Bulgarian split squats primarily target the quadriceps and glutes of your front leg, with significant secondary work from the hamstrings, core, and calves. What makes this exercise unique compared to a standard squat is how much more it demands from your stabilizer muscles and the back of your legs, thanks to the single-leg stance.
The Primary Movers: Quads and Glutes
Your quadriceps, the large muscle group on the front of your thigh, do the bulk of the work during a Bulgarian split squat. All three vastus muscles (the outer, inner, and middle portions of the quad) fire heavily to extend your knee as you push up from the bottom position. The rectus femoris, the quad muscle that also crosses the hip joint, contributes as well, though research comparing it to a standard back squat shows it actually activates about 16 to 21% less during the Bulgarian variation. This likely happens because the upright torso and split stance change the demands on that particular muscle.
The gluteus maximus, the largest muscle in your body, is the other primary driver. It controls your hip as you descend and powers hip extension on the way back up. How much your glutes work relative to your quads depends largely on your torso position. Leaning your trunk slightly forward shifts more of the load to the glutes and hip extensors, while staying more upright keeps the emphasis on the quads. Research published in BMC Sports Science, Medicine and Rehabilitation confirmed this relationship, finding that a forward trunk lean during the Bulgarian split squat significantly increased gluteus maximus activation compared to a neutral trunk position.
Hamstrings Work Harder Than You’d Expect
One of the biggest differences between the Bulgarian split squat and a traditional back squat is hamstring involvement. EMG studies measuring electrical activity in the muscles found that the biceps femoris (the outer hamstring) showed 63 to 77% greater activation during the Bulgarian split squat compared to regular squats. That’s a substantial difference, and it makes sense mechanically. Balancing on one leg while the other is elevated behind you forces your hamstrings to work overtime as both a stabilizer and a mover, controlling the descent and assisting with hip extension.
The semitendinosus, the inner hamstring, plays more of a stabilizing role. Its activation levels remain relatively consistent regardless of how you modify the exercise, suggesting it works at a steady baseline to keep your knee and hip joints tracking properly throughout the movement.
Core and Spinal Stabilizers
Standing on one leg with a load immediately challenges your core in ways a bilateral squat doesn’t. The external obliques, which run diagonally along the sides of your torso, show 58 to 62% greater activation during the Bulgarian split squat compared to regular squats. These muscles work to prevent your trunk from rotating or tilting sideways as you lower and rise on a single leg.
Your spinal erectors, the muscles running along either side of your spine, also contribute significantly. They keep your torso from collapsing forward under load. If you want to increase their involvement even further, performing the exercise with your rear foot in a suspension trainer (like a TRX strap) rather than on a solid bench ramps up spinal erector activation meaningfully. The added instability of the swinging strap forces your back muscles to work harder to keep you upright.
Hip Stabilizers Play a Smaller Role
You might assume the gluteus medius, the muscle on the side of your hip responsible for keeping your pelvis level when standing on one leg, would fire intensely during this exercise. It does work, activating at roughly 27 to 31% of its maximum capacity, but research shows it isn’t particularly challenged by the Bulgarian split squat. The movement happens primarily in a forward-and-back plane, and the gluteus medius is designed to control side-to-side motion. Changing your trunk angle or switching from a bench to a suspension trainer doesn’t meaningfully alter its activation.
If strengthening the gluteus medius is a priority for you (common for runners or people rehabbing knee or hip issues), you’ll want to add lateral exercises like side-lying leg raises, banded lateral walks, or single-leg hip airplanes rather than relying on the Bulgarian split squat alone.
How Stance and Torso Position Shift the Target
The beauty of the Bulgarian split squat is that small setup changes let you emphasize different muscles. Two variables matter most: where you place your front foot and how you angle your trunk.
- Shorter stance, upright torso: Keeps your shin more vertical and increases the range of motion at your knee. This puts more demand on the quadriceps, especially the vastus muscles.
- Longer stance, slight forward lean: Increases the moment arm at the hip, shifting more work to the glutes and hamstrings. Your knee travels less far forward, which can also feel more comfortable if you have anterior knee sensitivity.
The key is that both variations work the same muscles. You’re just changing the ratio. Neither version is inherently better. Choose based on what you’re trying to develop or what feels strongest for your body.
How It Compares to a Back Squat
A common question is whether the Bulgarian split squat can replace or match the back squat. For pure quad activation, particularly the vastus muscles, the two exercises are remarkably similar. Research found no significant difference in vastus lateralis or vastus medialis activation between the movements. So if building your quads is the goal, you’re not leaving gains on the table by choosing one over the other.
Where they diverge is in secondary muscle recruitment. The back squat activates the rectus femoris (the hip-flexing portion of the quad) more effectively, while the Bulgarian split squat recruits the hamstrings and obliques to a greater degree. In terms of building muscle size, a 2025 meta-analysis pooling nine studies found no significant difference in hypertrophy between unilateral and bilateral training. You’ll grow the same amount of muscle with either approach. Strength gains, however, follow the principle of specificity: training on one leg makes you stronger on one leg, and training on two legs makes you stronger on two legs.
The practical takeaway is that Bulgarian split squats are not a lesser substitute for back squats. They’re a different tool with overlapping but distinct strengths, particularly useful for addressing side-to-side imbalances, building single-leg stability, and loading the hamstrings and core more than a bilateral squat would.