How would you try to gain weight mostly muscle mass on the side but also try to get your endurance up by running and will running stop you or defeat the purpose of trying to gain weight?

Answer 1

There are two types of muscle fibers in your body. One is fast acting and for short duration and strength. These are the ones that you build up for bulk. The other are slower twitch and long acting. These are your endurance fibers. If you work them both properly you can increase both but if you do a lot of running you will probably develop more of the long acting fibers and not get too much bulk out of it all. Look at Armstrong. He has very little muscle mass in the upper trunk because of all of his type II muscle fibers. He does have some bulk in the legs though, because he uses them when he rides.