Bests & Worsts Reviews from Amazon

I was recommended this to help with lung capacity. I am 35 with the lung capacity of an 80yr old. I have yet to see how well it works from long term use. It is easy to use, clean, and the instructions are simple. Be warned! In the instructions it says not to bite down, well i did to hold it in place and the next day my jaw was killing me. I have never had jaw problems before. Almost a yr later and my jaw still hurts. I ended up being diagnosed with TMJ. This required doctor visits and an injection. None of which my insurance covers. So make sure you don't bite down. I tried it again this evening, but this time I did not bite down and if I wake up with jaw pains again I'll update my review. I will say about 20 minutes after using it I have crackling in my jaw, but no new pains yet. Update: The next day I had no issues with my jaw. Thank goodness.