How to Understand & Use Single Limb Training: Myths, Tactics & Biomechanical Advantages
Why using single leg training > squatting due to "sport specific functionality" is a myth and covering how to actually use single leg/arm exercises for maximum benefit.
Contents:
Myths, Half-Truths, and Misconceptions
“Sports are played on one leg” (No they’re not actually)
True Unilateral lifts vs Quasi-unilateral/asymmetrical exercises
Unilateral lifts do not just include “hypertrophy” exercises
The REAL advantage of single limb exercises
Multiple planes of movement
Neural drive & the “BLD”
“Hiding a limb” and targeted joint work
Glute & Niche Structure Loading
Work Capacity
SFR vs RSM
Injury Management
Time
Fatigue Types and Related Concerns
How to Incorporate SL Exercises Intelligently
Primary, Secondary & Tertiary Slots
Plyometrics
Alternating/Reciprocal Movement Variations
Fixed Position Movements
Hypertrophy & Killing 2 Birds with 1 Stone
Block & Week Wave Rotations
Most People Do Not Understand the Actual Differences Between Single and Double Leg Exercises…
It's insanely common that people make conceptual assumptions about the benefits of unilateral single-leg exercises (or single-arm… though ironically, it's less common) regarding functionality, common athletic transfer, etc. The reality is that these assumptions are somewhat shortsighted, often rooted in faulty models of human function, and tend to hold some truth for accidental reasons rather than the reasons prescribed.
If you ask someone to elaborate further on why a split squat would be more beneficial to athletics than a back squat, most would not be able to provide anything besides a vague conception of "athletic positions." The reason this is an issue for some is that if you lack a thorough understanding of what is going on during an exercise and the actual mechanical differences between unilateral and bilateral lifts, you are not going to make decisions in training that move the needle; instead, you may make redundant or harmful ones.
Not all bilateral or unilateral exercises are the same, and by simply throwing out vague buzzwords like stability, balance, athletic, etc., you will also be making more vague decisions. This is not how I program or train.
In this post, we're going to dispel myths surrounding single-limb training and enhance your understanding of how to look at exercise movement qualities. You should come away with a strong sense of when, where, why, and how to incorporate unilateral work into your programming. We will also cover with some detail some topics surrounding the context of how I apply unilateral training into programs for the sake of driving home their importance and where they need to be considered as they fit into your regimen.
First let’s cover common statements used to justify the use of unilateral exercises and explain the issues with their reasoning. I am specifically going to attempt to make the most “good-faith” representation of common positions and elaborate on some informative context that will help drive your decision making and efforts.
Myths, Half-truths, Misunderstandings, & Contradictions:
“Sports are Played on One Leg at a Time”
No doubt you have heard this before. The concept that because a sport is supposedly played on a single leg at a time that training exercises off of one leg will make you more athletic than a lift that's done on two legs at a time.
Does this ACTUALLY make sense? No. The reality is that sports are not truly played on one leg as much as many claim.
Examples below:
Rarely are actions taken with maximum force on a single leg. Athletes tend to utilize two legs when high forces are required like absorbing momentum and redirecting it.
It’s also common that many will look at the highlight reel actions they want to perform in and forget that most games are won in less bombastic but more crucial exchanges. Being able to produce force in general is important but the idea that single leg training is specific to athletes while bilateral exercises don’t have transfer to athletic tasks is nonsensical.
Frankly - MOST of our explosive athletic actions take place on TWO LEGS…not one. Even many actions that most don’t think about - like punching or throwing propulsion - actually demand synchronous actions and drive from two legs at once.
However, there is some important context to add here which this post will deep dive further into.
What people really mean by “sports take place on one leg” is primarily that RUNNING occurs with a single leg ground contact at a time with the swing leg off the floor. They somewhat unconsciously are identifying that human propulsive actions are tied to the GAIT cycle and that means that respecting this foundation has a place in all training because it's fundamental to our movement patterns (More on this later).
NOTE: In addition to the fact that running itself takes place in most sports - This concept is true - though I personally had to explain that full truth FOR most people who couldn’t really understand what they are trying to say as precisely.
Understanding this actually matters because:
Gait cycle mechanics do not always disappear when we move with two legs at the same time, its principles of IR and ER still apply. Thus, we are not necessarily ignoring an actual important part of training when using certain bilateral lifts.
Just because we utilize a single leg exercise doesn’t mean that we are training the joints through the ranges they will need in the gait cycle either. Details matter here.
This actually highlights that we don’t create our strongest muscular actions off one leg in sport. We actually create our most rapid elastic actions (sprinting). This is very different from raw strength. We are mostly *bouncing*off of one leg during sport - we get set on two legs when we need maximum strength and power.
The central point being made here is:
First, that sport actions taking place on a single leg at certain times doesn’t negate all the moments that our sport actions take place on two legs at a time… so the “either/or” approach that some coaches (yes, there are a number that do along with their proponents) take with this is moot.
Second, that bilateral exercises don’t necessarily ignore functional movement principles of athletic action.
And third, that movements in the gym will never fully replicate the motion of another action that isn’t weight training so the idea that more mimicry between sport movement and strength training will automatically enhance your athletic capacity is not true.
While some might say that “you don’t squat all the way up and down in basketball” or “we move like this in basketball so this loaded basketball specific exercise will work better” … we also don’t hold dumbbells in basketball either - so why would lifting with any weight at all be beneficial…?
If the idea that the more we imitate the movements in sport, the superior they will be for transfer - then why are you in the gym at all? Accepting that doing *anything* besides playing the sport - which is the only thing with full imitation of the sport movements - can help enhance performance is accepting that things don’t need to look like the sport movement at a glance to have benefit.
This has been covered in depth on the podcast before if you want to dive deeper into how to approach “sport specific” training. Summary is that we are in the gym to build qualities… not skills or sport mechanics. Strong, fast, healthy, mobile, and durable is why we train and anything that creates those outcomes for your body is worthwhile. If it holds you back from that then it’s not.
“Stability, Eliminating Imbalances, Etc.”
"If you are measuring a hip shift during your squats and using a single-leg exercise to fix this, are you measuring the potential hip shift that occurs during the single-leg exercise as well?"
Imbalances:
Unilateral work is commonly prescribed to address imbalances in muscular strength from side to side or supposed resulting movement inequities.
One of the most common examples is a hip shift in a squat. This is often attributed to a strength discrepancy between sides, labeled as dangerous, with coaches claiming that muscle imbalances will lead to injury. The reality is that muscular imbalances between limb sides, unless truly egregious, are normal and almost entirely benign. Additionally, hip shifts in squats may also be benign depending on severity.
I want to emphasize further that issues like hip or shoulder shifts during bilateral movements are more commonly due to coordination or mobility issues (usually both) rather than a raw strength problem. What often happens is that coordination issues persist because they are not properly addressed by teaching the athlete how to organize themselves over each leg, and the problem is never resolved.
A critical point to consider is, "If you are measuring a hip shift during your squats and using a single-leg exercise to fix this, are you measuring the potential hip shift that occurs during the single-leg exercise as well?"
For those interested, observing and recalibrating movement through a lens like that is much better for fixing mobility issues than simply applying a blanket solution to everyone without considering the mechanical details.
Stability:
“You build strength, muscle, balance and stability at the same time” is what most say with single leg work.” It’s true in many cases.
However, while the development of stability may be necessary in cases where it is a problem (rehab after injury), it generally hits a point of diminishing returns in the gym. Firstly, if stability and balance are traits you want to build and maintain (which you probably should) then yes, train it. But if you want to train something that will be challenged enough to keep building along with other qualities then having too many limiting factors in a single exercise will limit how good most of those qualities get.
This is why those who want to keep getting stronger on single leg exercises always seek to find more ways to increase stability with their setup, rather than just expect to be stable enough to keep getting stronger.
At a certain point - the instability of being on one leg at a time gets in the way of force outputs. While having elements of this in a strength & health routine aren’t bad - it pays to also understand tradeoffs so you can balance the program as a whole rather than throw out the whole toolset of bilateral squats/deadlifts/pressing.
Quasi-Single Leg Exercises vs True “Single Leg” Lifts
“Only an exercise that solely utilizes a single limb would be a single limb isolation exercise, others are quasi-single limb exercises that may be inherently more “asymmetrical” than they are unilateral.”
Many exercises that are considered to be unilateral are not the same. There is somewhat of a gradient even to various exercises. Deciding there is a hard differential between a single leg and bilateral exercise is a bit misguided at times.
Is a split squat the same level of “single leg” as a pistol squat is?
Or a single-leg leg press or a walking lunge?
Note: As many would claim that a single leg strength exercise is better for sport due to single leg action - somehow, they don’t tend to think a single-leg leg press fits into this category despite being as “single leg” as possible
A superior lens to potentially look at some exercise movements from this perspective might be symmetrical vs asymmetrical exercises. Only an exercise that solely utilizes a single limb would be a single limb isolation exercise, others are technically quasi-single limb exercises that may be inherently more “asymmetrical” in stimulus than they are truly unilateral.
The effect of asymmetrical movements can even be manipulated through the execution of exercises with similar setups. Sending the knee forward during a split squat vs dropping the back knee down will create very different results in stimulus.
You can observe from the above examples that even two exercises with the same stance can have difference emphasis on muscle groups and even the limb challenged. The first picture will actually demand significant work to be done by the back leg while the second picture will demand less of the trail leg (but still not fully isolate the front leg alone).
While this point doesn’t negate the use of the terms unilateral vs bilateral for practical use - it’s worth shining light on this concept to better understand the nature of our exercise qualities.
Upper Body Isn’t Held to The Same Standard
“If we need to focus on single-leg exercises because single-leg action is more specific, then why don't we apply this logic to the upper body as much?”
It's worth noting that it is just as true that we use most upper body actions through gait propulsion mechanics and use one arm at a time as well. Yet, it is far less common to promote single-arm lifts. Why? Most likely because the bilateral exercises most commonly used still feel effective (which shouldn't make sense compared to single-arm exercises per this logic), and people see no need to exclude them.
In reality, I think this is because there are other underlying motives for wanting lower body workarounds to the bilateral lifts (squat/deadlift, etc.).
In my opinion, a lot of people really just don't want the stress/trouble of loading heavy squats/deadlifts...which is okay and often a good choice for other reasons than athletic transfer. Let’s just address the actual reasons why someone might want to bias more single leg work instead of making up some faulty logic.
Unilateral Leg/Arm Exercises Are Not Exclusively “Hypertrophy” Exercises
“While training single leg strength is what will create sport transfer over bilateral lifts due to supposed unilateral nature of sport…suddenly this logic disappears when training plyometrics.”
As coaches often advocate for single-leg exercises in lifting, emphasizing the "one leg" theory, there's a notable discrepancy when it comes to applying the same principle to plyometrics, which are even more closely related to sport-specific movements.
This is a major point of hypocrisy amongst the “single leg specific” crowd. While coaches will claim a “Bulgarian split squat” is more sport specific/transferable due to its unilateral emphasis, they often don’t pursue the same logical end toward their plyometric and explosive efforts. Box jumps and hurdle hops are just as popular and don’t receive some sort of anti-bilateral feedback toward them. They are very easily perceived to be useful in an athletic context. This, however, somehow is not considered often when claiming that it is the 2-leg simultaneous action that prevents exercises from transferring to sport…
If symmetrical leg propulsion is not applicable to sport, then why don’t broad jumps, box jumps, depth jumps, hurdle hops and their derivatives get the same critical analysis from coaches…?
Ultimately, as you follow the logic of these considerations, we need to ask:
“Is it actually true that single leg work is what will transfer to sport and not bilateral lifts… or are coaches/athletes just looking for justification to not squat/deadlift?”
Note: I could provide arguments and context as to when we would not use a deadlift or squat or even bench press for athletes. It is a good idea to shine light on why people make these arguments though and deeply investigate our reasoning if we want to make the most effective decisions long term, however.
The REAL Advantages of Single Leg (and arm) Exercises
Okay, so we've covered enough of why single-leg exercises are justified using flawed logic. This isn't going to turn into a barbell back squat promotional post however, we are going to cover how some coaches are accidentally somewhat correct when using single-leg variations and what positives they bring to your program.
Key Point:
Human movement is ROTATIONAL at its foundation, and this occurs though gait propulsion (see hip mobility post). Sprints, throws, punches, jumps, COD, etc. occur with sequences of external and internal rotation of the body’s slings or hemispheres. Thus, its normal to see “single leg/arm” action in one direction at a time.
Take a moment to really observe how we produce propulsion in these athletes below:
Each leg cycles between internal rotation and external rotation over and over in order to move and propel the athlete forward. The spine, lats, and ribcage all rotate and flex accordingly in rhythm. As well as the shoulders and arms pumping on every step. Specifically, it can be eye opening to realize even the upper limbs don’t swing back and forth in perfectly straight lines either - the shoulder IR and ER’s too.
If this confuses you or you want a direct introduction to the basics of gait… it is covered more in the hip mobility post here.