You already know that your dog is very active during his or her waking hours, but did you know that some of the behaviors you see while your pup is awake can also occur during sleeping?

Just as humans can talk, move, and even walk in their sleep, so can your Shih Tzu. Take a look at these nine shocking things your dog does while sleeping - then observe your pup to see which ones apply to your dog.

1. Crying

When your dog goes into REM sleep, the deepest stage of sleep, he or she may cry or whimper. Some believe that it's because they're dreaming, while others think it's just a reflex. In any case, you don't have to worry about your pup in most cases. Just let sleeping dogs lie in this case, since they're getting some much needed rest.

2. Barking

Just as humans talk in our sleep, so do dogs. This is why you may sometimes observe your Shih Tzu barking. This isn't necessarily a bad thing. They may just be communicating in their dreams, and it projects itself outward in the form of a bark.

3. Muscle Spasms

While your Shih Tzu is dreaming, it may have muscle spasms. In most cases, this is completely normal. If, however, you notice that your dog has other symptoms and has spasms while awake, a vet visit may be in order.

4. The Three Stages of Sleep

Your pet goes through three stages of sleep. These include rapid eye movement, or REM, non-rapid eye movement (also known as NREM) and finally the shortwave sleep. The shortwave sleep is always characterized by deep breathing during sleep. Your pet can even start twitching at this stage.

5. Growling

Like barking or whining, your dog may also growl while sleeping. Again, this isn't necessarily an indication of a nightmare. Your dog may simply be communicating.

6. Shaking

Your dog may begin to shake while sleeping. This could be a sign that he or she is having a bad dream. While this is normal on occasion, observe your Shih Tzu to make sure that this isn't a regular occurance.

7. Kicking

Humans do a lot of moving while sleeping, and so do dogs. You may see that your dog is kicking his feet, particularly when he is sleeping very soundly.

8. Sleep Running

Once your dog reaches the REM stage and is in deep sleep, kicking can turn into full-on running! Again, this is just an indication that your dog is in a deep sleep.

9. Falling

Your dog may get so into sleeping that moving around calls him or her to fall in the floor. This is why it is advisable to keep your pup on the round while sleeping, as falling from a couch or bed can lead to injury.

9 Shocking Things Dogs Do In Their Sleep

6. Shaking