Related studies

The findings in this study relating to heart rate and energy cost are virtually identical to those in a well-publicized study reported several years ago. That study found that running on a treadmill was superior to exercising on stationary cycle ergometers, rowers, steppers and simulated cross-country ski machines, despite similar RPE values. Walking on the treadmill elicited the lowest heart rate (HR) and oxygen consumption values in the elliptical study and, in several other studies conducted at the University of Wisconsin-La Crosse, similar results were found. Individuals tend to exercise at a lower perceived exertion level (11.5 to 12.0 on the Borg scale) when walking on a treadmill and have lower HR, oxygen consumption and caloric expenditure responses.

In another related study, Len Kravitz and colleagues at the University of Mississippi compared four home brands of elliptical trainers. The results regarding the intensity of the workout were very similar to the University of Wisconsin-La Crosse findings. In the home elliptical study, subjects exercised at RPE values between 12.5 and 13.0 on the Borg scale, and exercised at an average of 72 percent of maximal heart rate values. While the intensity of the workout was similar on all machines, the quality and "feel" of the workout varied tremendously between brands. As a warning to members who purchase home equipment, make sure that they try the machines out to test their "feel" before making a purchase.

While the issue of quality is not as much of a problem with commercial units, the "feel" of different machines can vary substantially. This is because the shape of the ellipse varies on different machines. Some machines incorporate a more circular pathway, while others have a flatter (more egg-shaped) elliptical pattern. Don't be turned off on ellipticals because one machine doesn't feel right; try different brands.

What about going backward?

In a gym, you'll see people pedaling backward on a stationary cycle or walking backward on a stepper in attempts to target different muscle groups or to increase the intensity of their workout. The same holds true for elliptical trainers, as most commercial models allow the user to go forward or backward. But is there any benefit to the backward motion? A study found that when users went backward, they actually burned 7 percent more calories than when going forward.3 However, a study at the University of Wisconsin-La Crosse laboratory failed to substantiate this claim, and found that at identical speeds and resistance levels, exercising forward and backward on the Precor Transport resulted in the same intensity workout. Thus, it appears that the jury is still out on the backward issue from an energy-cost point of view, but going backward can provide variety to a workout, and future studies using electromyographs (EMG) may shed light on the muscle usage question.

The bottom line

Since a larger number of people are reaching an older age, more and more exercisers are seeking low-impact exercise alternatives. It has long been recognized that one of the major benefits of walking is that it is a low-impact activity, which results in relatively few orthopedic injuries to the lower extremities. A major drawback for more fit individuals, however, is that there is an upper limit to the workout intensity of walking. Elliptical trainers may be able to fill this void, as they can provide exercise over a wide range of exercise intensities, while minimizing the potential for lower extremity injuries.



REFERENCES

1. American Council on Exercise. Elliptical trainers go head-to-head. ACE Fitness Matters May/June: 11-15, 1998.

2. Bakken, A. A comparison of energy cost during forward and backward stepping exercise on the Precor C544 Transport. Unpublished master's thesis, University of Wisconsin-La Crosse, 1997.

3. Kravitz, L., B. Wax, J.J. Mayo, R. Daniels and K. Charette. Metabolic response of elliptical exercise training. Medicine and Science in Sports and Exercise 30: S169, 1998.

4. Porcari, J.P., J.M. Zedaka, L. Naser and M. Miller. Evaluation of an elliptical exerciser in comparison to treadmill walking and running, stationary cycling and stepping. Medicine and Science in Sports and Exercise 30: S168, 1998.

5. Zeni, A.I., M.D. Hoffman and P.S. Clifford. Energy expenditure with indoor exercise machines. Journal of the American Medical Association 275(18): 1424-1427, 1996.

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