Hamstring curls allow direct work of the muscles of the hamstrings group that flex the knee and can help with general knee stability and health.
 
Ideally hamstring curls are performed on a leg curl machine, which allows a complete range of motion and a more secure, adjustable and consistent method of loading, but they can also be done with a band if needed.
 
Performing them with one leg at a time is ideal to prevent any compensation that limits the work of the weaker leg and preserves the disparity side to side.
 
Keeping the hips pressed flat on the bench or floor by tightening the glutes and abs, bend the knee as completely as possible. Allow it to straighten again under control to full extension before the next rep.
 
Purpose
Hamstring curls can be a helpful exercise to balance strength around the knee for stability and general joint health, or to address a specific weakness of the hamstrings, especially asymmetry from left to right by doing them unilaterally.
 
Programming
Generally 2-4 sets of 6-15 reps is a reasonable protocol. The exercise should be performed at the end of a workout along with other accessory work after primary lifts.
 
Variations
Variations for the hamstring curl include using slow eccentrics or pauses in flexion.