Does the wind have more of an impact on smaller runners or on larger runners?

Just way above your level. Go back to your diets.

Just watch a cycling race (yes I know cycling is not the same thing as running). Headwinds and crosswinds negatively affect the smaller riders more so than the larger riders. Every year in the Tour one of the GC favorites (who are often small, climber types) loses like 5 minutes on a stage with wicked crosswinds. With a tailwind I'm not sure if a larger rider gets more of a boost than a smaller rider. I would surmise it ends up being a wash.

distracted wrote:

In the first order the mass of a runner is proportional to the square of his height (i.e. constant BMI).

Not all runners have the same BMI.

distracted wrote:

Assuming that a runner's width is proportional to his height,

Doesn't that fly in the face of guidelines from the W.H.O. that recommend a maximum healthy waist circumference regardless of height?

Even if that's not the case, how can you be sure that it is proportional to height, and not height to some exponent other than 1?

Excellent discussion here, folks.

size doesn't matter... wrote:

Size makes very little difference. The runner with the more "Horsepower" would be less effected. I'd say the runner with the higher strength/weight ratio would be less effected and would be able to stay more efficient.

Interesting thought. Why not just "horsepower" (i.e. strength), rather than one's strength/weight ratio? I am a little guy (5'6" 126 or so), and, if the weight aspect is factored in, I probably have some decent strength for my weight (though nothing outstanding). Yet, I get pretty beat up by a strong wind (anything over about 10 mph...that seems to be the "dividing line")..

Correct. And Kebede probably has a different body shape than Tergat, whatever their BMIs. But as I said, that's a first approximation. However, that doesn't say anything about what you get if you assume runners scale differently than according a constant BMI. For example, if you scale an airplane geometrically, the bigger it gets, the worse it will fly. Its mass increases more than the lift. (Lift= impact of different air speeds ("wind").) So a big airplane is less impacted by the air than a small airplane relative to their masses.

You would need a proper dimensional analysis to get a better estimate of what's going on.

I'm not sure. But it's a reasonable first approximation. If it's less than 1 it's impacting the lighter runner even more. A constant width as you hint to would give an exponent of 0 but that's unlikely.

I'm more interested in the validity of my assumption that the force a runner generates is proportional to his mass.

Anyway, only big salmons can swim up the river.

Another factor is the wind gradient. The wind is slower near the ground than 7 feet up.

I'm over 190 lbs now and running in the wind is harder than ever!

Definitely the smaller runner has an advantage. They just tuck behind the larger runner and let them break the wind. When it is their turn to lead, they provide little relief to the larger runner.

The smaller runner suffers in headwinds more, but gets more benefit from tailwinds. It's that simple.

It often amazes me how many middle distance track runners run in the lead or on the leader's shoulder regardless of conditions. As soon as there's any decent wind, tuck in behind someone, ideally someone who's bigger than you. Basic tactical stuff. A middle distance coach I know used to say "I want you so far up his backside that all I can see is your feet".

As everybody knows, Americans say garbage while the British say rubbish (and whilst). So you are probably a njathleticscoach.

distracted wrote:

In the first order the mass of a runner is proportional to the square of his height (i.e. constant BMI). The force exerted by the runner is roughly proportional to his mass. Combining these two assumptions we get that the force exerted by a runner is approximately proportional to his height^2.

Therein lies the rubbish so hold your breath whilst I explain.

The mass is proportional to the volume. Volume grows with ^3 of size. BMI is a simplification by neglecting that.

distracted wrote:

ukathleticscoach wrote:

Garbage

Just way above your level. Go back to your diets.

Well you failed to answer one question on diet and failed to answer the 2nd correctly.

This is just pure nonsense as are the rest of your made up figures: 'the force exerted by the runner grows with his height^2 '

If you are correct though I imagine they will start building F1 cars 3 metres tall

I don't think McLaren will be employing you as their wind tunnel technician

dont be a windbreaker..... wrote:

Definitely the smaller runner has an advantage. They just tuck behind the larger runner and let them break the wind. When it is their turn to lead, they provide little relief to the larger runner.

Sorry, but I meant my question in terms of running solo.

Alright I ran the numbers, using a 6ft and 5.5ft tall male, drag coefficient of ~1, 20mph headwind, with the runners running at 12mph (5 min/mile)

6ft: 92.7 lbf, 46W of power needed

5.5ft: 85 lbf, 42W of power needed

For the 5.5ft tall runner to experience the same drag force as the 6ft tall runner, he would need to run ~0.35mph faster (0.52 ft/s). This essentially means that the 6ft tall runner is having to run ~0.35mph faster to keep up with the 5.5ft tall runner.

Just to maintain pace with the 5.5ft tall runner, the 6ft runner must produce approx. 4W more than the shorter runner.

I couldn't find a good power-weight ratio for runners, but if I go by cyclists, using a 19.4 BMI for both runners (6ft tall 143lb runner, 5.5ft tall 120lb runner), the taller runner has about a consistent 15% advantage over a 120W to 390W power spectrum.

So correcting the power output needed, it will be 39.1W for the tall runner vs 42W for the short runner.

A 10% advantage would bring them closer--- 41.4W for the tall runner vs 42W for the short runner.

They would be exactly equal if the tall runner only has an 8.7% power-weight advantage over the short runner.

I guess you can make your own conclusions based on how much of a power-weight advantage the taller runner will have.

Let me know if ya'll have any questions, I have the piece of paper in front of me with the work on it.

However... If wind was such a strong factor why did the guys run so fast at Boston'11 but the women not so much?

Easy.....Women are not as important as men.

outsiderunner wrote:

dont be a windbreaker..... wrote:

Definitely the smaller runner has an advantage. They just tuck behind the larger runner and let them break the wind. When it is their turn to lead, they provide little relief to the larger runner.

Sorry, but I meant my question in terms of running solo.

I really wasn't answering your question, I was trolling your thread.

A straight on headwind or tailwind you might can calculate on your cocktail napkin. But what about swirling and crosswinds? Body surface area, weight, direction of wind, and frontal area (of wind direction and direction of movement) are important factors. As are speedsuits, tights, or loose flapping shorts and singlets.

Hahaha good one, I thought you were serious for a second.