Is it OK to go to sauna once a week for someone who is trying to build muscle and get mass?!?

Answer 1

Yes.

The only thing the sauna does is dehydrate you (and help eliminate toxins from your body). It will have little effect on your gaining mass. Just weigh yourself before hand and drink sufficent water to bring yourself back to the same weight. Some have suggested that the extra heat may even help expand the muscle cells post workout and speed the transport of the post-workout protein into the cells.

So feel free to use the sauna after your workout.

You can also use the sauna before your workout to do some general stretching and heating of your muscles. There was a study conducted (Med. Sci. Sports Exerc Vol 34;12: 1892-1899, 2002) which suggests that this will reduce muscle damage.

In either case you should make sure that you drink enough water to bring your weight back up to what you weighed prior to entering the sauna. You can lose several pounds of water in just a few minutes of sweating, so be careful.