My muscles were never sore, I just couldn't catch my breath and was exhausted. Altitude definitely affected me.
Congratulations!
There is an important medical story in your report. The reason your muscles were not sore was the slow pace forced upon you by not being acclimatized! I am not joking.
Even when you ARE acclimatized, workload capacity at altitude is reduced compared to sea level, so the muscles still have it "easier". They can only do as much work as there is oxygen to burn. Same thing for cars or piston-aircraft without turbo or superchargers.
