What’s so great about planks? They help you do everything better.
While crunches tone the top layer of abs, planks go deeper and tone more of your core. That means more benefits to everyday life. Consider that a tree would crack or snap in half when the wind blew if its trunk weren’t strong. Your core is the same way. When you strengthen it, it helps you become better at everything you do, including improving your balance and posture.
Plus, training your whole core hits your six-pack muscles as well as your internal and external obliques—the muscles that run up the sides of your midsection from your ribs to your pelvis. “These muscles give you those nice little lines we envy in all those Instagram #transformationtuesday shots, but they’re actually doing more for you than looking picture-perfect—they’re holding in your waist,” says exercise physiologist Michele Olson, PhD, adjunct professor of sport science at Huntingdon College in Montgomery, AL. “When strengthened, these muscles have the ability to pull your entire midsection in like a corset.”
So get to it! This doable 30-day plan starts with a basic plank that gets the key muscle groups working together in your core. (Can’t do a plank? Start by doing it on your knees, not your toes.) Then, you’ll add to the challenge by recruiting more core muscles each week and lengthening the time you’re toning the muscles. Ready? Here’s what to do:
Tips for keeping safe during your plank
1) Check yourself to be sure you’re not slipping out of form. The most common slips: letting your hips sag to the ground, hiking your butt in the air, and hunching your shoulders forward. “When your body starts to shake and you feel like you want to quit, this is when you’ll know change is happening,” says Olson. Power through your reps and you’ll see progress every day.
2) If you can’t hold the plank with good form for the whole time, modify your position. It’s better to switch from your toes to your knees and stick with the time frame than give up completely and cheat on time. “Doing the time is what sparks change in your body,” says Olson.
WeightWatchers® 30-Day Plank Challenge
Week 1
How to do a yoga plank: Place your hands on the floor, palms under shoulders, arms straight. Extend your legs behind you and balance your body between your toes and your arms. Your body should be in a straight line from ears to shoulders to hips to knees to ankles. Start on knees, if needed (see Tuesday).
Monday & Tuesday:
Challenge: Yoga plank (on knees image below)
Duration: Hold for 20 seconds
Wednesday:
Challenge: Yoga plank
Duration: Hold for 25 seconds
Bonus: Progress to toes, if you can
Thursday:
Challenge: Forearm plank
Duration: Hold for 25 seconds
How to do a forearm plank: Same as yoga plank, but rest your forearms on the floor. (on knees)
Friday:
Challenge: Forearm plank (on knees, illustrated above).
Duration: Hold for 30 seconds
Bonus: Repeat Friday’s workout on Saturday and Sunday.
WEEK 2
Monday:
Challenge: Forearm plank.
Duration: Hold for 30 seconds
Bonus: (If you were on your knees, try using just one knee, as seen above)
Tuesday:
Challenge: Forearm plank.
Duration: Hold for 35 seconds
Bonus: Be on one knee
Wednesday:
Challenge: Forearm plank.
Duration: Hold for 35 seconds
Bonus: Try without being on knees and balancing on toes 
Thursday:
Challenge: Forearm plank and Face-up plank (pic below).
Duration: Hold the forearm plank for 35 seconds and turn to do Face-up plank for 15 seconds
How to do a face-up plank: Lie on your back on the floor. Keeping legs together and knees straight, raise your legs off the floor until they’re at about a 45-degree angle (this is halfway between legs directly over hips and legs facing directly forward).
Tip: Point legs more toward the ceiling than the floor, or all the way toward the ceiling.
Friday:
Challenge: Forearm plank and Face-up Plank.
Duration: Hold Forearm plank for 35 seconds hold Face-up plank 15 seconds
Extra credit: Repeat Friday’s workout on Saturday and Sunday.
WEEK 3
Monday:
Challenge: Yoga plank and Forearm plank.
Duration: Hold yoga plank for 45 seconds and hold Forearm plank for 20 seconds
Tuesday:
Challenge: Yoga plank and Forearm plank.
Duration: Hold yoga plank for 45 seconds and hold Forearm plank for 20 seconds
Wednesday:
Challenge: Yoga plank and Face-up plank.
Duration: Hold the yoga plank for 45 seconds then do the Face-up plank for 15 seconds
Thursday:
Challenge: Forearm plank and Yoga plank.
Duration: Hold the Forearm plank for 45 seconds and then do the Yoga plank for 35 seconds
Friday:
Challenge: Forearm plank and Yoga plank.
Duration: Hold the Forearm plank for 45 seconds and then do the Yoga plank for 40 seconds
Bonus: Repeat Friday’s workout on Saturday and Sunday.
WEEK 4
Monday:
Challenge: Forearm and Side plank.
Duration: Hold the forearm plank for 45 seconds then switch to a Side plank (image below) for 20 seconds on each side
How to do a side plank: Lying on your right side on the floor, stack your legs so that your left leg is on top of your right, place your right forearm on the ground and press your hip toward the ceiling to lift your body; keep your left hand on your left hip.
Tip: Rest your right knee on the ground with your heel pointing behind you, or stack both knees on the ground.
Bonus: Perform this move with both legs stacked and arm fully straightened.
Tuesday:
Challenge: Yoga plank and Side plank.
Duration: Hold the yoga plank for 60 seconds and then switch to a Side plank. Hold the Side planks for 20 seconds on each side
Tip: Can be on knees (see image above).
Wednesday:
Challenge: Yoga plank, Side plank and Face-up plank.
Duration: Hold the yoga plank for 60 seconds and then switch to a Side plank. Hold the Side plank for 20 seconds on each side. Then do a Face-up plank for 20 seconds
Thursday:
Challenge: Yoga plank, Forearm plank and Side plank
Duration: Hold the yoga plank for 30 seconds then switch to a Forearm plank for 60 seconds. Next do Side planks for 20 seconds on each side and finish with a Face-up plank for 20 seconds.
Friday, Saturday and Sunday:
Challenge: Yoga plank, Side plank, Face-up plank and Forearm plank.
Duration: Hold the yoga plank for 60 seconds then switch to side planks for 30 seconds on each side. Go into a Face-up plank for 20 seconds and finish with a Forearm plank for 45 seconds.