The human body is made for movement, it's made to move side to side, forward and backwards, and rotate. Most of our traditional weight training is bilateral movements, when performing a lift both limbs are moving together in unison, most lifts can be performed in a bilateral way. In respect to our asymmetrical design bilateral movements all the time is not the best approach to programming. We have two sides of our body, a left side and a right side and our main form of movement is walking, gait and when we walk we rotate, trunk, head, hips, bones all rotate as we move. It is a natural movement for us and is great to restore balance of the human body systems. In our workout programs we want to have exercises that make us go to one side and then the other, we need unilateral movement in life because most of life is unilateral.
Most people favor upper body exercises vs lower body, there is less demand on the body, less fatigue, less heart rate, and you can feel the “pump” more which is more neurologically stimulating than a leg pump. So the tendency is there for people to press, row, curl, raise, and humans can get stronger as they progress through exercises, all things are going in the right direction. If you remember back to our talking of the thorax, rib cage and trunk we talked about the asymmetries underneath it and how those asymmetries drive an imbalance of the system. Humans are right side dominant and that acts on the trunk and hips to lateralize us more to the right. With that in mind, performing only bilateral exercises can continue to add to our lateralized body and/or even keep us and lock us further into that position. The body likes comfort and if you give it a comfortable consistent position/pattern it will adjust and be prone to go towards that more often. So what does this mean for our bilateral exercise? - They are very good to perform and need to perform, but we want to make sure we are complimenting them with unilateral movements.
The thorax and rib cage were built for rotation, so we must let it rotate. When we rotate one side come forward the other side goes back, one arm moves forward and the other moves back, adding single arm movements and alternating movements to allow the thorax to gain rotation. Exercises like alternating rows, dumbbell bench press, shoulder press the list can go on with all movements. This allows the body to shift into the left side and right side. It also creates a demand for muscle chains to activate in order to perform the exercise more than they would if their feet were in a squared stance (bilateral). It also trains the brain to work one side while the other side is doing a different task, training one hemisphere of the brain to have motor control on the side it controls.
Implementing this into training is not hard at all, it adds another dynamic to movement. For example let's take a Single arm dumbbell bench press, you will need more core activation to manage the movement of the arm and ribcage. Oftentimes we utilize unilateral training with single arm rows, but open yourself up to more; lat pulldowns, shoulder presses, curls, triceps, presses. All of these can be done in a single arm fashion and you will challenge the body to maintain a posture to lift the weight which will add more strength to your limb training and add an increase to your overall fitness.