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.
Scientific Claim
In adolescent male rugby players, unilateral leg press training improves unilateral strength to a greater extent than bilateral leg press training, despite producing similar gains in bilateral strength, suggesting that training specificity and the bilateral deficit phenomenon may enhance neuromuscular adaptations in unilateral movements.
Original Statement
“The 5-RM UL LP increased significantly more in the unilateral group (p < 0.05). The results indicated that unilateral leg press training was as effective as bilateral leg press training in improving bilateral strength and more effective in improving unilateral strength 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 and significant between-group difference (p=0.02) support definitive causal language. The authors correctly attribute the finding to training specificity and bilateral deficit without overreaching into unmeasured mechanisms.
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
Kids who trained one leg at a time got much stronger in that one leg, while kids who trained both legs together got just as strong in both legs—but not stronger in one leg. So training one leg at a time is better if you want to boost strength in just one leg.