Muscles out of nowhere?

[SootAndGrime]

I noticed that I am building a very visible amount of muscle in my arms and upper chest area. I have not been lifting weights or anything, where is this muscle coming from?

[Ryan_m_b]

How old are you? If you are young then this is a fairly typical occurrence.

[SootAndGrime]

How old are you? If you are young then this is a fairly typical occurrence.

I am 23 years old.

[Ryan_m_b]

There could be a number of reasons. Diet, exercise (not just lifting weights, just regular things like walking) etc. It might be rare but I don't think it is unusual for men even in their early 20s to undergo puberty like growth spurts in muscle mass.

[SootAndGrime]

I have been losing some body fat in various torso regions.

[DaveC426913]

What has changed in your life recently? New job? Summer sports?

[SootAndGrime]

What has changed in your life recently? New job? Summer sports?

I am constantly turning over in bed at night because I can't sleep. Perhaps this repetitive action developed arm and pectoral muscle.

[Ryan_m_b]

I am constantly turning over in bed at night because I can't sleep. Perhaps this repetitive action developed arm and pectoral muscle.

Doubtful. If you think something is wrong with your health go see your doctor. There is far to much variance in biology to come up with an accurate answer over the internet.