My point is, if you are hiking at 820 FSL, but the density altitude is 3900 FSL due to temperature, barometric pressure, and humidity; is it the equivalent to hiking at 3900 FSL? An IC engine aspirates air to burn fuel and our lungs aspirate air to metabolize fuel (food) at the cellular level.
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Just because you don't take an interest in politics doesn't mean politics won't take an interest in you.... Pericles (430 B.C)