Article in English: When you're just starting off, this is a great exercise. You don't want to strain those muscles too much by squeezing them for too long. If five is even too long for you, you can begin by squeezing those muscles for just 2-3 seconds. Ideally, you should always give those pelvic floor muscles a ten-second break before you repeat the exercise. This gives them enough time to relax and to avoid strain. Count to ten before you begin the next repetition. This can be considered one set of Kegels. If you started off by squeezing those muscles for five seconds, then squeeze them for five seconds, relax them for ten, and repeat this exercise ten times. This should be enough Kegels for one time and you should do the same set of ten 3-4 times a day, but no more. You can increase the amount of seconds that you squeeze those muscles each week. There's no need to do them for any longer, or to do more than one set of them per time. Once you've reached the magic number of ten seconds, stick to it, and continue to do one set of 10 10-second squeezes 3-4 times a day. This is another variation on the Kegel. To perform a pull-in kegel, think of your pelvic floor muscles as a vacuum. Tense your buttocks and pull your legs up and in. Hold this position for 5 seconds and then release it. Do this 10 times in a row. It should take about 50 seconds to complete.

Summary in Vietnamese:
Siết chặt cơ sàn chậu trong năm giây. Thả lỏng cơ bắp trong 10 giây. Lặp lại bài tập 10 lần. Thực hiện ép chặt cơ sàn chậu trong mười giây mỗi lần. Thực hiện bài tập Kegel “pull-in”.