Leg Curl: Execution, Benefits and Mistakes To Avoid

Leg curls, a popular exercise among fitness enthusiasts, are renowned for their ability to stimulate the posterior muscles of the thigh, known as the hamstrings. These include the biceps femoris, semitendinosus, and semimembranosus. The specific movement involved in leg curls is knee flexion. However, the muscles engaged in this exercise can also participate in other functions.

The Many Variations of Leg Curls

Leg curls can be performed using several methods such as isotonic machines, free weights, or low cables with an ankle strap. Each method offers unique benefits that can cater to various fitness goals and levels.

Isotonic Machines

The most common type of leg curl is performed on an isotonic machine. These machines come in different versions: standing, seated, or prone. Each version targets the hamstrings differently and may be more suitable for certain individuals based on their fitness level and comfort.

The standing leg curl machine is unique in that it typically requires working one leg at a time. The seated version, on the other hand, subjects the long head of the biceps femoris to the greatest degree of pre-stretch. The prone version allows for adjustments to the angle of the bench, which can differently manage the degree of hip flexion and thus the lengthening of the long head of the biceps femoris.

Free Weights and Low Cables

Leg curls can also be performed with free weights such as dumbbells, or on a low cable machine with an ankle strap. These variations provide a different stimulus to the hamstrings and can be a great way to add variety to your training routine.

Performing Leg Curls Correctly

When performing leg curls, especially on a machine, it's crucial to adjust the machine appropriately to prevent injury and maximize the effectiveness of the exercise. Here are some steps to ensure a safe and effective leg curl:

1. Adjust the support surface angle to allow adequate pre-stretch of the biceps femoris without altering the position of the pelvis.
2. Ensure the arm connected to the weight allows a full range of motion (ROM) without forcing hyperextension of the knee.
3. Position the ankle block at the height of the Achilles tendon.
4. Choose an appropriate weight and take a secure position. Grab the stops with your hands.
5. Inhale deeply, and as you gradually exhale, begin to bend the knee. Avoid over-activating the glute and spinal muscles.
6. The suitable ROM ends just beyond 90°. Avoid exceeding this as it would result in loss of tension on the muscles involved.
7. Lower the weight, controlling the movement well and exhaling. Avoid bouncing the weight on a hyperextended knee.

Benefits of Leg Curls

Leg curls are not typically used for high-intensity strength work. However, they can be extremely useful in strengthening the hamstrings, which play a vital role in stabilizing the knee during complex movements like squats. Leg curls are also considered one of the best exercises for maintaining knee joint health and restoring its functionality during rehabilitation.

However, it's important to remember that hamstring development should also consider their stretching capacity. Many movements depend on hamstring flexibility, suggesting that stiffness can be limiting.

Potential Disadvantages of Leg Curls

The disadvantages of leg curls are primarily related to altered anatomical-functional conditions. For instance, the standing leg curl is not recommended for individuals with a retraction of the rectus femoris muscle. The seated version can be uncomfortable for those with retraction of the hamstrings.

High-load leg curls should be approached with caution by individuals with compromised posterior cruciate ligaments.

Common Mistakes to Avoid

When performing leg curls, avoid these common mistakes:

1. Incorrect adjustment of the machine.
2. Pulling from the buttocks and back, or performing thrusts with the torso.
3. Improper breathing.
4. Excessive closure in maximum concentricity.
5. Bouncing in maximum eccentricity.

In conclusion, leg curls are a versatile exercise that can be tailored to various fitness levels and goals. Whether performed on a machine, with free weights, or on a low cable, leg curls can significantly contribute to hamstring development and knee joint health when performed correctly.