8. Leg curl
Your hamstrings are built to work with your glutes to create movement. Seated or prone leg curl machines, however, ignore your glutes, which increases your risk of hamstring pulls and knee injuries. By isolating the hamstrings alone, they become tight and overactive over time.
The best exercises to build strong hamstrings also maintain hip extension and glute activation.
Use these instead:
Swiss-ball Leg Curl, or Leg Curl on a Suspension Trainer
Glute-Ham Raise (shown in the picture above)