Being balanced doesn't necessarily mean that you can lift the same amount of weight with, for example, your biceps and triceps (front and back of arms). The ideal strength ratio between opposing muscles varies from person to person, but an average to shoot for is about 60 percent to 40 percent from back to front. So, if you can lift 60 pounds with your quadriceps in a leg extension exercise, you should be able to lift 40 with your hamstrings doing a leg curl exercise. The muscle pairs that benefit most from balancing are the biceps/triceps, glutes/hip flexors, quads/hamstrings, calves/shins, lower back/abdominals and chest/back.

When it comes to left-to-right imbalances, strive for no more than a 10 percent difference between the same muscle on opposite sides. In other words, if you can do a bicep curl with a 12-pound dumbbell on one side, you should be able to hoist at least 10 pounds on the other.