The 20-inch stride and adjustable, well-cushioned pedals make for a smooth and challenging workout.

But their look of pleasure in Mr. Elo's challenging full-body workout does inch the bar up a bit.

The AMT gives you the freedom to create a challenging and completely unique workout every time.

For a more challenging workout, hold on lightly with one hand and move the other arm, switching arms periodically.

As a matter of fact, our tester is considering trading in her old core-conditioning class for this more aerobically challenging and mentally empowering workout.

Generally speaking, if you want a good, challenging workout, you will have to pay more.

There was a summer day in 1998 when defensive end Michael Strahan begged his counterparts on the offensive line to give him a challenging workout.

Even serious athletes will be able to obtain a challenging and supremely comfortable workout from this health club-quality machine.

Also included in the project is a new enclosed "hilly" landscape to provide runners with a challenging workout and grassed paths for light walks.

But resistance training provides a more focused and challenging workout that will build muscle mass as well as core strength.