Update: Several years ago, I reported on a home strength-training machine called Nordic-Flex Gold by Nordic-Track. I was interested in this machine because research has shown the value of strength training, but many people would never go to a gym or fitness facility to train, and there was a need for a machine that could be used in the home. In addition, several strength machines were being advertised for the home market that were less effective than they could have been because of the type of resistance they used.

The NordicFlex Gold machine caught my attention because it used a centrifugal clutch device that produced an isokinetic resistance. The term isokinetic means that the speed of movement is the same, no matter what force is applied. This type of resistance is wonderful for home machines because there is no weight stack to drop, and anyone in the family can use it, because the resistance always matches the strength of the user.The only problem with this type of resistance is that it only works the muscle through the positive part of the movement. For example, in a bench press, there is resistance as you move the bar away from your chest, but no resistance as it returns to the chest. There is evidence that resistance both up and down increases the effectiveness of strength exercise.

The reason that I have reviewed the experience I had with the NordicFlex Gold is that just a little over a month ago, I received a new home strength machine from Nor-dic-Track called the Nor-dic-Flex Ul-tra-Lift. This machine addresses the problem associated with isokinetic exercise and provides resistance through the entire movement. Using a uniquely engineered leverage system, the UltraLift uses your own body weight as the "weight stack," adjusting the fulcrum of the lever to allow you to lift only a small part of your body weight up to 120 percent of your weight, depending on your strength.

Although it looks much like a typical health-club weight machine, there is no weight stack, so the machine can be smaller and lighter. In fact, the UltraLift is so compact, it can fit in a 4-by-4-foot space and looks nice enough that it really doesn't detract from the furniture in our basement family room. I have been impressed with how well it is put together; the frame is much more solid than the less-expensive models I looked at in sporting goods stores. And it can be moved much more easily than the weight-stack machines.

The machine came in two boxes so that one person could move it to the point of assembly. The assembly instructions were clearly written, and wrenches were included so that assembly was easy. A videotape showed clearly how to do the different exercises and also showed how to assemble the machine, for those who would rather watch than read.

I soon learned how to organize the set of exercises I did on the machine to minimize changing seat height and resistance settings, although neither of these is difficult to set. There is also an electronic device that shows the amount of weight lifted, the number of reps and the total time of the workout, for those who like to keep track of these factors.

The machine was wonderfully smooth to use, and I liked the feeling of being lifted slightly with each repetition. It compared very favorably to a weight-stack machine costing several hundred dollars more and took up less space. Because I am tall (6 feet 4 inches), I could not get full flexion on the arm curl, and I couldn't get full extension on a narrow lat pull-down. There is no butterfly motion on this or the stack machine I compared it with, but all in all, it is a perfect machine for home use.

Garth Fisher is director of the Human Performance Research Center at Brigham Young University.