Single Leg Work: Finding and Fixing Imbalances

Almost everyone has a stronger leg. A difference of 5 to 10% between sides is common in healthy adults, and larger gaps show up after an old ankle sprain, a knee surgery, years of a sport that favors one side, or simply a habit of standing on one leg more than the other. Two legged lifts hide this. In a back squat, the stronger leg quietly does more of the work, the bar goes up, and nobody knows. The imbalance only becomes visible when each leg has to work alone.

Why it matters

A gap between sides matters for two reasons. The first is injury. The weaker leg is more likely to give when you land awkwardly, change direction or miss a step, and the body tends to protect the weak side by loading the strong one even more, which widens the gap over time. Some studies tie larger gaps to more injuries in athletes, though not all do, and a 55 year old stepping off a curb faces the same mechanics.

The second is performance. Running is a series of single leg hops. Every stride is one leg producing force while the other swings. If one leg produces 10% less force, the stride is uneven, and the stronger side carries more of every mile.

The exercises that find it

Single leg work is simple to add and it does two jobs at once: it shows you the gap and it closes it.

• Split squats. One foot forward, one back, lower until the back knee is near the floor. Hold weights at your sides. Start with the weaker leg and match its reps with the stronger one, so the strong side never pulls ahead.
• Step ups. Onto a box at about knee height, driving through the whole foot, lowering slowly.
• Single leg Romanian deadlifts for the hamstrings and hips, and single leg calf raises for the ankle.

Two or three sets of 8 to 12 per side, twice a week, is enough. Always start with the weaker side and let it set the count. Six to eight weeks is a fair time to recheck the gap.

What a force plate shows

Feeling is a rough guide. A force plate measures it. Standing on two plates, one under each foot, a jump or a squat shows exactly how much force each leg produces and how quickly. A countermovement jump might show the left leg contributing 46% and the right 54%, a gap the person had no idea existed. Balance tests on one leg show how much the body sways and corrects, side by side.

The number is useful because it can be retested. Train the weaker side for a couple of months, stand on the plates again, and the 46 to 54 split closes toward even, or it does not and the plan changes. We use a 10% difference as the line where it earns attention.

That's the kind of thing we measure.

This article is educational and is not medical advice.

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