Thanks for signing up for BuzzFeed's 21-Day Strong Core Challenge!

Your core muscles — including your abs — stabilize your spine, which means you can thank your abs for helping control your head, neck, and pelvis. Your core helps you stand, walk, run, jump, and lift things. So basically no matter what you're doing, the stronger your core, the better.

Because of how important the core is, we asked a fitness expert to put together a 21-day core-strengthening challenge that requires only about 15 minutes a day. Meet Albert Matheny of Soho Strength Lab and Promix Nutrition. He put together a plan to help you get a stronger mid-section in three weeks, using three moves that are safe and effective and way more interesting than just holding a plank.

The Schedule

The moves, which we will teach you about tomorrow, are the Side Plank (with knee to elbow), Spiderman Plank Crunch, and Candlesticks. For now, though, here's a sneak peek at the road ahead!

Day 1: 5 reps of each move
Day 2: 7 reps of each move
Day 3: Rest
Day 4: 7 reps of each move
Day 5: 9 reps of each move
Day 6: Rest
Day 7: 9 reps of each move
Day 8: 11 reps of each move
Day 9: Rest
Day 10: 11 reps of each move
Day 11: 13 reps of each move
Day 12: Rest
Day 13: 13 reps of each move
Day 14: 15 reps of each move
Day 15: Rest
Day 16: 15 reps of each move
Day 17: 17 reps of each move
Day 18: Rest
Day 19: 17 reps of each move
Day 20: 19 reps of each move
Day 21: 21 reps of each move

Every few days, we will send you reminders about how many reps you should be doing, as well as extra tips and tricks that will help you through the challenge! So get ready, because the challenge officially begins tomorrow!