Elliptical trainer

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.

Elliptical riders use an arrangement of links known to the kinematics community as four-bar linkage. The pedals are attached to the floating link referred to as the coupler. The first published work on the subject of elliptical path generation is given in 1988 by researchers at Purdue University in which the path of a point on the floating link is shown to approximately follow an elliptical shape. 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 location of the motor or "drive." The oldest elliptical design is the "rear drive" type, the second generation elliptical design is the "front-drive" type, and the most recent elliptical design is the "center-drive" type.

On some models, the incline of sloping roller-ramps beneath the pedal-links can be adjusted to produce varying pedal-motion paths. An adjustable ramp, whether automatic or manual, alters the angle of the elliptical path which can vary hip actuation as well as vary the stride length. This can allow a user to alter his or her workout to target various lower body muscles. Some elliptical trainers even enable exercisers to use preset programs to automatically vary incline, resistance, and stride length over the course of a workout. In addition, some elliptical trainers can be driven in either a forward or a reverse direction.

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