After exercising, you are supposed to feel great emotionally, for having completed the task, and physically, as your body releases endorphins. However, many athletes complain of a side effect from working out that can be bothersome -- an odd taste in the mouth. There are several possible causes for odd tastes in your mouth during exercise, but if the metallic taste or taste of blood is accompanied by other symptoms or is persistent, consult your physician.
Your lungs have an area known as the blood-gas barrier or blood-air barrier, where gas and air are exchanged. During times of intense physical activity, pressure increases to a point that breaks this barrier and allows blood to enter the lungs and causes the taste of blood in the mouth. Research published by "American Journal of Respiratory and Critical Care Medicine" in 1997 supports this theory that intense exercise can cause mechanical failure of this barrier when athletes have a history of lung bleeding. According to emergency medical technician John Kenyon, this condition is not unusual when athletes push too hard. It's considered normal unless you produce blood when you cough.
Pulmonary edema, a common complication from heart failure, is a condition where fluid builds up in your lungs. An acute version of this condition found in swimmers, called swimming-induced pulmonary edema, is accompanied by hemoptysis, or coughing up blood. A study published in the journal "Chest" in 2004 points again to the blood-gas barrier and increased pressure from exercise. However, a higher number of pulmonary edema and hemoptysis occurrences in swimmers suggests that water temperature and body position during swimming increases risks more than other high-intensity exercises.
Taste Process Interference
Any condition that interferes with your taste process can cause a metallic taste in your mouth, referred to as dysgeusia. Breathing is accelerated during exercise, making symptoms of dysgeusia more noticeable. Some typical causes include the common cold, sinusitis or sinus infection, strep throat or viral infection; allergies or asthma, both of which can be aggravated by intense activity, can also be behind the sensation. Dehydration and breathing through an open mouth are both possible causes of a metallic taste, as well.
Other Causes and Warnings
An unusual taste in your mouth can caused by many factors, most of which intensify during vigorous physical activity. Other possible causes include neurological disorders like Bell's palsy, autoimmune disorders like Sjogren’s syndrome, vitamin deficiency or chemical poisoning. Complications from dysgeusia can get progressively worse, including depression and weight loss. Causes can be serious, requiring treatment. Consult your physician if you experience any persistent change in taste or smell.