I'm assuming that drafting isn't as benneficial for indoor, but is there still some bennefeit, or is there really no point? Anyone know the science behind it that can elaborate?
I'm assuming that drafting isn't as benneficial for indoor, but is there still some bennefeit, or is there really no point? Anyone know the science behind it that can elaborate?
Even still air has a drag value. I'm reasonably sure that drafting in such conditions is 8% easier so, there is a benefit to drafting, even inside.
-The Killer
Even when indoors the air is moving relative you. It's no different than running outdoors on a calm day. Now if you were trying to draft off someone on a treadmill, that's a different story.
Based on my back of the envelope calculation, I'd say it's about a 1% effect:
F_drag=1/2*d*v^2*A*c
d = density of air ~1.2 kg/m^3
v = velocity (say 4min/mile pace = 6.7 m/s, or 5min/mile=5.4m/s)
A = frontal area ~ 0.3m*1.8m
c = drag coefficient ~1 for a human body (conveniently)
x = distance (below)
F_drag(4min/mile) = 1/2* 1.2 * 6.7^2 * .3*1.8 *1 = 14.5 N
F_drag(5min/mile) = 9.3 N
Now, what's the energy involved in running a mile, and how does the energy dissipated by drag compare to this?
Generally, we say it's approx. 100 kcal/mile (though racing is probably a bit more) = 418400 J
Work done against drag over a mile: W_drag = F*x
So, W_drag(4min/mile) = 14.5 N * 1609.344m = 23400 J
and W_drag(5min/mile) = 15000 J
Or, fractionally, W_drag/Energy ~ 3.5 to 5.6 percent of energy is dissipated by drag.
Now, from what I understand, a "streamlined" cyclist can get a 30% benefit from drafting at 20mph. However, much more of a cyclist's energy goes into overcoming drag (thanks to F_drag ~ v^2), so suppose a all of a cyclist's energy goes into overcoming drag. Then, if ~5% of a runner's energy goes into overcoming drag, and if drafting were independent of speed (it's not, as the turbulence behind the lead object will depend on speed), 30% of 5% is 1.5%, so drafting would give you an energy gain of ~1%. Or, over a 4min mile, that's the equivalent of having an additional 17 watts of power (.01*418400J/240s).
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