Walking Is Already a Single-Leg Exercise
Almost nothing your body does in daily life happens with your weight evenly split between two feet. Walking, climbing a step, getting up out of a chair, reaching into the back seat of a car, catching your footing when a toe clips the edge of a curb: every one of those moments puts your full weight, briefly, on a single leg. A strength program built entirely around bilateral, two-footed lifts (a barbell squat in a rack, a leg press, a seated machine row) trains force production well, but it rarely asks your body to do the thing it actually needs most day to day: hold itself upright and under control on one base of support.
What Changes When You Take One Foot Off the Floor
The evidence
Lift one foot and the job changes immediately. The hip, knee, and ankle on your standing leg now have to coordinate continuously to keep you balanced, instead of sharing the work with a mirror image of themselves on the other side. Your core has to resist your pelvis dropping or rotating toward the unsupported side. None of that demand exists, no matter how heavy the bar gets, when both feet are planted and your base of support never moves. A single-leg exercise (a split squat, a step-up, a single-leg deadlift, a suitcase carry on one side) asks for that coordination directly, every rep.
Why This Matters More as You Age
Single-leg work builds the stability and balance you need to catch a stumble before it becomes a fall, and to keep moving through daily life independently as you age. A stumble (a curb misjudged, a rug that catches a heel, a step that's an inch higher than you expected) is a normal, unavoidable part of moving through the world. What determines whether that stumble turns into a fall or just a correction is whether the muscles and balance control on one leg can recover your position fast enough. That recovery is, by definition, a single-leg skill. Two-footed strength doesn't automatically transfer to it; it has to be trained the way it's actually used.
That's also why stability sits alongside strength, aerobic capacity, and mobility as one of the fitness targets Margin trains for, not as a bonus, but as one of the things a body needs to keep functioning well for decades. A program that only ever measures how much you can lift two-footed can tell you your strength is climbing while your single-leg stability quietly goes untrained, and it has no way to flag the difference.
How Single-Leg Work Shows Up in Margin's Program
Margin doesn't treat stability as a separate workout bolted onto strength days. Carries, single-leg exercises, lunges, jumps, and core work are built into sessions throughout the week, the same way squat, hinge, press, and pull patterns are. Everyone follows the same six-week program, resolved only by three things: the equipment you own, the movements you've ruled out, and the level you choose, Standard or Starting out. If a particular single-leg movement doesn't agree with you, you can rule it out, and Margin substitutes an equipment-appropriate alternative, that's a plain exclusion, not Margin diagnosing or treating an injury. Every program is checked against an internal framework and validated before you ever see it.
Fitting It Into a Realistic Program
Margin's week is five sessions: three strength and two conditioning. Within the strength days, each set carries an effort target rather than a fixed weight prescription: you pick the load that hits it, and the app shows you what you lifted for that same lift last time, including on single-leg work. Conditioning covers the rest: one day of bike-or-run intervals you choose per session, one day of athleticism and mobility work, plus some additional aerobic work outside the program each week. Rest is yours to manage; Margin doesn't police rest periods between sets, so take them as you need them. The point isn't to turn single-leg training into its own specialty. It's to make sure a realistic, maintainable program doesn't quietly skip a capacity you'll rely on for decades.
Margin is currently in private testing; get on the waitlist to hear when that changes.