Physical activity is a protective factor in many diseases and a sedentary lifestyle can be an aggravating factor. Physical activity globally reduces mortality. Pain is not an exception and physical activity is in first lines in the treatment of certain type of chronic pain. However, it can be difficult to convince patients to make an activity that can potentially increase symptoms. We will recall the effects of physical activity on pain mechanisms in the nervous and immune system, as well as on frequent psychological comorbidities in patient with chronic pain. We will also see how to manage the increasing of pain while patients begin the practice of physical activity.