The correct performance of the exercise
Lie down on a Roman bench. Put your anterior thighs on the seat. Push your Achilles tendon area against the lower cushion. Cross your arms on your chest. With the inhale start to bend your body in hips up to 90 degrees angle. Your back should be round while bending. With the exhale go back to the basic position tightening ischio-tibial and buttocks muscles, not erector spinae.