Walk into any gym, and you'll hear the debate. Free weights are for 'real' muscle, and machines are for beginners or bodybuilders. The arguments are passionate, often pitting the 'functional' strength of a barbell squat against the targeted isolation of a leg extension.
But when the goal is pure muscle growth—hypertrophy—does the tool you use to challenge your quads actually make a difference? A 2025 study published in the Journal of Bodywork and Movement Therapies decided to put this classic gym-floor argument to the test.
Note: This review is based on the abstract only, as the full text was not available.
The Head-to-Head Matchup: Lunges vs. Leg Press
Researchers designed a clever experiment to get a clean, direct comparison. Instead of comparing two different groups of people, they used a within-subject design. This is a powerful method that helps control for individual differences in genetics, diet, and recovery.
Here’s how they set it up:
- Who: Eight young, healthy, and previously untrained women.
- The Plan: For nine weeks, the participants trained three days per week.
- The Twist: Each participant trained one of their legs with a free-weight exercise (lunges) and their other leg with a machine-based exercise (inclined leg press). This way, each person served as their own control group.
Before and after the nine-week program, the science team used ultrasound to measure the muscle thickness (MT) of two key quad muscles: the rectus femoris and the vastus lateralis. They even measured them at two different points along the muscle (proximal at 50% and distal at 70%) to see if growth was uniform.
And the Winner Is... A Tie.
After nine weeks of consistent training, both legs got bigger and stronger. This isn't surprising—when you subject untrained muscles to resistance, they grow. But the key finding was in the comparison.
Both the free-weight lunge and the machine leg press led to significant hypertrophy across all measured sites of the quadriceps.
Here’s a look at the growth:
- Rectus Femoris (top portion): +10.7% (Lunge) vs. +8.9% (Leg Press)
- Rectus Femoris (lower portion): +24.8% (Lunge) vs. +27.3% (Leg Press)
- Vastus Lateralis (top portion): +13.3% (Lunge) vs. +12.1% (Leg Press)
- Vastus Lateralis (lower portion): +12.7% (Lunge) vs. +15.7% (Leg Press)
While the percentages vary slightly, the most important result was that there were no statistically significant differences in muscle growth between the free weight leg and the machine leg. The study concluded that free weights and machines were comparably effective for inducing muscle hypertrophy in this group.
Key Takeaways for Your Training
This study, while small, provides some clear, practical takeaways for lifters and coaches.
1. For Pure Hypertrophy, The 'Best' Tool Is The One You Use Well
When your primary goal is simply to increase the size of your quads, this research suggests you can stop agonizing over whether a lunge is 'better' than a leg press. Both are highly effective tools for stimulating muscle growth. The best choice for you is likely the exercise you can:
- Perform with excellent technique to target the muscle.
- Progressively overload consistently over time.
- Do without pain or discomfort.
- Actually enjoy enough to do consistently.
2. Context Is Everything
It's crucial to remember the context of this study. The participants were untrained women. It's possible that highly trained athletes, who need a more potent or novel stimulus for growth, might respond differently. We can't automatically apply these findings to a 250-pound male powerlifter with a decade of training under his belt.
Furthermore, this study only looked at hypertrophy. Free weights undeniably challenge the body in ways machines don't, requiring more stabilization, balance, and intermuscular coordination. If your goals extend to athletic performance, sport-specific strength, or overall movement competency, the argument for including free weights becomes much stronger.
3. Variety Is Still Your Friend
This study doesn't suggest you should throw out one type of equipment for the other. Instead, it empowers you to use both. You can lead your workout with a heavy, compound free-weight movement like a squat or lunge and then use a machine like the leg press or leg extension to accumulate more targeted volume with less systemic fatigue.
The Bottom Line
In the long-standing war between free weights and machines, this study calls for a truce—at least when it comes to quad hypertrophy for new lifters.
For building bigger quads, the evidence here shows that both lunges and leg presses deliver the goods. Instead of getting caught up in dogma, focus on the principles that truly drive growth: consistent effort, solid technique, and a relentless pursuit of progressive overload. Pick the tools that fit your body and your goals, and get to work.
Source: Amanuma MT, et al. (2025). Comparable regional hypertrophy of the knee extensor muscles in response to resistance training with machines versus free weights: a randomized within-subject approach. Journal of bodywork and movement therapies. https://pubmed.ncbi.nlm.nih.gov/41316621/