Major Muscles and Actions Involved


In the Yessis GHB machine sit-up the abdominal muscles are responsible for spinal flexion. In this action your abdominal muscles pull your head and shoulders up and forward from a lower than horizontal position. In some variants the hip flexors contract to rotate the pelvis (together with the trunk) up and forward from a below level position on an axis in the hip joint.

Muscles in Action


Yessis Glute-Ham-Back Machine Sit-Ups

Sports Uses


GHB sit-ups are unique in that they allow for strengthening through the full range of motion of the abdominal muscle action. In the regular sit-up and crunch you begin the action in a straight body position. In the GHB sit-up you begin the action with the spine in a hyperextended position, a position that is often seen in execution of many sports skills, especially in throws.

Important Facts to Know


  1. It is important to do the movements in this exercise at a slow to moderate speed in the initial stages while learning to do this exercise effectively. At this time you must keep your body under control at all times. You should not make any quick or jerky movements because these can prove dangerous to your spine or hips. When you move slowly into the down position, concentrate on a slight arch in the lower back and a stretching of your abdominal muscles. Feel your abdominal muscles contracting as you rise up.
  2. In addition to the abdominal muscles, the hip flexors are involved in both variants. However, it is important to understand that throughout these exercises, your abdominals and hip flexors are under very strong contraction. The hip flexors, in essence, hold your pelvis in place and provide a strong base for the abdominals to contract and prevent hyperextension of your spine.