How to Interpret Power Data and
What to Do with It
"I just bought a $2K Power Meter, I'm faster". Are you?
By Russell Stevenson and Hunter Allen
One of the single most important purchases any cyclist can make, who claims that they are or wants to be faster, is a Power Meter and the knowledge of how to use it. A Power Meter alone won't do you any good if you can't interpret the information.
Power Meters have been around since the early 1980's. SRM was the first to market with its crank based unit utilizing strain gauges within the spider of the drive side crank arm. This technology hasn't really changed much in 20 years although todays’ 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 powermeters. There are now more than seven direct force power meter manufacturers worldwide.
Important: I should mention that when I say "Direct Force Power Meter", I am talking about a device with a direct force measurement. Many computer and even cell phone manufacturers are offering wattage data that is calculated using a very complex algorithm to create a pretty close approximation of a rider’s wattage and while that might work for some people, it probably won’t work for serious racing cyclists and coaches. iBike uses an 'Opposing Forces' algorithm along with an accelerometer to get their data and do produce a pretty accurate numbers and offer an iphone application for those of you that want to use your iphone.
So what now? You spent big bucks on this device and it spits out all this data... how do you interpret it? This is where you separate yourself from the others: the knowledge of how to use a power meter.
I'll start by saying; it's not a quick and easy task. I strongly recommend reading this book; Training and Racing with a Power Meter, 2nd edition - By Hunter Allen and Andy Coggan PhD. Hunter Allen and Dr. Coggan go deep into explaining how a power meter works, along with giving you the simple steps to training with a power meter that guide you along the way. They explain how to find your training levels, your functional threshold power, your strengths and weaknesses and place a mathematical formula to create your "Peak Form". It's very in-depth, so let’s dive into some of their topics.
Winning at cycling has a lot to do with your power to weight ratio or ‘watts per kilogram’. It's a pretty simple formula. Power equals the amount of work divided by time in simple terms and on a bicycle it’s how hard you pedal multiplied by how fast you pedal. So training with "Watts" or "Power" really is measuring how much work you are producing. You propel your body (and bike) down the road battling all these counter forces. The biggest counter force is you, your mass. Simply put, if you decrease your mass and increase your wattage you will go faster. This is the objective all throughout sports around the world. If the bat swings faster (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 all things being equal. These are all examples 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 say, 600w for 1h, he'd be a TT world champ! I can tell you, 600w for 1H isn't really possible. Why, because the human body doesn't operate that way(we just aren’t strong enough nor have the cardiovascular capacity!) as there are too many internal stressors happening to allow that kind of work load as well. There is a sustainable output that applies to each individual athlete and we call this the FTP.
FTP stands for Functional Threshold Power. 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. To find out your FTP follow this simple calculation.
20min Time Trial average wattage X .95 = FTP.
The truth is, that FTP is really your 60 minute best wattage for a time trial. Unfortunately, a 60 minute time trial, for many of us isn't feasible. Using the 20 minute test and deducting 5% is much easier and is accurate within a few percentage points. If you do have a 60 minute Time Trial (from a race perhaps), that's even better.
Here's an example: 20 minute average is 300w. Less 5% = 285w FTP.
Once you have an FTP number you can begin to build your training levels around that number.
But let’s back up a little. 300w could be good, or it could be bad. This depends on who's doing the work and what they weigh. If Tony Martin (The current Time Trial World Champion) produced 300w for 1H, at his weight (I'm going to guess here and say he weighs 82K(180lbs)), he would only be producing 3.6-3.7 W/KG. This calculation is: 300w/82kilo = 3.65 watts to kilogram. Is this good? No, not at his level. 3.6 W/KG, for males, is about on par with a strong Cat 3 road racer of the same weight. So you can see, just focusing on the wattage numbers isn't the entire story.
Let’s keep going...
So we have an FTP now. We know what our longer duration abilities are. But for example when a rider races mostly Criteriums and Cyclocross Races and hardly ever competes in Time Trials or longer Road Races, Is FTP important? Yes. Your FTP is the starting point to which you will train in and around. 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... realizing after just 1min that ok, this can't be maintained and I'll have to slow down. This is 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 Hunter's book, but the bottom line is just that; the more intense the effort, the shorter you can hold it. Conversely, the less intense the effort, the longer you can maintain it. This is again where your FTP comes into the picture. At FTP we call this effort 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 we have identified what 100% is, and that we can feasibly sustain this for 1H, how much harder can we go and for how long? These Power training levels, developed by Dr. Andrew R. Coggan and time durations at each should help to explain things.
Lever 1 - 55% of FTP - Sustainable for most human's entire lifetime of 65-85 years. You could almost ride around the globe until you die at this pace. This is often referred to as Recovery.
Level 2 - 56-75% of FTP - 2.5H to 14 days. This is an easy pace, slightly over Recovery but still working. This is often referred to as Endurance.
Level 3 - 76-90% of FTP - 30min - 8H. We call this Tempo or your "Sweet Spot". This is where most of us live. Be it in a Road Race, MTB Race or even Criterium. It's sustainable to but not forever.
Level 4 - 91-105% of FTP - 10-60min. This is your FTP output. Many call the "Threshold" or "LT" or "AT". However you name it, this is and should be your mark of ability.
Level 5 - 106-120% of FTP - 3-8min. This is now taping into your bodies VO2Max (Total amount of oxygen you can take in). There is O2 usage but it's limited.
Level 6 - 121-150% of FTP - 30sec-2min. You are now exceeding your FTP and VOMax into what's termed your Anaerobic Capacity. This is when you produce energy without Oxygen and is very short.
Level 7 - 150+% of FTP - 5-15sec. Lastly, 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….as each athlete is gifted in their own right. Even if you surpass these durations, remember that as you cross these lines, one system will blend into the next and so on. It's not as if once you leave 100% of FTP, stepping 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 as well. A higher VO2Max will increase your FTP and so on.
So now we have to ask, which training level do you train in? The answer is simple: Train to the demands of your event. If you are an ultra-distance Marathon Mountain Biker, should you be spending 3h per week working on our Level 6 sprinting? Probably not. Your best bet is to work to raise your FTP and subsequent level 5 VO2Max and level 3 "Sweet Spot" ability. Growth of your FTP will trickle into both and if your event demands long hours you will have to put in long hours at the correct pace, simulating race pace.
What if I trained for this longer Marathon race in level 1 and 2? Wouldn't that get me the preparation I need? Yes and No.
Let’s go back to Dose and Response. If you "Dose" yourself with many hours in level 1 and 2 (Recovery and Endurance), you will adapt to that pace. You will teach your body to ride long hours at a slow pace. You won't have much ability beyond that. Could you benefit? Sure, your endurance would be there but your speed would be low. Your body is responding to the stimulus of Level 2.
Pretty simple, you are what you train for. Much like the age old saying "You are what you eat". Same principal.
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 and 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, doesn't mean you need to produce that to beat him. One wattage number can't be equated to everyone as power to weight ratio also plays a huge role.
The next step you must take is to calculate your W/KG across the power yraining levels, to create your own Power Profile. 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? The power profile is a tool that Dr. Coggan and Hunter developed in the TrainingPeaks WKO+ software and once you have created a Power Profile you can come back to it, regularly comparing gains or losses to better understand how you are improving within each specific strength and weakness. As a coach, I use the Power Profile all the time, keeping an eye on my athletes progress. How else would you know? Regularly 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...
Say you are a Crit racer with a mean sprint and can crack out 1400w for 5-10sec 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 W/KG conversion still applies. We are in the ball park of 15.5-17w/kg, which for a heavier guy is still strong. If this sprinter weighed 71kg he'd be on par with a professional rider. So you have to remember this is all relative to the individual. But can this sprinter do 1400w once or 30times? Of course if he did 30 sprints you would have to assume that fatigue would catch up with him right? Correct.
Let’s say this same Sprinter has this incredible 1400w 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 also a strong Vo2max and Anaerobic Capacity to put yourself in the right place at the right time to delivery 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, to get to the finish is a series of well-orchestrated sprints. A rider has to continually accelerate to stay in position. These of course can't be 1400w each time. This leads me to my final point.... Fatigue Resistance.
I won't go too deep into this one but Fatigue Resistance is as, if not more important than the wattage itself. If a sprinter of our above caliber can crank 1400w once, that's fine. But 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 say one or two hard short efforts Enter sprinter B! Our new "B" Sprinter has a max of only 1100w. He weighs about the same as our rock star does so the W/KG ratio favors Sprinter A. What Mr. B can do however is produce 1100w over and over again AND maintain 1000watts for 350meters… Who would you bank on to win? ... Sprinter B? Well,…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 if you have good or bad Fatigue Resistance by using a tool called “Fatigue Profiling”. This is a widget built into the www.PeaksCoachingGroup.com website. An athlete can have an incredible peak but an equally incredible drop off as we stretch the time duration out. World Class track sprinters, for example, are just that, sprint only. They can jump at amazing numbers but only for 200M. That’s it. If you asked them to do that at the end of a 4H 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, taking us back to ground zero, our FTP.
Other examples of why fatigue resistance is important lie in the road race or crit efforts. If you can bust out big numbers, over and over for only 5min 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. Ever hear this one? "I am strong throughout the race but I can never seem to win!?” Well that could be true. This rider probably has a stellar 30min "Strong" effort in him, can keep 350w 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. So please don't use power meter to limit yourself and sometimes there are riders become slaves to the number. Your power meter becomes your worst enemy, regularly telling you that you're slow, tired or just flat that day. There will be days like that. I make it a habit to make sure my athletes learn to feel out the efforts internally as well as using their power meter. The use of 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 5min effort, attempt to bring your 20min numbers up. If you strive to be a better, more balanced rider you need to spread the energy around. If you are just a track racer then buckle down and place yourself within the specifics of your events. Good things will happen!