The wall sit strengthens the muscles in your trunk, your upper legs, and your buttocks.

Here's how to do it.

Stand with your back against the wall.

Now take a small step forward.

Now lean back into the wall.

Reach back with your hands if you need to steady yourself.

Next, press your lower back flat into the wall, and slowly slide down the wall until your knees are slightly bent.

Hold it for about 6 seconds, then slide back up.

Do this 8 to 12 times.

Remember, if an exercise makes you feel worse, stop doing it.