A plank doesn’t look like much, but it’s an amazing workout. Planking tones and strengthens all the muscles in your core – abdominals, obliques, hips, and back. It also works your glutes and hamstrings while improving posture and balance. The smallest, most controlled exercises are often the more effective. But, eight hours? Nope. Planks should be measured in seconds, not minutes, and certainly not hours.