One works on hamstring curls in the seated position, and the other works while lying prone on your stomach. The seated option ...

Gym Smarts: Lower Body Hamstring Curls. This machine is called the hamstring curl. Could for working out the hamstrings. I am going to show you the proper way and improper way to use it.

“I like to use the prone, or lying, curl machine in the gym as I find I’m able to focus on tucking the hips under and concentrating on the hamstrings better than I can on the seated hamstring ...