The ab crunch machine is good for anyone who is tired of doing dozens of crunches. To properly train a muscle, you need to apply enough pressure on it, which cannot happen if body weight exercises are too easy for you.
This is where the ab crunch machine comes on, it lets you adjust the weight you use, and apply the right pressure for your rep goal.
But there are some drawbacks, With this machine it is crucial to adjust the machine correctly for your height and body. Failing to do so, might cause your workout to be ineffective, and will increase your risk of injury.
Also, crunches of any type might cause lower back pain, So it is better to do a different ab exercise if you have trouble with your lower back.
How to do
Make sure you have a proper form:
Sit your hips back as far as possible into both the back pad and seat pad. Sitting back will center your butt and pelvis in the seat and reduce the likelihood of any unwanted pelvic shifting during the dynamic movement.
Position the abdominal pad just below the level of your sternum to create the right length lever arm.
your starting spinal position should be in slight extension. Though this position is unique to every body type, you can find it by first getting yourself into neutral posture and then arching your thoracic and upper lumbar spine slightly.
Do a crunch in a slow controlled manner while slowly breathing out.
Pause at the bottom of your crunch for a second and return to the starting position
Make sure to use weight you can handle, choosing too much weight can easily cause injury.
Sitting is one of the worst positions for your spine. while seated the spine changes from its normal S shape to a C shape. This position puts a lot of stress on the discs.
So you start with a seated position, then you make it worse by crunching forward sometimes way too much forward, putting even more pressure on the discs.