If you want to master this method, I suggest you start with the captain's chair, so that you can feel the principle and effect of the method more directly. It will be much easier to learn to use this action in the captain's chair than to learn directly from the horizontal bar.
In normal times, when we train with the captain's chair, we always lean our forearms against the equipment, and at the same time, our backs will cling to the cushion behind us. At this time, due to the large contact area, the cushion near the back will help you keep your body stable when lifting your legs. So now you need to learn to control your body on the basis of the general leg lifting action on the bench.
You can go a little further, hold the two forward grips with both hands instead of the two vertical grips you usually hold, and then you need to do physical support. At this time, you need to face the problem of controlling your body stability, so you need to use your trapezius muscle to lower your scapula, so you find that your body becomes more controllable and stable, but this stage is not so easy, so that's why you should train in the captain's chair first.
When you support yourself, you need to put your toes down a little, and then raise your legs as high as possible so that your ass can be fully displayed in front. You need to keep your shoulder blades down during exercise, and you can't collapse during exercise.
When you are familiar with this process, you can try to apply this method to more difficult horizontal bar movements. The principle is to stabilize your body by using the scapula downward. When you are on the horizontal bar, your contact with the horizontal bar is only your hand, and your hand is connected with your shoulder blade through your arm. If you don't control the scapula well and keep active, the stability of your body on the horizontal bar will be greatly reduced and it will be easy to swing.
If you want to improve this situation, first of all, you need to control your body from the bottom up. For example, you need to move your feet slightly forward. In other words, when you hold the horizontal bar, it is better to lift your legs a little forward than to straighten your body, so that you can use muscle contraction to stabilize your body.
Secondly, in fact, most of us do not provide support when hanging, which means that your body is just relaxing and hanging. Then what we need is to use the trapezius muscle below you to keep your shoulder blades down and your arms straight, just like we practiced before. At this time, your body will be a little higher than when you are relaxed.
There are also many people who speed up their movements in normal training, such as lifting their legs, to improve their swing when they are suspended. But this only uses the back and forth swing to complete the action, ignoring the muscle contraction of the abdomen.
In other words, speeding up seems to improve the swing, but in the process of speeding up, you have never exercised where you want to exercise. So don't speed up, it's not worth the loss.