Mishnah 6 in this chapter deals with various forms of physical exercise and bodily care on Shabbos, and with the question of which of them are considered a form of healing that is forbidden on Shabbos, and which are permitted.
Anointing and rubbing the stomach:
The Mishnah opens by permitting a person to anoint his body with oil and to rub his stomach. This permission is conditional on the act being done in a manner different from the weekday practice - for example, that the application of the oil and the rubbing be done at one and the same time, in a way that differs from the manner customary during the week.
The activities the Mishnah forbade:
"Mis'amlin" - strenuous exercise, whose purpose is to exert the body to the point of sweating, is considered a form of healing. The Rambam writes that this refers to a type of eastern massage, in which a person would tread on his friend's back until the friend broke into a sweat. Any strenuous physical activity that brings a person to exertion and perspiration falls under "mis'amlin," and is not permitted.
Scrubbing the body with a brush - forbidden, because it is considered a weekday activity. However, a person who became dirty may take the brush and clean himself with it.
Going down into the Chordima - Chordima was the name of a river whose bed was extremely slippery mud, and the concern was that one who goes down into it might slip, his clothing would become completely soaked, and he would come to wring it out. Some explain it slightly differently, that this refers to an area containing a sort of quicksand. This is not necessarily a concern of danger to life, but rather a concern that a person would get stuck and need to call for help, and the Sages did not want this to happen on Shabbos.
"Apiktresin" - taking a drink intended to make a person vomit, which is considered a form of healing. This is very similar to the syrup of ipecac taken when a person has swallowed poison, or in order to induce vomiting. However, the Gemara says that a person is permitted to put his finger down his throat in order to vomit, if he needs to do so.
Straightening a newborn - one may not straighten the bones and the spine of a newborn infant, as was the practice. But it is permitted to swaddle the infant in the manner we call diapering.
Setting a fracture - one may not return a broken bone to its place and fix it in its proper position on Shabbos. This refers to a case in which there is no danger to life.
In practice, the halachah in the Gemara is that one is permitted to set a bone in its proper place on Shabbos, unlike the words of the Mishnah.
One whose hand or foot was dislocated:
The accepted method of healing in such a case included vigorously rubbing the limb in cold water. Regarding this the Mishnah says that one may not shake and agitate the limb vigorously in cold water, since this is an act of healing. However, he is permitted to wash the limb in cold water in his usual manner, and if it heals on its own, it heals. This is the way in which it is permitted on Shabbos.
In summary: In this Mishnah we learned that anointing and rubbing the stomach are permitted when done differently from the weekday manner, while strenuous exercise that brings a person to perspiration, scrubbing the body with a brush, going down into the Chordima, apiktresin, straightening a newborn and setting a fracture are forbidden. We also noted the permitted acts alongside them: cleaning oneself when dirty, putting a finger down the throat, swaddling the infant, and washing a dislocated limb in the usual manner, so that if it heals, it heals.