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.
Scientific Claim
Five weeks of twice-weekly unilateral or bilateral leg press training causes significant improvements in bilateral lower body strength in adolescent male rugby players, with increases of 8.9% (d = 0.53) and 10.9% (d = 0.55), respectively, demonstrating that machine-based leg press training effectively enhances maximal strength in this population.
Original Statement
“After five weeks of training, both the UL (t6 = −8.556, p ≤ 0.01, ES = 0.53) and BL (t6 = −8.773, p ≤ 0.01, ES = 0.55) groups experienced significant improvements in the 5-RM BL LP, while no improvement was seen in the CON (t4 = −0.09, p = 0.933, ES = 0.01).”
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 study is a randomized controlled trial with a control group, allowing causal inference. The reported p-values and effect sizes support definitive language. No overstatement is present.
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
The study found that doing leg press exercises twice a week for five weeks made teenage rugby players significantly stronger in both legs, just like the claim said — no matter if they trained one leg at a time or both together.