An isometric plank is an exercise that builds the strength of the body’s core muscles. In the plank position, your body is supported by your forearms, elbows and toes. It looks like a push-up on your elbows, except there’s no movement. The work is done when your muscles contract and hold the plank position.

Here are three benefits of skipping sit-ups and doing planks instead.

1. More muscles involved
Sit-ups focus only on the abdominal muscles. Planks target more core muscles on the front, back and sides of the body.

2. Less stress on your back
Sit-ups are hard on your back because they push your curved spine against the floor. If planks are done correctly, they don’t put undue stress on the spine.

3. Fitness for everyday life
Sit-ups and crunches strengthen your abdominal muscles in isolation. Doing planks as part of your core workout helps strengthen groups of muscles that work together in the same patterns of movement you use in everyday life.