An elliptical trainer or cross-trainer is a stationary exercise machine

Exercise machine

An exercise machine is any machine used for physical exercise. These range from simple spring-like devices to computerized electromechanical rides to recirculating-stream swimming pools...

 used to simulate stair climbing, walk

WALK

WALK may refer to:*WALK , a radio station licensed to East Patchogue, New York, United States*WALK-FM, a radio station licensed to Patchogue, New York, United States...

ing, or running

Running

Running is a means of terrestrial locomotion allowing humans and other animals to move rapidly on foot. It is simply defined in athletics terms as a gait in which at regular points during the running cycle both feet are off the ground...

 without causing excessive pressure to the joints, hence decreasing the risk of impact injuries. For this reason, people with some injuries are able to 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. A more compact elliptical trainer was invented by Larry D. Miller for Precor

Precor USA

Precor USA is a manufacturer of fitness equipment for home and commercial uses. Paul J. Byrne is the president of Precor USA. The corporate headquarters of Precor USA is located in Woodinville, Washington, and is a brand name of the Amer Sports corporation....

 and was patented in 2004. Miller created the idea for the machine by filming his daughter running alongside a car, while watching the motion of her legs. His idea was to take that exact motion and put it into a machine that puts less strain on the joints.

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.

Types

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 result of such adjustment changes the burdens on various muscle

Muscle

Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

 groups in the legs. Some models can vary the incline, resistance and stride length over the course of a workout according to a preset program. Some trainers can be driven in a reverse as well as in a forward direction.
Elliptical trainers are primarily driven via the legs, and most are combination designs having handle-levers attached to each pedal-link for the purpose of enabling a burden on the arms to provide a secondary source of driving power. The user grips the handles below shoulder height and pushes/pulls them while shuffling the feet back and forth within their 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 as a result of 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 commercial models, which focus on durability and are made to withstand the more frequent use of the fitness club

Health club

A health club is a place which houses exercise equipment for the purpose of physical exercise.-Main workout area:...

 environment. These units typically sell for well over $4,000 (US), offering greater durability and programming than the typical home user would ever need. There are also models available for use in one's home. These can be purchased for less, with some machines starting at under $200 (US) or 130 EUR.

Benefits

An elliptical cross trainer is comparable to a treadmill

Treadmill

A treadmill is an exercise machine for running or walking while staying in one place. The word treadmill traditionally refers to a type of mill which was operated by a person or animal treading steps of a wheel to grind grain...

 in its exertion of leg muscles and the heart. Ellipticals produce an intermediate range of leg motion between that of stationary bike

Stationary Bike

"Stationary Bike" is a novella written by Stephen King, which was originally published in the fifth edition of From the Borderlands in 2003. It was recently released as part of King's 2008 short story anthology, Just After Sunset.-Synopsis:...

s and treadmills.

There are claims that the dual action exercise of an elliptical trainer can actually be more efficient in burning calories. The logic is that by exercising more muscle groups simultaneously, a more intense workout can be achieved in less time. It is also suggested that the perceived rate of exertion is lower. However, other studies have shown that the rate in which calories are burned on an elliptical trainer is similar to that on a treadmill. 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. According to Altena, the "physiological responses associated with elliptical exercise were nearly identical to treadmill exercise".

Regardless, elliptical trainers sell well. One reason may be that users do not take their feet off the pedals, and exercise can be done at a gentler rate, still getting the same degree of results as with a treadmill. Also, at home, especially in an apartment setting, they are said not to make as much noise as a treadmill may make for one's downstairs neighbors.

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 lends credibility to the claims made about the adjustable stride length feature on some newer ellipticals.

Motor fitness

By using the elliptical without holding onto the handgrips, the user can improve his or her motor fitness and balance. In this position, the core muscles are held in a state of constant tension. This hands-free position also promotes better posture. This is not recommended for beginners, and caution is advised as falls from the machine could be harmful.

Common usage

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.