Finally! The six-pack you’ve always dreamed of is only a plank (or two!) away. You’ve even mastered the plank upgrades that can reshape your body. But there’s just one catch: While the act of planking is pretty straightforward, how long you should actually hold one is probably a bit less clear. Thankfully, the experts have you covered.

To reap the most rewards, holding three planks for up to 60 seconds each is ideal, according to Doug Sklar, a certified personal trainer and founder of PhilanthroFIT in New York City. Check out these weight loss tips from people who have lost 50+ pounds—and kept it off.

But if you’re new to planking, don’t risk injuring yourself in the name of a slimmer waistline. ‘It’s OK to start with shorter sets and work up to 60 seconds,’ Sklar told Women’s Health. ‘Forcing yourself to hold a plank for an excessive amount of time can put a lot of strain on your lower back. As fatigue sets in, the lower back may start to arch. This is where you put yourself at risk for injury.’

If one minute is too challenging, try holding a plank for 10 seconds, relaxing for five to 10 seconds, then re-engaging for 10 seconds. Repeat each set three to six times.

And don’t worry about losing out on any gains in the meantime; planking for shorter periods of time can still amount to a solid workout. ‘You receive very similar strengthening benefits because you are engaging your muscles for the same amount of total time as if you just held the plank for 30 to 60 seconds without stopping,’ said Sklar.

On the flip side, holding a plank for one minute might be a breeze for you. If that’s the case, Matheny recommends increasing the difficulty by contracting your abs, as well as squeezing your glutes and quads. Also, try this one exercise that will give you a flat stomach in 10 minutes.

Form should always come before figure, of course. Although planking can strengthen your entire body, you should only do it for as long as you can hold the correct position, experts say. ‘Keeping perfect form is goal—only do it as long as you can keep this,’ Albert Matheny, R.D., C.S.C.S., co-founder of SoHo Strength Lab and advisor to Promix Nutrition, told Women’s Health.

Tired of the same old plank position? Mix up your workout routine with these exercises that flatten your belly—without a single crunch. Or skip the gym completely with a few flat-belly tricks that don’t require a lick of exercise. You’ll be on your way to amazing abs in no time!