Having an imbalance is more common than you may think! For example, I spent 10 years carrying a heavy laptop bag on my right shoulder. This resulted in a severe imbalance that is very noticeable. The musculature on my right side is tight and packed, and my head naturally leans to the left side to compensate. While it may never be entirely reversed, this is a great candidate for the weak side rule!

I always want to give credit where credit is due, so I must share that I learned the "weak side rule" from Ian King, author of The Book of Muscle.

The weak side rule is simple:
  1. Use unilateral movements. Unilateral means one-sided. If it's your arm, do one-armed curls rather than using both arms. If it's your back, like me, do one-armed rows or one-armed lat pull-downs so you can focus on one side at a time.
  2. Always train the weak side first. There are two reasons for this. First, you want to assess the strength of the weakest side so you can adjust the strong side. Second, your first muscle worked is what is prioritized in the workout — it receives the most energy and attention.
  3. Never do more with the strong side than the weak side can handle. This is the heart of the rule. Basically, if you can only handle 10 curls at 20 pounds on the weak side, this is ALL you do on the strong side! Work the weak side to failure, if that is your routine, but always use the same weight with the strong side and stop at the same number of reps that your weak side could handle. This allows the weak side to be the side that is stressed the most and grows to "catch up" with the strong side. Don't worry, you won't lose major muscle mass on the strong side — it receives enough stimulation to maintain while the weaker side is catching up!