Will running decrease my muscle mass? I need cardio. But dont want to lose my muscle mass at the same time.
It can if you eat less than you burn off. It's a balance act but I love running. You might have to measure how many calories you lose and what your recovery meal is going to cover. I use this equation for my soldiers:
0 - 200 = -200
You're now in the hole by 200 calories which means your body needs twice as many calories to recover so you won't burn off muscle. You would need to eat 200 to get back to zero and eat more for an actual recovery. Plain greek yogurt with oatmeal with a protein shake works well for me.