You're holding it for too long.
If someone says the word "ab exercise," we have a hunch your first thought is plank. Aside from assisting to sculpt a strong core, the basic movement has a slew of total-body benefits. "Planks are a total-body exercise that, when done right, are great," says Denzel Allen, trainer at SoHo Strength Lab in New York City. "Aside from strengthening your anterior abdominals and lower back, they also help connect your upper and lower body" — a connection that's important for any aspect of fitness, Allen says, since it can improve your performance everywhere from the squat rack to barre class.
There's just one problem: although the exercise looks simple enough, it's frequently done wrong. Not to fret! We connected with top trainers to identify the four mistakes you're likely making in plank and how to fix them: