Women can do this at all times except during their physiological period. It is a form of health care, during which you only need to breathe and exhale, without entering the grains. Generally speaking, spring and autumn are more suitable, when the temperature is moderate and the human body is most comfortable, so it is not easy to get sick. In winter, it is relatively cold, and after fasting, energy is reduced, body temperature drops, the ability to protect against cold decreases, immunity decreases, and it is easy to get sick. Summer is relatively hot, water loss is relatively the largest, in the case of energy and water significantly reduced susceptible to heat stroke, affecting health. But its not absolute, people with excellent physical fitness or experience in Purgatory can Purgatory at any time of the year. All in all, the science of the valley is conducive to good health, if the blind valley may lead to insufficient intake of calories, hypoglycemia, serious cases can be life-threatening.