The Leg Press and Leg Extension Builds Different Parts of Your Quads

Key Points:

• In a new study, 30 trained participants trained leg presses with one of their leg and leg extensions with the other. They also trained straight-legged or bent-legged calf raises with each leg.
• After 8 weeks of training, the vastus lateralis had grown more in the leg that trained leg presses, and the rectus femoris had grown more in the leg that trained leg extensions.
• Both calf exercises were equally effective for growing the soleus muscle, but the straight-leg calf raise was superior for growing the gastrocnemius.

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When it comes to building strong, well-defined quadriceps, choosing the right exercises is crucial. A recent study sheds light on this by comparing two popular leg exercises: the leg press and the leg extension.¹

Both exercises target the quadriceps, but which one is more effective for muscle growth?

Understanding Your Quadriceps Muscle

As the name implies, your quadriceps muscle consists of four heads that merge into a single tendon below your knee.

The three vastii muscles originate on your thigh and only cross one joint: your knee. The rectus femoris muscle, on the other hand, originates in your pelvis and crosses both your knee and hip.

Because of this difference, the three vastii muscles are recruited and used in slightly different movements than the rectus femoris and need to be trained in a slightly different manner.

• Because the vastii muscles only cross the knee joint, they’re active in any exercise where you extend your knee.
• Because your rectus femoris also crosses your hip, it’s not very active in exercises like the squat or leg press, where your hip is extending at the same time your knee is extending. Any force it exerts to extend the knee will also prevent your hip from extending.

Exactly to which degree the above theory is an issue and how the quadriceps should be trained is still a matter of research, and the new study helps clarify the picture.

Leg Press or Leg Extension Training for 8 Weeks

In the new study, 30 participants with resistance-training experience were recruited to follow an eight-week leg training program.

It was a within-subjects design, which in this case meant that one leg performed one exercise, and the other leg performed the other exercise.

This is an excellent design choice for this type of research question, as it removes much variance and uncertainty from the impact of genetics, lifestyle, diet, training background, and so on.

Each participant had one leg assigned to training the leg press for eight weeks while training leg extensions with the other leg.

In addition to the leg press and leg extension, they also performed one of two calf exercises: either a straight-legged calf raise or a bent-legged calf raise.

The idea of this comparison is similar: of our two biggest calf muscles, the soleus and gastrocnemius, the soleus only crosses the ankle, and thus, it shouldn’t matter which position your knee is in.

The gastrocnemius, on the other hand, crosses both your knee joint and ankle, and a bent-leg position puts it in a shortened position where it has a hard time contracting simply because it is already shortened and “out of room” for further contraction. (The technical term for this is active insufficiency)

Like with the quad exercises, one calf exercise was assigned to each leg in a randomized order.

The Training Program

The participants then trained twice per week for eight weeks, performing four sets of each exercise, with 8–12 reps per set to failure and two minutes of rest between sets.

All training sessions were supervised by the research team, and loads were adjusted to keep the participants in the 8–12 rep range throughout the study.

The Results

Muscle thickness was measured using ultrasound before and after the eight weeks of training.

It turned out that the leg press was far more effective for building the vastus lateralis, with an average thickness increase of 8.7%, compared to just 3.0% from leg extension training.

However, the leg extension was far superior for growing the rectus femoris, with an average growth of 9.0% compared to just 4.8% from leg pressing.

As for the calf muscles, the straight-leg calf raise resulted in the most total growth:

• The gastrocnemius grew far more from straight-leg calf raises than from bent-leg calf raises (where the gastrocnemius is in active insufficiency because of it’s shortened position).
• The soleus muscle didn’t display much of a difference in growth between the two exercises; both seemed fairly equally effective.

How to Use This in Your Training

If you want to train and develop all of your quadriceps heads equally, it seems that you should combine:

1. A squat or leg press type movement, with
2. A leg extension.

While there are plenty of squat variations, there are fewer alternatives to the classic leg extension machine. In order to train the rectus femoris effectively, you want an exercise where your knee extends under load, but your hip remains still or fixed. Two exercises that come to mind are the sissy squat and the reverse Nordic curl, but these two are certainly not as comfortable and easy to perform as the leg extension.

For the calves, the standing calf raise seems to be the superior exercise. It works the outer calf muscle, the gastrocnemius, and the inner calf muscle, the soleus, whereas the seated (or bent-leg) calf raises only properly works the latter.

In our leg day workout, we combine the squat, leg extension, and straight-leg calf raise to provide optimal development of your quads and calves. It also includes exercises for developing your other leg muscles.

Check out our leg day workout routine on the link below:

• How to Train Your Quad Muscles (Workout)
• The 12 Best Quad Exercises for Muscle & Strength
• The Best Push Pull Legs Split for Building Muscle

References

1. Burke, R., Piñero, A., Mohan, A.E. et al. Exercise Selection Differentially Influences Lower Body Regional Muscle Development. J. of Science In Sport and Exercise (2024).