How much does muscle weigh?

[MamaChicken]

I recently lost 15+ lbs. I was taking a break from exercise while I lost and now I am starting to run again. I was holding steady at my new weight (139) for 5 weeks. Now the weight is climbing, dropping, climbing and it is up a few pounds. I am starting to see some muscle definition, so I suspect it might be muscle weight. How much should I expect the gain by running a few miles 3-4 times per week?

[sewaneecook]

Why not focus more on how clothes fit rather than a number on the scale? I recently trained for and ran a marathon and while I didn't lose any weight I did lose more than a pant size! If your weight is creeping back up, but it's muscle mass, I wouldn't worry about it. I've always been a fairly muscular person and can weigh up to 20 pounds more than someone wearing the same pant size and is the same height as I am.