If you want large strong thighs but not the spinal compression and shear forces of barbell squatting, 4-zone split squats are a tough, effective high-intensity alternative.
To do the 4 zone split squat properly, you need a sturdy platform about 3-4” high on which you will place one of your feet, either the right or left, during the exercise. This is the platform I use. It is made of 6 1-ft long pieces of 2x4, screwed to at least 2 other pieces of 2x4 that are 20-24” in length.
The photos below show how you set yourself up for the 4-zone split squat.
I always train my left, non-dominant leg first. The platform should be high enough so that when your active foot is on it, the hamstrings touch the calf and the top of your thigh is below parallel to the floor. At the beginning, the passive leg will be flat on the ground, and the passive foot should be resting on the instep. This posture ensures that you will be able to provide balance but not pushing strength with the non-working leg. You don’t want the inactive foot on the ball because this would allow it to contribute more force to the motion; you don’t want this because you are trying to load the other hip and thigh. You should lightly grab on to some immovable upright, such as a power rack upright post, with the hand on the same side as the working leg. This is to provide balance only, and you should not use this arm to assist the working leg at all.
With zone training, you divide the full range of motion into several zones and work each one separately. I always start with working in the most difficult or weakest range of motion, then move to the next most difficult range, and so on.
With the 4-zone split squat I start by slowly and smoothly pushing up with the working leg to a point where the thigh is just below parallel, then return to the bottom, and perform 5-6 repetitions in this zone - the bottom quarter of the full range of motion – until I come to or near failure.
I then push up to where my thigh is just above parallel to the ground, then return to just below parallel, and repeat this 5-6 times until at or near failure.
I then push up to a somewhat higher range of motion, dipping back down into the level I just finished, again for 5-6 repetitions until at or near failure.
During the whole set, the inactive leg and the hand serve only to control balance. You move only by pushing with your planted foot.
Finally I push up to just short of lock out, and dip back down to overlap the previously trained range of motion. I work this upper quarter range of motion until I reach momentary muscular failure.
I demonstrate the performance of 4-zone split squats in the video below.
Done as just described and demonstrated, you will spend about 15 to 30 seconds working each quarter of the range of motion, and the whole set should take 60-120 seconds.
Studies show that most people have a higher proportion of type 1, slow twitch, endurance-tolerant fibers in their hips and thighs (like poultry dark meat). When training for hypertrophy, these muscles may respond best to training with a lighter load and longer time under load for most effective stimulation of all the fibers in these muscles. This is probably why 20-rep squat routines were so well known to build muscle fast among old-school body builders in the early 20th century.
I have done fatigue testing on my thighs and through this and training experience I have found that I generally prefer and my thighs and hips gain strength and size fastest when I train them with sets lasting about 90 seconds, sometimes up to 120 seconds. These longer sets also have a side benefit of providing intense cardiovascular training.
If you are having trouble increasing the size and strength of your hips, thighs or calves using low repetition, high load training routines, you might want to try using lower loads and longer set times.
If you have done this correctly, with adequate resistance, which is simply bodyweight for a beginner, at the end of the set the active leg will be burning with fatigue and you will barely be able to lock out. In one set you will have reached near momentary muscular failure 4 times and pushed that thigh and hip to a level of fatigue far greater than possible with barbell squats.
You should add resistance only if your total time under load exceeds 2 minutes and you feel you can control the movement completely without providing the working leg with any assistance from the passive leg or your arm. You can use a Brute Belt with a wooden dowel to add resistance around your waist in the fashion described in the video below.