To perform this exercise, you will need a special machine called a hack slide, a popular piece of equipment found in most gyms and health clubs.

 

Step into the machine and face forward (with your back against the body of the machine).

 

Position yourself under the shoulder pad, and place your feet about hip-width apart, with your toes pointing slightly outward.

 

Release the safety latches, and slowly slide up and down by bending and straightening your knees. It is not necessary to dscend lower than 90 degrees.

 

Perform the exercise for the recommended number of sets and repetitions.

 

An apparatus known as a "Smith machine" can also be used for this exercise.