Nature’s Stairmaster from the photo stream of John Huang.

John’s description:

Walking up a steep sand dune feels like being on a stairmaster. Every step upwards you take, it sets you back half a step. To prevent yourself from slipping back you need to make faster steps. The Eureka dunes are over 600 ft high from base to peak, probably the tallest dunes in N. America. Hiking up was quite a workout — especially with camera gear and tripod!