Do runners slipstream?

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blackpoolkev
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Do runners slipstream?

Postby blackpoolkev » Fri Aug 03, 2012 20:30 pm

Cyclists are well drilled on the advantages of using the slipstream of the rider in front.

With the Olympic athletics season upon us,it seems to me that runners don't seem bothered with the slipstream effect.If marathon runners used the same principles as cyclists,surely they would line up behind the runner in front.

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CiB
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Re: Do runners slipstream?

Postby CiB » Fri Aug 03, 2012 23:35 pm

They're not going fast enough for it to make a difference. It's about splitting air; at 12mph there's virtually no advantage in following someone unlike blatting along at 32mph behind the guy making all the effort has a big advantage, as we all know.

Power is either squared or cubed for each doubling of speed. Someone who's had fewer wine units will be along soon to confirm. :|

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team47b
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Re: Do runners slipstream?

Postby team47b » Sat Aug 04, 2012 06:55 am

you are correct, cubed.

If you double the wind speed the power is increased by 8 times.
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daviesee
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Re: Do runners slipstream?

Postby daviesee » Sat Aug 04, 2012 07:02 am

I always thought distance runners did it but may have been tactical, like a sprinter wanting to come from the back.
It may not save much energy at that speed but at the top level, any efficiencies can make all the difference I would have thought.
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jibberjim
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Re: Do runners slipstream?

Postby jibberjim » Sat Aug 04, 2012 07:11 am

They are going fast enough that there's a benefit - it's part of why pacemakers are required in a marathon, but the benefit is not very large and there's an associated cost of having to make micro changes of pace to stay behind the other athlete, but they do draft. When it's windy - which you won't really see on TV then drafting can become more significant.
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pb21
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Re: Do runners slipstream?

Postby pb21 » Sat Aug 04, 2012 08:42 am

Do runners get in breakaways?

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Monty Dog
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Re: Do runners slipstream?

Postby Monty Dog » Sat Aug 04, 2012 09:00 am

It can make a difference on the longer distance, road events - as someone who used to race marathons weighing 8.5 stone, I found it a distinct advantage to tuck-in behind a big guy when running into a headwind at 10mph.
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Rick Chasey
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Re: Do runners slipstream?

Postby Rick Chasey » Sat Aug 04, 2012 10:06 am

Course they do.

It's just a lot less significant.

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ILM Zero7
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Re: Do runners slipstream?

Postby ILM Zero7 » Sat Aug 04, 2012 13:49 pm

an an ex -runner with some international experience - on the road, yes they do slipstream, although the benefits are greater on the road than in a protected stadium. And much depends on temperature too, there is an energy saving, but it is negated by lack of cooling on hot days.
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Smokin Joe
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Re: Do runners slipstream?

Postby Smokin Joe » Sat Aug 04, 2012 13:55 pm

Being out of the wind isn't the only benefit of sitting behind someone. There is also the psychological edge of having the pace set for you and having the advantage of surprise when you break.

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TLW1
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Re: Do runners slipstream?

Postby TLW1 » Sat Aug 04, 2012 14:00 pm

plus the added motivation if its a female in front with a nice ar5e

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dw300
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Re: Do runners slipstream?

Postby dw300 » Sat Aug 04, 2012 18:20 pm

Don't forget that if you're in behind you can accidentally drag your spikes down the runner in front's achilles ..
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Smokin Joe
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Re: Do runners slipstream?

Postby Smokin Joe » Sat Aug 04, 2012 19:35 pm

matthew h wrote:plus the added motivation if its a female in front with a nice ar5e

And the "Concorde Effect".

When it was getting up to speed it's nose came up to give a more aerodynamic profile...

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daviesee
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Re: Do runners slipstream?

Postby daviesee » Sat Aug 04, 2012 20:17 pm

Smokin Joe wrote:
matthew h wrote:plus the added motivation if its a female in front with a nice ar5e

And the "Concorde Effect".

When it was getting up to speed it's nose came up to give a more aerodynamic profile...


I thought the nose went down to give the pilots visibility when climbing. :?:
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pipipi
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Re: Do runners slipstream?

Postby pipipi » Sat Aug 04, 2012 22:14 pm

So what speed does it start becoming significant at?

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Rick Chasey
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Re: Do runners slipstream?

Postby Rick Chasey » Sat Aug 04, 2012 22:25 pm

pipipi wrote:So what speed does it start becoming significant at?



Depends how long you're running for as much as speed.

I notice it on the bike at 20kph in a headwind.

airbag
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Re: Do runners slipstream?

Postby airbag » Mon Aug 06, 2012 08:11 am

Being really technical, the force required to balance drag is proportional to the square of the airspeed. The power required is the force multiplied by the groundspeed for a wheel-driven vehicle. In still air, air and ground speed are equal, so power is proportional to groundspeed cubed - in head or tailwinds, a little more complicated. To demonstrate this - try holding the bike still in, say, a 30mph headwind by e.g. using the brakes - you're not developing any power but you're balancing drag. To do 30mph in still air takes more effort, but the drag force is the same.


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