Does the flywheel squat work your quads more than the leg press?

A 2026 randomized crossover trial in 18 resistance-trained men found no clear difference in quadriceps muscle activity between the flywheel squat and the leg press. The biggest gap was for the rectus femoris, where the flywheel squat read 9.90 percentage points lower, but the confidence interval included zero. If you train for strong quads, both machines look like reasonable choices, and the data cannot yet pick a winner for any single muscle.

Flywheel squats use a spinning disc instead of plates. You pull the disc up to speed on the way up, and it pulls you back down on the way down. The leg press is a fixed, supported machine. A team led by Topçu and Konrad wanted to know if these two very different setups load the front of the thigh differently.

What did the study do?

The researchers measured surface EMG, which is the electrical activity a muscle gives off when it works, picked up by pads on the skin. They looked at 3 quadriceps muscles: the rectus femoris (the one that also crosses the hip), the vastus lateralis (outer thigh) and the vastus medialis (inner thigh, near the knee).

Item	Detail
Who	18 resistance-trained men, age 22.4 ± 3.6 years, body mass 77.7 ± 11.2 kg
Design	Randomized, counterbalanced crossover: everyone did both exercises
Gap between sessions	7 days, after 2 familiarization sessions
Workload	3 sets of 6 analyzed repetitions, 2-min recovery
Flywheel setup	Individual inertia, maximal effort on the way up, 2 warm-up repetitions per set
Leg press setup	Load based on each person's 6RM, with a set tempo
Outcome	EMG across each whole repetition, up and down combined, scaled to a maximal contraction

The main result was the average across 18 repetitions per exercise. The team used statistical models that accounted for which exercise came first, and they corrected for testing 3 muscles at once. The study appeared in Frontiers in Physiology in 2026 (Topçu et al. 2026).

What did it find?

1. Rectus femoris: −9.90 percentage points for the flywheel squat (95% CI −20.81 to 1.01). The leg press looked higher here, but the range runs from a large leg press advantage to a tiny flywheel advantage. That means the study cannot rule out no difference.
2. Vastus lateralis: 2.58 points in favor of the flywheel squat (95% CI −7.33 to 12.49). This is close to zero, and the range sits on both sides of it.
3. Vastus medialis: 8.57 points in favor of the flywheel squat (95% CI −2.76 to 19.89). The inner thigh leaned toward the flywheel, but again the interval included zero.
4. Changes across sets were tiny. Activity shifted across sets for the rectus femoris and vastus lateralis, but the changes were about 0.5 percentage points. The pattern did not differ between the two exercises.
5. The inner-to-outer thigh balance was unclear. The ratio of vastus medialis to vastus lateralis came out at 1.07 (95% CI 0.89 to 1.29), so neither exercise clearly shifted the work toward the inner thigh.

The authors were careful about what this means. In their words, the intervals "remained compatible with both no difference and potentially meaningful muscle-specific effects" (Topçu et al. 2026). They also did not run an equivalence test, so "no significant difference" is not the same as "proven equal".

How does this compare with earlier evidence?

The closest earlier evidence points the other way for one muscle. A 2020 systematic review of muscle functional MRI studies by Dooley et al. found 7 qualifying studies out of 1,946 screened. Only 1 of them looked at the quadriceps, and it reported greater rectus femoris activation in flywheel squats than in barbell squats (Dooley et al. 2020, J Appl Physiol). MRI measures where a muscle used energy after exercise, not its electrical signal during it, and the comparison was a barbell squat, not a leg press. So the two findings do not directly clash, but the new trial's point estimate (lower rectus femoris activity on the flywheel) does not echo that MRI result.

For the leg press, a 2020 systematic review of EMG studies by Martín-Fuentes et al. concluded that the vastus lateralis and vastus medialis showed the greatest activation during the leg press, followed closely by the rectus femoris (Martín-Fuentes et al. 2020, Int J Environ Res Public Health). It also found that quadriceps activity rose with deeper knee bend. The new trial fits that picture: the leg press produced solid activity across all 3 muscles and held its own against a demanding flywheel squat.

The prior reviews here are small and mixed in method. None of them pooled data on flywheel squat versus leg press, so this trial adds a direct head-to-head comparison that did not exist before.

What are the limits?

• Small sample. With 18 people, the intervals are wide. The rectus femoris interval runs all the way from −20.81 to 1.01.
• Only young trained men. The results may not apply to women, older lifters or beginners.
• EMG is a stand-in. Surface EMG shows electrical activity, not muscle growth or strength gains. A higher reading does not prove an exercise builds more muscle.
• Whole-repetition averages. Combining the up and down phases into one number can hide differences that show up in only one phase of the repetition.
• Two things changed at once. The exercises differed in resistance type, body support, posture and loading strategy, as the authors note. So any difference, or lack of one, cannot be pinned on the flywheel alone.
• One session per exercise. This was an acute test, not a training study.

What should you do with it?

1. If you like the leg press, keep it. Quadriceps activity was not clearly lower than on a flywheel squat in any of the 3 muscles tested, so you are not missing out by staying on the machine.
2. If you have access to a flywheel, it is a fair swap. The flywheel squat produced similar overall quad activity, so you can rotate it in for variety without expecting to lose quad work.
3. Do not pick an exercise to target one quad head based on this study. The leg press leaning toward the rectus femoris and the flywheel leaning toward the vastus medialis were not confirmed, and the intervals were wide.
4. Beginners and anyone outside the tested group should read this with care. The trial only tested resistance-trained young men, so let comfort, safety and progress guide your choice.

Is the flywheel squat better for muscle growth than the leg press?

This study cannot answer that. It measured muscle activity during one session, not muscle size after weeks of training. EMG is only a rough guide to how hard a muscle is working.

Does the leg press work the rectus femoris more?

The point estimate leaned that way, with the flywheel squat 9.90 points lower. But the confidence interval ran from −20.81 to 1.01 and the gap was not significant after correcting for testing 3 muscles, so the study did not confirm it. A larger trial would be needed.

Why did the flywheel squat include warm-up repetitions?

A flywheel needs a couple of pulls to get the disc spinning before the resistance builds. The researchers gave each flywheel set 2 preparatory repetitions and then analyzed the 6 that followed, so both exercises were compared on the same number of working repetitions.

Sources

• Topçu et al. 2026, Front Physiol
• Dooley et al. 2020, J Appl Physiol
• Martín-Fuentes et al. 2020, Int J Environ Res Public Health

This brief was drafted with AI from the sources listed above and passed automated source checks before publishing. Pedro Rodrigues, founder of Actus, is the responsible author.

Educational content, not medical advice. Training and diet changes carry risk; stop if you feel pain and talk to a physician before changing your program.