Leg Curl Muscles Worked: Boost Your Leg Day Results

Understanding the Leg Curl: Muscles Worked

Ever wondered what makes leg curls such a valuable addition to your leg day routine? Maybe you’re chasing muscle growth or perhaps stronger legs. Either way, understanding exactly which muscles are activated during leg curls can level up your results. This exercise isn’t just another move to get through on leg day—it's about engaging key muscle groups like your hamstrings, calves, and even your glutes and core, to build both strength and stability.

In this article, we’ll also break down how your muscles are worked in various leg curl variations, from the seated leg curl to the lying and standing versions. We’ll examine the primary and secondary muscles involved, helping you understand the benefits of each movement and how proper muscle activation can take your workouts to the next level. Whether you're using a leg curl machine, free weights, or your body weight, leg curls are a fantastic exercise for building strong hamstrings and lower body strength. Let’s get right to it!

Primary Muscles Worked by Leg Curls

The leg curl exercise primarily targets the hamstrings and calves [1]. Let’s talk about how the exercise focuses on these muscles and what benefits you can get from working on them.

Hamstrings

The hamstrings are a group of muscles located at the back of your thigh. They include the biceps femoris, semitendinosus, and semimembranosus. These muscles play a key role in knee flexion and hip extension. This is exactly how leg curls target your hamstrings:

• Concentric motion: As you curl the weight upwards, your hamstring muscles contract and shorten [4]. This motion primarily activates the hamstrings, particularly the biceps femoris, which helps flex the knee joint.
• Eccentric motion: When you lower the weight, the hamstrings lengthen while controlling the movement. This phase targets the hamstrings in a different way by working on muscle strength and endurance through a controlled extension.

Strengthening the hamstrings through this isolation exercise can increase force production, particularly during activities requiring eccentric and concentric muscle contractions, like sprinting and jumping [5]. Strong hamstrings also support your lower back and improve your overall balance.

Calves

The calves, particularly the gastrocnemius muscle, are another important muscle group targeted by leg curls. These assist in providing knee joint stability and control throughout the movement. As you bend your knee during the exercise, your calves work together with your hamstrings to maintain balance and stability.

This movement improves ankle flexibility, which enhances your performance during exercises and helps in daily activities like walking and climbing stairs [3]. Strengthening the calf muscles improves contraction, supporting better blood flow and reducing symptoms like swelling and discomfort. As a result, working on them can reduce the risk of injuries.

By focusing on the hamstrings and calves, you can achieve better lower body strength that helps with day-to-day tasks and also improves your athletic performance. 

Secondary Muscles Activated During Leg Curls

When performing leg curls, you also activate several secondary muscles. These secondary muscles include the glutes and core muscles, which provide added stability and support. Understanding how these muscles contribute to the exercise can help you enhance your workout routine.

Glutes

The glutes play a supportive role during leg curls. As you flex and extend your knees, your gluteal muscles help stabilize your pelvis. This is especially noticeable with variations like the standing leg curl and lying leg curl. By engaging the glutes, you can ensure better form and reduce the risk of suffering lower back strain. Strengthening the glutes also enhances overall lower body stability, which is crucial for movements that involve bending and lifting.

Core Muscles

Your core muscles stabilize your torso during leg curls. Whether you use a seated leg curl machine or a lying hamstring curl, keeping your core tight helps maintain proper posture and prevents undue stress on your spine. A strong core aids in aligning your lower body movements, ensuring that the force exerted by your hamstrings and calves is efficiently transferred without compromising your back or hips.

Benefits of Focusing on Leg Curl Muscles

Why learn about the muscles targeted by leg curls? Whether you’re chasing better performance on the field or looking to enhance your physique, targeted muscle engagement during leg curls brings key benefits that you don't want to miss. We’ve already discussed some of them, now let’s take a look at how these advantages might be useful in improving your quality of life: 

• Injury Prevention and Muscle Balance: Strengthening your hamstrings helps prevent muscle imbalances and reduces the risk of injuries like knee problems or strains.
• Enhanced Lower Body Strength and Stability: Leg curls build stronger hamstrings, calves, and glutes, improving overall stability for athletic movements and daily tasks like walking or squatting.
• Better Athletic Performance: Strengthened hamstrings improve force generation and control in both concentric and eccentric movements, boosting sprinting, jumping, and agility.
• Support for Lower Back and Core: Engaging your glutes and core during leg curls enhances overall body stability, reducing lower back strain and improving posture during heavy lifts.

By focusing on these key benefits, leg curls become more than just an exercise for building stronger hamstrings—they become an essential movement for injury prevention, enhanced athletic performance, and overall lower body stability.

How to Target Muscles Effectively with Leg Curls

To effectively target both primary and secondary muscles, consider varying your leg curl exercises. Try incorporating dumbbell leg curls or using a resistance band to increase resistance and engage more muscle fibers. Always maintain proper form by keeping your core tight and your pelvis stable, especially during seated hamstring curls and lying hamstring curls.

Another pro tip is to focus on controlled movements to maximize muscle engagement and prevent injury. Regularly switch between different leg curl variations and positions to hit all the stabilizing muscles effectively. By following these guidelines, you can ensure you are working all necessary muscles, leading to a more effective and safer workout regimen.

Leg Curl Machines Muscles Worked

Different types of leg curl machines offer unique angles and resistance, which can lead to varying levels of muscle activation. Here’s a breakdown of how each type of machine targets the muscles differently:

• Seated Leg Curl Machine: With hips flexed at 90 degrees, this variation targets the lower hamstrings (semitendinosus and semimembranosus) and lightly engages the glutes.
• Lying Leg Curl Machine: In the prone position, this machine emphasizes the upper hamstrings, especially the biceps femoris. It also recruits the gastrocnemius in the calves, offering a more complete lower-leg workout while demanding core stability.
• Standing Leg Curl Machine: This machine isolates one leg at a time, targeting the glutes, hamstrings, and engaging stabilizer muscles in the calves and core. It’s commonly used in home gym systems or multi-gyms, but can also be performed with a cable crossover or any pulley system, offering versatile resistance and positioning for a full lower-body workout.
• Kneeling Leg Curl Machine: This setup targets the hamstrings similarly to the lying leg curl but with a slightly different angle, providing a focused contraction of the hamstring muscles and reducing hip flexor involvement.
• Cable Leg Curl Machine: The adjustable resistance of the cable machine enhances hamstring activation throughout both the lifting and lowering phases. It also engages your glutes and core.

Each machine variation can be used to target different areas of the hamstrings, glutes, and calves, depending on your goals, and they all provide unique benefits for muscle activation and strength development. Incorporating multiple types of leg curl machines into your routine also helps ensure a comprehensive lower-body workout that addresses both primary and stabilizer muscles.

Leg Curl Variations and Their Impact on Muscle Activation

Leg curls come in different variations, each impacting muscle activation in unique ways. Choose one or more to incorporate into your routine depending on your fitness goals—enhancing hamstring strength, injury prevention, or correcting muscle imbalances.

Seated Leg Curl Muscles Worked

The seated leg curl primarily targets the hamstrings, including the biceps femoris, semitendinosus, and semimembranosus [2]. In this position, your hips are flexed, which can engage the gluteus maximus slightly. It also engages the gastrocnemius for stabilization, particularly when the toes are pulled towards the shin.

Lying Leg Curl Muscles Worked

The lying leg curl primarily targets the hamstrings and also engages the gluteus maximus to a greater extent than the seated version. The prone position helps in activating more of the lower leg muscles, such as the soleus and gastrocnemius, due to the angle of the knee. This variation is excellent for building muscle strength and flexibility but requires more core stability.

Muscles Worked in Less Common Leg Curl Variations

Less common leg curl variations include the standing leg curl and Nordic curl. The standing leg curl isolates the hamstrings while promoting a more natural range of motion. It also engages the lower legs and helps improve balance. The Nordic hamstring curl is an advanced exercise targeting both the hamstrings and glutes intensely. It’s highly effective for injury prevention and improving muscle imbalances.

There are also great leg curl alternatives such as the Romanian deadlift that focuses on the hamstrings and glutes, offering a compound movement that works multiple muscle groups. You might also want to do both leg curls and leg extensions, as the latter primarily works on your quads. This can be a great addition to your routine if you're aiming for a comprehensive leg workout routine.

Leg Curl Muscles Worked: Conclusion

Integrating leg curls into your leg day ensures the back of your legs gets as much attention as the front, balancing your overall leg development. This exercise primarily targets the hamstrings, including the biceps femoris, semitendinosus, and semimembranosus. These muscles aid in knee flexion and hip extension, helping you build strength in the back of your legs. But it’s not just the hamstrings that get a workout—leg curls also engage the calves, glutes, and even your core for stability.

Different variations of leg curls, such as seated, lying, and standing versions, offer unique benefits, targeting the hamstrings from different angles on the leg curl machine, while also activating the calves and glutes. Incorporating resistance bands, dumbbells, or cable machines can further enhance muscle engagement and growth. Next time leg day rolls around, you’ll know which part of the movement is crucial for firing up your hamstrings, calves, glutes, or core.

By integrating leg curls into your workout routine, you’ll build stronger, more defined hamstrings, which are essential for better athletic performance and injury prevention. So don’t forget to hit those hams—learning about the muscles worked during leg curls is key to stronger legs and building an unstoppable lower body!

References:

1. Electromyographic activity of the hamstrings during. . . : The Journal of Strength & Conditioning Research. (n.d.). LWW. https://journals.lww.com/nsca-jscr/abstract/1999/05000/electromyographic_activity_of_the_hamstrings.12.aspx
2. Marchetti, P. H., Magalhaes, R. A., Gomes, W. A., Da Silva, J. J., Stecyk, S. D., & Whiting, W. C. (2021). Different knee and ankle positions affect force and muscle activation during prone leg curl in trained subjects. The Journal of Strength and Conditioning Research, 35(12), 3322–3326. https://doi.org/10.1519/jsc.0000000000003333
3. Silva, K. L. S., Figueiredo, E. a. B., Lopes, C. P., Vianna, M. V. A., Lima, V. P., Figueiredo, P. H. S., & Costa, H. S. (2021). The impact of exercise training on calf pump function, muscle strength, ankle range of motion, and health-related quality of life in patients with chronic venous insufficiency at different stages of severity: a systematic review. Jornal Vascular Brasileiro, 20. https://doi.org/10.1590/1677-5449.200125
4. Thapa, S. B., Basnet, S., & Khanal, R. (2021). Eccentric and Concentric Motion Motion of Hamstring during the Leg Curl. Journal of Institute of Science and Technology, 26(2), 111–117. https://doi.org/10.3126/jist.v26i2.41546
5. Worrell, T. W., Smith, T. L., & Winegardner, J. (1994). Effect of hamstring stretching on hamstring muscle performance. Journal of Orthopaedic and Sports Physical Therapy, 20(3), 154–159. https://doi.org/10.2519/jospt.1994.20.3.154