Recently I went for a run on the track in the morning.
About 68 degrees, humidity reasonably low.
A steady state effort was worth about 7 minute pace.
(not really, I'm old and fat and my times suck but
I don't want to get flamed for being slow)
I went for another run in the evening.
A storm system had come through.
The temp was now 58 and the humidity was high,
though maybe humidity is the wrong word.
The air was still very damp.
Now that same steady state effort was worth about 7:20 pace.
I specifically was listening to the same music to try and
run at the same tempo. My turnover was spot on.
Also I noticed my lungs were burning much more than in the morning.
My theory is that water (even in gaseous form) is heavier than air
and it took more energy to push my body through the thicker air
of the evening as opposed to the thinner air of the morning.
Also that the thicker air took more effort to breath in and out and
tired out my lungs more.
And that 10 degrees cooler in the evening meant my muscle were
not as flexible as in the morning, meaning shorter strides.
Even 1/4 inch per step means an extra 7 strides
(15 meters equivalent) in an elite 1500.
Does this make sense?
So, if all of the above is correct, what is the perfect atmospheric
conditions for attempting a world record?
Is it different for a 1500m versus a 10000m?
Temp? Humidity?
While we're on the subject, has it been established that
high altitude hurts distance people, but helps jumpers,
throwers, and sprinters?