I show a lot of love for big, compound barbell movements like squats, deadlifts, and cleans—and rightfully so! They get you strong, they make you fast, and they keep you in the game. Now, you may notice that all of these movements load the entire body evenly, and challenge both limbs (either both arms or both legs at once) to work in the same plane in order to produce force effectively. In other words: these movements use BOTH sides of the body, and thus are bilateral. This fact may not seem that important, until you consider how little bilateral movement actually happens when you throw, sprint, or do basically anything on a court or field. In fact, in the world of athletics, most movement is unilateral. Which makes sense, especially when looking at sports injuries: rolled ankles, pulled hammies, and overuse injuries—these happen due to discrepancies in strength, mobility, or activation between the left/right or anterior/posterior sides of the body. So while bilateral movements like squats and deadlifts help develop overall strength and power production, unilateral training can remedy imbalances in the body unique to the individual athlete and the specific demands of his or her sport. Single-limb movements are necessary for the development of a strong, balanced, and injury-free athlete.
Unilateral Training = Strong Core
One of the biggest causes of injury for an athlete is poor core strength. More specifically, having weak stabilizers that cannot brace the spine effectively in demanding positions. Poor core strength means that the transfer of power from the base of support is less efficient, and places undue stress on muscles and joints that are likely to get injured or overused. This weakness in stabilization can transfer up- and downstream, and lead to poor mechanics—and poor mechanics means risk of injury to the shoulders, hips, and everything else under the sun. Training bilateral movements will help develop your strength overall, but may not give you the stability you need to maintain good positions in single-limb actions like kicking a ball or swinging a bat. (Or throwing a Frisbee during our “non-competitive” Volt team Sunday Ultimate games.) Unilateral movements stress only one side of the body, forcing you to compensate for this uneven load distribution by activating your core muscles properly. Movements like lunges and split squats challenge you to not only balance the load over one limb, but also activate the muscles of the hips, groin, and low back to stabilize this uneven load. Reducing the stability of bilateral movements by making them unilateral forces the musculature of your core to maintain alignment of your spine, while keeping your torso in an efficient position to produce force. Makes sense, right? This also translates to injury prevention—by challenging the smaller motor units in the small muscles stabilizing the moving limb, you reduce your chances of developing imbalances in your stabilizing core muscles. This improved stability not only lowers your risk of injury, but also helps increase your body’s transfer of power during unilateral movements. For example: a soccer athlete with a strong core will put more force through their plant leg, and maintain that force output as the striking leg drives through the ball. It’s all unilateral.
Move Well In All Planes
Unilateral movements also allow the athlete to move in multiple planes of direction against resistance. Squats, deads, and cleans all happen in the same plane, but in athletics, you need to be able to produce force every which-way. And just like on the field, you also need to decelerate your moving body while under load. These specific features of unilateral training can help you develop better proprioception during movement. Once again, being a good athlete boils down to being able to control your body’s position while maintaining efficient motor recruitment. Walking lunges are a prime example of moving from a stable to an unstable base, all while under load. This dynamic element challenges the neuromuscular system to recruit all necessary motor units in order to keep you in strong, balanced positions during movement. Improved body awareness means that you can change direction, land from jumping, and initiate an explosive jump or leap with more confidence—and better mechanics.
A Word From Volt Advisory Board Member
Of course, I could wax on and on about the performance benefits of unilateral training, but I feel that is better suited for one of the best guys in the business. Devan McConnell is one of our Volt Champions, and consulting strength coach for Volt Hockey (one of the most unilateral sports in existence), and he has a very unique way of implementing unilateral training for his athletes at University of Massachusetts-Lowell. Here is a quick breakdown of how his system builds some of the strongest hockey players on the ice.
"We really don’t use unilateral lifts with the goal of improving proprioception or reducing asymmetries, although those are things that occur. We utilize exercises such as Rear-Foot Elevated Split Squats, Single-Leg Box Squats, and Single-Leg Rack Pulls to develop high levels of strength. In fact, when the goal of the training phase or exercise selection is to develop maximal strength levels in our athletes, we almost always use these single leg variations. From the perspective of reducing the chance of injury in training and in sport (which are beyond a doubt our primary goals in training), single-leg variations are safer than their bilateral counterparts for myriad reasons, not the least of which being less spinal loading. Compression and shear forces are the primary enemies of the spine, and by reducing overall loads we automatically reduce the wear and tear on the lumbar spine, as well as reduce the chance of traumatic injury.
From a performance standpoint, utilizing unilateral training takes advantage of a physiological phenomenon called “bilateral deficit”. Bilateral deficit basically means that you are stronger on each leg individually than you are on both together. So if an athlete can squat 300lbs bilaterally, they can actually squat more than 50% of that load on each leg (for instance, 160lbs per leg). Part of this is because in the squat, the weak link at high percentages of your max is actually the low back. Picture someone missing a 1RM attempt in the back squat. When they are trying to come out of the hole, if they can’t make the lift they will invariably shoot their hips up, while their chest falls forward and they miss the lift. This is because the legs can handle the load, but the back cannot.
"In the case of an exercise like the Rear-Foot Elevated Split Squat (RFE, or Bulgarian Split Squat), while the overall loads are lower, they are not enough to overwhelm the back. This means that an athlete can overload their legs (which is the goal of heavy squatting) and continue to develop leg strength. Our Single Leg Rack Pull follows the same concept in the dead lifting pattern. Our athletes consistently are much stronger on one leg than 50% of their two leg strength. In fact, our RFE numbers are equal or better than our Front Squat numbers, and our Single-Leg Rack Pull numbers are similarly equal or better than our Bilateral Rack Pull numbers.
In the following video, this player RFE’s 390lbs for 2 reps on each leg.
Clearly, his ability to develop strength on each leg individually eclipses his ability to develop leg strength on two legs. Since the goal is leg strength development, there becomes no equal alternative in my mind when selecting exercises for this purpose. In addition to all of the above reasons for utilizing unilateral exercises for strength development, keep in mind that my job is about developing team sport athletes. Running, cutting, jumping, etc. all occur on one leg at a time, or unbalanced on two legs. The combination of lower chance of spinal injury, increased strength development, and functional athletic development make the choice very clear in our programs when we are choosing the most appropriate exercises for our athletes."
One Last Thing
Understand that Coach McConnell is one of the best in the business and you shouldn't be maxing out your split squats unless he is in the room prepping you for the Frozen Four. To conclude, let me just say that unilateral training has many merits that often get overlooked, and too many athletes settle for just performing bilateral movements. If you're looking to maximize your performance and ability on the ice/court/Frisbee field, be sure to utilize both bilateral and unilateral movements to fully develop your potential.
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