Here's what happens to your body when you've been in virtual reality for too long

In every guide to getting started with VR, step number one is always to make sure that the area around you is clear of any furniture, cables, animals, small children or other things you could trip on, run into, or knock over.

This is especially true for full-room VR experiences like those provided by the HTC Vive, but is equally important for those who are using a stationary or seated game.

Spending more than the recommended 30 minutes in VR will — in nearly every case — cause you to lose spatial awareness of the room around you. After 30 minutes, it is much more difficult to identify where things are in the physical world, from inside your headset.

Here's an example of what can go wrong when this happens

Disorientation varies very widely among VR users. Those who are prone to motion sickness or vertigo are much more likely to experience uncomfortable disorientation while in VR, but the feeling can happen to anyone that hasn't taken a break in awhile.

Games that involve flying, high-speed movement, heights and falling are known to cause extreme disorientation and should be avoided by anyone prone to this kind of reaction.

Makers of VR headsets say that you should take off the equipment immediately if you feel dizzy at all, to avoid accidents like the one this guy had

Most makers of VR equipment don't recommend people with epileptic conditions or special sensitivities to rapidly changing light try the experience, but these symptoms can occur even if the user has never experienced a seizure before. 

According to the instructional booklet that comes with the Oculus Rift:

Some people (about 1 in 4000) may have severe dizziness, seizures, eye or muscle twitching or blackouts triggered by light flashes or patterns, and this may occur while they are watching TV, playing video games or experiencing virtual reality, even if they have never had a seizure or blackout before or have no history of seizures or epilepsy.

The likelihood of having a VR-induced seizure is compounded by the number of hours you spend in the headset without a break, so a good rule of thumb is to treat VR like playing a sport. Every so often, take a break for water, and catch your breath.

VR is well-known to cause nausea, mostly as it's related to motion sickness and the speed of the objects moving in the game you're playing.

A few studies have looked at a another condition known as "cybersickness" or "sim sickness" that is caused by being overwhelmingly immersed by a simulated reality. In the real world, all of your senses work in sync to take in observations from the world around you, and are typically in agreement with one another. But in VR or while watching a 3D movie, your eyes and ears are taking in observations that don't agree with your other senses.

According to the theory, this lack of agreement between senses starts to make you feel sick after extended periods of time. 

Again, the best solution to this issue is to take off the headset if you start feeling sick. In a popular subreddit dedicated to the HTC Vive, many users have noted that just "getting used to it" is largely a myth, and VR-induced nausea actually gets worse over time, so there's no benefit to just powering through it. 

Have you ever tried on a friend's glasses and been surprised by the sensation of your eyes struggling to adjust and refocus through the lenses? Depending on the strength of your friend's prescription, you may have even gotten a splitting headache afterward.

That's exactly what your eyes go through when you put on or take off a VR headset. 

Short-term eye strain while in VR is very normal, and very similar to the experience of looking at a computer screen or TV for too long. This and can be prevented by simply adjusting the focus settings in the headset, and taking regular breaks. 

Some experts have suggested that VR might also have long-term effects on the eyes' abilities to focus interchangeably between close and far objects, but consumer-level VR hasn't been around long enough for experts to conclusively study the long-term effects of extended use. 

Shockingly, McNee doesn't experience any of the extreme side effects that most VR manufacturers warn against, although at the end of the video, he says he can't feel anything below his neck. I'm not sure what the medical term for that is, but it doesn't sound pleasant.

With that said, this length of time spent in VR should not be attempted at home, and could cause serious long-term effects that experts aren't even aware of yet.