You finish the workout, stop the stopwatch, and a few minutes later you notice an annoying pressure or a pulsating headache. Although it often goes away with rest, hydration, and eating, it isn’t wise to assume it is always caused by a lack of water. The context, the pain’s intensity, how it appears, and the accompanying symptoms offer important clues to understand what is happening.
Dehydration: the most well-known cause
When we run, we lose water and electrolytes through sweat. If that loss isn’t compensated, the circulating fluid volume decreases and the effort required by the cardiovascular system to transport blood to the muscles and the skin increases. The headache may be accompanied by intense thirst, dry mouth, fatigue, dizziness, a faster pulse, and darker, reduced urine output. However, none of these signs alone can precisely quantify the magnitude of dehydration. Weighing yourself before and after running can help estimate the losses. Each kilogram lighter roughly corresponds to about one liter of fluid, although you would need to subtract 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 under different conditions. The solution isn’t to drink several liters at once. It’s preferable to hydrate gradually and pair the fluid intake 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 provoke more than thirst
A headache is one of the possible symptoms of heat exhaustion. In that case it usually appears together with heavy sweating, weakness, thirst, dizziness, nausea, 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 while the heart works harder. In the presence of a headache accompanied by malaise during a hot run, you should stop exercising, move to a cooler or shaded area, remove unnecessary clothing, and begin cooling the body. The Centers for Disease Control and Prevention (CDC) in the United States include headache, nausea, dizziness, weakness, thirst, and heavy sweating among the symptoms of heat exhaustion. If confusion, abnormal behavior, difficulty speaking, lack of coordination, loss of consciousness, or seizures appear, it could be a heat stroke. It is a medical emergency and cooling should begin immediately while help is sought.
When you have run with insufficient energy
Heading out for a run after many hours without eating, finishing a long session with depleted stores, or performing an intense workout without proper fueling can also contribute to headache. In a healthy person it does not always imply clinical hypoglycemia. It is often a combination of hunger, fatigue, reduced carbohydrate availability, heat, and dehydration. A feeling of emptiness, weakness, trembling, cold sweat, difficulty concentrating, or irritability may occur. 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 pain appears repeatedly when you run on an empty stomach but not when you eat beforehand, it is worth reviewing the timing and composition of the pre-run meal. People with diabetes or those taking medications able to alter glucose should follow the specific instructions of their healthcare professional.
Primary exercise headache
There is a type of pain known as primary exercise headache. It tends to occur during intense physical activity or shortly after finishing, and is often pulsating and may affect both sides of the head. The International Classification of Headache Disorders states that this diagnosis requires episodes triggered exclusively by intense physical exercise and lasting less than 48 hours. However, the classification itself warns that at the first episode, potential serious secondary causes must be ruled out. Its mechanism is not fully understood, though it is related to vascular changes and the increased pressure that accompanies intense efforts. It is more likely to appear during very demanding sets, steep climbs, competitions, or workouts conducted in hot conditions. A progressive warm-up, avoiding starting at maximum intensity, and reducing the exertion in hot conditions can help. If the pain recurs, it is not advisable to limit oneself to taking analgesics each time: it should be evaluated by a physician to confirm the diagnosis and determine the appropriate treatment.
Exercise-triggered migraine
Regular exercise can help some people control migraine, but a particular session can also act as a trigger. Heat, bright light, lack of sleep, fasting, dehydration, or a sudden increase in intensity may coincide in the same workout. Migraine typically produces a pulsating 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 was performed, 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 headaches after a run come from heat or dehydration. Running with elevated shoulders, clenching the jaw, or accumulating neck tension can promote a tension-type headache. It is usually felt as a pressure or band around the head, rather than a sharp pulsation. It may be accompanied by neck stiffness and tenderness in the shoulders muscles. Fatigue worsens posture and makes some runners raise their shoulders, tilt the head forward too much, or keep the arms rigid. Relaxing the hands, checking shoulder position, and gradually strengthening the core and the scapular girdle can help.
What you should do when it appears
Stop the training and check for other symptoms. Find a cool place, sit or walk slowly, and begin drinking gradually. If you have gone several hours without eating, have something easy to tolerate. Do not resume the run simply because the pain subsides for a few minutes. It is also advisable to note how it started, how long it lasted, where it was located, and what surrounding conditions were present. If it recurs, that information will be useful during the medical consultation. It is not advisable to make analgesics your automatic response. In addition to masking a pattern that should be investigated, frequent use can contribute to headaches from medication overuse. Some anti-inflammatory drugs can also be problematic when taken in a dehydration context.
When you should seek urgent medical help
A headache that reaches its peak intensity suddenly, within 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. Mayo Clinic recommends seeking evaluation for a headache that appears during or after exercise, especially if it starts abruptly or is the first of its kind. The first exertion-related headache should not be self-diagnosed. A headache that recurs, worsens progressively, lasts many hours, forces you to interrupt training, or has changed from your usual pattern also deserves medical consultation. Most headaches after running are not indicative of a serious problem. However, understanding the context helps you respond better. Drinking may be part of the solution, but it doesn’t always explain the entire episode. Heat, exertion, fueling, migraine, and muscle tension should also be considered in the equation.
