Editor's Note:  Do ab machines work better than the crunch? Researchers put six of the most popular ab machines to the test. Surprisingly, only one works better than the crunch and it's not even available! 

Promising a flatter stomach and smaller waistline, abdominal exercise machines form a big part of the multi-billion dollar home exercise industry. Do any of them work better than the traditional abdominal curl? A group of researchers from California decided to find out [1].

They tested six home abdominal machines: the Ab-ONE, Ab Scissor, Ab Swing, 6 Second Abs, Perfect Ab Roller and the Torso Track.

Forty-six volunteers (20 men and 26 women) took part in the study. After being told how to use each device, they performed one set of 8-10 repetitions for each exercise.

The researchers used electromyography (known simply as EMG) to measure recruitment of the abdominal muscles during each exercise. EMG activity was assessed for five consecutive repetitions in each set. Movement speed was controlled across devices and subjects. The machines with variable resistances were all tested at their highest resistance setting.

Surface electrodes were placed on the skin over the right upper portion of rectus abdominis (the upper abs), the right lower portion of rectus abdominis (lower abs), and the right external oblique muscle. Learn more about abdominal muscles (pop-up window).

And the results?

The numbers in the table below refer to the activity of the upper rectus abdominis (upper RA), lower rectus abdominis (lower RA) and the external oblique (EO) muscles relative to the abdominal curl (also known as the crunch).

NOTE: Although this study measured muscle activity in the upper and lower abs, it's debatable whether a distinct upper and lower rectus abdominis exists in most people [2].

What do all the numbers mean?

To assess the effectiveness of each device relative to the crunch, EMG values for the upper and lower rectus abdominis and the right external oblique were assigned a value of 100%.

If the value was lower than 100%, the machine was less effective in recruiting that muscle than the crunch. A value higher than 100% means that the machine is more effective than the crunch in recruiting that muscle.

"Contrary to many of the claims accompanying several of the devices tested," write the researchers, "the Ab Scissor, Ab Swing and 6 Second Abs were significantly less effective than a crunch at eliciting upper and lower rectus abdominis activity."

Except for two machines showing greater activity in the right external oblique, all the machines showed less EMG activity than the traditional crunch. This suggests that these machines were less effective than the crunch in recruiting these muscles.

The only machine that showed greater EMG activity than the traditional crunch was the Ab-ONE, a banded exercise device with a bar that's held with an underhand grip, with your palms facing toward your face.

To perform a crunch with the Ab-ONE, you lie on your back on the floor in a position similar to a crunch. Your hips are flexed to a 45-degree angle and your knees are bent.

A pad is placed on your stomach at the level of your navel. You then perform a crunch-type movement while simultaneously pulling down toward the floor with your elbows.

The researchers think that the Ab-ONE was more effective in recruiting the abdominal muscles because of the resistance provided by the elastic bands. The force applied to the abdominals with the pad placed at the level of the navel also resulted in a contraction of the abdominal muscles.

So, is the Ab-ONE worth a try?

Personally, I don't use or recommend any of these machines. I usually train my abs twice a week using a variety of exercises. In one workout, for example, I might do cable woodchops, hanging leg raises and standing cable crunches. In the next workout, I'll use a few different exercises, such as barbell rollouts or ball reverse curls.

Editor's Note: Interestingly enough, at the time of this review (January 2006) the Ab-ONE wasn't available for sale. I searched high and low and couldn't not find it anywhere. I stumbled across a blog that confirmed what I suspected - the Ab-ONE is not available for sale but it didn't say why.

Most people who buy these kinds of products want a smaller waist or a flatter stomach. This will require losing fat. The best way to do this is to combine regular exercise with a diet that contains the right number of calories, adequate amounts of protein, a healthy blend of fats, and carbohydrates with a low energy density.

And what if you want a six-pack?

Rectus abdominis, which is the six-pack muscle, extends down the stomach from your ribs to your hips. When you lie down on your back and lift the shoulders from the floor, rectus abdominis is the muscle that's doing most of the work.

The six-pack look is the result of bands of connective tissue that "cut" into rectus abdominis. The more developed the rectus abdominis muscle, the deeper the grooves. To see your six-pack, you need a well-developed rectus abdominis combined with low levels of subcutaneous fat (fat stored under the skin).

The Ab-ONE may work rectus abdominis a little harder than a crunch done on the floor without any added resistance. But holding a dumbbell across your chest while doing a crunch will probably have a very similar effect. There are also several ways to make the crunch more effective, such as "bracing" the abdominals rather than pulling them in.

Although it came out top of the list, I'm not convinced that a 25-30% difference in muscle activity during five consecutive unweighted crunches means that the Ab-ONE is worth spending your money on.

Editor's Note: Be sure to read Christian Finn's article titled, A Simple Way to Make Your Abs Work Harder During the Crunch.

Read other articles by Christian Finn

About the Author

Christian Finn is a Certified Personal Trainer and holds a masters degree with distinction in exercise science. He's lectured at a number of universities and private training organizations around the United Kingdom on fitness training, weight loss and the effective use of nutritional supplements. He writes extensively on the subject and his articles have been published in numerous magazines, leading industry journals and websites worldwide, including Men's Health, Men's Health Muscle, Fit Pro (April/May 2001), CAM magazine (February 2003), Image (January 1997), Zest (March 2004), and Body Life magazine (March/April 1997). He was also featured in the July 2004 issue of Muscle & Fitness (UK edition). His website, TheFactsAboutFitness.com, is dedicated to providing its members up-to-date, unbiased information and research on the world of fitness.

References

1. Sternlicht, E., Rugg, S., Bernstein, M.D., & Armstrong, S.D. (2005). Electromyographical analysis and comparison of selected abdominal training devices with a traditional crunch. Journal of Strength and Conditioning Research, 19, 157-162

2. Lehman, G.J., & McGill, S.M. (2001). Quantification of the differences in electromyographic activity magnitude between the upper and lower portions of the rectus abdominis muscle during selected trunk exercises. Physical Therapy, 81, 1096-1101