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An elliptical trainer or cross-trainer (also called an X-trainer) is a stationary exercise machine used to simulate stair climbing, walking, or running without causing excessive pressure to the joints, hence decreasing the risk of impact injuries. For this reason, people with some injuries can use an elliptical to stay fit, as the low impact affects them little. Elliptical trainers offer a non-impact cardiovascular workout that can vary from light to high intensity based on the speed of the exercise and the resistance preference set by the user.
Elliptical trainers first entered the market in the 1990s, invented by Precor.
Most elliptical trainers work the user's upper and lower body (although some models do not have moving upper body components). Though elliptical trainers are considered to be minimal-impact, they are an example of a weight-bearing form of exercise. They can be self-powered by user-generated motion or need to be plugged in for adjustment of motion and/or for supplying their electronic consoles and resistance systems.
In 1995, Precor introduced the Elliptical Fitness Crosstrainer (EFX), the first piece of exercise equipment to allow the foot to roll from heel to toe just like in running. Its patented mechanism weds a rear flywheel with a forward foot pedal, creating a smooth, elliptical movement. This is key to foot comfort and reduces numbing of the foot experienced on other stationary cardio equipment.
This approach is classified as "low impact" as it keeps a person's heels in contact with the pedals, reducing muscle and tendon stress. Exercisers move fluidly and can have a lower Relative Perceived Exertion (RPE). In other words, the person does not feel like they are working as hard as they actually are.
There are three types of elliptical trainers, categorized by the motor or "drive" location. The oldest elliptical design is the "rear drive" type. The "front-drive" elliptical was the second generation design. The latest design technology is the "center-drive".
On some models, the incline of sloping roller ramps beneath the pedal-links can be adjusted to produce varying pedal motion paths. The adjustable ramp, whether automatic or manual, alters the angle of the elliptical path and increases hip actuation as well as lengthens the stride. This allows an exerciser to alter his or her workout to target the various major lower body muscles. Various elliptical trainers enable exercisers to use preset programs to automatically vary incline, resistance and stride length over the course of a workout. Some trainers can be driven in either a reverse or forward direction.
Elliptical trainers are primarily driven via the legs, and most are combination designs having handle-levers attached to each pedal-link to enable a burden on the arms to provide a secondary source of driving power. The user grips the handles below shoulder height and pushes and pulls them while shuffling the feet back and forth within elliptically-shaped paths. Thus the oscillating handle motions are dependently coordinated with the constrained pedal motions. Poorly designed machines are too dependent on the user's leg power, producing excessive handle speeds due to mechanical ratios that do not provide enough advantage to the handle-levers. Consequently such machines feel to the user as if his or her arms are simply going along for the ride, rather than sharing in the work. The better models offer a harmonious combination of arm and leg exercise in the correct ratios.
Some manufacturers produce durable commercial models with extensive programs and made to withstand frequent use in a fitness club environment, at prices typically in excess of US$4,000. Models are available for home use at prices starting at about US$200.
An elliptical cross trainer is comparable to a treadmill in its exertion of leg muscles and the heart. Ellipticals produce an intermediate range of leg motion between that of stationary bikes and treadmills.
Studies have found that the rate at which calories are burned on an elliptical trainer is similar to that on a treadmill.[medical citation needed] Thomas Altena, a professor of nutritional and exercise physiology at the University of Missouri-Columbia, measured oxygen retention, lactic acid build-up, heart rate, and perceived rate of exertion to compare treadmills and elliptical trainers, finding that the "physiological responses associated with elliptical exercise were nearly identical to treadmill exercise". However, it is important that the resistance set on the elliptical machine is at a relatively high setting, depending on the user.
Since users do not take their feet off the pedals, there is no footfall noise in contrast with other fitness trainers such as treadmills.
A 2002 study by the University of Idaho shows that varying the stride length on the elliptical trainer can recruit a larger variety of muscle groups. The study also showed that as the stride is lengthened, more calories are burned without any higher rate of perceived exertion by the user. This study is in agreement with the claims made about the adjustable stride length feature on some newer ellipticals.
Though procedures vary between various models, most are similar in that the user adopts a comfortable standing position with his or her spine in a neutral position (with a straight back). The user aligns their knees, hips and ankles; and ensures that their weight is distributed between the heels and the balls of the feet. The user grips the handrails in a smooth controlled motion, striding either in a forward or reverse motion, working through a full natural range of movement smoothly and continuously.
- By Roy Wallack, Los Angeles Times. "The latest in popular ellipticals." April 27, 2013. December 2, 2013.
- Briley, John L. (July 27, 2004). "Bone Health: A Weight-Bearing Argument". The Washington Post. Retrieved 2008-12-12.
-  IHRSA
- American Fitness, "Treadmills vs. Elliptical Trainers," Jul/Aug2002, Vol. 20 Issue 4, p9.
- "Elliptical Trainers: Keep Up the Resistance". Gym Source. Retrieved 10 January 2014.
- Browder, K. D; D. G Dolny (2002). "Lower extremity muscle activation during elliptical trainer exercise". Medicine & Science in Sports & Exercise 34 (5): S35. doi:10.1097/00005768-200205001-00198.