A rush of blood to the head when working out is actually a normal response --- blood is pumped harder everywhere in the body when you exercise. The result, however, can be an exertion headache. If the rush of blood doesn't cause a headache but does make you aware of blood pumping in your head, use that as a sign to take it easy and see whether the sensation dissipates.
Exertion headaches are uncommon, affecting about one percent of the population. However, it is a diagnosable condition that could be serious. One characteristic of an exertion headache is that it begins soon after physical activity begins. If a physician determines that the condition is a benign exertion headache and not something more serious, such as a narrowed blood vessel feeling pressure from the rush of blood to the brain, initial treatment may include avoidance of heat during exercise, the use of non-steroidal anti-inflammatory drugs and weight loss.
To help prevent the complications of a blood rush during exercise, take some precautions ahead of time. For example, minerals such as zinc, potassium and magnesium can help keep blood vessels open a little wider, thus improving circulation and diminishing the effects of an exertion headache. Zinc is found in nuts and seeds, while potassium can be found in avocados and potatoes. Magnesium is packed into whole-grain products.
Healthy Blood Rush
When you are under stress, either because of a strenuous workout or because something has angered you, blood rushing to your head is actually a sign that your carotid arteries are functioning well and that your blood pressure may be healthy rather than too high. In a healthy individual, the body's response to stress should be dilation of the blood vessels, allowing blood to flow more freely to the head.
Watch for Dehydration
The same sensation of blood rushing to the head when working out may be a sign of dehydration, with your blood becoming a little thicker due to reduced fluid levels in the body. Other signs of dehydration include thirst, of course, but also less-frequent urination, dizziness, fatigue and sometimes a rapid heartbeat. Be sure to drink water or sports drinks that include electrolytes before, during and after your workout.