Recent recent shows that Hip-extension exercise selectively activates the biceps femoris long head, and the knee-flexion exercises, like Nordic Curl exercise, preferentially recruits the semitendinosus.
So when you want to train the entire hamstring you need to pick exercises from both groups.
When you want to be specific with your exercises because of certain condition, you can do that.
- For example for people after an ACL reconstruction with a hamstring graft, typically semitendinosus, you might want to go easy of knee flexion exercises early one to avoid a flare-up and then gradually add more exercises like the nordic curl.
- Sprinters who pull their hammie, usually have biceps femoris issues. So start early on avoid to many hip extension exercises for the biceps and later on you want to really focus on that type of exercises
Good Extension based hamstring exercises
- Stiff leg Deadlift
- Hip extension kicks
Good Flexion based hamstring exercises
- Nordic curl
- Prone or seated leg curl
Bourne MN, Williams MD, Opar DA, et alImpact of exercise selection on hamstring muscle activationBritish Journal of Sports Medicine 2017;51:1021-1028.