What Is The Bilateral Deficit In Strength Training
Why Combined Single Leg Strength Exceeds Your Double Leg Strength
Test your single leg press on each side and add them together. The total is almost always higher than your bilateral press. This is the bilateral deficit. The standard explanation is neural coordination. The positional explanation is more important and more actionable.
What Is The Bilateral Deficit
The bilateral deficit is the measurable gap between combined unilateral output and bilateral output. It has been documented in research for decades. The standard explanation is that bilateral movements are a coordination skill that improves with practice. This is partially correct but misses the positional component.
The Standard Explanation vs The Positional Explanation
When the pelvis is rotated in the Left AIC pattern, each hip is in a different position. Each leg produces force from different mechanics. During a bilateral movement, the nervous system must coordinate two asymmetrical limbs into a symmetrical movement.
How Asymmetry Creates Neural Conflict In Bilateral Movements
The brain resolves this conflict by reducing output from the stronger side to match the weaker side, or by allowing asymmetrical force production and compensating through trunk shift or rotation. In either case, bilateral output is less than the sum of unilateral outputs because the nervous system is managing positional conflict.
Why Bilateral Practice Does Not Close A Positional Deficit
If the deficit is positional, bilateral training reinforces the compensation pattern. The nervous system gets better at managing asymmetry, but the asymmetry itself does not change. Performance improves slowly and injury risk on the compromised side increases.
How Restoring Symmetry Resolves The Deficit
When the pelvis is repositioned and both hips have symmetrical range and neural drive, bilateral movements can be coordinated without conflict. The deficit closes not because the brain got better at compensating, but because there is nothing to compensate for. MOVECHECK quantifies this asymmetry through Hip Mobility, Pelvic Position, and Integration stages.
See This In Your Own Body
Every concept in this article is tested in the MOVECHECK assessment. Find out which patterns apply to you.
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