Have you experienced, that you are stronger on one leg than on two legs? ‘What?!?’ you might be asking, but let me explain.
Let’s say you can do a Back Squat with 100 kg for 6 repetitions, but you can do Forward Lunges with 60 kg for 6 repetitions per leg. So now you make your calculations 60 kg on the left leg and 60 kg on the right leg equals 120 kg for 6 repetitions, right?
60 kg plus 60 kg is 120 kg, but there is no way you can do 120 kg in a Back Squat with two legs.
This phenomenon is called the bi-lateral deficit’, you are able to do more weight in the sum of your two single-legged sets, than you are able to do in one double-legged set.
And what does it mean?
Well, first and foremost it means you are proportionally stronger on one leg than on two legs. Recent studies have again indicated that fact, that higher joint angles and muscle activation occurs during single-legged activities as opposed to double-legged activities.
Plus a difference in activation between the right leg and the left leg in a double-legged exercise. This indicates, that one side works harder and also helps the ‘weaker’ side to compensate and both legs do not receive the same stimulus.
As a quick side-note, only highly trained Olympic Weightlifters and Rowers, don’t seem to have the bi-lateral deficit. Which makes sense, since everything they do in competition and training is on both legs simultaneously.
So, what is the solution to this problem?
The answer is simple and straight-forward, include single-legged squat variations into your training program. But what exactly are the benefits of single-legged squat variations, that double-legged squat variations cannot provide?
#1 Concentrated work
During Single-legged squat variations the focus is on one leg and this leg has to do the heavy lifting, in the purest sense of the word. In case that leg has any weaknesses, there is a compensation or help from the other leg as it happens during double-legged squat variations is not possible.
#2 Identify strength imbalances
Following on #1, not only is the work concentrated on one leg, you will also be able to identify strength imbalances between the left leg and the right leg. Similar to a dominant hand, we also have a dominant leg and most likely you are stronger on one leg than on the other.
If you have already included single-legged training into your training routine, you will have realized, that if you use the same weight for the left leg as well as for the right leg, you will be able to do more repetitions with one of the two legs.
We see this all the time with our athletes, that one leg is stronger than the other leg.
#3 Greater adductor and abductor activation
Due to reduced balance in a single-legged stance, the muscles of this leg have to work much harder. And especially the muscles that keep the leg in place in the frontal plane (resisting movements to the left or to the right of the body).
These muscles are either on the inside of the leg, the adductor group or the outside of the leg the abductor group. So forget these machines, where you sit and bring your legs together, include some single-legged squat variations.
#4 Unloading the spine
You might be relatively stronger on one leg, than on two legs, but you are not absolutely stronger. What that means, the absolute load you are using in a single-legged variation is less than in a double-legged variation.
Let’s take the example from before, you can Back Squat 100 kg for 6 reps and you can do Forward Lunges with 60 kg for 6 reps.
This means you have 100 kg on your back and your spine is axially loaded with 100 kg in the Back Squat, while you have 60 kg on your back and your spine is axially loaded with 60 kg during the Forward Lunge.
#5 Greater sport-specificity
For those of you, who use strength training as a means to improve sport-performance, which is my day to day responsibility. Single-legged squat variations have a greater sport-specificity than double-legged squat variations.
Let me explain.
Most sport activities happen on one leg, the stance phase during running, jumping or kicking is on one leg, even in stance phases were both legs are on the ground there is more weight on one leg than on the other leg or the force are transferred from one leg to the other leg.
Think about any sport where the athlete has to change directions, both legs are probably in contact with the ground, but the athlete pushes off from one leg more than from the other.
Consequently, working and strengthening one leg at a time has a high carry over to your sport performance.
If you want to maximize strength, size, speed or endurance in your legs, you should integrate single-legged variations into your training program, if you haven’t already.
Single-legged squat variations will:
– help you to concentrate the work fully on one leg
– show you whether you are stronger on one leg, than on the other
– activate the adductor and abductor muscles of the leg in a unique way
– give your spine some rest
– help you in your sport
But be careful, if you don’t want to see a steep increase in your Back Squat after a few weeks, you better not include single-legged squat variations.
The articles explains the unique benefits of single leg squat variations and explains what you are missing out, if you don’t do them.
Christian Bosse has worked as a strength & conditioning coach for various national and international governing bodies in different countries, such as India, China, Spain and England. He is currently working as a Strength & Conditioning Coach for the National Olympic Committee of the Netherlands, where he prepared athletes for medal success at the Olympic Games in London 2012 and Rio 2016.
Christian studied Sport Science in Germany and Spain, is a Certified Strength and Conditioning Coach by the NSCA and an Accredited Strength and Conditioning Coach from the UKSCA and holds a Master in Sport Management.