a chair, and raise left leg to hip height behind you. Bend elbows straight back, lowering chest toward the chair, as you bring left knee ...

Plank Knee Cross: Place both forearms on the seat of the chair and step your feet back into a plank position. Keeping your hips low and core tight, bring your right knee to the inside of your left ...

Push-ups are a tried-and-true exercise that work on the arms, chest, and shoulders. By working on various muscle groups, ...

Ready for a challenge? Grab a medicine ball and try the juggling plank, which might just be the hardest upper body exercise you'll do all week.

The plank exercise works the abs, arms, back and glutes. But performing it properly is key to reaping the benefits and reducing back pain.

Not sure your plank form is on point? Watch this trainer do the plank exercise correctly with step-by-step form tips, plank benefits, and plank variations.