Throughout life, your body accrues imbalances. Maybe an overused tennis shoulder has left your right arm stronger than your left, or your left calf muscle is still weak from an old soccer injury. Left unaddressed, these weaknesses can lead to major injuries as we rely on our "good side" to take up the slack. That's why unilateral workouts — or working one side or limb at a time — are essential to strengthen weak spots, and improve your overall performance. A nice bonus? The exercises drastically improve core strength too, because stabilizing weight on one side of the body forces more core muscles to fire to keep you upright. Here's how to get started.