Take a position with your side to the bench, with feet shoulder-width apart. Hold the top of the bench with one hand.
From the starting position, lift the leg that is farther from the bench sideways to as high as it will go. Then bring the leg back to the starting position and move it to slightly crossing the standing leg, with the moving leg going in front. Do the required number of repetitions and then switch legs.
Make sure your torso is firm while doing the exercise. Begin with less intensive and slower movements. As you warm up, increase the intensity and speed. Avoid moving your pelvis sideways.
Perform this exercise only when your body has been warmed up to avoid injuring your abductors by overstretching or even tearing them.
Side leg raises strengthen the inner part of the thighs (adductors). You should lift your leg as high as possible to both sides. Start slowly to warm up, then you can increase the range of motion and speed.