Yes my dear, being fit (and possibly younger) has a great impact on your succeptability to hypoxia.
If you are a smoker, then you already "fly" at 5,000 feet, so to speak.
But you cannot tell who will have an adverse reaction to altitude prior to going up. The people who live longer at higher alt adapt, and typically, if their blood was compared to yours, you would find a greater concentration of red blood cells in theirs. Adaptation is wonderful eh?
I had a flight made at 10,000 from Bermuda back to Pax river, Md. Fun hop in the 130, but you could get tired easily going from one end of the aircraft to the other. and avoiding weather was a fun issue too (we had suffered a decompression earlier and the aircraft could not be pressurized, hence the flight back to 10K)
I loved the alt chamber when going thru training, fo it really does give you a demonstration
If you have the ability to get to one to try high alt, explosive decompression, effects of hypoxia, that sort of thing, by all means, do try it!