You'd be hard-pressed to find a fitness expert (or model, for that matter) who doesn't swear by the full-body benefits of a plank. Just holding your body in that static position tones your muscles from head to toe, and many pros say that a single plank can do the core work of dozens of crunches.
That being said, proper form is essential and can be the difference between reaping all these benefits and really not doing much of anything. But Real Simple just revealed a simple yet genius pro tip for guaranteeing perfect alignment every time.
Geralyn Coopersmith, global director of performance and fitness training for Nike, says that while in a standard plank (push-up position with both hands on the ground), imagine a glass of water balancing on your lower back to ensure that your spine isn't sagging. Picturing a ball rolling from your neck to your heels without getting stuck in a sunken valley also works. Keeping your back aligned is essential for getting the most out of the move, as it all but guarantees that your core is engaged and your shoulders and triceps are working as well.
If you're having trouble picturing it, you could even try to actually balance your water bottle on your lower back. (We love Mara Hoffman x S'well's Blue Feathers bottle, $42, FWIW.) Another tip that we picked up from a trainer is to recruit a buddy to amp up your typical plank: Have your friend press gently on different parts of your back and legs while you try to keep your form, which engages your muscles even more as you try to maintain balance.
What's your favorite way to soup up a plank? Tell us in the comments below!