A recent article recommends to gain the best abdominal results from planks is to, perform three sets of planks and hold them for 60 seconds This is according to Doug Sklar, a certified personal trainer and founder of PhilanthroFIT in New York City.

If you can’t hold the planks that long you still get results and it is reasonable to work up to that time interval.

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 for three to six sets.

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.

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.

Other good exercises for your abdomen include bridges (shown below)

Source: This Is Exactly How Long You Need to Hold a Plank to Flatten Your Belly