I sometimes get a terrible headache a few hours after my bikeride. First I thought it was due to dehydration, so I use an extra water bottle. That didn't do it, the headaches continued. Then I thought it could be a 'mineral deficiency' (salt/magnesium?) so I fill my water bottles with a mixture of water, lemonade and salt now and take some extra magnesium. I hoped that was it, especially because I didn't experience any headaches for the week after! However, last monday the headache started during my ride already and ended up in something close to a migraine. I think my bike fit is good, my helmet isn't too tight etc. Anyone have a clue what could be the issue?
Are you sure it's not due to hydration? Do you weigh yourself before and after the ride? Recently the weather near me has been very oppressive and my sweat rate has increased significantly. My usual drinking strategy of ~20-24 ounces an hour has had to increase to 30-36 ounces an hour. I was getting headaches on my rides until I started upping my drinking. Weigh yourself before and after. If more than 1 lb or 0.5 kg lighter, drink more.
I've suffered from headaches during and after riding for years and have never got to the bottom of the physiological reasons. For me it's not hydration or positional so i've I learned to ride around it and keep my temperature down as much as possible. Oddly i get a lot less headaches from riding the trikes.
How much do you drink on a ride? If you drink two bottles on 100km it is far from enough. Maybe an electrolyte drink could help as it makes hydration easier. I personally don't use them as I am running quite fine with water.
I drink two bottles on a 30-40km ride. The thing is, I don't break a sweat easily but I do get thirsty really quick when I work out.
Most common cause of this sort of headaches is neck/shoulder tension. I don't know when you started riding as you do now but if you just started this might explain it. On bikes such as yours you are slightly crouched forward with your head raised up to look forward. This can cause you to 'hang' into your shoulders too much causing a lot of tension in that region which can lead to headaches. Most of the time you won't feel this in the way of sore muscles for instance. However that kind of tension can severely impair bloodflow in your neck and shoulders. You mention you think your bike fit is good but one thing you can measure just to be sure is the width of your handlebars. The general rule here is that the width between your hands is roughly the same as your shoulders. On most mtb's the handlebars are wider because it adds stability in rough terrain but for more casual rides it may be too wide. This influences the way you stretch your arms when riding. It's more comfortable to ride with slightly bend arms and if you have narrow shoulders and handlebars that are too wide you can't do that. Another thing you can experiment with is the height of the handle bars. If it is too low it causes you to lean on it too much which translates into tension in the shoulder. An added benefit of raising the bars is that you will sit more upright and that translates in how much you have to raise your head when looking forward thus releaving some tension. I've noticed with rebuilding my bike that the slightest adjustments here can make a huge difference. Your bike shop can help you figure this out. On a side note, you say you don't sweat easily. I would not add salt to your drinks then because salt retains moisture and you need too shed that in the form of sweat.
