If the nervous system is repetitively triggered into "fight or flight" mode it can get confused, resulting in "sympathetic wind-up," a constant, heightened resting state. In this stressed state the nervous system has a hard time calming down, resulting in possible pain sensitivity, stress, difficulty sleeping, anxiety, and fatigue. Yoga has been shown to reduce pain, stress, anxiety, depression, and irritability. Yoga practice can also increase blood flow, improve concentration, and improve sleep quality. In short, yoga can produce the opposite effect of "sympathetic wind-up."