The key here, of course, is to do it with proper form, which means keeping your elbows aligned directly beneath your shoulders, and maintaining a neutral, straight spine from heels to head. Aim for just 10-second holds to start, gradually building to 60 seconds.
Christian Heria, founder of the calisthenics training program Thenx.com, emphasizes that it's the isometric nature of the exercise that's so important, "Most athletes do concentric movements, but fail to work on isometric holds. Keeping time under tension in your muscles (when you hold any move) is essential in muscle development and creating a strong foundation in your physical capabilities."
And if you tend to have shoulder pain? Conrad says planks are a good way to build strength: "When your forearms are parallel to your body during the plank, it puts the shoulders in 'external rotation,' which gets the rotator cuff active, becoming a better shoulder stabilizer. When you link this with core activation for your body's overall health, it's game over!"