It seems appealing, the ass-to-grass squat. It’s certainly not a quarter-squat, so it passes the seriousness test. No one can doubt your sincerity, your commitment to no-bullshit training. Nobody else in the gym is doing them, so they always provide the moral High Ground. And they are easy to teach, since the bottom is hamstrings touching calves, or some version thereof. But they are not optimum, and here’s why.
Our criteria for judging the effectiveness of an exercise have proven their usefulness over the years. They are:
The exercise must involve the most possible muscle mass.
It must allow the greatest amount of weight to be lifted,
over the longest effective range of motion.
These three when satisfied result in you getting stronger.
ATG squats superficially satisfy these criteria. But when more closely examined, it becomes obvious that they really don’t.
1. For muscle mass to be involved in a movement, it has to be actively producing contractile force concentrically, eccentrically, or isometrically. The sweet spot in squat depth is just below parallel, where all the muscle mass of the knee extensors, the hip extensors, and the spinal stabilizers are working at their optimum capacity. Higher than that, they don’t have as much work to do (work in the Force x Distance-sense of the word).
Lower than that, something has to relax to get down there. A more closed hip and knee angle means that the hip and knee extensors have bailed out of their position-holding job at parallel. Glutes, quads, and adductors have to let go to permit a squat 6 inches below parallel. For most people of normal flexibility an ATG squat requires some lumbar flexion as well, so erectors have relaxed too.
Interestingly enough, hamstrings may not have relaxed, although it seems likely that they have. As hips and knees flex, the distance between hamstring origin and insertion may well remain constant, although even at constant length they may have reduced their isometric force production.
2. How can you squat more weight? ATG or just-legal below-parallel? Since quarter-squats are not an option, this is pretty obvious. At legal depth, all the muscle mass of the knee and hip extensors is in a position to contribute to the stretch reflex, and therefore to contribute to more force production. All experienced lifters can squat more weight with an effective stretch reflex.
3. The longest effective range of motion is the ROM that facilitates Number 1 and Number 2 at the same time. Quarter-squats are not an effective ROM because they provide no stretch reflex, rather merely less Force x Distance-type work, even though the weights are heavier. ATG reduces Number 1 by the mechanism discussed, while at the same time reducing Number 2 by the same mechanism and increasing the Distance-part of the equation. Adding 6 inches to your squat ROM at the expense of reducing the load by 25% is a bad trade-off if force production is your goal.
The majority of people will display a stretch reflex at our depth with minimal coaching, and can actually squat more weight from there as a result. The downside is that they’d rather cut it off, and they will do so unless coached. Depth means use of the hips, and decades of muscle-magazine brainwashing has everybody “doing legs” instead.
Good depth is uncomfortable, unfamiliar, and incompatible with the conventional back-angle/stance/knee position/eye-gaze direction wisdom. This is why the correct squat remains the hardest of the lifts to perform and coach correctly. But it’s not optional, so you’d better apply yourself instead of just going 6 inches deeper.