Overexertion can damage your heart and raise your risk of stroke or sudden death if you already have heart trouble, according to the Heart Failure Society of America and Johns Hopkins Medical Center. Symptoms of heart strain may occur with overexertion if you exceed target heart rates for your sex and age. Consult your physician to determine optimum exercise levels.
Heart trouble can be caused by coronary artery disease. This is when your coronary arteries are too narrow to supply extra blood -- with its extra oxygen and nutrients -- to your heart muscles during strenuous exercise, according to a 2003 report published in "Clinical Chemistry" by researchers at the Cardiac Rehabilitation Centre of the University Hospital of Ghent in Belgium. When you reach a state of overexertion, your heart muscle can become too weak or can't conduct electrical impulses improperly. Over time this can damage portions of your heart muscle or cause abnormal heart rhythms, leading to a heart attack or sudden death.
With atrial fibrillation, your atria -- the collecting chambers that receive blood from your body and lungs before your ventricles pump it back out -- twitch feebly instead of beating. This allows blood to stagnate in your atria and form clots. Overexertion can break the clots loose and allow them to travel to your brain, to clog arteries and to cause a stroke. If you have atrial fibrillation, your doctor may prescribe medicine to prevent blood clotting, which may allow you to enjoy more exercise.
According to a November 2009 report released by Johns Hopkins Medicine, individuals who develop erratic heartbeats during or after extreme exercise are at no excess risk of dying from a heart attack if they have a normal heart. However, the same erratic heartbeats during or after exercise in a person with underlying coronary heart disease could increase her risk of dying from a fatal heart rhythm. She should avoid arduous exercise if this is the case.
The Heart Failure Society of America advises people with heart trouble to become aware of the symptoms of overexertion. If you exercise too strenuously, you may become so short of breath that you can't finish a sentence without gasping for a breath, and this may persist even after you stop working out. Abnormal heart rhythms, which you may feel as skipped beats by checking your pulse, can cause dizziness or extreme fatigue, sweating, nausea and vomiting. Chest, chin, arm or back pain may also accompany overexertion. Heart Failure Society of America advises calling 911 if these symptoms persist or worsen.