Even though the players got stronger from doing leg presses, they didn’t run any faster after five weeks — meaning just getting stronger on a machine doesn’t automatically make you sprint better.

Scientific Claim

Five weeks of unilateral or bilateral leg press training does not improve linear sprinting performance in adolescent male rugby players, as no significant changes were observed in 30-meter sprint times despite measurable strength gains, suggesting that strength gains from machine-based leg press training do not transfer to sprint speed in this population within this timeframe.

Original Statement

“There was no significant effect of time for the 30-m linear sprint (F2, 13 = 0.002, p = 0.968, ≤ 0.01), nor was there a significant interaction effect of time and group for the 30-m linear sprint (F2, 13 =1.251, p = 0.319, 0.720, = 0.161).”

From study:The Effect of Unilateral and Bilateral Leg Press Training on Lower Body Strength and Power and Athletic Performance in Adolescent Rugby Players

Evidence Quality Assessment

Claim Status

appropriately stated

Study Design Support

Design supports claim

Appropriate Language Strength

definitive

Can make definitive causal claims

Assessment Explanation

The RCT design with pre-post measurements and statistical non-significance (p=0.968) supports definitive language. The authors correctly avoid overgeneralizing beyond sprint performance in this population.

Evidence from Studies

Supporting (1)

The Effect of Unilateral and Bilateral Leg Press Training on Lower Body Strength and Power and Athletic Performance in Adolescent Rugby Players

Randomized Controlled Trial

Human

2023 Mar

Even though the players got stronger from doing leg press exercises, they didn’t run any faster after five weeks — so stronger legs from this machine didn’t help them sprint better.

Contradicting (0)

No contradicting evidence found

Source Study

The Effect of Unilateral and Bilateral Leg Press Training on Lower Body Strength and Power and Athletic Performance in Adolescent Rugby Players

Score: 54

DOI: 10.5114/jhk/159626

Similar Assertions

Doing leg press exercises twice a week for five weeks makes teenage rugby players much stronger when pushing with both legs at once, whether they use one leg or both legs at a time.

87%

Even though the players got stronger, their ability to jump higher or more powerfully didn’t improve after five weeks of leg press training — meaning strength on the machine doesn’t automatically make you jump better.

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Training one leg at a time makes that leg much stronger than training both legs together — even though both methods make you equally strong when using both legs at once.

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When teenage rugby players train one leg at a time on the leg press machine, they get much stronger in that single leg than when they train both legs together at the same time.

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Both training methods made athletes jump higher and turn faster, but didn’t make them run straight-line sprints any faster.

72%