The reason behind the Sundance, it was a personal sacrifice to the creator, the great spirit. It was like a rebirth and renewing of the earth by offering to sacrifice themselves to give back to the Great Spirit and to celebrate good fortune. If someone was in a difficult or dangerous position and asked the Great Spirit for help, he would offer a personal sacrifice in good faith. If the request was granted then the beneficiary had to give back. If the person did not participate in the sun dance ceremony, it was believed that bad luck would come, not just personal bad luck but also to the entire village.
This type of ceremony could be done privately away from prying eyes, there were usually two men overseeing this. The village always got behind the ceremonies as they thought it will bring positive energy to the people. The participants often fasted from food and water, how many days could vary.
To start the ceremony the skin was pinched above the right and left breast and an incision was made through the skin. A wooden skewer was placed through the incision and was then tied to a rope which was attached to the sun dance pole. The idea was through physical movement such as going backwards, moving around the pole the skin would break.
The Sun Dance was physical and gruelling. In some cases, the skin would not break even after hours. It was up to the participant if he should continue, there was no disgrace if the task could not be completed.
Another way the Sun Dance could be done is by using bison skulls that were attached to ropes and then to the skewers where an incision was made over the shoulder blades. The participant would run around hoping to break free.