Analysis by Dr Paul Batman

Client Instruction

Starting Position

  1. Lie in a supine position on the floor with your right ankle crossed and resting on the knee of your bent left leg
  2. Support your head in your hands without interlocking your fingers
  3. Keep your elbows out to the side of your head and avoid any pull of your arms

Up Phase

  1. From this starting position, begin to raise your left shoulder up and forward towards your right knee
  2. Attempt to curl up and rotate gently by the contraction of the internal and external obliques

Down Phase

  1. Pause momentarily and then slowly lower your body by uncurling your spine, bringing your left shoulder back to the starting position
  2. Repeat the exercise lifting your right shoulder up and towards your elevated left knee

Muscle Analysis

Up Phase

Joint                                    Action                         Contraction                                    Muscle Group

Spinal Joint                        Rotation                        Concentric                                    Spinal Joint Rotators

Down Phase

In the down phase of the exercise the body is lowered slowly with gravity. The same muscles that concentrically contracted to lift the body are those that are eccentrically contracting to lower the body.

General Kinesiological Analysis

In an oblique crunch the spinal joint is rotated by the concentric contraction of the rectus abdominis, external obliques and the internal obliques.

Advanced Kinesiological Analysis

The prime movers for the oblique crunch are the external obliques and the internal obliques. The rectus abdominis is classified as an assistant mover. In the oblique crunch movement to the right side is caused by the contraction of the right internal oblique and the left external oblique. Movement to the left side will recruit the left internal oblique and the right external oblique. As the obliques contract to cause rotation of the spine they neutralise any unwanted trunk flexion.

By rotating the spine immediately from the supine position more emphasis is placed on the obliques. If the movement begins with some spinal flexion, there is the additional recruitment of the rectus abdominis.

Twisting movements of the spine that recruit the oblique muscles can also be performed on a trunk-twisting machine.

Another variation to recruiting the obliques is in a pendulum exercise. The client lies in a supine position on the floor with the hips flexed to 90 degrees and the feet pointing towards the ceiling. The client then slowly lowers the extended legs down to one side until the outside leg touches the ground. At this point the client raises the extended legs back to the upright position and slowly lowers them down to the other side. The rotation of the spine is occurring due to the pelvis moving in transverse pelvic rotation as the hips are drawn into horizontal adduction and horizontal abduction.