Leg Curl
The leg curl is a machine exercise that bends the knee against resistance to isolate the hamstrings. It is listed in the NSW guide's lower body exercises and balances the quadriceps-dominant work of the leg press, squat, and lunge.
How to Perform It
Lie face down on the leg curl machine, or sit in a seated curl, with the pad resting just above the heels and the knees aligned with the machine's pivot. Curl the heels toward the buttocks by bending the knees, keeping the hips pressed into the bench so the lower back does not arch. Pause at the top, then lower the weight under control until the legs are almost straight. Do not let the weight stack drop between reps. The guide's prescription is one set of 8 to 12 reps with a weight that cannot be lifted more than 8 to 12 times with maximal effort and proper technique.
Why It Matters for BUD/S
The hamstrings decelerate the leg on every stride and drive the scissors kick in the combat sidestroke. They are also the muscle group most often strained by candidates who run a lot and lift only with the quadriceps. The leg curl gives the hamstrings direct work so they keep pace with the front of the thigh. The guide's core instruction for strength training is to alternate pushing (extension) with pulling (flexion) and to target several major muscle groups. The leg curl is the flexion movement that pairs with the extension of the leg press and squat, and it is the only lower body exercise in the list that isolates the back of the thigh.
Where It Sits in the 26-Week Plan
Leg curls sit in the Lower/Push-Sit-Pull sessions on Tuesday and Saturday across the 26 weeks. The guide's session format is 8 to 12 exercises with one working set each and only enough rest to set the next machine. The leg curl typically follows the heavier compound lifts like the dead lift and leg press, since it is an isolation movement that recovers quickly. Progress by adding a plate when 12 controlled reps are possible. The guide's allowance for an occasional lighter set of 15 to 20 reps is a good fit for the hamstrings when the legs are tired from the week's running.
Lower the weight slowly. The eccentric half of the leg curl is where the hamstring builds the resilience that prevents strains on the run.
Related Terms
Lower body strength training in the NSW preparation program builds the leg and posterior chain strength needed for running, swimming kicks, load carriage, and the high-volume physical demands of BUD/S. These sessions target the quadriceps, hamstrings, glutes, and calves through compound movements.
The dead lift is a barbell exercise in which you lift the bar from the floor to a standing position by extending the hips and knees together. It trains the entire posterior chain, the grip, and the trunk, and it is the heaviest lift in the NSW guide's lower body list.
The leg press is a machine exercise in which you push a loaded sled away from the body with both legs, and the squat is its free-weight equivalent, lowering the body under a bar and standing back up. The NSW guide lists them as alternatives, and either one is the main quadriceps and glute builder in the lower body list.
The combat sidestroke (CSS) is a hybrid swimming technique developed for military applications that combines elements of sidestroke, freestyle, and breaststroke. It is the preferred stroke for the PST 500-yard swim and the primary swimming technique used throughout BUD/S training and NSW operations.
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