This exercise is one of the oldest exercises for stimulating the hip flexors and abdominals. However, individuals with low back pain should avoid performing this exercise; abdominal crunches might be a safer alternative.
Adjust the incline of the bench for the desired level of resistance (e.g. more incline equals greater resistance due to the force of gravity). Next, brace the body by placing the feet or shins (depending on the model) behind the support pads and lie down. The arms should be crossed over the chest with the chin tucked in. For a greater challenge, the arms can be extended overhead, while holding a medicine ball or light dumbbell. Next, slowly curl the trunk forward and upward until the reaching a vertical position with the trunk perpendicular to the floor. The trunk should maintain a flexed posture throughout the movement to keep the abdominal muscles engaged. Do not allow the low back to hyperextend at any time throughout the movement.
Cross arms over chest.
Lie back until your upper back makes contact with the bench.
Slowly curl the trunk forward and upward until the reaching a vertical position.