With your feet a shoulder’s width apart, hold each dumbbell at your side using an underhanded grip. Start with the dumbbell perpendicular to the side of body.
Rotating the dumbbell 90 degrees, raise it as shown. While you raise the dumbbell, your elbow rotates as the dumbbell rotates; however, its position relative to your body does not change.
Once you completely raise the first dumbbell, simultaneously lower it as you raise the other one. One dumbbell’s movement mirrors the other’s. As one lowers the other raises and visa versa. Since you exert effort at all times, remember to breathe constantly
Keep control while raising and lowering the weight. Don’t bounce with the weights. It’s easy to throw your back out if you lift too much or cheat by using your back muscles.