Originally Posted by
cubewheels
Strange. Everything you said here happened in the opposite manner to me.
I lost around half my fat with cycling despite eating more (more of the same foods I've been eating before I took cycling). Most of my 14 to 20 hour weekly training is in z3 to z4 in the 5HR zone system.
I had muscle gain in the legs mostly and some in the upperbody and arms due to high resistance training in the bike, outdoors - staying in the high gears, including long uphill climbs where I had to pedal standing couple minutes at a time and similar high resistance training in the stationary bike indoors. I also pedal out of the saddle with most of my weight over the bottom bracket so I can use higher gear and higher resistance (forces me to pull harder on the handlebar and make more use of my arms and core muscles).
Haven't experienced any issues at all. I even feel a lot stronger now in running now despite zero training in running.
It's unlikely you've gained any muscle at all. You may have cut some subcutaneous fat, so there's the appearance of increased musculature. And as I and others have pointed out-- you're very new. Everybody sees real (and perceived) gains in the first few months as their body adapts. You are absolutely not going to gain muscle in the upper body on a bicycle. Look at any pro. They're scarecrows. Look at any track cyclist... oh, that's right-- they spend as much time in the gym as they do on the bike.
Trying to sustain that kind of training load indefinitely is gonna catch up with you-- ask me how I know.