Why Unilateral Movements?

A unilateral movement in terms of strength training is a movement that is performed on one side of the body at a time. For example, a bent over single armed row.  

Unilateral movements are WIDELY under utilized in training. Whether people recognize they are weaker on one side rather than the other or not, almost everyone has an imbalance in their musculature somewhere. Some of the most common imbalances you will see are the bodybuilders elbow (where the elbows are constantly bent at a 45-degree angle because of an imbalance between the biceps and triceps). Another example of this is chronic low back pain, a lot of the time LBP is caused by an imbalance in the abdominal muscles as compared to the back muscles causing our lower back to round and becomes unstable and sore.  

Back on the topic of unilateral movements. Our dominant hand side tends to be stronger than the opposite (I.e. if you are right-handed the right side of your body will tend to be hypertonic (tighter) and have more muscle tone because we use that side more often than the weaker side. When performing compound movements, we tend to subconsciously compensate my utilizing our stronger side to be able to increase the weight and make it “easier”. 
 
By utilizing unilateral movements, you can lessen the gap in difference between limbs and improve overall performance.  
 
TIP: work your weak side first – only perform the amount of reps you could on the weak side on the strong side. This way you are still maintaining muscle mass but not worsening the imbalance.