Wednesday, August 24, 2011

Bike-o-nomics: Why Lighter Bikes Don't Make You Faster

[I am on a bit of a Felix Salmon kick these days and here is another little gem he uncovered]

From the British Medical Journal an interesting little paper about one person's experience moving to a lighter bike for his 27 mile commute.  He found that it made him no faster.  The entire paper is summed up nicely by the abstract (which is of course the purpose of an abstract):

Objective To determine whether the author’s 20.9 lb (9.5 kg) carbon frame bicycle reduced commuting time compared with his 29.75 lb (13.5 kg) steel frame bicycle.

Design Randomised trial.

Setting Sheffield and Chesterfield, United Kingdom, between mid-January 2010 and mid-July 2010.

Participants One consultant in anaesthesia and intensive care.

Main outcome measure Total time to complete the 27 mile (43.5 kilometre) journey from Sheffield to Chesterfield Royal Hospital and back.

Results The total distance travelled on the steel frame bicycle during the study period was 809 miles (1302 km) and on the carbon frame bicycle was 711 miles (1144 km). The difference in the mean journey time between the steel and carbon bicycles was 00:00:32 (hr:min:sec; 95% CI –00:03:34 to 00:02:30; P=0.72).

Conclusions A lighter bicycle did not lead to a detectable difference in commuting time. Cyclists may find it more cost effective to reduce their own weight rather than to purchase a lighter bicycle.

Salmon wonders what is going on and proffers this theory:
So, what’s going on here? Groves has his own theories, mainly surrounding the idea that big factors, like the weight of the rider and the amount of drag, completely obliterate smaller factors like the weight of the bike and the resistance of the tires. But I think there might be something else going on, too. Here’s Joshua Foer on what he calls the “OK plateau”:

In the 1960s, the psychologists Paul Fitts and Michael Posner described the three stages of acquiring a new skill. During the first phase, known as the cognitive phase, we intellectualize the task and discover new strategies to accomplish it more proficiently. During the second, the associative phase, we concentrate less, making fewer major errors, and become more efficient. Finally we reach what Fitts and Posner called the autonomous phase, when we’re as good as we need to be at the task and we basically run on autopilot. Most of the time that’s a good thing. The less we have to focus on the repetitive tasks of everyday life, the more we can concentrate on the stuff that really matters. You can actually see this phase shift take place in f.M.R.I.’s of subjects as they learn new tasks: the parts of the brain involved in conscious reasoning become less active, and other parts of the brain take over. You could call it the O.K. plateau.

The skill of riding a bike fits perfectly into this scheme. It’s not easy to learn at first, but over time we get better at it, until we’re so good at it that we basically stop thinking about it, and stop trying to get any better than we are. I’m sure that a doctor like Groves has much better things to think about on his commute than his bicycling technique.

As for me I wonder about the folks I see around on weekends in Portland riding super lightweight road bikes. If the objective is to get a good workout, surely you are better off riding an old heavy one speed bike? Ditto commuting. I suppose making it easier promotes commuting, but I have a friend who will go from his downtown office to his Sellwood home via Terwilliger just to get the extra workout. Of course he rides a lightweight road bike. Why not just get an old three speed bike and go home via the much easier Springwater Trail route?


The Oriole Way said...

I found this fascinating. I wonder if traffic conditions (stoplights, cars, other cyclists, etc) overwhelmed any gains from the lighter bike and essentially forced him to ride at a "safe" speed that was below potential for each bike?

Mark Parascandola said...

I remember seeing the original article a while back. This is an interesting test, but I wouldn't have expected to see a difference here. Bike weight makes a difference when you have dozens of skinny and superfit cyclists racing eachother seperated by seconds. For the average commuter, fitness, body weight and skill will be far more important. And, as you suggest, one might actually gain more fitness riding a heavier bike.

Jeff Alworth said...

"Why not just get an old three speed bike and go home via the much easier Springwater Trail route?"

Because then those young punks on their fixies blow past you and you grind your teeth in cold fury. Or because going faster is more fun. Or because a carbon frame ultralight is like a sports car: it just seems cool and gadgety. But I put my money on the punk on the fixie.