Friday, September 5, 2014

How to Interpret Power Data and What to Do With It


Peaks Coaching Group How to Interpret Power Data

“I just bought a $2,000 power meter, and I'm faster.”

Are you?

One of the single most important purchases for any cyclist who wants to be faster is a power meter. Just as important, however, is knowing how to use it. A power meter can't do you any good if you don’t know how to interpret the information.

Power meters have been around since the early 1980s. SRM was the first on the market with its crank-based unit utilizing strain gauges within the spider of the drive side crank arm. This technology hasn't changed much in twenty years, although today’s products are more reliable, lighter, and wireless. The use of ANT+ wireless protocol is an advancement that allows users to mix and match computers and power meters. There are now more than seven direct force power meter manufacturers worldwide.

It is important to note that when we talk about direct force power meters, we mean a device with a direct force measurement. Many computer and even cell phone manufacturers offer wattage data calculated with a very complex algorithm to create a pretty close approximation of a rider’s wattage. While that might work for some folks, it probably won’t be enough for serious racing cyclists and coaches. iBike uses an  “opposing forces” algorithm and an accelerometer to gather data, and iBike power meters do produce pretty accurate numbers, along with an iPhone app for those Apple fans out there.

So what now? You spent big bucks on this device, and it spits out all this data, but how do you interpret it? This is where you separate yourself from everyone else by gleaning the knowledge of how to use your power meter.

It's not a quick and easy task. We strongly recommend that you purchase Hunter's book, Training and Racing with a Power Meter, 2nd Edition. In that book we go deep into explaining how a power meter works, along with giving you the simple steps to training with a power meter to guide you along the way. We explain how to find your training levels, your functional threshold power, and your strengths and weaknesses, as well as how to place a mathematical formula to create your peak form.

In case you don’t yet have the book, let’s take an overview look at some of the topics covered in it.

Winning at cycling has a lot to do with your power-to-weight ratio, or watts per kilogram. It's a pretty simple formula. In simple terms, power equals the amount of work divided by time, and on a bicycle this means how hard you pedal multiplied by how fast you pedal. Training with watts (or power) really is measuring how much work you produce. You propel your body (and bike) down the road battling all sorts of counter forces, the biggest of which is you—your mass. Simply put, if you decrease your mass and increase your wattage, you will go faster. This is the objective in all sports around the world. If the bat swings faster (with more power), the ball goes farther. A lighter race car means the car can accelerate quicker. A lighter bike can mean a rider moves faster uphill. These are all examples of the watts-to-kilogram principal.

So what can we produce and for how long? That truly is the biggest question we all constantly try to answer. It's best to break this down to identify intensity levels before reaching for some far-out wattage numbers. If a rider could produce 600 watts for an hour, he'd be a TT world champ! We can assure you that 600 watts for a whole hour isn't possible. Why? Because the human body doesn't operate that way. We just aren’t strong enough and don’t have the cardiovascular capacity, as there are too many internal stressors happening to allow that kind of work load.

There is a sustainable output that applies to each individual athlete, and we call this functional threshold power (FTP). FTP is the amount of wattage a rider can produce for one hour without fatigue. This is the simplest way to look at and gauge someone's ability.

FTP is relevant to nearly all cyclists. Where it is less important is within the very short sprint disciplines, perhaps on the track, or in BMX where events are 200-1200m. A high FTP number here won't do much for such a short effort. But for the vast majority, knowing your FTP is important. Click here to find out how to calculate your own FTP. Once you know your FTP, you can begin to build your training levels around that number.

But let’s back up a little. Three hundred watts could be good, or it could be bad. It depends on who’s doing the work and what that rider weighs. If Tony Martin (the 2011 and 2012 time trial world champion) produced 300 watts for 1 hour at his weight (let’s say he weighs 82 kilograms or 180pounds), he would only be producing 3.6-3.7 watts per kilogram (300 watts/82 kilograms=3.65 watts to kilogram). Is this good? No, not at Tony’s level. 3.6 watts per kilogram is, for males, about on par with a strong Cat 3 road racer of the same weight. So as you can see, focusing just on the wattage numbers isn't the entire story.

So now you know your FTP. You know what your longer duration abilities are. But is FTP important for the rider who races mostly criteriums and cyclocross races and hardly ever competes in time trials or longer road races? Absolutely. Your FTP is the starting point of your training. Knowing your FTP gives you a focus so you can plan your future training.

Have you ever gone out and just hammered as hard as you can go for as long as you can take the pain and had to slow down after just one minutes because you couldn’t maintain the power? This illustrates the relationship between strain and intensity within your abilities. The harder you go (strain), the shorter you can maintain that effort. There are gigabytes of data on the subject, most of which are covered in the book we mentioned above, but the bottom line is that the more intense the effort, the less time you can hold it. Conversely, the less intense the effort, the longer you can maintain it.

This is where your FTP comes into the picture. We call FTP 100%. Below FTP is sustainable for longer and longer periods of time as the intensity decreases away from FTP. 120% of FTP is hard, but it's maintainable for a shorter time.

Now that you know what your 100% is and that you can feasibly sustain this for one hour, how much harder can you go and for how long? The following power training levels (developed by Dr. Andrew Coggan) and time durations should help answer that question.
  • Level 1: 55% of FTP. Sustainable for most humans' entire lifetime of 65-85 years. You could ride almost around the globe at this pace until you die. This is often referred to as recovery level.
  • Level 2: 56-75% of FTP. Sustainable for 2.5 hours to 14 days. This is an easy pace, slightly above recovery but still working. This is often referred to as endurance level.
  • Level 3: 76-90% of FTP. Sustainable for 30 minutes to 8 hours. We call this tempo, or your sweet spot. This is where most of us live, whether in a road race, mountain bike race, or even criterium. It's sustainable, but not forever.
  • Level 4: 91-105% of FTP. Sustainable for 10-60 minutes. This is your FTP output. Many call it threshold, LT, or AT. Whatever you call it, this is and should be your mark of ability.
  • Level 5: 106-120% of FTP. Sustainable for 3-8 minutes. At this level, you’re tapping into your body’s VO2Max (the maximum amount of oxygen you can take in). There is oxygen usage, but it's limited.
  • Level 6: 121-150% of FTP. Sustainable for 30 seconds to 2 minutes. You are now exceeding your FTP and VOMax and entering what's termed your anaerobic capacity. This is when you produce energy without oxygen, and it’s very brief.
  • Level 7: 150+% of FTP. Sustainable for 5-15 seconds. This last level is your neuromuscular power. This is what your muscle can produce maximally—your max sprint.
These power levels represent a rider’s real-world capabilities. Can you push beyond each time range? Maybe; each athlete is gifted in his or her own right. Even if you surpass these durations, however, remember that as you cross these lines one system will blend into the next. It's not as if once you leave 100% of FTP and step into your VO max system that your FTP system immediately shuts off. All these systems work synergistically, one assisting the other. A higher FTP output will bring your Level 3 tempo output up, a higher VO2Max will increase your FTP, and so on.

So which level should you train in? The answer is simple: Train to the demands of your event. If you’re an ultra-distance marathon mountain biker, should you be spending three hours a week working on your Level 6 sprinting? Probably not. Your best bet is to work at raising your FTP and the subsequent Level 5 VO2Max and Level 3 sweet spot abilities. Growth of your FTP will trickle into both, and if your event demands long hours, you’ll have to put in long hours at the correct pace, simulating race pace.

If you train for a longer marathon race in Levels 1 and 2, will that get you the preparation you need? Yes and no. If you dose yourself with many hours in Levels 1 and 2 (recovery and endurance), you’ll adapt to those paces; you will teach your body to ride long hours at a slow pace. You won't have much ability beyond that. Can you benefit from it? Sure, your endurance will be there, but your speed will be low because your body is responding to the stimulus of Level 2.

It’s pretty simple. You are what you train for, much like the age-old saying that you are what you eat. In order to be faster, you have to train faster and smarter.

One of the many benefits to using a power meter is racing with a power meter. The information collected is invaluable. When you can look at the demands of an event and adjust your training to be specific, you will make huge gains. Again, keep in mind the specificity to the individual. Just because you see a race file from a buddy that shows X wattage average over a certain time, it doesn't mean you need to produce that to beat him. One wattage number can't be equated to everyone, as the power-to-weight ratio also plays a huge role.

The next step you must take is to calculate your watts per kilogram across the power training levels to create your own power profile. The power profile is a tool that Dr. Coggan and Hunter Allen developed in the TrainingPeaks’ WKO+ software. Creating a power profile is like giving yourself a pop quiz across all subjects. Which is your stronger subject, math or science? Literature or gym? Are you strong at the longer efforts or at the shorter efforts? Once you create a power profile you can come back to it often to compare gains or losses to better understand how you’re improving within each specific strength and weakness. Our coaches use the power profile all the time to keep an eye on our athletes’ progress. How else would you know? Regular testing of each system is key to a well-designed training plan. Training is testing, and testing is training. It all adds up, and the data you collect becomes your tool for training smarter, harder, and with a purpose.

Let’s take this just one more step. Let’s say you are a crit racer with a mean sprint and can crack out 1400 watts for 5-10 seconds at the drop of a hat. 1400 watts is pretty good for just about anyone! It's easy to say that, because even for some of the heaviest riders (82-90kg) the watts-per-kilogram conversion still applies. If this sprinter weighed 71 kilograms, he'd be on par with a professional rider. (Remember, this is all relative to the individual.) But can this sprinter do 1400 watts once or 30 times? If he does 30 sprints, we would have to assume that fatigue would catch up with him, right? Correct.

Let’s say this same sprinter has this incredible 1400-watt burst but never won races. How can that be? He's the fastest, right? Well, to win you have to be there to sprint, and to get there requires a high FTP and a strong Vo2max and anaerobic capacity to put yourself in the right place at the right time to deliver your blow. If all a sprinter did was sprint training and never trained at FTP or near FTP, we would never know his name. He'd never be present at the end of a race because he'd be dropped well before. Training for specifics is always the focus, but the other levels can't be ignored. Any experienced crit racer or sprinter knows that getting to the finish requires a series of well-orchestrated sprints. A rider has to continually accelerate to stay in position. These naturally can't be done at 1400 watts each time, which leads us to our final point—fatigue resistance.

We won't go too deep into this one, but fatigue resistance is just as important, if not more important, than the wattage itself. If our sprinter above can crank out 1400 watts once, he'll need an armchair ride to get to the line, because that's all he's got. He never trains his lower levels and can't sustain anything longer than one or two hard, short efforts.

Enter Sprinter B. Our new B sprinter has a max of only 1100 watts. He weighs about the same as our rock star does, so the watts-to-kilogram ratio favors Sprinter A. What Sprinter B can do, however, is produce 1100 watts over and over again and maintain 1000 watts for 350 meters. Who would you bank on to win? Sprinter B? Me, too.

Fatigue resistance measures the decline rate of one's effort. If you monitor your sprints in training or racing, you can learn quickly whether you have good or bad fatigue resistance by using our fatigue profiling tool on our website.  An athlete can have an incredible peak but an equally incredible drop off as we stretch out the time duration. World class track sprinters, for example, are just that—sprint only. They can jump at amazing numbers, but only for 200 meters. That’s it. If you asked one of them to do that at the end of a four-hour road race, the chances are high that our 90kg Cat 3 would clean his clock. Those specialists are so special that putting them in the road world really doesn't apply, which takes us back to ground zero, our FTP.

Other examples of why fatigue resistance is important can be found in road race or crit efforts. If you can bust out big numbers over and over for five minutes at a time but lack a killer blow in the sprint, it would behoove you to wait for the final field sprint. You are better to attack a little ways out, trying your luck solo or in a small group nearer the finish. The fact that you know where you stand makes the use of your power meter that much more important. Have you ever heard someone complaint, "I am strong throughout the race, but I can never seem to win”? This rider could be telling the truth. He probably has a stellar 30-minute strong effort in him and can keep 350 watts humming along, but once the speed increases and the accelerations come, he's off the back. Why? Because his weaknesses are exposed. To combat this you have to change your tactics and your training. This rider needs to work for separation, distancing himself from the fast guys well before the line. Again, he knows what he can and can't do because his power meter proves it.

One last point and a few caveats. Power meters are not going to make you faster per se. Great athletes always push beyond what they are supposed to be able to do. That's what greatness is—the ability to rise to a higher level. Pain management is still, and always will be, the name of the game. If you can handle it, you will likely excel. A power meter now gives you a number to associate with that pain.

Please don't use a power meter to limit yourself. Some riders become slaves to the number, and their power meters become their worst enemy, regularly telling them they’re slow, tired, or just flat. There will be days like that. We make sure our athletes learn to feel out the efforts internally as well as using their power meter. The use of a power meter and all its sophistication can still create problems for some. Use the data both objectively and subjectively. The subjective approach can sometimes net you more than you think!

So go for it. Test yourself! Your power meter will have answers at the end of the day, so study your data and ask questions. Put some goals out in front of you and make sure to test yourself with some power goals. If you score well in the 5-minute effort, attempt to bring your 20-minute numbers up. If you strive to be a better, more balanced rider, you need to spread the energy around. If you’re a track racer, then buckle down and place yourself within the specifics of your events. Good things will happen!

by Hunter Allen and Russell Stevenson

Photo: PCG Director of Engineering Kevin Williams


Hunter Allen is a USA Cycling Level 1 coach and former professional cyclist. He is the coauthor of Training and Racing with a Power Meter and Cutting-Edge Cycling, co-developer of TrainingPeaks’ WKO software, and CEO and founder of Peaks Coaching Group. He and his coaches create custom training plans for all levels of athletes. Hunter can be contacted directly through PeaksCoachingGroup.com

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