"The brain is very sensitive to changes in pressure and temperature, and to
(exercise-induced) trauma," notes Margot Putukian, M.D., director of Primary Care Sports Medicine at Pennsylvania State University. That's why people who rarely get headaches at home may find themselves with a tension, or vascular, headache in the backcountry. The discomfort is caused by changes in blood flow, and usually feels like a constant pressure, as if a vise is squeezing your head, Dr. Putukian says.
But tense you're certainly not, so why the headache? Blood flow can change for reasons other than stress or anxiety:
Altitude: Avoid ascending too quickly so your body can acclimatize to changes in air pressure. If you're a flatlander, the rule of thumb is to ascend no more than 2,000 feet a day when you're at more than 5,000 feet. If you get a headache at altitude, slow down or stop for the night to give yourself a chance to acclimate. (For more on hiking at altitude, see "Heave Ho," August 1999.)
Heat: In summer, you can get too much sun too quickly. Wear protective clothing, including a wide-brim hat. Find a shady spot and soak your head and hat in cold water to cool off. If that's not possible, moisten a bandanna with water from your bottle and wrap it around your head. Carry the lightest load possible, and hike at a slow to moderate pace.
Dehydration: This is how heat usually takes its toll. Start drinking extra water
2 or 3 days before your trip. When you're on the trail, have water easily accessible for frequent sipping, and try to drink 2 to 4 cups of fluids
Exertion: The pounding starts suddenly, usually as you make a big effort, like climbing over a fat log while carrying a 60-pound pack. Breathe deeply during strenuous efforts to make sure your blood pressure doesn't shoot sky high. Relax your neck and shoulder muscles so they don't clamp down and reduce blood flow.
Things to avoid: Alcohol, caffeine, preservatives like MSG, and some medications, such as antihistamines or antibiotics, may induce headache. If you're on medication, talk to your doctor before your trip to see if you need to take special precautions. If the pounding persists, take nonaspirin pain relievers and avoid whatever seemed to bring on the headache.