Office Chair Cushion

I have a good president ... it is commercial quality ... but my buttocks and the backs of my thighs hurt. All suggestions will be appreciated.

From what you said it sounds as if your chair can not be properly resolved. Usually the pain in these body parts is caused by undue pressure on the underside of your thighs.

This article will help you ensure that your chair is properly configured.
http://www.officechairadvice.com/ergonom ...

Try to take regular breaks and do some simple exercises to lighten the weight of your body and muscles. If you're still having problems, there may be a piece of foam in your chair is worn and you may need to consider getting a new one.