Leg Curls
The leg curl is an isolation movement that trains the hamstrings through their knee flexion function — pulling the heel toward the body against resistance. Where hip hinge movements load the hamstrings through hip extension across a long range of motion, the leg curl loads them through a completely different mechanical function. Both patterns are necessary for complete hamstring development because the hamstrings are responsible for both movements and training only one leaves the other underdeveloped.
The leg curl is one of the more important isolation movements in lower body training for that reason. The hamstrings are a muscle group that’s both commonly injured and commonly underdeveloped relative to the quadriceps, and the leg curl directly addresses the knee flexion function that compound movements don’t load in isolation. Including it consistently alongside hip hinge work produces more complete hamstring development and better resilience over time.
Three primary variations exist based on body position — lying, seated, and standing. The seated leg curl deserves particular mention because it trains the hamstrings in a lengthened position at the hip simultaneously, which research suggests produces more complete muscle development than the lying variation where the hip is in a more neutral position. If you have access to both, the seated variation is worth prioritizing.
Below are the leg curl variations in the library.
Reference Card
Movement Pattern: Knee flexion — isolation Primary Muscles: Hamstrings — biceps femoris, semitendinosus, semimembranosus Secondary Muscles: Gastrocnemius, popliteus
Variations
- Lying leg curl machine
- Seated leg curl machine
- Standing leg curl machine
Considerations
- The seated variation trains the hamstrings in a lengthened position at the hip — worth prioritizing if available
- Control the eccentric — the hamstrings respond well to a slow, deliberate lowering phase
- This is a complement to hip hinge work, not a replacement for it — both patterns belong in a complete program
- Full range of motion produces better hamstring development than partial reps
Programming Notes
- Best placed after compound hip hinge and squat work in a lower body session
- Responds well to moderate to higher rep ranges (10–15)
- The seated and lying variations provide slightly different stimulus — including both when available is worth doing