If you have trained long enough, at some point you have said some variation of the following statement: “why is this side stronger than the other side?” There is an assumption that the dominant side is the stronger side, but this is not always the case. In fact, it’s quite possible that, for example, the right arm can be stronger than the left, while the left leg can be stronger than the right. Other than injury, what would be the reason for this phenomenon?
GENETICS. Simply put, you’re flawed…but that’s OK because we all are in some way. Whether a limb is shorter than the other (mechanical advantage), a muscle origin or insertion varies from side to side, or there is slight variation in fibers (Type I or II) in the opposite side muscle; all these slight genetic differences can change the amount of weight lifted on either side. Also, range of motion (ROM) can vary around joints on either side of the body. These small differences, over time, can cause significant strength differences in opposing limbs.
DOMINANT vs. NONDOMINANT SIDE. By habit most of us generally will lead with or stand on the same leg, will carry items with one arm (dominant side) and tend to lead with or rely on the dominant leg more often than not. The same thing is seen during exercise wherein a person will unconsciously start each set with the dominant side of the body…when fresher and less fatigued.
TRAINING METHODS. What does your training look like? Are you focusing on mostly bilateral (both sides at the same time) movements with barbells and/or exercise machines? Training in this capacity allows for the stronger (can be dominant or nondominant side) body part to take over and do more work than the weaker body part. Essentially acting as a crutch.
Over time creating these muscle and strength imbalances can increase the chance of future injury. How do we fix/keep these imbalances from happening?
BE CONCIOUS. This takes some work and really paying attention. We are changing long-standing, unconscious habits. This takes patience. If you always carry bags in your left hand, carry them in your right. If you lead with your left leg standing up, switch to your right. This will feel very strange at first (I have done this, trust me, I know), but keep at it and it will get more comfortable and help decrease those strength differences.
CHANGE YOUR TRAINING. This is where you can make the most significant gains in correcting bilateral differences. First, eliminate all machine training. The mechanical advantages gotten from using machines creates the perfect environment for bilateral asymmetrical muscle strength. Second, incorporate unilateral (one side at a time or independently) movements with kettlebells, dumbbells, bands, and cables. Barbell work can still be done, but should be considered secondary. There is no percentage associated with the ratio, but I would suggest 75-85% unilateral exercises until strength differences have decreased. Within your unilateral training, start each set with the weaker body part. Again, this will take some thinking and awareness. Include mobility and ROM specific movements and testing such as dynamic stretching, yoga, pilates, myofascial release, and even active foam rolling into your daily routine.
While muscle strength imbalances are extremely common, they are also easy to fix with some conscious effort. By changing a few unconscious movement patterns and focusing on unilateral training, bilateral strength differences can be eliminated. In turn, this decreases risk for injury, which is always damn good!