Why does yoga hurt?

Yoga actually can be a pretty difficult exercise, in contrast to what many people believe.
While it is generally a more slow paced exercise that mainly utilizes your body weight, it can still be a very difficult workout.

Yoga uses muscles you may not actually use on a daily basis or in other sports, and it puts you in positions that are quite difficult to hold for those that are not used to it or new to yoga.

In addition to the difficulty on the muscles in terms of holding positions, yoga also puts you in positions that require more flexibility than you may have. These poses may stretch your muscles in ways that cause slight pain or discomfort, just as stretching before or after exercises.

If the pain you are feeling is different or is more intense, then it may actually be a more serious reason and is something that should be checked. You can ask the yoga instructor about this pain, it may be a sore muscle, or a weakness in some muscles, in this case, they can give you different poses or variations of the poses for you to do until you build the strength and flexibility to be able to do the original pose.