Over the past years, full sit ups have fallen out of favor with personal trainers, and crunches have taken over as the most popular stomach exercise.

The main reason crunches have taken over is the belief that full sit ups are bad for your back, and in this article we’ll explore the difference between the 2 exercises.

The big difference between the 2 exercises is the joints that are involved. In crunches, only your spine moves; however, in sit ups your spine and your hips move. The hip movement is the big difference between the exercises.

The muscles that move the hips during sit ups are the hip flexors. The hip flexors attach to the lower back and the pelvis. When the hip flexors contract, they add pressure to the lower back, but this is a normal biomechanical process. The problem occurs when the lower back is irritated or injured because extra pressure from the hip flexors may increase discomfort.

When you think of any exercise, you must weigh the benefit versus the risk. Sit ups serve a very significant benefit for athletes. They are a great exercise for abdominal strength, and they train your body through its full range of motion. Athletes in running, jumping, and throwing sports can improve their performance by including sit ups in their workouts.

However, for non-athletes or people with lower back problems the risk of injury might outweigh the benefit. If you have poor flexibility, bad posture or alignment, weak abdominal muscles, weak back muscles, a previous injury to the back, or poor exercise technique sit ups may pose a higher risk of injury.

The truth is that sit ups are not bad for your lower back. Previous Injury, bad flexibility, poor posture, weak back muscles, weak abdominal muscles, and poor exercise technique are bad for your back.

Crunches work the abdominal muscles really well without putting too much compression on the joints of the lumbar spine, and when the feet are placed on a bench or ball during crunches there is slightly less pressure on the lumbar spine. But crunches on the floor are also flawed because they utilize very little range of motion.

In order to maximize functional strength, you should strive to exercise your joints through as much range of motion as possible while keeping good form and avoiding pain. A great exercise for the abdominals is crunches on a stability ball.

Crunches on a ball work your abs through a greater range of motion than when done of the floor, and since they don’t involve the hip flexors there is less pressure on the lower back than full sit ups.

Hopefully, that gives you a little more of a perspective about the difference between sit ups and crunches. Before beginning any exercise program, you should consult with a health care professional. If you ever feel discomfort when you’re exercising, that’s also a sign you should consult with a professional.

Author's Bio: 

Charles Inniss is a Physical Therapist and Personal Trainer. Visit his website to learn lower back exercises and core training tips.