Putting a lizard on its back.

Question
If you could please answer this question for me It would greatly appreciated.

I have heard that putting a lizard on its back has a calming affect and relives stress but I have also heard that the reason they are acting calm is because they have trouble breathing on their back and therefore pass out.

I'm not going to try this with my lizard (black throat monitor) until I know It's completely safe for him as I don't want to harm him in anyway, but it would sure make doing his nails a lot easier since he is getting quite large and doesn't like to stay still.

Thank you very much for your time, Tracie.

Answer
Hello Erica,

No, it is not a good idea to place your black throat monitor on his back.  They do not have diaphrams which help the lungs push air in & out with the assistance of the ribs.  
Placing him on his back could cause a collapse of his lungs.  The reason why they seem to "calm down" when they are on their backs is because it slows the respiration down almost to a catatonic state during that time which is not ideal.  
Try wrapping him up in a large towel to where you can pull out one arm or leg at a time to clip his nails.  

Tracie