You’ve finished the workout, you stop the clock, and a few minutes later you notice an annoying pressure or a pulsating pain in your head. Although it often goes away after resting, drinking, and eating, it isn’t wise to assume it’s always due to not drinking enough. The context, the intensity of the pain, how it appears, and the accompanying symptoms provide important clues to understand what is happening.
Dehydration: the most well-known cause
When we run, we lose water and electrolytes through sweat. If this loss isn’t compensated, the circulating fluid volume decreases and the effort the cardiovascular system must make to transport blood to the muscles and the skin increases. The headache can come with intense thirst, dry mouth, fatigue, dizziness, increased heart rate, and darker, scant urine. However, none of these signs alone allows calculating the exact magnitude of dehydration. Weighing yourself before and after running can help estimate losses. Each kilogram lighter represents roughly a liter of fluid, though you would need to account for what you drank during the workout. It isn’t necessary to repeat this procedure daily: it’s enough to use it occasionally to learn how much you sweat in different conditions. Drinking several liters at once isn’t the solution either. It’s better to rehydrate gradually and accompany the liquids with a normal meal. When the session has been long, the heat substantial, or sweating very heavy, it may also be necessary to replenish sodium.
Heat can cause more than thirst
Headache is one of the possible symptoms of heat exhaustion. In that case it usually appears together with heavy sweating, weakness, thirst, dizziness, nausea, irritability, or an elevated body temperature. The body sends more blood to the skin to release heat and increases sweat production. If the environment is very humid, sweat evaporates with difficulty and loses its cooling effectiveness. The body accumulates more heat as the heart works with greater intensity. When a headache appears accompanied by general discomfort during a hot run, you should stop the exercise, move to a cool or shaded space, remove unnecessary clothing, and begin cooling the body. The United States Centers for Disease Control and Prevention include headache, nausea, dizziness, weakness, thirst, and intense sweating among the symptoms of heat exhaustion. If confusion, unusual behavior, difficulty speaking, incoordination, loss of consciousness, or seizures occur, it could be a heat stroke. It’s a medical emergency and cooling should begin immediately while help is sought.
When you’ve run with insufficient energy
Heading out for a run after many hours without eating, finishing a long session with depleted reserves, or performing intense training without proper fueling can also contribute to a headache. In a healthy person, this does not always imply clinical hypoglycemia. It is often a combination of hunger, fatigue, reduced carbohydrate availability, heat, and dehydration. You may feel empty, weak, tremble, break into cold sweat, have trouble concentrating, or become irritable. After a demanding session, it makes sense to combine fluids with a source of carbohydrates and some protein. A yogurt with fruit and oats, a sandwich with a piece of fruit, or a meal with rice, potato, pasta, or legumes can fulfill this function. If the headache appears repeatedly when you run on an empty stomach but not when you eat beforehand, it’s worth reviewing the timing and composition of the pre-work meal. People with diabetes or those taking medications that can alter glucose should follow the specific guidelines of their healthcare professional.
Exercise-induced primary headache
There is a type of pain known as exercise-induced primary headache. It tends to occur during intense physical activity or shortly after finishing, is often pulsatile, and can affect both sides of the head. The International Classification of Headaches states that this diagnosis requires episodes provoked exclusively by intense physical exercise and lasting less than 48 hours. However, the classification itself warns that, at the first episode, potentially serious secondary causes must be ruled out. Its mechanism is not fully understood, though it is linked to vascular changes and the rise in pressure that accompanies strenuous efforts. It is more likely to occur during very demanding sets, hills, competitions, or workouts performed in heat. A progressive warm-up, avoiding starting at maximum intensity, and reducing effort in hot conditions can help. If the pain recurs, it’s not enough to simply take analgesics each time: it should be evaluated by a physician to confirm the diagnosis and decide on the appropriate treatment.
Training-triggered migraine
Regular exercise can help some people manage migraines, but a particular session can also act as a trigger. Heat, bright light, lack of sleep, fasting, dehydration, or a sudden increase in intensity can coincide in the same workout. Migraine typically produces throbbing pain, often more intense on one side, that worsens with activity and may be accompanied by nausea, sensitivity to light or sound, and, in some cases, visual disturbances known as aura. Those who already suffer from migraines can track when the pain appears, what training they did, how much they had slept and eaten, and what the environmental conditions were. That small diary can reveal patterns that are hard to identify from memory.
Neck tension also influences
Not all post-run pains come from heat or dehydration. Running with shoulders raised, clenching the jaw, or accumulating neck tension can foster a tension-type headache. It is typically felt as pressure or a band around the head, rather than a throbbing. It can be accompanied by neck stiffness and soreness in the shoulder muscles. Fatigue worsens posture and makes some runners raise their shoulders, jut the head forward too much, or keep their arms rigid. Relaxing the hands, checking the shoulder position, and gradually improving core and shoulder girdle strength can help.
What to do when it appears
Stop the training and check for other symptoms. Find a cool place, sit down or walk slowly, and begin drinking gradually. If you’ve gone several hours without eating, have some easily tolerable food. Do not resume the run simply because the pain diminishes for a few minutes. It is also advisable to note how it began, how long it lasted, where it was located, and what conditions surrounded the episode. If it recurs, that information will be useful during a medical consultation. It is not advisable to turn painkillers into an automatic response. In addition to masking a pattern that should be investigated, frequent use can promote headaches from medication overuse. Some anti-inflammatories can also be problematic when taken in a dehydration context.
When to seek urgent medical help
A headache that reaches its maximum intensity suddenly, in seconds or less than a minute, requires urgent medical attention. Help should also be sought if it appears with loss of consciousness, confusion, fever, neck stiffness, seizures, double vision, difficulty speaking, weakness, numbness, or loss of coordination. The Mayo Clinic advises seeking care for a headache that occurs during or after exercise, especially if it starts abruptly or is the first of its kind. The first headache clearly provoked by effort should not be self-diagnosed. A headache that recurs, worsens progressively, lasts many hours, forces you to abandon training, or has changed from your usual headaches also warrants medical consultation. Most headaches after running do not conceal a serious problem. However, understanding their context helps you respond better. Drinking can be part of the solution, but it doesn’t always explain the entire episode. Heat, effort, fueling, migraine, and muscle tension should also be taken into account.
