If you're a young adult who hasn't trained much before, slowing down the lowering part of a leg extension from 2 seconds to 4 seconds won't make you significantly stronger, even though your muscle is under tension longer.

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Against

Evidence from Studies

Supporting (1)

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Community contributions welcome

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Effect of different eccentric tempos on hypertrophy and strength of the lower limbs

Randomized Controlled Trial

Human

2022 Mar

The study had people do leg extensions with either a slow (4-second) or fast (2-second) lowering phase, and found that both groups got just as strong — so slowing down the lowering part didn’t make them stronger.

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Source Study

Effect of different eccentric tempos on hypertrophy and strength of the lower limbs

Score: 54

DOI: 10.5114/biolsport.2022.105335

Similar Assertions

If you're a young adult who doesn't lift regularly and you do leg extensions slowly (4 seconds down), your inner thigh muscle gets a little thicker than if you do it faster (2 seconds down)—but the outer and front thigh muscles don't change much.

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If you take four seconds to lower the weight during leg extensions instead of two seconds, your muscles are under strain for about 95% longer—without doing more reps—over eight weeks of training.

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If you're a young adult who hasn't trained before and you do leg extensions slowly—either taking 2 seconds or 4 seconds to lower the weight—your thigh muscles will grow about the same amount, and you'll get just as strong either way.

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78%