How to Do Leg Curls

Proper Form, Variations, and Common Mistakes

The leg curl
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Also Known As: Hamstring curls, seated leg curls

Targets: Hamstrings, calf muscles, glutes, quads, shins

Equipment: Gym bench

Level: Beginner

The leg curl is a basic isolation exercise the targets two primary muscle groups: the calf muscles (gastrocnemius and soleus muscles) and the hamstrings (the biceps femoris, semitendinosus, and semimembranosus muscles).

Leg curls are performed on a gym bench with a levered lifting bar at the foot end of the machine. The classic version of the exercise is done lying flat on your stomach with your ankles tucked under a padded roller.

Benefits

The leg curl
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While the primary benefits of leg curls are strengthening and improving flexibility in your hamstrings, the exercise also targets other muscle groups.

To do a leg curl, you pull your heels toward your buttocks from your position on the machine (either seated or prone). This movement will smoothly pull the weights that are connected to the machine's pulley system. As you lower your feet back down, the resistance shifts slightly, which works your buttocks (gluteus muscles), thighs (quadriceps), and the front of the shins (tibialis anterior).

Having strong, flexible hamstrings is an important factor in your overall strength, balance, and stamina. Hamstrings that can withstand the demands of your workout aren't just helpful when you're at the gym, however. Their strength will also help you avoid injury as you go about your day-to-day life. Good posture and balance protect your muscles as you do everything from play with your kids to household chores.

Overall strength and flexibility in these key muscle groups will also help you as your body ages, especially if you are prone to knee problems, joint, or back pain.

When leg curls are part of your overall strength training, you are also contributing to improved cardiovascular strength and weight management, both of which are factors that can reduce and help prevent chronic pain.

Step-by-Step Instructions

leg curl
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Before you begin, you'll want to become familiar with the machine leg curls are performed on. The first time you try it out, you may want to have a trainer or fitness instructor show you the correct position and help you adjust the roller pad on the lifting bar.

  1. Start by lying flat on your stomach.
  2. Adjust the roller pad so that it rests comfortably on the back of your ankles, just above the heels. Check to make sure the pads aren't too high up on your calves as this can place pressure on your Achilles tendon and reduce your range of motion.
  3. Inhale and lightly grasp the support handles on each side of the machine.
  4. Lift your feet smoothly as you exhale, keeping your hips firmly on the bench.
  5. Inhale as you flex your knee and pull your ankles as close to your buttocks as you can.
  6. Hold this position for a beat, allowing yourself to make sure you are focused as you prepare to lower your legs.
  7. Inhale fully as you return your feet to starting position in a smooth, slow, controlled movement.
  8. Repeat for 8 to 12 reps.
Hamstring curl
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To a certain extent, you can use your toes to target your hamstrings and calf muscles throughout the movement. The hamstring can be targeted by dorsiflexing the toes (curling them toward the shin), while the calf muscle (gastrocnemius) can be isolated by pointing your toes (plantar flexion).

Common Mistakes

You Aren't Using the Right Weight

To properly execute a leg curl, always start with a lighter weight. You don't want to force your body to overcompensate by lifting the hips and flexing your lower back. This fails to isolate the calves and hamstrings and can also cause injury to your back.

Select a weight that allows you to do 8 to 12 repetitions with reasonable effort and good form.

Modifications and Variations

Need a Modification?

Depending on what's available at your gym, you may be able to avoid lower back strain by using a newer ergonomic machine. Many leg curl machine models now place your hips in a bent position to reduce pressure on your lower back.

Most machines allow you to perform leg curls lying or seated. You may prefer the seated leg curl variation if it is uncomfortable for you to be in a prone position. The other benefit to seated leg curls is having the bar rest on your upper thighs, which prevents you from lifting your legs as you curl. When you are doing leg curls in the prone position, you have to work a little harder to keep your hips against the bench.

Seated leg curls are generally a better option if you have lower back pain or neck pain, as this position provides support and prevents overextension.

Up for a Challenge?

If you want to build muscle mass, gradually increase the amount of weight as you get stronger. However, keep in mind that if your goal is to increase power and performance, you don't want to overload the weights. Make sure you are countering leg curls with leg extensions to strengthen your body in a balanced way.

If you feel pain with additional weight, it is best to go back to a lesser weight until you gain strength. However, if you still want a challenge, try increasing the number of reps or sets you do at your original weight.

Safety and Precautions

Bodybuilders use hamstring curls to increase muscle mass. However, fitness pros and athletes who play certain sports don't always favor the exercise as it can cause the foreshortening (or tightening) of the hamstrings.

If you overtrain and fail to stretch properly, repeated contraction and muscle growth can impair hamstring flexibility. To keep your hamstrings limber, always do stretches after a workout.

In some cases, you may want to avoid leg curls. If you're recovering from illness, injury, or surgery, the exercise may exacerbate an existing problem, slow healing, or put you at risk for increased pain.

You may want to avoid leg curls if you:

  • Have injuries or instability in your knee
  • Have recently had knee or hip surgery
  • Are recovering from injury or surgery involving your back, spine, or neck
  • Have ruptured or torn ligaments in your knee or ankle, such as your Achilles tendon or anterior cruciate ligament (ACL)

As always, it's best to check with your doctor before starting a weight training program. If you work with a physical therapist or trainer, check in with them for guidance on using the leg curl machine and whenever you feel ready to increase weight.

Try It Out

If you are ready to make leg curls part of your gym routine, here are some workouts that feature the move:

Try pairing leg curls with these moves to create your own balanced strength-training workout:

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