Seated Leg Curl

Why This Exercise Works

The seated leg curl is an isolation exercise that targets your hamstrings as the sole primary mover. What makes the seated variation unique is the position of your hips — when seated, your hamstrings are placed in a stretched position before you even begin the movement. This stretched starting position increases tension on the muscle and may enhance muscle growth. Your hamstrings consist of three muscles: the biceps femoris (long and short heads), semitendinosus, and semimembranosus. All three work together to flex (bend) your knee against resistance. The seated leg curl targets these muscles through their primary function — knee flexion. Unlike compound movements like deadlifts, which work hamstrings through hip extension, the leg curl isolates pure knee flexion. The stretched position in the seated leg curl deserves special attention. Research suggests that training muscles in their lengthened position may produce superior hypertrophy gains. When you sit with your legs extended, your hamstrings are stretched across both the hip and knee joints. This stretched starting position increases mechanical tension — one of the primary drivers of muscle growth. Your gastrocnemius (calf muscle) assists slightly because it also crosses the knee joint. However, the hamstrings do the vast majority of the work. The machine's fixed path eliminates the need for stabilization, allowing you to focus entirely on contracting your hamstrings. The seated leg curl is particularly effective for building the lower portion of your hamstrings near the knee. This area is often underdeveloped compared to the upper hamstrings, which receive more work from hip extension exercises. Including seated leg curls ensures complete hamstring development from top to bottom. For maximum hamstring growth, combine seated leg curls (stretched position) with lying leg curls (shortened position) and Romanian deadlifts (hip extension). This three-movement approach targets all hamstring functions and positions.