Home
Articles
Training
Lean On the Leg Extension: A Novel Approach to Quad Development

Lean On the Leg Extension: A Novel Approach to Quad Development

One simple technique tweak could lead to greater quad growth on the leg extension exercise.

Written By Jim Stoppani, PhD

Updated January 3, 2025

When trying to build bigger quadriceps with the classic leg extension exercise, most of us stick to the standard approach of performing the exercise seated upright at a 90-degree angle. But that might not be the best way to do it.

Groundbreaking new research suggests that there’s a more effective way to enhance your quad growth. It turns out that leaning back about 40 degrees during leg extensions could be the key to significantly boosting your quad size, particularly the rectus femoris — the large quad muscle that runs down the front and middle of the thigh.

Breaking Down the Study

Norwegian researchers set out to investigate whether stretching a muscle could enhance its growth when contracted. They conducted a study with healthy, untrained men who trained one leg using the conventional upright leg extension at 90 degrees and the opposite leg while leaning back at a 40-degree angle.

The training regimen consisted of working each leg twice a week for 10 weeks. For the first five weeks, participants performed 3 sets of 15-20 reps; for the final five weeks, they increased to 4 sets of 15-20 reps.

The Results

The findings were impressive. After 10 weeks, the growth of the rectus femoris muscle increased by around 14% in the leg trained with a 40-degree lean. In contrast, the leg trained in the traditional upright position showed only an 8% increase. That’s nearly double the growth! Interestingly, the growth of the vastus lateralis, another major quad muscle, was similar in both legs.

Why It Works

The quadriceps consist of four muscles that converge into one tendon crossing the knee joint to facilitate knee extension. However, only the rectus femoris muscle crosses the hip joint, which means it gets stretched when you lean back during leg extensions. The other three quadriceps muscles (vastus lateralis, vastus medialis, and vastus intermedius) do not change length based on hip flexion, so the stretching effect specifically targets the rectus femoris.

Practical Application

This study supports the concept that a muscle can contract with more force and potentially grow more when it’s stretched during exercise. Therefore, despite the traditional advice to perform leg extensions while seated upright, research now confirms that leaning back to about 40 degrees is more beneficial for rectus femoris development.

If you’re looking to maximize your quad growth, particularly in the rectus femoris, incorporating this slight modification into your leg extension routine could make a significant difference. Give it a try and observe the changes in your quad development over time.

Remember, the key is in the angle — lean back about 40 degrees to experience the benefit. How you do this will depend on the machine you’re using. If you’re able to adjust the seat back, that will make it easy. If not, you’ll need to scoot your butt forward on the seat to achieve the 40-degree angle. This may require moving the back of the seat further back than normal to make sure your knee joint is still lined up with the machine’s axis of rotation.

As always, it’s important to listen to your body to ensure that your form is correct to prevent any potential injuries. Adjusting the angle of your leg extensions is a simple yet effective tweak that can lead to impressive gains. Let me know if you see a difference in your quad growth!

Get the Shortcut to Shred Workout Program