I’ve been training for my first half-marathon; running a lot of long distance lately. I’ve found it difficult to maintain muscle mass in my arms and chest, due to all of the calories I’m burning while running; I have a high(ish) metabolism as it is.
I had been attending crossfit classes 2 or 3 times per week, but have dropped that to once per week, in order to make room for running.
Any quick/easy methods of building (and maintaining) muscle mass during non-running days?