Certainly all the ingredients have been there. Long, windblown hours under direct sun. Physical exhaustion and dehydration. Hasty departures without morning coffee. Tightly adjusted helmets. Tail lights of cyclists in front of me shining directly into my eye on group rides. And yet it has never happened. I've had headaches after bike rides and before bike rides, just never during. And I've had headaches during other forms of exercise - namely running (well, attempting to run). Could there be something special about cycling that prevents them?
According to a neurologist friend, that is not impossible. The research on headaches and exercise is mixed. In some instances exercise can actually induce headaches ("exertional headaches"), and there appears to be a higher risk of this with high-impact exercise and weight lifting. In other instances, exercise can be used therapeutically to treat headaches, including migraines. These would be exercises that are low impact and promote relaxation and tension-reducing posture alignment. Yoga is probably the most typical. But it is plausible that cycling could play that role as well - depending on how it makes us feel and how our body is positioned on the bike. And I suppose all that fresh air couldn't hurt either.
Whatever the reason for it, I am thankful to be headache-free when I pedal. I will continue to carry pain meds on rides, just in case. And I hope to continue not needing them.