When you exercise, or exert yourself physically, the muscles of the head, neck, and scalp need more blood to circulate. This causes the blood vessels to dilate, which can lead to a condition called exertional headaches. Headaches that most frequently occur due to exercise or over-exertion include jogger's headache and orgasmic headache (sex headache). While these may occur in isolation, they are most common in people who have an inherited susceptibility to migraine (one or both parents have migraines).
Closed beta is beta testing only available to a select few individuals or only company employees. How to be a beta tester. Many games (especially online games) in the final stages development have an open beta for several months that allows anyone interested in the game to play and report problems.
beta is usually a trial version of a game for a company. betas are usually experimental and often have problems w/ them. Beta is the third stage in most software - not only video games. It all starts out with demo builds and stuff like that, and is reaaaaaaly incomplete. Then, later on, the software enters alpha stage, where the program is complete enough to be ran properly, but is still not fully complete and full of bugs.