Single-leg training

What works

Unilateral lower-body training earns a core place in programming because it loads the legs hard while sparing the spine. Mike Boyle argues one leg can produce nearly the force of two (the bilateral deficit), so single-leg squats and split squats create high leg stress with low back stress, and he prefers split squats, rear-foot elevated split squats, and skater squats over heavy back squats for adults (Mike Boyle, preference). Jeff Cavaliere echoes that skater squats overload one leg with full body weight without compressing the spine (Jeff Cavaliere), Dr. Mike Israetel rates the front-foot-elevated Bulgarian split squat an effective glute builder and mobility enhancer with a controlled pause at depth (Dr. Mike Israetel), and Judd Lienhard recommends roughly 20% of total training volume come from unilateral or cross-pattern movements (Judd Lienhard). Dr. Jordan Shallow calls the walking lunge the most underrated exercise in the gym for its combination of unilateral loading, force absorption, and pelvic stability (Dr. Jordan Shallow).

Torso angle and knee travel steer the stimulus: upright torso with forward knee drive biases quads, forward lean with a vertical front shin biases glutes and hamstrings. Cavaliere details both versions, including the posterior-chain "sprinter lunge" (Jeff Cavaliere, Bulgarian version). Dr. Sohee Carpenter and Dr. Michelle Boland teach the identical rule for lunges and split squats (Dr. Sohee Carpenter, Dr. Michelle Boland), and Neal Hallinan adds that heel contact and a neutral pelvis keep the movement from collapsing into pure quad dominance (Neal Hallinan).

Reverse lunges are the knee-friendly default. Stepping backward keeps the front leg grounded, reducing impact and patellofemoral stress compared with forward lunges (Jeff Cavaliere, reverse lunge detail). Carpenter tells anyone whose knees complain about forward or walking lunges to switch to reverse (Dr. Sohee Carpenter), Hallinan prefers reverse lunges because they keep the pelvis posteriorly tilted and calm overactive quads and hip flexors (Neal Hallinan), and Lienhard uses front-foot elevated rear lunges to cut knee shear for sensitive knees and older adults (Judd Lienhard).

Regress freely; there is a full ladder from assisted split squats to loaded Bulgarians. Beginners start with assisted or static split squats with limited range, holding the bottom 2 to 3 seconds and progressing depth gradually (Joan MacDonald, Jeff Cavaliere). If Bulgarians are too hard, drop to split squats or front-foot elevated split squats, elevate the front heel on a small plate, or add an anterior counterbalance load (Dr. Jordan Shallow). Gray Cook uses overhead-anchored bands to reduce effective body weight through the full range, and reminds coaches that making an exercise easier is often the fastest route to better movement (Gray Cook). Bracing against support for balance is fine (Dr. Sohee Carpenter), so long as the support hand balances rather than pulls (Michelle MacDonald).

Single-leg work is balance and fall-prevention training, especially past 50. Managing your center of mass in alternating lunges helps prevent falls in adults over 50 (Mike Boyle), walking lunges in resistance programs protect against falls and fracture (Dr. Lauren Colenso-Semple), rear lunges train the balance that deteriorates with age (Gunnar Peterson), Dr. Vonda Wright has people retrain balance by standing on one leg during daily activities like brushing teeth (Dr. Vonda Wright), and Lienhard says older adults should prioritize unilateral leg movements outright (Judd Lienhard).

Where you hold the load is a programming tool. Contralateral loading raises frontal-plane core and glute medius demand, ipsilateral or anterior (goblet) loading adds stability and lets prime movers work heavier (Judd Lienhard, Dr. Jordan Shallow). Dr. Pat Davidson layers frontal-plane muscle activation by pulling a cable across the body during split squats (Dr. Pat Davidson), and Cook uses a band pulling the knee into valgus so the brain reactively corrects alignment without conscious cueing (Gray Cook).

Shared form standards. Build a tripod foot (big toe, small toe, heel), track the knee straight over the foot, keep total-body tension through hips and torso, and use the trailing toe as a landmark for step length (Michelle MacDonald, Joan MacDonald, Jeff Cavaliere). A wider base (step back and out, roughly shoulder width or more) keeps balance from stealing the training effect (Jeff Cavaliere).

For specific situations

• Knee pain or arthritis. Build quads with concentric-dominant, knee-friendly work: heavy sled pushes and high-resistance bike sprints of 2 to 3 minutes, plus a split approach of heavy partial-range lifts and slow-eccentric full-range lifts at lighter loads (Judd Lienhard). Boyle scales lunges slower and shallower for knee pain and deconditioning (Mike Boyle).
• Second-trimester pregnancy. Move the bar lower on the thighs, reduce depth, and switch toward landmine single-leg, B-stance, or single-leg dumbbell hip thrusts as comfort decreases (Dr. Sohee Carpenter).
• Athletes testing heavy single-leg strength. Allow 4 to 6 weeks of specific preparation before loaded one-leg squat testing, use a consistent box height with knee-to-pad contact every rep, and compare athletes only to themselves (Mike Boyle). A 75% bodyweight single-leg load projects to roughly 2.5 times bodyweight bilaterally (Mike Boyle).
• Runners. Poor glute strength drives inward collapse in single-leg stance (Gray Cook); Boland uses split squats to mimic running stance phases and coaches sled walks with a sit-back position and toe-to-heel contact (Dr. Michelle Boland, sled).
• Restricted hip internal rotation. Bill Hartman uses front-foot elevated split squats, staggered-stance flips, and low-load positions (side lying, half kneeling) before progressing to single-leg RDLs; forcing the position without internal rotation capacity invites spinal twisting and hip pressure (Bill Hartman, caution).
• Split-stance load sharing. In Bulgarian split squats the front leg takes about 65 to 70% of load, drifting lower with fatigue; a B-stance RDL is about 90/10, so plan rest between legs accordingly (Dr. Jordan Shallow).

Open questions

• How heavy should unilateral work go? Boyle programs heavy single-leg lifts as primary strength work, into sets of 3 at loads like 75% of bodyweight, precisely because leg stress is high while back stress stays low (Mike Boyle), and Lienhard likewise treats lunges like a main lift loaded fairly heavy (Judd Lienhard). Dr. Jordan Shallow counters that unilateral movements are inherently less loadable, that maximal loading (his example, a five-plate Hatfield squat triple) wastes time and fatigue, and that their best use is coordination and stability against a shifting center of mass (Dr. Jordan Shallow). Both agree unilateral work matters; the split is over its role as a maximal strength lift.
• Front knee position. The Starretts warn against lunges where the knee stays vertical under the hip because they fail to train hip extension (The Ready State), Lienhard cues pushing the front knee forward (Judd Lienhard), while Hallinan favors shorter steps, heel pressure, and a neutral pelvis to avoid quad dominance (Neal Hallinan) and Cavaliere keeps the front leg vertical in heavy split squats for knee stability (Jeff Cavaliere). Treat knee travel as a dial set by the goal (quad emphasis versus hip emphasis versus joint comfort), not a universal rule.

Cautions

• Cossack squats should not be the heaviest lift of the day; they place the adductors in a vulnerable position, so slot them second or third (Judd Lienhard).

Putting it into practice

• Allocate roughly 20% of lower-body volume to unilateral or split-stance movements for all populations; raise that share for adults over 50 and for athletes in high back-load phases.
• Default knee-sensitive users to reverse lunges or front-foot elevated rear lunges; reserve forward and walking lunges for pain-free trainees.
• Encode the emphasis dial: upright torso plus forward knee travel tags quads; forward lean plus vertical shin tags glutes and hamstrings.
• Use the regression ladder in order: assisted split squat, static split squat, front-foot elevated split squat, rear-foot elevated (Bulgarian) split squat, skater or pistol squat; regress on instability rather than forcing depth.
• For heavy single-leg strength blocks use low reps (sets of 3 to 5) after 4 to 6 weeks of preparatory exposure; use anterior or ipsilateral loading for max loads and contralateral loading for core and glute medius emphasis.
• Include one step-up or step-down variation with a 3 to 5 second eccentric (12 to 18 inch box, light floor tap) for control and knee health.
• Program balance micro-doses for older adults: single-leg stands during daily activities plus one lunge variation per session.
• Insert rest between legs on split-stance work; the trailing leg contributes 30 to 35% in Bulgarians, so legs are not fully independent.

Experts in this guide: Bill Hartman, Bulgarian version, Dr. Jordan Shallow, Dr. Lauren Colenso-Semple, Dr. Michelle Boland, Dr. Mike Israetel, Dr. Pat Davidson, Dr. Sohee Carpenter, Dr. Vonda Wright, Frans Bosch, Gray Cook, Gunnar Peterson, Jeff Cavaliere, Joan MacDonald, Judd Lienhard, Mark Bell, Michelle MacDonald, Mike Boyle, Neal Hallinan, The Ready State, caution, preference, reverse lunge detail, sled, source.

Before you act. Entrain is a free knowledge resource. It brings together what named doctors, scientists and coaches teach publicly, with sources, so you can explore and discuss it with your own clinician. It does not diagnose, treat or prescribe, and it is not a substitute for medical care.