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I understand horizontal split to require flexibilities such as hamstring flexibility and hip flexibility. I understand this answer so that the user recommends sumo squats to improve hip flexibility where back straight like below
by this video and this example does not target the hips that much
where the squatter targets more the lower back, quads and some people call this "bad form" but I see it as a form that will have extra stress on back and abs so you need to be very careful. If your goal is to get into horizontal split, you should try to sumo-squat more like the first squatter. The second activates far more the lower quads as you can see from the second picture. Wrong squat form will only make you frustrated so choose carefully, bad form caused by inflexibility for example in hips require time and patience -- to improve your active range of motion use variety of training: very light weight to get your range of motion to the limit and heavier weights to strengthen the muscles. My recommendation is to combine both trainings so you get support muscles at the same time as better range of motion. This will ensure that you avoid accidents caused by weak muscles and insane static range of motion. Support muscles are important part of healthy training.
By the below classification, the sumo squat can be done in multiple ways. Active stretching is where you hold the position 10-15 seconds. I cannot understand how the classification really works so I won't comment on it more. I used the word "active" earlier in the context of "range of motion" by which I did not refer to the "active stretching". I understand active so that you hold your position short time like 1-4 seconds while the word below in the context of "stretching" refers to longer time like 15 seconds.
- ballistic stretching
- dynamic stretching
- active stretching
- passive (or relaxed) stretching
- static stretching
- isometric stretching
- PNF stretching
by this source.
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