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QOTW: Which Matters More- Power, Weight, or Aerodynamics?

You may have heard long-time cyclists discuss their efforts to make their bike lighter and more aero, geeking out over saved grams of weight in expensive bike parts or the latest aero helmet or water bottle. But how do the three factors of weight, power output, and aerodynamics work together to dictate cycling performance? Which is the most important or which factor do you need to personally work on?

Weight
Weight does matter, but it’s the weight of the body and not the bike where most of us could stand to make the most gains and improve performance. Check out this chart of past champions and you’ll see that the range for these elite cyclists is actually pretty narrow.

Also, cycling performance isn’t just about maximizing the power you can put out, but maximizing your power to weight ratio. Power to weight is something we talk a lot about at Energy Lab, for the higher watts per kg you can achieve the faster you will ultimately go. More on this later in our example.

Aerodynamics
You’ve probably noticed by watching the tour that even amongst skinny cyclists, body type varies significantly. And the guys winning sprints are not usually contenders for the king of the mountain

For a triathlete riding flat courses or a time trial what matters more is watts/CDA instead of straight watts per kg. CDA is the drag coefficient (Cd= dimensionless) times size (frontal area= M2) Without getting too in depth, basically you need to consider your aerodynamic profile as an essential part of your speed.

Picking your course
There are several important factors that go into race results and reasons why we actually need to have a race versus just tabulate our relevant stats and name a winner. And depending on what your strength is, you can definitely pick a course that suits you.

Like we alluded to, heavier cyclists will be less penalized on a flat course, especially if they have a good position. Larger, heavier cyclists will also have an advantage in an indoor time trial, since Dragfactor on a computrainer is an approximation of your drag but treats all riders equally regardless of weight (unless you adjust it manually) Lightweights with a good power to weight ratio will be at an advantage on a hillier course, while a cyclist of any size and weight with a great position (and an ability to hold it) will be able to maximize their performance on any type of course.

Comparing the effect of weight and power
So which angle should you focus on for optimal performance-weight, power, or aerodynamic position?Ideally, you will be able to work from all angles for optimal performance. Let’s say your goal is to get your Functional Threshold Power from 3.0 to 3.5 watts per kg, a competitive amateur goal for local racing Cat 4 cyclist for men and a competitive cat 3 for women

Here is a simple example which illustrates the effect of weight loss.

Starting Point
Man: 175 lb = ~80 kg x 3.0 watts per kg = 240 watts at Threshold
Woman: 135= ~61 kg x 3.0 watts per kg = 183 watts at Threshold

Power Gains Needed to reach 3.5 watts per kg
Man: 175 lb= ~80 kg x 3.5 = 280 watts at Threshold
Woman 135- ~61 x 3.5= 215 watts at Threshold

In our example above, you can see that the male rider will have to increase his FTP by 40 watts to reach 3.5 watts per kg while the female rider must increase hers by a whopping 32 watts. Unless you’ve only been cycling for a short time, or are coming back from a long hiatus, those are some tough gains.

Now let’s take a look at the impact of training gains versus a 10 lb weight loss for each rider, assuming they can successfully keep the same power output.

Starting Point
Man: 175 lb = ~80 kg x 3.0 watts per kg = 240 watts at Threshold
Woman: 135= ~61 kg x 3.0 watts per kg = 183 watts at Threshold

Power Output Gains to reach 3.5 watts per kg
Man: 175 lb= ~80 kg x 3.5 = 280 watts at Threshold
Woman 135- ~61 x 3.5= 215 watts at Threshold

Method Two: 10 lb weight loss
Man: 165 lb= 75 kg x 3.5 = 262 watts at Threshold
Woman: 125 lb= 56.8 kg x 3.5 = 198.8 watts at Threshold

By losing only ten pounds, that decreases the gains needed by our male rider to 22 watts and our female rider to only 16 watts, less than half the increase needed if they both were ten pounds heavier.

Depending on your starting weight and what you can comfortably lose while keeping your power, a combo approach is the best bet. Notice that we did not try to calculate the effect of improved aerodynamics on the performance of our two riders. If you feel like your position may be lacking, we recommend seeking the counsel of our next door neighbors at Podium for an expert bike fitting.




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