There are studies that show unilateral and bilateral training lead to similar effects in terms of strength, sprint speed, and change of direction speed. There are proponents of one method over the other. Ultimately, the choice should be to do what is best for the trainee and to ensure symmetry. So, today, we ask the question, what are the most effective applications for unilateral vs bilateral training?
Firstly, it’s important to note that any well rounded strength and conditioning program should include both unilateral and bilateral movements. Anyone who claims that unilateral movements make you weak, or that bilateral movements are unnecessary, is missing the point. Both bilateral and unilateral exercises are associated with different applications and training adaptations, so don’t neglect one for the other. That being said, let’s talk about how and when to implement each of these variations.
For the sake of argument, we’ll compare the single squat to the back squat. If you’ve ever performed these exercises, there are a few obvious differences that immediately come to mind. The single leg squat is much more challenging in terms of dynamic stabilization. This has the consequence of drastically limiting the amount of weight you can lift compared with the back squat, due to the structural advantage you have during the bilateral squat. The added demands of the single leg variation will challenge your ability to stabilize dynamically and control your movements through space.
Bilateral exercises like the back squat are associated with more overall strength and power development. There has been some evidence to suggest that the back squat is more effective for building linear velocity, while unilateral leg exercises are effective in developing lateral change of direction, perhaps because they challenge us to stabilize in the frontal and transverse planes, even during movements that are usually considered to take place in the sagittal plane. Unilateral exercises can be effective during a strength-stabilization phase of your periodization to address any asymmetrical strength deficits and strengthen the smaller stabilizer muscles at a particular joint.
Both of these adaptations are critical in maintaining healthy joints and decreasing the likelihood of injury. You can also use a unilateral exercise like the single leg deadlift before a bilateral deadlift to increase activation and proprioception. Single leg exercises have a way of making any imbalances from side to side very obvious. These are the kinds of observations that if addressed now, could prevent an injury down the line.
Odds are that whether you tend to favor bilateral or unilateral exercises, you need to be doing more of what you’re neglecting.
Unilateral exercises are indispensable for preventing injury and correcting asymmetrical strength deficits, while bilateral movements are superior in developing maximal strength and power.
Both unilateral and bilateral training help athletes perform better for their individual reasons. It is important to train both, especially because bilateral strength doesn’t transfer very efficiently to unilateral and visa versa; a 150 pound person may be able to squat 300 pounds, but not be able to perform a single leg squat on one or both limbs to parallel.
Most sport takes place on one leg at a time; this includes running, certain jumping movements and lateral movements. When training unilaterally, many stabilizers are activated to a greater extent, which can help to develop knee stability and reduce the likelihood of non-contact injuries occurring. Further, we tend to develop imbalances between limbs at a very young age, in fact it has been shown that even babies favor one limb more often than another.
Training unilaterally can significantly close that gap, although many of us will never accomplish true symmetry. An imbalance such as this can increase the likelihood of injury, due to the fact that one limb may not be able to tolerate the levels of power output that the other can produce.
Bilateral movements can help to establish a base of strength that can translate into bilateral movements, as well as to help develop the core musculature; these include pushing, pulling, certain jumping movements, and anything that requires a combination of these movements, such as a lineman in American Football, trying to hold an opponent.
Many coaches preach that some of the bilateral lifts, such as squats and deadlifts, can train the core musculature well enough that any extra core training becomes unnecessary. In my opinion, these lifts help significantly with core development, however, I also believe that it is important to perform other movements to fully develop the core properly.
Each form of training has their merits, thus, it is important not to neglect one for the other in order to create carry over to the field of play.
Symmetry, dominance, and laterality are fundamental concepts that need to be well understood in order to prevent and, if necessary, to correct motor patterns that can expose an athlete to a higher risk of injury. Nevertheless, performance itself can be significantly affected if a higher degree of asymmetry is present between the lower and/or upper extremities.
The rational implementation of unilateral and bilateral exercises are by far the most efficient way to reinforce and/or correct erroneous motor behaviors. It is mandatory, however, to understand when to apply them and, most importantly, why.
Asymmetry is the inevitable consequence of laterality, the development of preferential motor patterns based on the use of the left and/or right lower and/or upper extremity. Laterality emerges from dominance, the process of establishing left versus right handedness/footedness naturally occurring during the first decade of life. Laterality and dominance, therefore, are words that should not have a negative connotation. However, excessive asymmetry – the result of years of sport-specific practice and competition – can lead to structural and functional imbalances.
Evidence has shown that more than 15% of asymmetry between left and right leg can significantly increase the risk of injury and negatively affect performance.
There are no data available for the upper extremities, although postural imbalances will result from excessive asymmetry between right and left arm. In my opinion, symmetry between dominant and non-dominant, upper and lower extremities should be measured in order to assess a potential source of imbalances: if the discrepancy goes above what appears to be a tolerable deficit (10-15% as an average) unilateral strength training should be implemented to counterbalance the effect of years of preferential use of the dominant limb.
Sport-specific adaptation will tend toward a certain degree of asymmetry, also know as sport-specific kinetic adaptation: unilateral strength training does, therefore, represent the most effective strategy to increase symmetry between dominant and nondominant limb.
Training the upper and/or lower extremities independently from each other allows to systematically overload the weaker arm/leg improving strength and coordination while progressively decrease the functional deficit between left and right limb.