Unilateral Leg Training
By Stephen Brandis, CSCS
Another hot topic in the fitness and sports training world is that of bilateral vs. unilateral leg training. Bilateral training refers to working both legs simultaneous as in your traditional back squat, deadlift, and leg press. Unilateral training is when each leg is working independently on its own as in a single leg squat, split squat, or single leg dead lift.
What makes this such a talked about topic is can you still make strength and hypertrophy gains when training unilaterally since the external load you are using will be less than that when you would train bilaterally? There are advocates on both sides of the argument and no one is necessarily wrong, it’s just how to apply one of or both training methods into a program that works with the individuals needs, goals, and anatomy. If you have no back issues, good posture, healthy joints, and can keep good form, bilateral squatting should give you no troubles and by all means, have at it. However, say you have a history of low back pain, a kyphotic thoracic spine (hunched over posture) and/or poor ankle, hip, or shoulder mobility, chances are you will not be able to perform a squat with a barbell correctly or pain free. This is where unilateral leg training would come into play because the external load is less, you are not directly loading the spine, and you do not need to force yourself into an uncomfortable position under a barbell to perform the lift.
Bilateral Deficit:
Not only is unilateral training more user friendly, but there is also a noted difference in the amount of force production between bilateral and unilateral training. This occurrence is called bilateral deficit, which means that the sum of individual leg force production is greater than that of bilateral force production. In other words, if you were to perform a single leg deadlift on your right leg and then on your left leg, and then added these two forces together, it would be greater than if you performed a traditional deadlift where both legs act simultaneously. In fact, the bilateral deficit has been shown to be as high as 20% in slow contraction movements and up to 45% in fast contraction movements! Why is this? Is it an adaptation we have developed to producing force on one limb? Whenever we walk, run, skip, and even crawl, we are producing force on one leg in triple extension, while the other does the opposite and goes into triple flexion producing no force. Since our neural circuitry becomes wired to one leg producing force while the other is not, perhaps this is why the sum of force production is greater using one leg at a time rather than both simultaneously. Further research still needs to be conducted to adequately explain this phenomena.
Single Leg Exercises:
Okay, now lets get into the fun stuff and how to perform some of these movements. Here are 5 of the most effective single leg movements for developing strength, hypertrophy, and balance.
Single Leg Squat:
To perform the single leg squat you simple lift one foot off the ground, gain your balance, and squat down. For many this will be challenging enough as is because it requires a lot of balance and strength. To make this movement easier, squatting to a bench is a great way to start until you build up your strength enough to perform it without assistance. Make sure at the top of the movement you are squeezing your glute and driving your hip forward into full hip extension.
Rear Foot Elevated Split Squat:
This is similar to the single leg squat, except your one foot is elevated behind you. Keep your weight on the heel of your front foot, shift your hips back, and squat down until your thigh is parallel to the floor. This is a great substitute for those who can’t do traditional barbell squats and is easy to load once you have the movement down. Simply hold dumbbells in either hand at your sides.
Single Leg Deadlift:
This is a great variation for those who lack the hip and/or ankle mobility to perform a traditional deadlift. It will still load the posterior chain but will not compress the spine as much due to the lighter external load. Make sure to keep your back flat and neutral without any rounding, push the heel of your trail leg back behind you, and hinge at the hip. Always finish the movement with full hip extension by squeezing the glute and coming up to a full stand.
Single Leg Step-Up:
This movement can easily be over looked and discarded for something more complicated simply because it looks easy! However, done correctly and loaded it is great for developing force, muscle mass, and will definitely get your heart rate up. Quite the humbling exercise. You do not always have to drive your opposite knee up like in the video. If you are having trouble maintaining your balance just bring your foot to the top of the bench. This movement can also be loaded in a variety of ways; you can hold the bar like you would a back squat or front squat, or hold dumbbells/kettle bells at your side.
Slide Board Reverse Lunge:
Last but not least, the slide board reverse lunge is a great variation of the reverse lunge and demands much more control from the working leg. If you do not have a slide board available you can use furniture slides or a small towel on a wood floor will due just fine.
Summary:
Bilateral training is a great way to develop muscle mass and strength in the lower limbs, but if you have certain physical limitations that prevent you from performing it correctly you can seriously injure yourself. It may not be in your first weeks of training or even the first year but it is a ticking time bomb waiting to go off, and no one likes being injured. Even if you do not have any issues with traditional bilateral training, incorporating unilateral movements would be a great way to vary your training and provide a different stimulus. So give single leg training a try and see how it feels! Here is a recap of some of the benefits to unilateral training:
1.) Develops balance
2.) There are less compressive forces on the spine because it cannot be loaded as heavily which is great for low back pain sufferers.
3.) Puts a greater load on each individual leg than you would get working each leg simultaneously
4.) Reinforces neural wiring that is common to athletic movements. If we are always producing force on one leg at a time when we walk/run, why would you not train that way?
References:
Breaking Down the Single Leg Squat
5 Superior Single Leg Exercises
