Thursday, April 19, 2007

Thoughts on weight, genetics

Someone recently asked my opinion about the importance of power-to-weight ratio. I've been thinking about that some lately and thought I'd throw in my two cents, which includes no great insight, just my rehash of the subject.

The power-to-weight ratio is most important in two situations: accelerating and climbing. To maintain a constant speed in a flat time trial, it makes little difference what you weigh, just how much air and rolling resistance you have and how much power you can maintain (losing weight might affect your frontal area a little, but not much).

The climbing aspect is obvious: The less energy you use to fight gravity the more you can put into getting to the finish line. As an example (put in your own numbers at this web site: let’s take the Georgia Cup Gainesville road race course (estimated numbers here). We did six laps around a course that had an average 9% climb that was about 0.7 mile long. I averaged about 285 watts for that climb over 6 laps and I weigh 148 lbs. It should have taken me 5 minutes 3 seconds to do the climb on each lap. If I gained 10 lbs and maintained the same power, I would finish the climb in 5 minutes 19 seconds, 16 seconds slower. It’s obvious that 16 seconds is more that enough time to get me dropped from the front group in a single lap. Five seconds might be enough to get dropped if the group accelerated at the top and I had nothing left. So in climbing, weight is very important. And the lighter you are, the more important it is to pay attention to bike weight becase it's a bigger percentage of your total climbing weight. If I weighed 200 lbs, a 2-lb reduction in bike weight would only save me a couple of seconds on that climb, but at 148 lbs, shaving 2 lbs off my bike weight would save me almost 4 seconds. So I get much more benefit from being a weight weenie than a heavier guy would.

The acceleration benefit of being lighter is less obvious except in criteriums. I'm a poor crit racer because I can’t accelerate. But my acceleration problems aren’t primarily due to weight, they are due to low neuromuscular (5 sec) power. I don’t think I could never lose enough weight to compensate for my limiters there, but I should probably race more crits to improve my acceleration ability.

But there is another area where acceleration is very important and I think most people don't consider it. Over the course of a race or a hard group ride, there are hundreds of short accelerations required to stay with a fast peloton or paceline. Those accelerations aren’t always intense, but a lighter rider wastes much less energy in the short accelerations required when riding in a group. Your legs will pay the price quickly if doing a hundred mini-intervals when the other guys in your group are riding with more constant effort or less taxing acceleration effort. So being able to ride smoothly is very important. When I pop in a pace line, it often happens all of a sudden because I get fatigued, I ride less smoothly, which causes me to need more accelerations to keep up, which speeds my fatigue. It can also annoy the other riders in the group. In a fast pace line the whole accelerate-fatigue thing can snowball very quickly. I still have lots of work to do there. One way to handle these types of short accelerations more easily is by riding at a higher cadence, which has helped me recently.

I was also asked my opinion about the role of genetics in the performance of pro and elite riders. I’m sure that their results are not just due to good genetics. Genetics plays a big role, but there are a lot of good training years in those guy’s and gal's backgrounds. I subscribe to this theory that I read once -- can't remember where:

If you could take 10 athletes of varying genetic ability and put an identical brain in each of them, they’d all be riding at about the same level in five years. If you take 10 athletes having the same genetic potential and put 10 different brains in them, you’ll have a very wide array of talents in five years. Genetics plays a big role -- I used to think it was most important variable, but I don’t think so anymore. It's important but not crucial.

The problem for us mortals with normal genetics is that there will always be Lances and Floyds out there that get the genetics and the brain. Nobody’s ever going to regularly beat them. And getting good quickly is much easier for those with genetic talent.