Due to electrolyte loss.
Thanks for posting your query.
The headache and the muscle pain
is due to the electrolyte imbalance
associated with the fluid loss due to working continuously in excessive heat. You need to have an electrolyte rich fluid like Garotade or fresh fruit juices to make up for the loss.
The headache that you have now will gradually subside in next few days. Please do not worry. For the sore throat
you can do warm saline gargles. This is also due to the dryness of your mucous membranes.
I hope this answers your query.
In case you have additional questions or doubts, you can forward them to me, and I shall be glad to help you out.
Wishing you good health.
Dr. Praveen Tayal.
For future query, you can directly approach me through my profile URL http://bit.ly/Dr-Praveen-Tayal