Blood in the urine is known as hematuria
. What you are experiencing seems to be what we call exercise induced hematuria also known as March Hematuria (meaning blood or blood products that spill into the urine). The way it works is that when you exercise vigorously, some of your red blood cells break apart spilling their contents into the blood which then makes its way into the urine. Another possibility is that your exercise is causing mild muscle damage which is spilling muscle contents into the blood (making urine red). This is less likely. Finally, there is a small possibility that you have an issue with your kidneys that is unrelated to exercise.
While this type of hematuria is most likely what you have, there is now way to rule out other causes until you get evaluated. The best type of physician for you to see is a primary care physician
such as an internal medicine doctor
. He or she can take a more detailed history of when you develop these symptoms and perform a thorough physical exam. In addition, your doctor can order urine tests which can be sent to the laboratory. These test can determine if you have blood cells in your urine, hemoglobin or myoglobin (all of which can be red). This will help narrow down the cause and make sure that you do not have any other kidney problems.