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.

About Your Ab Muscles Rectus abdominis 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. The external and internal obliques run down the side of your waist. They actually "help" rectus abdominis during various curling exercises, and are also active during resisted twisting movements. Transverse abdominis acts a little like a corset, helping to hold your abdomen flat. You can't actually see transverse abdominis, as it "hides" away underneath the other abdominal muscles. Psoas (the "p" is silent) is a muscle that crosses the spine and hip. The main role of psoas is to flex the hip. Stand up straight and raise one leg. It's psoas that's doing most of the work.

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 (for a sample ab workout, see, "Lift weights and lose fat: How to drop pounds by picking them up, Part II" in the Members-Only Area of my website).

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.

C. Finn

About Christian Finn Christian Finn holds a masters degree with distinction in exercise science. He has 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. If you live in the UK, you may have seen Christian in the BBC TV series Body Hits. More recently, Christian was the fitness expert for the Bravo TV series All About Men. Christian writes extensively on the subject of exercise science, fitness and nutrition. You can find his articles published in numerous magazines, leading industry journals and websites worldwide, including Men's Health, Men's Health Muscle, Fit Pro, CAM magazine, Image, Zest, and Body Life magazine. You also might have seen Christian featured in the July 2004 issue of Muscle & Fitness. A tireless researcher, Christian has lost count of the number of long hours and late nights he has spent reviewing the latest scientific research in the areas of diet and exercise for the benefit of his numerous fans and readers. Christian’s research on high-intensity intermittent training has been published in the online journal Sport Science (March 2001), and a study Christian authored on the nutritional supplement HMB has also been published in the Journal of Sports Sciences. As a certified personal trainer, Christian has spent more than a decade working with people of all shapes and sizes, as well exercising regularly himself for over 15 years. He has entered the Body-for-LIFE challenge contest and was the first ever winner of the Outstanding Male Achievement award in the UK. If and when you are given advice from Christian Finn, you can be sure he is not only speaking the research-based facts, but also speaking from experience. There is nothing Christian has ever written about, be it a food supplement, diet or exercise routine, which he hasn’t used himself. As if his outstanding academic credentials and achievements aren’t impressive enough, the fact that Christian walks the walk and speaks from experience is enough for us here at Amazing Abdominals.com to be thrilled to have him on our team of writers. We highly recommend you listen to everything Christian has to say, subscribe to his FREE newsletter at www.TheFactsAboutFitness.Com and take a look at his members only website at: www.ChristianFinn.Com