I have very strong heartbeats after running and sometimes they cause pain or near blackouts. sometimes they are just annoying. is this a problem?

It could be a sign: of underlying heart condition including irregular heart rhythm or nerve conduction,structural heart abnormality or heart valve disorder,thyroid and endocrine disorders. Go see your Dr for a thorough exam ASAP. Take care and God bless you! http://www.medicinenet.com/palpitations_overview/article.htm

It could be: Very strong heartbeats associated with pain and near blackouts should be considered a warning sign. It is a good idea to be evaluated by a physician before starting a running program. You should definitely slow down and/or decrease duration of running to avoid this reaction. If you have risk factors for heart disease, consider having an exercise tolerance test.