For hamstring growth
For hamstring growth, lying leg curl rates well ahead on our research criteria: more of the work on the hamstrings, easier to progress.
45° back extension gives more stretch.
Both are good choices, and they train the hamstrings differently. Using both across your week covers more of the muscle than either alone: in studies, varied exercises grew parts of a muscle that one exercise missed. (Fonseca et al., 2014; Costa et al., 2021)
The research score comes from these, scored by hand from the studies. Lifter scores appear once an exercise has 10 ratings. How scores work
45° Back Extension. A 45° hip extension grew the long head of the biceps femoris more than Nordic curls did in a 10-week study.
Lying Leg Curl. Still a strong choice; hips are extended, so the hamstrings are less stretched.
For hamstring growth, lying leg curl rates well ahead on our research criteria: more of the work on the hamstrings, easier to progress. 45° back extension gives more stretch. Both are good choices, and they train the hamstrings differently. Using both across your week covers more of the muscle than either alone: in studies, varied exercises grew parts of a muscle that one exercise missed.
About the same: both are easy to learn.
45° back extension needs a GHD or back-extension bench, so for most people it’s a gym exercise. Lying leg curl needs a machine, so for most people it’s a gym exercise.
45° back extension: it rates Excellent for joint and recovery cost in our research rubric, against Strong for lying leg curl.