by Chris Dellasega, M.S.Ed.

A muscle imbalance occurs when a muscle (agonist), or a group of muscles, are overactive while other muscles, frequently their counterpart (antagonists), are under-active. If left uncorrected these imbalances can eventually lead to faulty muscle recruitment patterns and/or postural distortion patterns. A muscle recruitment pattern is how specific muscles produce a given movement, e.g. locomotion. Postural distortion patterns are essentially the same as faulty muscle recruitment patterns, but typically involve muscles responsible for posture, e.g. rounded shoulders, necks that protrude forward, etc. If left uncorrected over time these imbalances can lead to further muscle and joint problems and disrupt body alignment, therefore leading to an increased chance of injury. This is especially true of individuals who start a strength training program with little or no attention given to these imbalances. An untrained individual will almost always have imbalances of some kind.

It is very common for someone to have muscle imbalances between limbs, especially an untrained individual. A muscle group imbalance between limbs is known as the bilateral deficit, simply put this means that one arm, or leg, will usually be stronger than the other. It is common for the dominate side of the body to be stronger than the none dominate side because it is human nature to do ordinary, daily tasks with our dominate arm, or leg, therefore working them more frequently than the non-dominant side. So, if someone is right handed it is very common for their right arm to be stronger than their left arm and their right leg to be stronger than their left leg, or vice versa, although this is not always the case. A very effective way to correct muscle imbalances and to also assist in correcting the bilateral deficit is to utilize unilateral exercises.

The initial workouts for a new trainee should include unilateral exercises for both the upper and lower extremities. This would include, for example, variations of dumbbell presses for the upper-body and variations of split squats for the lower-body. Performing single-limb (unilateral) exercises helps to correct muscle imbalances ensuring that muscles are in balance with other muscle groups, especially their antagonist, or opposite muscle group. Charles Poliquin, a world renowned strength coach who has coached hundreds of Olympic level athletes, states that, “…beginning with a program of unilateral exercises for the legs often results in faster gains in the squat in the long term than if no unilateral exercises are performed.” This also holds true for unilateral exercises for the upper extremities in that increased strength gains achieved through unilateral exercises will transfer directly to bilateral exercises, such as the bench press, when performed in the same plane of motion. Put another way, performing a bench press with dumbbells (unilateral) can make you better at performing a bench press with a barbell (bilateral).

Unilateral exercises can also help develop core strength and stability at the joints due to each limb having to work independently of the other, thereby recruiting more of the body’s stabilizing muscles. This will also prepare the trainee for more complex skills in the long term, such as variations of the Olympic pulls and front squats, and compound exercises such as deadlifts and chin-ups. An untrained individual (including those with one year or less of strength training) should always begin a program with unilateral exercises before complex and compound exercises in order to achieve muscular balance and to also help correct the bilateral deficit.

Foregoing unilateral exercises increases the chance of injury due to an inability to properly stabilize the body in space and to properly stabilize the joints. Since proper stabilization of the body and joints is of critical importance when performing complex and compound exercises unilateral exercises can and should be used when preparing a trainee for complex and compound exercises. This can help to ensure that proper technique will be used when performing complex and compound exercises because the muscles of the core and the muscles responsible for stabilization at the joints will be better conditioned. This can help the trainee get the most bang for their buck out of their training because they will be able to properly perform the complex and compound exercises.