The other morning, I woke up to a soreness in my shoulder. Not only was it sore, but I could barely move it. I started thinking, "What did I do that made my shoulder so sore?" I sleep on my back so I knew that wasn't it. I haven't lifted anything heavy in a while. Nor have I been in any wrecks. Then it hit me, as I walked by my Nintendo Wii, the thought struck me. "Not the Wii," I told myself. I shrugged it off, got dressed, and headed to work. As the day progressed, my arm started to fell better. No pain and no soreness. When I got home that evening, I decided not to play the Wii incase I did hurt my shoulder some how. The next day when I woke up, all was fine. Again, no pain and no soreness. That night, my fiancée came over and wanted to play the Wii so, being the man I am, I had to throw in some competition. We played for around 2 hours. After losing to her in almost everything we played, she left. Shortly after that I went to sleep. To my surprise the next morning, the pain and soreness was back. That answered my question. The Wii was the cause of my shoulder pain; commonly known as "Wiiitis." Below is an article, where a doctor actually diagnosed "Wiiitis."

BOSTON (Reuters) - "When Dr. Julio Bonis awoke one Sunday morning with a sore shoulder, he could not figure out what he had done. It felt like a sports injury, but he had been a bit of a couch potato lately.
Then he remembered his new Wii.
Bonis, 29, had spent hours playing Nintendo's new video game in which players simulate real movements. Bonis had been playing simulated tennis.
It was not quite tennis elbow, he decided.
"The variant in this patient can be labelled more specifically as 'Wiiitis,'" Bonis, a family practice physician, wrote in a letter to the New England Journal of Medicine.
"The treatment consisted of ibuprofen for one week, as well as complete abstinence from playing Wii video games. The patient recovered fully."
Wiiitis -- pronounced "wee-eye-tis" -- is the latest ailment to develop from the video game era, beginning with Space Invaders' wrist in 1981, which was caused by the repeated button mashing required by the popular arcade game.
Nintendo's Wii game can captivate for hours and "unlike in the real sport, physical strength and endurance are not limiting factors," Bonis of the Research Group in Biomedical Informatics in Barcelona, Spain, wrote.
"What convinced me to send the case report was that a friend of mine, after playing 'Wii Sports' suffered from a similar complaint," Bonis told Reuters in an e-mail. "I have not found other cases in my clinical practice, but it is probably an underdiagnosed condition."
It is not the first time Nintendo has received attention in the medical field.
In 1990, a Wisconsin doctor characterized the thumb soreness brought on by pushing the buttons on a controller as "Nintendinitis" after it affected a 35-year-old woman who played a Nintendo game without interruption for five hours.
With virtual golf, boxing, baseball and bowling already on the market, "future games could involve different and unexpected groups of muscles," Bonis said. "Physicians should be aware that there may be multiple, possibly puzzling presentations of Wiiitis."
Bonis said he still plays the games, "but I try to use it with moderation. Sometimes it's hard to do!" "

Article: http://www.reuters.com/article/technologyNews/idUSN0616721120070606