How to Do Leg Curls: Build Stronger Hamstrings

Your hamstrings do a lot of work—they extend your hips, bend your knees, and stabilize everything in between. But they're often underdeveloped compared to quads, creating imbalances that lead to injuries.

The leg curl is the most direct way to target hamstrings. Here's how to do every variation correctly.

Why Leg Curls Matter

Leg curls isolate the hamstrings through knee flexion—bending the knee against resistance. While compound movements like deadlifts and squats work hamstrings, they emphasize hip extension. Leg curls provide the knee flexion stimulus hamstrings need for complete development.

Benefits:

• Direct hamstring isolation
• Addresses quad-hamstring imbalances
• Supports knee health
• Complements hip-extension exercises
• Reduces injury risk

Hamstring Anatomy Basics

Your hamstrings are three muscles:

• Biceps femoris: Two heads on the outer thigh
• Semitendinosus: Inner thigh
• Semimembranosus: Inner thigh, deeper

All three cross both the hip and knee joints, which is why complete hamstring training includes both hip extension (deadlifts) AND knee flexion (leg curls).

Lying Leg Curl

The most common leg curl variation.

Setup

1. Lie face-down on the machine
2. Pad should be just above your heels, below your calves
3. Knees positioned at or just off the edge of the bench
4. Grip the handles
5. Keep hips pressed into the pad

Execution

1. Curl your heels toward your glutes
2. Squeeze hamstrings at the top
3. Don't let hips rise off the pad
4. Lower under control
5. Stop just before weights touch the stack

Key Points

• Keep hips down throughout
• Full range of motion
• Squeeze at peak contraction
• Control the eccentric

Common Mistakes

Hips lifting: Reduces hamstring tension, uses momentum. Fix: Keep hips pressed into pad, reduce weight if needed.

Partial reps: Not bringing heels all the way up. Fix: Full contraction at top—heels toward glutes.

Fast negatives: Letting weight drop. Fix: 2-3 second controlled lowering.

Seated Leg Curl

Different angle that many find more comfortable.

Setup

1. Sit in machine, back against pad
2. Lower leg pad positioned just above heels
3. Upper leg pad secures thighs
4. Adjust so knees align with machine pivot point

Execution

1. Start with legs extended
2. Curl heels down and back
3. Squeeze hamstrings at bottom of movement
4. Return under control

Advantages

• No hip rise to worry about
• Often more comfortable for lower back
• Good mind-muscle connection
• Different stretch angle

Key Points

• Keep upper body stable
• Full range of motion
• Controlled throughout
• Don't use momentum

Standing Leg Curl

Single-leg version for addressing imbalances.

Setup

1. Stand facing the machine
2. Pad positioned just above heel
3. Hold handles for stability
4. Working leg slightly behind you

Execution

1. Curl heel toward glute
2. Keep standing leg stable
3. Squeeze at the top
4. Lower under control
5. Complete all reps, then switch legs

Advantages

• Works one leg at a time
• Identifies imbalances
• Functional standing position
• Can focus on weaker leg

Tips

• Don't swing your body
• Keep hip extended (leg behind you)
• Full range of motion
• Match reps on both sides

Nordic Curls (Bodyweight)

The most challenging hamstring exercise—no machine needed.

Setup

1. Kneel on soft surface
2. Anchor feet under something sturdy (partner, bar, strap)
3. Body upright from knees to head

Execution

1. Keep body straight from knees to shoulders
2. Slowly lower toward the ground by extending knees
3. Use hamstrings to control the descent
4. Lower as far as you can control
5. Push off the ground to return (initially)
6. Progress to using only hamstrings to pull back up

Progression

Beginner: Lower only partway, use hands to push back up. Intermediate: Lower further, minimal hand assistance. Advanced: Full range with no hand assistance.

Why They're Special

Nordics emphasize the eccentric (lengthening) contraction, which builds hamstring strength through a longer range than machines allow. They're excellent for injury prevention.

Programming Leg Curls

For Muscle Building (Hypertrophy)

• 3-4 sets of 10-15 reps
• Moderate weight
• Focus on squeeze and stretch
• 60-90 seconds rest

For Strength

• 3-4 sets of 6-10 reps
• Heavier weight
• Full range of motion
• 2-3 minutes rest

For Injury Prevention

• 2-3 sets of 12-15 reps
• Moderate weight
• Include eccentric emphasis
• 2-3x per week

Weekly Frequency

• 2-3x per week works well
• Can be done every leg day
• Pair with hip-extension hamstring work (deadlifts, RDLs)

Sample Leg Workout Including Leg Curls

Balanced Lower Body:

1. Squat: 4 x 6-8
2. Romanian deadlift: 3 x 10
3. Leg press: 3 x 12
4. Lying leg curl: 3 x 12
5. Calf raises: 4 x 15

Hamstring Focus:

1. Romanian deadlift: 4 x 8
2. Lying leg curl: 4 x 10
3. Seated leg curl: 3 x 12
4. Nordic curl: 3 x 6 (or as many as possible)
5. Glute bridge: 3 x 15

Tips for Maximum Hamstring Activation

Mind-Muscle Connection

Focus on feeling your hamstrings work. Don't just move the weight—contract the muscle.

Full Range of Motion

Complete stretch at the bottom, full squeeze at the top. Partial reps mean partial results.

Control the Eccentric

The lowering phase builds muscle. Take 2-3 seconds on the way down.

Pause at Peak Contraction

Hold the fully contracted position for 1-2 seconds. Squeeze hard.

Pointed vs Flexed Feet

Toes pointed: May increase hamstring activation. Toes flexed: Involves more calf.

Experiment with both.

Leg Curls and Knee Health

Strong hamstrings support knee stability. The hamstrings work as antagonists to the quads—they balance forces across the knee joint.

Quad-hamstring balance: Aim for hamstrings to be roughly 60-80% as strong as quads. Many people have weaker hamstrings, which increases injury risk.

Leg curls help build this balance.

Common Questions

How many times a week should I do leg curls? 2-3 times works well for most people. Hamstrings can handle frequency.

Lying or seated—which is better? Both are effective. They hit the muscle from slightly different angles. Use both over time.

Should I do leg curls before or after squats? After. Fatiguing hamstrings before squats can compromise stability. Do compound movements first.

Why do I cramp during leg curls? Usually dehydration, electrolyte imbalance, or the muscle isn't used to the contraction. Start lighter, stay hydrated.

Can leg curls hurt my knees? Not when done correctly. If you have knee issues, start light and see how it feels. The motion is generally joint-friendly.

Do I need leg curls if I deadlift? Deadlifts emphasize hip extension. Leg curls provide knee flexion work. For complete hamstring development, include both.

Leg Curls vs Other Hamstring Exercises

| Exercise | Primary Action | Emphasis | |---|---|---| | Leg Curl | Knee flexion | Direct hamstring isolation | | Romanian Deadlift | Hip extension | Hamstring stretch and hip hinge | | Good Morning | Hip extension | Lower back and hamstrings | | Glute-Ham Raise | Both | Hip extension + knee flexion | | Nordic Curl | Knee flexion | Eccentric strength |

Best approach: Include both knee flexion (leg curls) and hip extension (RDLs, deadlifts) for complete hamstring development.

Leg Curl Alternatives (No Machine)

Stability Ball Leg Curl

How to do it:

1. Lie on back, heels on stability ball
2. Lift hips into bridge
3. Curl ball toward you by bending knees
4. Extend back out
5. Keep hips elevated throughout

Slider/Towel Leg Curl

How to do it:

1. Lie on back, heels on sliders or towel
2. Lift hips into bridge
3. Slide heels toward you
4. Slide back out
5. Keep hips up the whole time

Band Leg Curl

How to do it:

1. Anchor band low behind you
2. Loop around ankle
3. Stand or lie face-down
4. Curl heel toward glute against resistance

The Bottom Line

Leg curls are essential for complete hamstring development. They provide the knee flexion work that compound exercises don't emphasize.

Use full range of motion, control the weight, and squeeze at the contraction. Include both lying and seated variations over time. Pair with hip-extension movements like Romanian deadlifts for balanced hamstring training.

Strong hamstrings mean healthier knees and better performance. Put in the work.