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Exercise Response to Elliptical Trainers

Autor Ryan

Each year, new, innovative exercise machines are developed to try to capture the popularity in this multi-million-dollar fitness industry. One of the latest products on the market is the class of machines called elliptical trainers. With elliptical trainers, the lower body motion is a cross between an upright stationary cycle and a stepper, except that the feet move in an egg-shaped, or elliptical pattern, as opposed to a circular path. Since the feet never leave the footpads, ground reaction or impact forces in the feet are purported to be lower, resulting in fewer orthopedic injuries to the lower extremities. This is good news for the large number of people who are looking for a high-intensity, low-impact substitute to jogging. While the popularity of elliptical trainers has virtually exploded, research on their benefits is relatively scarce.

The elliptical study

Since research on elliptical trainers is so limited, a two-part study was conducted at the University of Wisconsin-La Crosse to shed some light on the effectiveness of these new machines.4 The first portion of the study compared the intensity of a workout on an elliptical trainer to several other common exercise modalities. Specifically, the study compared exercising on the NordicTrack Ellipse to running or walking on a Trimline 1000 motorized treadmill, stepping on a Precor 921e hydraulic stepper and riding a Tunturi cycle ergometer. The second portion of the study involved documenting the vertical ground reaction forces in the feet while exercising on these modalities. One of the major problems with jogging and other high-impact aerobic activities is, because the body becomes airborne and has to land, forces equal to 24 times a person’s body weight must be absorbed on landing. These forces are initially absorbed by the foot and then are transmitted to the ankle, knee, hip or back, often resulting in injury.

Sixteen volunteers between the ages of 27 and 54 practiced on each machine until they were comfortable setting workloads and consistently exercising on them. The participants then completed a 20-minute exercise bout on each modality on a separate day.

Each bout was conducted at a self-selected intensity. This model is more realistic for the public, as most people who buy or use exercise equipment tend to exercise at their own pace. During each exercise bout, oxygen consumption, heart rate, ratings of perceived exertion and caloric expenditure were recorded.

On a separate day, the subjects completed a 5-minute bout of exercise on each modality and had vertical ground reaction (impact) forces measured in their feet. This was accomplished by placing a wafer-thin insert into both shoes. These inserts were interfaced with a computerized program that measured force production throughout the entire gait cycle. Peak forces were then determined, which were subsequently represented as a percentage of each subject’s body weight.