The best elliptical trainers offer smooth, silent resistance as you pedal. But this type of high-functioning, low-maintenance braking system comes at a cost. If you are shopping in the low- to mid-range elliptical trainer market, be prepared to endure slower, noisier resistance adjustments than you would get with a high-end model. You may even have to make the adjustments manually.
Direct Tension
With direct-tension, also called belt-tension, elliptical trainers, your pedaling efforts spin a heavily weighted wheel, known as a flywheel. The friction from a belt wrapped around the flywheel circumference offers resistance as you pedal. Belt tension is typically adjusted manually by twisting a knob. The tighter the belt, the harder pedaling will be. Only the very lowest end elliptical trainers have belt-tension resistance. Belt-tension systems are usually less noisy than air resistance systems, but can still produce annoying sounds from the friction of the belt against the flywheel, and you must be alert for signs that the belt is giving out and needs to be replaced.
Air Resistance
Air-resistance elliptical trainers have fan blades that spin as you pedal. The faster you pedal, the more resistance the fan blades generate as they move through the air. As with direct-tension elliptical trainers, only very low-end elliptical trainers will have air-resistance mechanisms, and the fan tends to be very noisy. However if the fan happens to blow air onto you, it acts as a cooling fan while you exercise.
Magnetic Resistance
Low-end and some mid-range elliptical trainers offer magnetic resistance. Moving a powerful magnet closer to the cast-iron flywheel increases resistance, and moving it away from the flywheel decreases resistance. You may move the magnet manually, by twisting a knob, or by pushing a button and waiting for the elliptical motor to move the magnet for you. Magnetic resistance is quieter than direct-tension and air-resistance systems, but the resistance-adjustment motor can still be noisy when in use.
Eddy-Current Resistance
The eddy-current braking system is the best elliptical resistance system possible because there are no moving parts, just an electromagnet positioned near the flywheel. This makes eddy-current braking smooth, silent and low-maintenance. Pushing a button on the elliptical-trainer console adjusts the amount of current flowing to the electromagnet, which causes an immediate adjustment in resistance.
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