By Nadia Popescu, Strength & Conditioning Writer · Updated 6 November 2026
An ATG split squat is a long-stance split squat where your front knee travels as far past your toes as it can go, your front heel stays flat and your back knee touches the floor at the bottom. "ATG" is short for ass to grass, and the point is full-depth knee bend on the front leg: hamstring resting on calf, shin angled well forward. It trains your quads at their longest length and builds control in a position most people avoid.
A normal split squat stops when the back knee hovers just off the floor, and the front shin often stays close to vertical. The ATG version changes three things at once:
Keep the front heel planted the whole time. If it lifts, you've run out of ankle range and you're cheating the depth by going onto your toes.
Put a folded mat or cushion where your back knee will land. A rail, wall or broom held in one hand is fine while you learn; balance is not what you're trying to train here.
The cue that makes it click
Watch your front knee, not your hips. If the knee isn't moving forward past your toes, you're doing a regular split squat with a long stride. Let the shin travel and let the heel stay heavy.
Very few people can do a full ATG split squat on flat ground on day one. Ankle dorsiflexion runs out, the heel pops up, and the back knee never reaches the floor. Raising the front foot fixes this, because the back knee has further to drop before the front leg runs out of room.
Here's a sensible progression, spread over four to eight weeks depending on your starting point:
A word on the slant board: the ATG split squat itself doesn't need one. It's for people who've mastered the floor version. If your heel lifts on flat ground, go back to a raised front foot rather than adding the board, and spend some time on ankle mobility exercises.
Online claims for this exercise run well ahead of the evidence. The honest version is narrower, and still worth having.
It trains deep knee flexion under control. Most gym exercises stop the knee well short of full bend. Getting strong in that last part of the range makes kneeling, getting up off the floor and landing from jumps less of a shock to the system.
It loads the quads at long muscle lengths. With the shin forward and the knee fully bent, your quads (including the inner part of the thigh, often called the VMO) work at their most stretched. That's the main reason it pairs well with other knee strengthening exercises. Be wary of claims that it "isolates" the VMO; the quads share the work and there's no solid evidence any exercise targets one head on its own.
Knees past toes isn't the danger it was made out to be. In a small 2003 study of seven trained men, researchers compared parallel squats with the knees free to travel against squats with a wooden barrier stopping the knees passing the toes. Blocking the knees reduced knee torque, but hip torque jumped roughly tenfold and the lifters leaned much further forward, so the authors concluded the knees may need to move past the toes for sensible load sharing (Fry et al., 2003). It's a barbell squat study with a tiny sample, so treat it as a reason to drop the blanket rule, not proof that the ATG split squat fixes knees.
Deep knee bend isn't inherently harmful. A 2013 review of more than 160 papers found the highest kneecap compression in squatting around 90 degrees, with compressive stress dropping as the knee bends further. It concluded that concerns about deep squats causing knee degeneration were unfounded, provided technique and loads progress sensibly (Hartmann et al., 2013). A more recent scoping review reached a similar position on the deep squat and healthy knees (scoping review on the deep squat and the knee). None of these studied the ATG split squat specifically, so the transfer is reasoned rather than proven.
Don't use this as a rehab tool on your own. If you've got a diagnosed knee problem, recent surgery or a meniscus injury, deep loaded knee flexion is exactly what your physio needs to sign off first. The same goes for anyone with knee replacements, where flexion range is often limited by the implant.
You should regress (raise the front foot, cut the depth, drop the load) if:
Mild discomfort in the front of the knee during the first couple of weeks is common. Pain that sticks around into the next day, or gets worse session to session, is a signal to back off. If the knee feels fine but you want even more knee-forward quad work later, a sissy squat is the next rung.
Short stance. Feet too close together, and the front heel lifts as soon as the knee travels. Set the stance from half-kneeling every time so it's consistent.
Hips going back instead of knee going forward. This turns it into a hip-dominant lunge. Keep your torso upright and lead the movement with the front knee.
Crashing onto the back knee. Lower under control and touch the pad. Dropping onto a hard floor is how people end up with bruised kneecaps and a dislike of the exercise.
Front knee caving in. Keep it tracking over the middle of your foot. If it drifts inward at the bottom, lower the load or the depth.
Loading too early. Holding 20kg dumbbells before you've got full depth bodyweight just trains a shallower pattern with more stress. Earn the range first.
Elevated front foot. The default starting point and still useful later for high-rep work. Height decides difficulty: higher is easier.
Slant board ATG split squat. Heel raised on a wedge for even more knee travel. Advanced, and best kept light.
Dumbbell-loaded ATG split squat. A dumbbell in each hand is the simplest way to add load without wrecking balance. A pair of adjustable dumbbells lets you climb in small jumps, which matters here because the jump from 8kg to 12kg feels huge at full depth.
Bulgarian vs ATG. The Bulgarian split squat puts the back foot on a bench and usually keeps the front shin fairly vertical, so it's the heavier, more glute-friendly option for building strength and size. The ATG version keeps the back knee on the floor and trades load for knee range. They do different jobs, and plenty of people run both: Bulgarians heavy, ATG split squats light and slow as a warm-up or finisher. For how the basic split squat compares with a moving lunge, see split squat vs lunge.
ATG stands for ass to grass. In this split squat it means taking the front knee as far forward past the toes as your ankle allows, until the back of your front thigh rests on your calf and your back knee touches the floor. It's about full knee bend on the front leg, not just a deep hip position.
Not for most healthy knees. The old rule came from a fear of knee stress, but a 2003 study found that blocking the knees from travelling forward in a squat cut knee torque and sent a far bigger load to the hips and lower back. What matters is building up to deep knee bend gradually with loads your knees can handle.
Start with your front foot raised on a step or plates and use a rail or stick for balance. Lower the height over a few weeks until your front foot is on the floor, then add a slant board under the front heel or hold dumbbells. Only add load once you can touch the back knee down with the front heel flat for 8 to 10 reps.
No. In a Bulgarian split squat your back foot sits on a bench and the front shin usually stays fairly upright, so it loads the glutes and quads in a stable, heavy way. The ATG split squat keeps both feet on the floor (or the front foot raised) and drives the front knee far forward, so it's built around deep knee flexion and quad loading at long lengths.
For mobility and knee resilience, 2 to 3 sets of 5 to 8 slow reps per leg with a 2 to 3 second pause at the bottom works well, two or three times a week. For strength, once you're comfortable, 3 sets of 6 to 10 reps per leg holding dumbbells is plenty. Leave a couple of reps in the tank because form breaks down fast at full depth.
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