The concept of a plank is pretty simple: You hold yourself up in a pushup position for a set period of time to tone your core, glutes, and hamstrings.

But while you probably already know how to do a plank, you might be hazy on how long you should actually hold one to max out results.

The answer is not as simple as you think. Albert Matheny, R.D., C.S.C.S., co-founder of SoHo Strength Lab and advisor to Promix Nutrition, says you can plank daily, but the length of time you should hold a plank for can vary from 10 seconds to a minute. Here’s why: Your form matters most. “Keeping perfect form is goal—only do it as long as you can keep this,” Matheny says.

As a general guideline, Doug Sklar, a certified personal trainer and founder of PhilanthroFIT in New York City, recommends striving to do three sets of up to 60 seconds. “It’s OK to start with shorter sets and work up to 60 seconds,” he says.

Plus, shorter planks can still give you a solid workout, Sklar says. If you’re more into shorter sessions, he suggests holding a plank for 10 seconds, relaxing for five to 10 seconds, then re-engaging for 10 seconds, and repeating for three to six sets. “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,” he says.

A minute seems to be the ideal time frame. “Longer time under tension is more of a challenge,” Matheny says. But, he adds, if you can easily plank for a minute, you increase the difficulty by contracting your abs more, and squeezing your glutes and quads more.

Again, don’t push yourself to do it or hold a plank for even longer if you’re not ready. “Forcing yourself to hold a plank for an excessive amount of time can put a lot of strain on your lower back,” Sklar says. “As fatigue sets in, the lower back may start to arch. This is where you put yourself at risk for injury.”

So, plank when you can and do it as long as you can hold good form, for up to a minute. You should see great results. “When done correctly, planks can help strengthen almost your entire body,” Sklar says.