Figured I toss this one to some athletes who have some experience with altitude training ect. I was in Co. Springs for 5 days for some R and R. I have been there before and did take a day or two to adjust to the altitude. (I’m from Texas) I usually feel a bit sleepy the first day or two and then I’m good to go. While there I did two 6 miles runs at a good effort level on hills with a day of rest between. I felt good and didn’t feel that I over did it. The next day I drove to the top of Pike’s Peak (awesome experience if you’ve never been) and spent about 45 minutes at the top. That evening when I returned to my room I started feeling a pain in my left chest. Not inside my chest but underneath my pec muscle. It was a burning sensation and it wasn’t constant. It would “flare up” randomly if I moved in a certain way. Well I returned home and did not get relief but it got worse. Finally after 5 days I went to the ER to get it checked since by this time I was getting concerned. They checked my heart and lungs ect. and said I was fit as a fiddle and that it was most likely an irritation in the nerves located in my chest. Well now it’s the 8th day and the pain has subsided but not disappeared. I did a swim (for the first time in a week) and it seemed to agitate it more. Does anyone have a clue what this fluke pain could be and if the altitude could have any possible connection? Thanks for any help.
TTT.
I doubt the altitude was the source of your problem. COS is about 6000 feet and if you can run there from Texas, going to the top of the Peak in a car is not going to cause you any trouble. And, you don’t acclimatize much in a week - you just get rid of the headache. Sounds like it was something else. The drive up PP is interesting isn’t it. Having done multiple Pikes Peak Marathons and Ascents, I used to fly into COS from DFW and drive to the top and sit there for 4 hours and go down. Do the same thing the next day and then race on the third. Best.
Could be costochondritis – irritation of the cartilage near your sternum. Did you do anything to strain your ribcage or sternum before the pain started? (Lifting weights? Bar fight? 
Or even coughing or laughing?) I experienced similar pain after a bike crash last year. I had a flare-up recently without any obvious cause. Running downhill was painful, but other heavy exertion like running uphill or riding didn’t hurt at all. If the ER folks said your lungs and heart were fine, my non-expert guess is that it’s totally unrelated to altitude.