Every step you take, every stair you climb, every time you push up off the floor — you’re doing it on one leg. And yet most gym programs spend almost no time actually training that way.
At Ascend, we do things differently. Single-leg training isn’t an afterthought. It isn’t a warm-up drill or something we add at the end if there’s time. It is one of our six foundational movement patterns — trained every week, in every program, without exception.
This post explains what single-leg training is, why we prioritize it, and why any program that neglects it is building a version of fitness that doesn’t hold up in real life.
What Is Single-Leg Training?
Single-leg training is any exercise where one leg is doing the majority of the work. This ranges from split squat variations — where both feet stay on the ground, but one leg is doing the driving — all the way to true single-leg movements where the non-working leg is completely off the floor.
The spectrum runs from the most stable (split squat, both feet down, relatively easy to balance) to the most demanding (true single-leg squat, all your weight on one foot, significant strength and control required). Most of our clients spend the bulk of their training time in the middle of that range.
Why We Train This Way
Because this is how you actually move.
Walking, running, climbing stairs, stepping over something, catching yourself when you stumble — every one of those actions requires your body to generate, control, and absorb force through a single limb. Bilateral exercises like squats and deadlifts build strength, but they do it with both feet on the floor simultaneously, which is not how most human movement actually works. If your program only trains you bilaterally, there’s a meaningful gap between your gym strength and your real-world capability.
Consider something as simple as getting up off the floor. Most people don’t think about it, but when you push yourself up from the ground without grabbing something for support, you end up in a split-stance position — one foot forward, one foot back — and you drive through that front leg to stand. That’s a split squat. If you’ve never trained that pattern under load, that movement is harder than it needs to be. As we age, the ability to get off the floor unassisted is one of the most direct markers of functional independence. We train for that.
Beyond the movement-pattern argument, single-leg training exposes something bilateral training hides: the strength difference between your left and right sides. Every person has a dominant leg. In a bilateral squat, the stronger side compensates for the weaker one — quietly, invisibly, every rep. The imbalance gets reinforced, not corrected. Single-leg training forces each limb to do its own work.
The Muscles That Only Turn On During Single-Leg Movement
The gluteus medius — the muscle on the side of your hip — and the deep hip stabilizers have one critical job: keeping your pelvis level while you’re standing on one foot. Every stride you take requires these muscles to fire. But in a bilateral squat, they’re largely passengers. The bilateral stance provides enough base of support that these muscles never have to work as stabilizers.
When they’re undertrained, you see the consequences: knees caving inward during squats or stairs, a hip drop during walking or running, persistent low back pain, and elevated injury risk across the hip, knee, and ankle. That “knee problem” most people assume is about their knee? It’s almost always a hip problem. The knee is caving because the hip isn’t controlling it. Single-leg training is one of the most direct interventions available for building that hip control, because the moment you lift one foot off the ground, those muscles are forced to take over.
The Bilateral Limb Deficit — Your Legs Are Stronger One at a Time
This one is worth understanding because it changes how you think about training. Research has documented a phenomenon called the bilateral limb deficit (BLD): when you test how much force each leg can produce individually and add those numbers together, the sum is often higher than what both legs produce when they contract simultaneously. In other words, your legs can generate more total force working separately than they can working together.
The deficit isn’t a fixed number — reported magnitudes vary considerably across studies, and the phenomenon itself isn’t perfectly consistent. Some research has found deficits as large as 25% in certain populations; other studies on highly trained athletes have actually found the opposite effect, where bilateral output matches or exceeds the sum of unilateral outputs. The research is clear that the effect is real and meaningful, but less clear on exactly how large it is or why it happens.
Researchers have proposed several mechanisms. One frequently cited candidate is interhemispheric inhibition: your left motor cortex controls your right leg, your right motor cortex controls your left leg, and these two hemispheres are connected through a structure called the corpus callosum. The hypothesis is that during bilateral contractions, the hemispheres partially inhibit each other’s output through these connections — essentially, the two sides of your brain dampen each other’s signal in a way that reduces motor drive to each limb. Reduced motor unit recruitment during bilateral efforts is another proposed mechanism that has been studied directly. The honest answer from the research is that the exact origin of the deficit is still being worked out, and it may not be purely neural.
What does this mean for your training? Here’s our take: the BLD research measures acute force output, not long-term adaptation. The direct leap from “your legs test stronger separately” to “unilateral training builds more strength” isn’t something the BLD studies prove on their own. What we can say is that single-leg training removes the compensation patterns that bilateral training allows, forces each leg to work independently, and — as the force plate data shows — can deliver a high per-leg stimulus at loads that feel manageable. Whether you call that a neurological advantage or simply good program design, the argument for including it is strong.
The Research: How Much Is Really on Each Leg?
One of the most useful bodies of research in this area comes from sport scientist Alex Natera, who used force plates — equipment that measures the exact ground reaction force produced by each foot — to map what actually happens across the split-stance spectrum. His findings changed how coaches think about loading these movements.
Not all single-leg exercises are equally unilateral. The degree of demand on the working leg scales predictably as you move along the continuum:
The practical implication: each step along the progression from split squat → RFESS → true single-leg squat isn’t just a stability upgrade — it’s a quantifiable increase in how much force the working leg is required to produce. The numbers give coaches a principled basis for loading and progressing these movements rather than guessing.
The 200-Pound Example: More Leg, Less Back
One of the most compelling arguments for single-leg training is what it does for the relationship between per-leg training stimulus and spinal loading. Consider a 200-pound athlete/client performing two exercises:
Back Squat — 200 lbs on the bar:
Total system load: 200 lb bodyweight + 200 lb bar = 400 lbs
Per leg: 400 ÷ 2 = 200 lbs on each leg
Spinal loading: 200 lbs sitting directly on the spine, pressing down on the vertebrae from above
RFESS — 50 lb dumbbell in each hand (100 lbs total):
Total system load: 200 lb bodyweight + 100 lbs = 300 lbs
Front leg at 78% split: 0.78 × 300 = 234 lbs on the working leg
Spinal loading: None — weight is in the hands, not on the back
The front leg in the RFESS is working harder than either leg in the back squat — 234 lbs vs. 200 lbs per leg. And the spinal loading comparison isn’t just a matter of less weight on the back: a barbell physically sits on the spine and creates direct axial compression. Dumbbells held at the sides don’t. The spine still works to stabilize the movement, but it’s never bearing the load of anything pressing down on top of it. For clients managing back sensitivity or previous injuries, that distinction is significant — and it means single-leg training lets us load the legs hard without the compressive cost that comes with a barbell on the back.
There’s a broader joint health argument here too. Heavy bilateral loading — squats, deadlifts, leg press — creates significant compression through the hips, knees, and ankles in order to generate the stability needed to move that kind of weight. In the short term, that’s exactly what those joints are designed to handle. But over time, exclusive reliance on heavy bilateral training can gradually reduce range of motion and movement variability as the joints adapt to that narrow, high-compression movement pattern. Look at high-level powerlifters — extraordinary strength, but often with real limitations in how freely they can move outside of their trained positions. For our clients, longevity is the goal. That means maintaining full range of motion, movement variability, and joint health across decades — not just maximizing what’s on the bar.
None of this is an argument against bilateral training. Squats and deadlifts are foundational — they build the kind of total-body strength that single-leg work alone can’t replicate. The answer isn’t either/or. It’s both. Bilateral lifts raise your force ceiling; single-leg training ensures every part of your body can actually use it. Train both, every week, and you have a program built for the long game.
“Single-leg work is not accessory work. It is a primary strength exercise — one you can train harder per limb, with substantially less stress on the spine.”
How Single Leg Training Fits into the Ascend System
All programming at Ascend is built around six foundational movement patterns:
Squat · Hinge · Single Leg · Push · Pull · Core / Carry / Rotation
Single leg sits alongside squatting and deadlifting — not below them. These six patterns are the pillars of every well-constructed program. Leave one out, and you have an incomplete athlete/client, regardless of how strong they are in the others.
Single-leg work does not replace bilateral training. Both are necessary. Bilateral lifts raise your force ceiling — they allow you to move the most total load and build peak strength. Single-leg training teaches each limb to access and apply that strength independently. You need both. They answer different questions.
Our gold standard for most clients is the Rear Foot Elevated Split Squat (RFESS). With the back foot on a bench, this exercise drives the front leg to roughly 78% of total system load — close enough to a true single-leg squat that the training stimulus is genuinely unilateral, but with enough stability to allow serious loading across a wide range of clients. It is the most important lower body exercise most people have never taken seriously.
Some clients will eventually progress to true single-leg variations — single-leg squats, skater squats — as their strength and motor control develop. But for the majority of our clients, the RFESS is where the deepest foundation of single-leg strength gets built, and it will never stop being relevant.
The Benchmark: What We’re Chasing
Here’s how we know whether your RFESS is where it needs to be. The goal: the force on your working leg in the RFESS should be at least 10% greater than the force on each leg in your bilateral squat. Because your bodyweight is already part of the system in the RFESS, the dumbbell weight you need to hit that target is less than you might expect — but it’s a specific number we can calculate.
Use this formula to find your own target:
Here’s how that plays out for two different clients:
Example 1: 225 lb male, bilateral squat = 315 lbs
Step 1 — Total bilateral load: 225 lb bodyweight + 315 lb bar = 540 lbs
Step 2 — Per leg in the squat: 540 ÷ 2 = 270 lbs each leg
Step 3 — RFESS target (10% over): 270 × 1.10 = 297 lbs on the working leg
Step 4 — Find the dumbbell weight: 225 lb bodyweight + 160 lbs (80 lb dumbbells) = 385 lbs total system load
Step 5 — Working leg at 78%: 385 × 0.78 = 300 lbs ✓ (exceeds the 297 target)
For this athlete/client, holding 80 lb dumbbells in each hand during the RFESS puts 300 lbs of force through the working leg — 30 lbs more per leg than the bilateral squat delivered, with no barbell sitting on the spine.
Example 2: 150 lb female, bilateral squat = 100 lbs
Step 1 — Total bilateral load: 150 lb bodyweight + 100 lb bar = 250 lbs
Step 2 — Per leg in the squat: 250 ÷ 2 = 125 lbs each leg
Step 3 — RFESS target (10% over): 125 × 1.10 = 137.5 lbs on the working leg
Step 4 — Find the dumbbell weight: 150 lb bodyweight + 26 lbs (13 lb dumbbells) = 176 lbs total system load
Step 5 — Working leg at 78%: 176 × 0.78 = 137 lbs ✓ (meets the target)
For this athlete/client, holding 13 lb dumbbells clears the bar. That’s a modest external load — but because her bodyweight is already part of the system, she’s generating meaningful force through her working leg with relatively light dumbbells. As her squat strength grows, her RFESS target grows with it.
These are floors, not ceilings. Hitting these numbers means your single-leg and bilateral strength are developing in proportion. Falling significantly short is a signal that your RFESS is lagging behind — and that gap will show up as a limitation somewhere, eventually.
The Bottom Line
Programs that skip single-leg training aren’t training for longevity. They’re building a version of strength that only works in a gym, on two feet, under controlled conditions. Real life doesn’t operate that way. The stairs, the curb, the floor you have to get back up from, the sudden change of direction — those demand what only single-leg training can build.
At Ascend, we train for the Sport of Life. That means training the way the body actually moves — and the body moves on one leg far more than it moves on two.
Single-leg training isn’t a nice-to-have. It’s a non-negotiable.
