Does density altitude come into play?

This type of calculator is used for aviation and motorsports because density altitude affects lift, drag, and combustion. Density Altitude Calculator

Right now at my house at 820 FSL, it is 82 deg F, 28.9 in/Hg, and 67 deg dew point. My density altitude is 3947 ft and my absolute pressure is 28.048.

Another question is how does this relate to hiking at altitude. If an internal combustion engine is affected by density altitude, wouldn't the human body also be affected? I assume it would affect combustion at the cellular level, or not?
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