In its most basic form, stretching is a natural and instinctive activity; it is performed by humans and many other animals. Stretching often occurs instinctively after waking from sleep, after long periods of inactivity, or after exiting confined spaces and areas.
Muscles, like other tissues in our body, need to be well circulated and healthy. We spend most of our day in the same posture. By not stretching, we continue to overuse and fatigue our muscles, making them short and tight. In return, we form adhesions and connective tissue that is not needed, decrease circulation, decrease flexibility, increase the risk of tendonitis, increase aches and pain.