Stair climbers

Stair climbers are excellent machines that exercise the major muscle groups of the lower body.  The best stair climbers keep your feet on an even plane with the floor at all times, allowing natural foot articulation.  Look for enclosed flywheels and cylinder driven mechanisms to provide the greatest durability and quietest operation.

You'll need to shop around as pricing and quality do vary considerably.

Due to the fact that stair climbers only work the lower body they are not as calorie burning efficient as other forms of aerobic exercisers.