How does yoga relieve stress and pain?

If practiced regularly, yoga can relieve muscular tension or pain by improving range of motion, relaxing tense muscles, and increasing muscle strength. Practicing yoga when you are feeling anxious may help to reduce stress when you are on the job or at home. In fact, findings show that, for some, just three months of weekly yoga training results in an increase in physical well-being, significant improvements in perceived stress, and a marked reduction of headache and back pain. Yoga also reduces blood levels of cortisol, which is important for reducing inflammation.

There have been several recent studies on yoga and pain and the findings are all encouraging:

• In one study, researchers concluded that yoga was effective at
  improving function and reducing low back pain and the benefits
  persisted for at least several months.

• Another study revealed that yoga improved carpal tunnel syndrome
  after just three weeks of practice.
 
• A revealing study of patients with rheumatoid arthritis found that hand
  grip strength of both hands increased in patients following yoga
  practice.