Aaron Small, Master Personal Trainer Athletic Club Northeast: 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. Improper way where people do, typically, when they start to fatigue through there hamstrings perhaps the weight is too much and they start to kind of kick the weight up which causes some compression in the low back region which can cause back injury or further exacerbate a back injury. This is the proper way to do it. You should be able to slowly smoothly bring the weight up. This is the improper way to do it. In order to get the weight up, you have to kick it up. And your rear comes up, off, you actually get an arch or extension in your back. Once again this is the proper way.