"One of the biggest mistakes someone can do on the elliptical is to ride with low resistance," Thornhill says. Resistance is what causes your muscles to change, he says. As a general rule, you should always "feel" the tension as you push and pull the pedals and handlebars, he says. Determining the right amount of resistance for your workouts can take some finessing. But if you find your legs are moving with momentum, rather than effort, it's a sign that you're not using enough resistance. As far as incline, goes, "the higher the incline, the more you work your glutes, so crank up that incline," he says.