2-3 times/week for 1 month i went to infrared sauna.last time i felt sundburned and my muscles feel weak.it feels like it tremble since 2week.normal?

Not sure...: Saunas are very good for pain control from sore joints and muscles, however, you need to take precautions to avoid heat exhaustion. Infrared saunas should be set in the range of 100-120 degrees. You should always drink water before, during, and after the sauna session. Also, if you just started using the sauna, you need to slowly increase the time and temperature as your body gets used to it.