If you judged them solely by popularity in the gym, the leg press would absolutely crush barbell squats. While the leg press can generate lines two deep during morning and 5 p.m. rush, you could often roll a plate through the power rack and not hit a soul (not that we recommend it).
There's an easy explanation for this — the leg press is relatively easy, and the barbell squat is very, very hard. (Indeed, that skinny dude pushing six plates per side on the leg press probably would crumple to the floor under a 225-pound squat.)
If you’re one of those squat sidesteppers, here's a big reason to rethink your leg workout: Your hormones. As in growth hormone, that all-important precursor to muscle gains. The barbell squat elicited higher testosterone and growth hormone (GH) release than the leg press — and it wasn't even close.
For the recent study, published in The Journal of Strength and Conditioning Research, 10 male subjects performed squats and leg presses; in both instances, they did six sets of 10 reps at 80 percent of their one-rep maximum. After squatting, the guys had 200% more GH in their systems than when they did the leg press. Even one hour later, the squatter’s GH levels were still elevated 100% more, demonstrating a lasting effect that would translate to more muscle building over time.
Because the squat involves more overall muscle, including stabilizers that are not needed on a leg-press machine, it is a much more efficient exercise, putting your muscle fibers under loading that’s impossible to replicate with the press. Essentially, if you could only do one leg exercise and you really crave results, you'd better choose the squat.
That said, an even better solution is to use both in your leg routine, along with an array of ancillary exercises that bolster your gains from all angles, from the quadriceps to the hamstrings through the glutes. The following workout — which can be done once a week (or once every 4–5 days on a more aggressive bodybuilding split) — puts the squat and leg press into action as the one-two punch at the top of your workout.