body weight & bike performance correlation (Page 3)

Math is wonderful. Here's what going downhill means for someone 5'10 @200 watts on a triathlon bike (CdA is calculated for you, I used all other defaults):

150lbs, 0% incline = 22.3 mph

170lbs,  0% incline = 21.9 mph

150lbs, 1% decline= 25.6 mph

170lbs, 1% decline = 25.4 mph

150lbs, 2% decline = 28.7 mph

170lbs, 2% decline = 28.9 mph

150lbs, 4% decline = 34.8 mph

170lbs, 4% decline = 35.3 mph

So the speed advantage for the heavier rider is only apparent on anything >1% decline. But here is the real take-home, as Shane points out. On a 2% grade hill (assuming incline and decline are the same) the lighter rider only needs to expend 5 more watts to match the heavier rider on the downhill, but it takes 16 more watts for the heavier rider to go uphill. At 4% the lighter rider needs to expend 25 more watts to match the heavier rider on the downhill, but it takes 40 more watts for the heavier rider to go uphill. Either way the lighter rider expends less total wattage.

Light is right!

A short article by one of Lance's docs (although I'll probably be called into the USADA case as a witness just for reading this):

http://www.53x12.com/do/show?page=article&id=98

Yep, at higher speeds wind resistance becomes the bigger issue, which is why the heavier rider can't get the same gain from going downhill as opposed to uphill.

On a related note, it's best to take drinks/nutrition and sit up during uphills where it isn't as much a penalty... i know it's hard sometimes to do that on steeper uphills, but this is the best place to do it since the aero penalties are not as great at lower speeds.

I really feel that the biggest factor overall as it seems some people have stated is where you're losing the weight from. If you're not eating properly (recovering completely) from training and breaking down your muscles, you're going to be losing your muscle mass on top of any other excess weight you have. I've struggled with this myself, and it's really come down to eating properly if I want to make the gains, and lose the weight. I was around 210 when I started racing a couple years ago. I was more into lifting weights and running. 

I look at it this way, if you're fast you're fast. You have to put out the watts no matter what. Whether that be climbing or sprinting. But on top of that, you need to be aero (especially in a fast course). But even as you mention hilly courses like IMWI, you still need to be concerned with aero. Coming downhill, if you're cranking the uphills and crushing out some watts, and you're not aero, you will completely negate all the efforts of the uphill portion. I just saw this at the last race I did. Guys were killing the uphills, then when it came to the downs, they weren't worried about getting aero. While there's me in full tuck nearly hitting 50mph, smashing past them. 

I dunno, this is how I view it.

With all the years I have been riding and racing at my weight, I have found the following, and would be hard pressed to be convinced otherwise.

1.  Weight is more important on the climbs.  I was 20% faster on a flat IM course (at basicallly the same fitness) than a hilly course.  I didn't do the math, but I don't think then entire field was 20% faster (the field WAS faster, just not 20%).  My weight affected me (and other heavier riders LESS on the flat course).  Even while I'm racing, I can hold even or make up ground on smaller guys on the flats, but they kill me on the climbs.

2.  I'm faster downhill due to weight.  I have been told it's hard to keep up with me even when I'm freewheeling and they are biking hard.  BUT, I don't think the advantage descending is equal to that going up.  I can't make up the gap I lose on the ascent on the descent.

When I'm looking to lose 20-30 lbs just to be a thin but reasonable weight, that could be a couple MPH over a rolling course, easy.  That could be an hour off my time in an IM.

I think you can be at a high level of cardiovascular fitness and carry extra weight. One of the guys in my tri club is an absolute beast, done Ironman for at least 12 years, and yet in his trisuit looks like he's in his third trimester. He made podium at the his last half this spring, and I have yet to podium, so there ya go

lots of talk about differences in absolute weight of triathlete's on the bike but the reality is that when you lose 10 pounds, you become a faster cyclist and runner because you've improved your v02max-which is one of the measures of exercise performance (really maximally extract oxygen but we're not going to go into that here)-usually described in ml of 02/kg of body weight/minute

therefore your race pace improves-on the bike and on the run; on the hills and in the flats

so all athlete's should try to find their optimal weight for optimal performance and for many of us lighter is better-depending on where the starting point is

(of course, I've seen some athlete's who are quite muscular and fit yet when they lost weight, they lost a lot of muscle along with fat so they did not gain as much as they thought they would in terms of speed/pace, but we are all 'experiments of one')

If you starve yourself to lose the weight and don't work out,do you think you'll get more fit? I think you'd get less fit, as you would be losing muscle as well as fat. Now if you're already working out and lose weight, yest, I think you'd be more fit, as defined by a muscle-to-fat ratio.