A former client of mine would often complain of feeling lightheaded immediately following a her run. This is a common problem that I want to address today. 

When you workout, you heart pumps harder and faster, increasing blood flow to the actively exercising muscles. In response to that, blood vessels expand to compensate for the added blood flow.  When exercise ends suddenly, the heart slows down its pumping activity, decreasing blood circulation even though blood vessels remain dilated. As a result, blood pressure can drop and you can become dizzy or even faint.

It can be common to feel lightheaded or dizzy when you abruptly stop intense physical activity. Feeling this way after exercising is usually not dangerous. However, feeling lightheaded or faint during exercise is more serious and may be a sign of a heart condition.  If you feel dizzy during exercise stop the activity immediately, tell someone in charge about your symptoms, and get medical attention if necessary.

To help limit or prevent feeling dizzy or lightheaded after exercise in general, cooling down adequately is key.  It is commonly understood that a brisk walk is one option to cool down, but this may not be sufficient for everybody.  A good 5-10 minutes of walking and stretching will help return your body back to rest in a controlled manner.  Ending your workout in this way can help maintain a healthy heart rate and good blood circulation. When running, it may be best to jog slowly and then walk before you call it quits.