Qigong practices can be classified as martial, medical, or spiritual. All styles have three things in common: they all involve a posture, (whether moving or stationary), breathing techniques, and mental focus. Some practices increase the Qi; others circulate it, use it to cleanse and heal the body, store it, or emit Qi to help heal others. Practices vary from the soft internal styles such as Tai Chi; to the external, vigorous styles such as Kung Fu. However, the slow gentle movements of most Qigong forms can be easily adapted, even for the physically challenged and can be practiced by all age groups.