Get your barbell ready for rolling. Take a stance with your feet in a shoulder-width position. Bend forward and grab the barbell with a pronated grip with your hands in a slightly wider position than your shoulders. Keep your back straight with no arching (kyphosis) in your upper back.
Roll the barbell towards your feet until your arms get all the way to eye level. Keep your torso straight all the way to eliminate straining your lower back. Go back to the starting position in the same way as you went down. Try to engage your abdominal muscles, which will help you to keep correct posture. Inhale as you roll down towards your feet and exhale as you roll back to the starting position.
Repeat as many times as needed and maintain correct technique.
As you go upwards, your main driver should be abdominal muscle contraction.
In the lower position, hands go all the way to the shoulder level or to the eye level and further, respectively; correct lower position must be maintained at either level.
This is a challenging exercise and you are advised to roll down only to the position from which your body can always go back to the starting position without risk of incorrect exercise technique.
This is a demanding exercise. Many people will choose to do it from the position on their knees instead from standing position.
If you chose the harder variant it is important to keep stretched legs and arms almost perpendicular to the floor through the whole movement.
If you do not keep the hands in 90-degree angle with the floor you will not train your abdomen but rather the shoulders and triceps.
This is not an exercise for beginners: wrong posture can hurt your back.