# The penalty of extra weight & cold conditions

siamon
Posts:

**274**
There is a way of working out how much extra flab costs you in terms of performance for runners. It works out to about 2 seconds per lb. I thought this was a load of codswallop until I piled on the wobbly stuff like a baby whale over Xmas and the extra 10lbs I managed to stack on costs me 25 seconds per mile .

Does anybody know if there is a similar formula for cycling?

Secondly, what about winter? How much does the cold thick air cost you in terms of average speed on one of your regular rides? I'm hoping it's about <2mph.

Does anybody know if there is a similar formula for cycling?

Secondly, what about winter? How much does the cold thick air cost you in terms of average speed on one of your regular rides? I'm hoping it's about <2mph.

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## Posts

4,161At same barometric pressure and altitude, difference between 0C and 20C will be ~ 0.5mph on flat windless terrain at 200 watts. However in cold weather you are typically riding with more clothing and the impact on aerodynamics could be quite substantial, maybe 1-1.5mph less speed.

Add the extra mud around the middle and well there you go.

3,908274Leicester - glad it's not just me!

4,161simpleformula.The reason for that is the speed-power relationship in steady state cycling is much more a function of aerodynamics (cubic) and gradient (linear), making the overall equation a cubic one. Then throw in accelerations and descents and it's not quite as simple. All you need is a road with variable gradient and you can see why it's not simple.

In running the speeds are much lower and aero has a much reduced impact, meaning body mass has a proportionally higher influence on speed.

So if cycling on the flat, then the impact of mass change (ceteris paribus) on speed is minor (a bit less speed due to slightly increased rolling resistance and slightly worse aerodynamics cause you are fatter), but if you are on a steep uphill then the impact is almost inversely linear with the increase in mass. The equation is here:

http://i220.photobucket.com/albums/dd22 ... ling-3.png

However that's just the physical. Extra flab usually means there is also a physiological impact (lower fitness/power).

631I have since bought a windproof jacket (very good fit so probably as good if not better aero than my fleece jerseys I had been wearing) and my torso is noticably warmer/not chilled after a long ride in cold conditions. Although I haven't tested my top speed just yet my average speed appears to have improved. Now it's perhaps a little early to compare but it appears that by keeping my torso warmer my average speed is better .. I was just wondering if all of this is b*llocks with way to many variables to prove anything either way or whether people had noticed an efficiency vs core temperature corelation themselves?

I will give the top speed on descent a go and try out and see what happens .. if that has improved then perhaps it's was just the better aero of the jacket all along (like I said, it is a very good fit ).

Just wondering.

strava profile

4274Dax, where are the 50mph descents Gloucester way? From what Alex said and the link, if top speed is unaffected then your aero profile can't have changed much, if the jacket is a proper corset job and you can still get in the right position top end might increase a bit!!

631strava profile

2,0292741,696In terms of being overweight, I'd suggest that, besides the benefit of fat loss from muscles and organs, the sensation of

feelinglighter and healthier is of greater benefit than the drop in weight itself.An article on the effect of weight when climbing:

http://cyclinginfo.co.uk/blog/3945/cycl ... s-on-bike/

A commuting doc found the lighter bike didn't make his daily journey significantly quicker:

http://www.bikeradar.com/commuting/news ... tor-28693/

I've been commuting on lumpy country roads and found my Giant SCR on 25mm tyres (9.9kg) feels lighter and better than my old Kona rigid MTB with 26x1.5" slicks (13kg) but the time differences aren't as large as I had expected.

bemore.784Sorry, despite your linked articles, that's codswallop. Simple maths tells a different story. Say you push 200 watts at 100kg to achieve a certain time, that's a power to weight ratio of 2. Then you drop 10kg, you're now pushing 200/90 = 2.2 watts/kilo, purely from losing weight, i.e. a 10% increase in performance for no additional power output. And this ignores the fact that in dropping that 10 kilos you will have (probably) been training, therefore increased your maximum power, such that 200 watts is a lower percentage of your maximum power, i.e. easier to attain and maintain.

- eccolafilosofiadelpedale

1,723Power/Weight does not = performance.

The maths is not so simple, see Alex's post.

784- eccolafilosofiadelpedale

4,161speedon flat terrain as power to aerodynamic drag (W/m^2), but W/kg is still an excellent overall indicator of performance (better than most).It isn't however as good a predictor of performance as performance itself.

1,696I was suggesting a less mathematical angle on improvement in riding speed uphill. As mclarent rubbished my suggestion (which is all it was) without providing any proof why then I take it he may be just another 'internet expert'.

I propose that one should

notunderestimate the power of the brain in this context.bemore.4,161http://www.bikeradar.com/fitness/articl ... ting-19175

Wind conditions can still be a factor though on hillclimbs, as shown in this item:

http://alex-cycle.blogspot.com.au/2011/ ... rtals.html

784Glad you posted that, give me an excuse to post this.

Never underestimate the power of science.

- eccolafilosofiadelpedale

784Damn, you beat me to it! Fair do's though, it is your blog!

- eccolafilosofiadelpedale

4,161Hmm, pic isn't sizing well, so here's a link to view:

http://i220.photobucket.com/albums/dd22 ... orce-2.jpg

As the road gets steeper, so gravity dominates the equation, and that part of the power-speed equation is linear. 10% faster on a steep climb = 10% higher power to weight (nearly).

784Alex - given that that graph is calculated based on a bike+rider of 75kg, is it fair to say that gravity would play an even bigger proportional effect for heavier riders?

- eccolafilosofiadelpedale

1,696bemore.784True, which is why there are Sports Psychologists. But even they follow the scientific method.

- eccolafilosofiadelpedale

950Of course most of this is irrelevant in this country as climbs are short.

4,161It's the general trend from the dominance of air resistance on flatter terrain to gravity on ascents that I was showing - the chart will have the same overall shape for everyone, but the precise breakdown at various gradients will be different for each individual (depending on their aero and mass properties).

Of course on descents, there is a return of energy from gravity which assists heavier riders more.

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