If it is too high, use a low bench or stand. Importantly, to hanging on straightened arms and legs, you do not touch the floor. If you have a weak grip, use the special straps. Arms and legs fully extended. The back is slightly bend at the waist.
Take a breath. Visit gastroenterology for more clarity on the issue. Hold your breath Pull the legs back a little and powerful movement lift them as high as possible. Try to always keep our legs straightened (but not locked at the knees). If you have strong hamstrings, feet can be slightly bent, but fix the angle at the knees until the end of the set. Raise your hips above the waist! At the top point even more tense press and try to stay in this position a couple of seconds. Gently lower the leg, pause, and then do next iteration. If hard to carry out the ups with straight (or almost straight) legs can bend them any more. The main thing with this – do not change the angle at the knees until the end of set! Tips The more you raise the legs, the greater the load on press.
In the initial phase of the movement are working almost exclusively hip flexors. Abdominal muscles while in a state of isometric contraction (tense, but did not change their length), and the proportion of the burden on them is minimal. They begin to shrink in length and are actively involved in the job only after you lift your feet higher than 30-45 from the vertical.