Analysis Version
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Analysis v1
Strong Opposition

Leaning back during leg extensions might make your front thigh muscle work harder and grow more because it stretches the muscle more during the move.

0
Pro
48
Against

Evidence from Studies

Supporting (0)

0

Community contributions welcome

No supporting evidence found

Contradicting (4)

48

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48

Hip flexion angle affects longitudinal muscle activity of the rectus femoris in leg extension exercise

Cross-Sectional Study
Human
2023 Jun

The study tested whether leaning back more during leg extensions works the front thigh muscle more, but found that leaning back actually made that muscle less active.

40

Effects of knee and hip flexion angle on region-specific and longitudinal compartmental muscle stiffness of the rectus femoris using shear wave elastography in male bodybuilders

Cross-Sectional Study
Human
2025 Oct

The study found that leaning back during knee extensions actually reduced tension in the front thigh muscle, contrary to what the claim suggests.

27

Enhancement of knee extension voluntary and electrically-evoked strength with the body tilted backward

Cross-Sectional Study
Human

The study found that leaning back helps you push harder during knee extensions, but it doesn’t make the thigh muscle activate more, which goes against the idea that it works better that way for muscle growth.

20

The role of agonist and antagonist muscles in explaining isometric knee extension torque variation with hip joint angle

Cross-Sectional Study
Human
2017 Oct

The study looked at whether lying back during knee exercises helps the front thigh muscle work harder. It found that even though the muscle is stretched more when lying back, it doesn’t activate as much as when sitting up.

Gold Standard Evidence Needed

According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.

Similar Assertions

The rectus femoris muscle exhibits greater hypertrophic adaptation to isolated knee extension exercises than to compound movements involving hip and knee flexion due to biomechanical limitations in force production during multi-joint movements.

54
0
75%

When lying down, your leg muscles don't get stronger even if one key muscle gets longer — and that's mostly because your brain isn't fully turning on those muscles, not because opposing muscles are getting in the way.

20
0
75%

For people who don't usually work out, using a knee extension machine grows the front thigh muscle much more than using a leg press machine.

53
0
75%

If you're a guy who lifts weights, your front thigh muscle works way harder during leg extensions than during leg presses — probably because the movement challenges how that muscle crosses two joints at once.

34
0
74%

If you want to make the front part of your thigh (rectus femoris) bigger, leg extensions work better than leg presses — after 12 weeks, leg extensions made it grow 12% more than leg presses did.

31
0
74%

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