Every runner has a dominant side that's stronger and more stable. In fact, which side you favor is genetically coded, says Reed Ferber, Ph.D., director of the Running Injury Clinic at the University of Calgary

. A simple balance test (below) will tell you if you have a weak side. What's the value of knowing which side is stronger? When you favor one side, the resulting weakness on the opposite side can leave you more vulnerable to injury.

Your body uses two strategies to balance on one foot. First, it tweaks ankle and foot muscles. The second is a "hip strategy"—you twist your torso to steady yourself. But when you run, you're not using the ankle strategy at all, putting the strain of compensating for your weaker side entirely in the hips. "Leg dominance won't cause injury," he says, "but strengthening the hip and working on balance will help you avoid it."


Taking Sides
Races - Places:

The Benefits of Running 10 Minutes a Day
Stand on one leg, eyes closed. Time how long you can hold without toppling or putting down your foot. Switch legs. If both sides are close (30 seconds on each side, or 30 on one and 25 on the other), you've got good equilibrium. But if the difference is wide—five or 10 seconds on one leg, up to 30 on the other—you're out of balance, and may have hip-muscle issues.


Get Even
Perform these two exercises daily for three weeks, after a run. (Doing them before might tire key core muscles.) Then repeat the balance test; you should be closer to equilibrium. Thereafter, do these moves twice a week for maintenance.


HIP-ABDUCTOR STRENGTHENER
HOW: Loop an exercise band around the ankle on your strong leg. Keeping your outside knee straight, raise the outside leg to the side. Lift for two seconds, return for two seconds, controlling the movement. Do three sets of 10 reps.
WHY: By training only the weak side you build symmetry. There is twice as much muscle activity for the support leg, so your inside leg is the one reaping the balance-improvement benefits.


CORE STABILIZER
HOW: Stand with your weak leg on a pillow. Balance for 30 seconds (you can use a light touch on a wall). Repeat three times. Tip: When you can balance relatively easily for 30 seconds, increase the intensity by closing your eyes, which makes it harder to balance.
WHY: Supporting yourself on your weaker leg while standing on an unstable surface forces you to employ an ankle and a hip strategy to balance, and helps your weak leg catch up to your strong one.