What are Legs Curls? (A guide to building hamstrings)

What are leg curls?

What are leg curls? This guide will tell you everything that you need to know about leg curls. How to do them, the benefit of using them and the correct form. Firstly, let's answer the question 'what are leg curls'?

The leg curl is a resistance exercise that targets and isolates the hamstrings at the back of the upper leg. It can be performed on a seated leg curl machine, lying leg curl machine, or standing leg curl machine. 

The majority of commercial gyms will have at least one form of leg curl station, but, if yours does not, you can always use a cable machine. 

Hamstrings are generally activated with compound lifts such as deadlifts and squats. Although these are great for building mass and strength in the legs, they also involve a lot of other muscles making them taxing on the central nervous system and very fatiguing.

 If you want to isolate the hamstrings without bringing the quads and glutes into action, leg curls are the way to go. They allow you to train the muscle to absolute failure and really connect with it. 

Which muscles are targeted with leg curls?

All forms of leg curls specifically target the hamstring muscles at the back of the upper leg. The calves and glutes are bought in as secondary assisters, but only to a small degree. 

The hamstrings are a group of muscles below the Gluteus Maximus and are responsible for flexing the lower leg at the knee. They also make up part of the posterior chain so they help with posture and the straightening of the body. 

It is not really possible to isolate specific hamstring muscles as they work in tandem as a group, but when fully developed, it is possible to see the definition in them.

How do I perform leg curls?

The seated leg curl

The seated leg curl is performed on a seated leg curl machine. These can either be plate-loaded machines or cable machines with a weight stack. The plate-loaded machines allow heavy loads so they are great for strength trainers and experienced bodybuilders. 

Cable machines will usually be enough for the majority of trainers and have the advantage of quick weight selection. This makes them ideal for drop sets and pyramid sets.

1. Adjust the seat so that you can sit upright, with a straight spine. The backs of your knees should just be on the edge of the seat so that you can flex your legs to around 90 degrees.
2. Adjust the lower pad so that it is just above the backs of your ankles and the knee pad so that it is holding your legs in a secure position.
3. Select your weight from the stack.
4. Take a deep breath, and upon exhaling, curl your legs by flexing at the knee. Once the leg is curled to around 90 degrees, hold for two seconds.
5. Squeeze the muscle before slowly letting the feet come back up to their starting position.
6. Before your feet get to the top, curl the leg again and repeat the movement.
7. Carry out the required number of reps and sets. 

Hamstrings are delicate muscles and very easy to injure if not thoroughly warmed up. Make sure you go through a good warmup protocol including dynamic stretching. Before carrying out your working sets, perform 2-3 sets of warm-up leg curls with a low weight and pyramid up to heavier sets. 

How to do the lying leg curl.

The lying leg curl targets the hamstring muscles in the same way as a seated leg curl does. It is performed on a lying leg curl machine. Lying leg curl stations are usually cable machines with a weight stack.

1. Select your weight from the stack. Start low and pyramid up to working sets.
2. Adjust the lifting pad so that it sits on the backs of your ankles when you are lying down.
3. Lie on the machine with your knees just over the edge and tuck your ankles under the pads.
4. Grab the support handles, take a deep breath, and upon exhaling, curl your feet upwards towards the glutes.
5. Squeeze the hamstrings at the top of the movement for 2-3 seconds.
6. Slowly lower your feet to the starting position in a controlled motion. 
7. Before your legs are straightened, repeat the movement. Carry on for the required number of reps and sets. 

How to do standing leg curls.

Standing leg curl machines are quite rare in modern gymnasiums, but it is possible to perform them on leg extension machines or cable stations. The downside to a standing leg curl is that you can only work one leg at a time and, if using a cable station, it is not easy to stabilise the upper leg. 

1. Select your weight from the weight stack.
2. Stand with your knee against the knee pad or the upper pad on a leg extension machine. 
3. Tuck your ankles into the lower pads and curl your foot upwards.
4. When your leg is flexed to around 90 degrees, squeeze the hamstring muscle for a few seconds. 
5. Slowly lower the foot down. 
6. Before it gets to the starting position, repeat the movement. 
7. By not allowing the leg to rest at the bottom, you are increasing the time under tension for the hamstring. 
8. Repeat for the required number of reps and sets. 

What are the advantages of performing leg curls?

Most exercises that activate the hamstrings are compound movements that focus on eccentric movements. The leg curl is the only one that shifts attention to the concentric movement where the muscle shortens and contracts. This makes it a great option for hypertrophy and strength gains. 

Having developed hamstring muscles will help strength trainers with pulling movements. Bodybuilders benefit from having a thicker upper leg with definition between the gluteal and calf muscles. 

Having strong hamstrings will make you a lot less likely to suffer from a hamstring injury. You probably hear it all the time that professional footballers or athletes are sidelined for weeks with hamstring injuries. 

A torn hamstring makes it impossible to train and will lead to setbacks in achieving your fitness goals. By regularly performing isolation exercises such as leg curls, you are activating and strengthening the muscle, making it much less likely to tear. 

Another advantage to using hamstring curls is if your quads are highly developed and your rear legs are lagging. This is particularly common with bodybuilders who perform squats and leg extensions to achieve high definition in their quads. 

Using a leg curl is a way of allowing the hamstrings to catch up without stressing the quads. 

Common mistakes made with hamstring curls.

The most common mistake is swinging the feet up and down without connecting with the muscle and properly contracting it. The hamstrings react well to time under tension, so using a slow and controlled motion is the way to go. 

Use a two-second count for the lift, hold the contracted position for another two seconds while squeezing the hamstring and use a 3-4 second negative motion. You will not be able to lift as heavy with this method, but the extra time under tension will break down the muscle fibres and give you a great pump. 

This leads us on to the other common mistake, training too heavy. By training with a weight that will not allow you to use a full and controlled range of motion, you will not get a great connection with the muscle or controlled contraction. 

Much better results will come from lowering the weight and focusing on time under tension as detailed above. 

Alternatives to leg curls.

There are a few other ways to activate the hamstring if you do not have access to leg curl machines. 

Nordic hamstring curl.

You can perform a concentric hamstring movement with just your body weight. You will need somebody to hold down your ankles or a solid support bracket.

Simply lie on your front with your ankles securely pinned down and use your hamstring muscles to flex the knee and lift your upper body up. This is a relatively hard movement to perform for beginners as a fair amount of hamstring and glute strength is required. 

The movement can be made harder by using a slow negative movement or holding a weight plate on your chest. Although this has been listed as a hamstring movement, it activates the gluteal muscles to a high degree also. 

Glute ham raises.

Glute ham raises predominantly target the gluteal muscles, but the hamstrings also play a large part in the movement, making it worth a mention. It is effectively the same movement as a nordic hamstring curl but performed on a dedicated bench.

There are many other exercises that target the hamstrings, such as Romanian deadlifts, but none isolate them in a way that the leg curl does. If you have never used leg curls, add them to your split and develop strong, well-rounded upper legs. Be prepared for the DOMS, though!

We hope that you have found this article informative. 

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Leg Curls FAQs:

Q: What is the leg curl?

A: The leg curl is a weight training exercise that primarily targets the hamstrings.

Q: How do I perform a leg curl?

A: To perform a leg curl, you will need to use a machine. You will start by lying down on your back and placing your ankles under the padded lever. Then, you will raise the lever up until your legs are fully extended. From here, you will slowly lower the lever back down to the starting position.

Q: What muscles does the leg curl work?

A: The primary muscle group targeted by the leg curl is the hamstrings. However, this exercise also works the glutes and calves to a lesser extent.

Q: What are the benefits of the leg curl?

A: The leg curl is a great exercise for developing strength and power in the hamstrings. This exercise can also help to improve knee stability and prevent injuries.

Q: Are there any risks associated with the leg curl?

A: As with any weight-bearing exercise, there is always a risk of injury when performing the leg curl. However, this risk can be minimized by using proper form and technique. Additionally, it is important to warm up before performing any exercises and to use appropriate weights that suit your fitness level.

Q: What are some alternatives to the leg curl?

A: Some alternatives to the leg curl include the deadlift, Romanian deadlift, and Good Morning exercise.

Q: How often should I perform the leg curl?

A: The frequency of your leg curls will depend on your goals and training program. However, most people can safely perform this exercise two to three times per week.

Q: What is the best time of day to do a leg curl?

A: The best time of day to do a leg curl is typically in the evening, after your workout. This will allow your muscles to recover from the exercise and prevent any potential injuries.

Q: What is the ideal weight to use for a leg curl?

A: The ideal weight to use for a leg curl depends on your fitness level and goals. If you are new to this exercise, it is best to start with a lighter weight and gradually increase the amount of weight as you get stronger.

Q: Can I perform the leg curl without using a machine?

A: Yes, there are variations of the leg curl that can be done without using a machine. However, these variations are typically more challenging and should only be attempted by experienced lifters.

Q: What are some common mistakes people make when doing the leg curl?

A: Some common mistakes people make when performing the leg curl include using too much weight, not maintaining good form, and not warming up properly.

Q: Is the leg curl effective for building muscle?

A: The leg curl is an effective exercise for developing strength and power in the hamstrings. This exercise can also help to improve knee stability and prevent injuries. However, if your goal is to build muscle, you should focus on exercises that target multiple muscle groups, such as the deadlift or squat.

Q: Can women perform the leg curl?

A: Yes, both men and women can safely perform the leg curl exercise. However, it is important to use appropriate weights and to maintain good form throughout the exercise.

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