PRODUCT REVIEWS: WHAT'S UP WITH WATTAGE
July 4, 2012


Let’s face it, for even the most devout tech geeks among us, discussing the topic of how to go about riding with power meter and watts can be confusing. Mention the word “watt” to your non-cycling friends, and their first thought is bound to be about the electricity bill. For cyclists, however, no discussion of serious, performance-oriented cycling can take place without broaching the topic. In fact, if you could get the pro peloton to agree to one thing about their training regimens, it would be how training technology with power meters has been the single most important advancement of late. When power meters first found their way out of the lab and onto the road in the late 1980s, they were only available to the stars of the sport, such as rider Greg LeMond who helped pioneer their use in races.

Today, the market is flush with many different types of power meters, allowing professionals and amateurs alike to access the benefits power meters can offer in refining their cycling experience. Unfortunately, a lot of people who purchase power meters don’t understand how to use them correctly, and they end up becoming nothing more than expensive speedometers. A ProTour rider once told us, “I use my power meter every day, but I never actually download the information from it!” Even at the top level of the sport, some riders are barely scratching the surface of what a power meter can do.


Frank Schleck's climbing ability is due to his extraordinarily high power to weight ratio; and while Cancellara's ratio is not as high, his overall power is much higher, making him a master of flat and undulating terrain.

SO WHAT IS A WATT?
A watt is simply a measurement of power, just as miles per hour is a measurement for speed. From a scientist’s point of view, power is how fast a cyclist produces work, and work is simply the force the legs can generate pushing the pedals, multiplied by the distance. The more work per time, the more powerful the force applied to accomplish that work, thus resulting in higher watts. The work, or energy, is measured in “joules,” which are more commonly known as “calories” in the U.S. One joule is equal to the amount of energy required to produce one watt for one second. Power meters measure in “kilojoules,” and one kj is equal to 4.184 Calories. How does all of that relate to cycling? Well, from a rider’s point of view, power  how well one can push the pedals. Allen Lim says, “Power is a measurement of intensity. Just like a thermometer inserted into a turkey that is cooking in your oven, the power meter can be used like a thermometer to measure the intensity of your riding experience.”

To measure wattage, a power meter measures two things: torque and cadence. To achieve a higher wattage, you must either increase your cadence in a given gear, or keep your cadence the same and shift to a higher gear; either one will have you putting out more watts, thus increasing speed. Simply shifting into a higher gear and slowing the cadence will increase your torque, but not necessarily your watts. Since everyone’s physiology and riding styles differ, there’s not a specific cadence that is the most efficient for everyone. Think back to the Jan Ulrich and Lance Armstrong Tour de France battles a decade ago. They each had their own distinct pedaling style; Ulrich would grind out around 70 rpm up the climb, while Armstrong would be dancing on the pedals at 20–30 rpm higher. They both put out a huge amount of power; it was just generated differently.

The first production power meter was introduced in 1988 by German Schoberer Rad Messtechnik, and was appropriately named SRM - it has forever changed the way cyclists train.
POWER AND WEIGHT
To better understand power hierarchy, a rider’s ability is measured in watts per kilograms (1 kilogram equals 2.2 pounds). Climbers such as Alberto Contador churn out many watts per kilogram, and very efficiently. The less bodyweight, the faster a rider will go—at a given power. Contador climbs with much less power than Mark Cavendish produces in a sprint, but Contador sustains those watts for longer distances, while Cavendish does it for just over 400 meters. As a rule, bigger riders can usually produce higher watts than smaller riders. But the benefit of having more power, which is best evidenced on the flats, tends to disappear as the road goes up. When it comes to the climbs, the biggest equalizer among all riders is their power to- weight ratio. Wind resistance aside, if a 150-pound cyclist rides uphill at 300 watts, a 180-pound rider would have to ride at 360 watts just to maintain the same speed; that’s a 20 percent increase in wattage. How much power a cyclist can produce is directly related to the amount of oxygen that can be supplied to the muscles.

 In turn, this supply of oxygen is  by the amount of blood the heart pumps with each beat, as well as how well the muscle cells are able to extract the oxygen. Taller riders, like George Hincapie, may have a natural advantage in sports like cycling; this is because they can “lay down” more watts over flat roads than lighter riders. Their advantages, such as better torque angle, more muscle mass, larger hearts that pump more oxygenated blood to muscles, more mitochondria to produce the energy to drive the muscles, all lead to the production of more watts. However, when the road goes up, there is a point when a larger rider must produce additional watts solely to overcome the effects of gravity. Nothing is absolute, and there are always exceptions, but most cyclists follow this pattern.

THE LIE-DETECTOR TEST

Training with a power meter is one of the most precise methods of measuring your exact workload. To put it simply, watts don’t lie. Power meters provide an objective measurement of actual energy output. Power output (unlike heart rate) is not affected by outside influences like heat, altitude, hydration, recovery, stimulants and temperature. Dirk Friel, co-founder of Training Peaks and coach of numerous ProTour riders says, “Training by heart rate alone can be ambiguous. It’s hard to know what your true progress is.” A heart rate monitor does not show if a rider is under-performing, whereas a power meter will. For example, a rider training by heart rate alone could be under-performing if one of the aforementioned outside influences affected their heart rate zones. Looking at the wattage numbers during a workout is only a small part of the overall advantages; it’s the post-ride analysis that shows the entire picture. “Collecting ride data over time paints a picture of a cyclist’s training.

When looking back over six months, you can spot your best power values and trace back to the training you did leading up to it. Spotting trends in training and performance is easy with the analysis software available, and you don’t need to be a coach to make sense of it,” says Friel. Once training zones have been set based off your power-meter data, you can more precisely track changes in fitness, especially when coupled with your heart rate. Watching your power and heart rate together produces a clearer picture of the work being done and your body’s response to it.


It can be beneficial to race with a power meter since often times that's when you'll record your best numbers. It can also help you pace your efforts in a break away or time trial.

FINDING YOUR FTP (FUNCTIONAL THRESHOLD POWER)
If you’re new to using a power meter, the first step to getting its full benefits requires doing a field test to calculate your Functional Threshold Power (FTP) to keep it from just becoming an expensive speedometer. FTP is the maximum power you can sustain for a 60-minute effort. To find your FTP, perform a 20-minute time trial (at full effort) on a trainer or outside on a stretch of road you know very well. And by “full effort,” we mean that you should not have anything left at the end. Take your average power from the 20-minute test and subtract 5 percent from it; this compensates for the power drop you would experience during a full 60-minute effort. This number is your FTP. For example, if you averaged 280 watts for 20 minutes, your FTP would be 266 after subtracting 5 percent.

If you’re really motivated, do a 60-minute time trial, and your average power for the test would be your FTP. Now you can calculate training zones based off percentages of your own FTP. It’s a good idea to retest every month or two; this keeps your training zones in line with your current level of fitness. Dirk Friel says that often your best FTP measurements are going to be from race data, because you produce numbers in a race that you do not typically produce while training. To figure out your watts per kilogram for a 20- minute maximal effort, take your FTP and divide by your weight in kilograms (1 kilogram equals 2.2 pounds).

POWER-TO-WEIGHT RATIO: HOW DO YOU STACK UP
How many watts per kilogram does it take to win a race such as the Amgen Tour of California? Chris Horner’s ride up Sierra Road on Stage 4 ended up being the defining moment in the race for the overall title. The 3.75-mile, 9-percentaverage gradient climb took Horner about 16 minutes, 45 seconds; he averaged approximately 425 watts, putting him at about 6.5 watt/kg on the fourth day of the race. To put this into perspective, on the same climb, a top Cat 3 road racer, or one of the strong men of the Saturday group ride, would be in the 4-watt/kg ballpark. The 2.5-watt/kg difference between them would have “Johnny Cat 3” losing more than one minute every mile to Horner over the 3.75-mile ascent.

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