Tap Your Potential
by Brandon Davis [December 2014]
What is wattage? What is the difference training with power AND HR vs. ONLY an HR vs. even RPE (rate of perceived exertion)? How do I get started training with power and which powermeter should I buy? These are all questions the current cyclist seeking progression in their riding is thinking or has asked. With the race to the bottom with pricepoint currently underway we have seen powermeters go from well over the $1k mark and accessible to elitists only.....to becoming accessible to the everyday rider/racer with a host of options now as low as $499!! With most of us spending almost that for the latest Garmin headunit + HRM.....the excuse, "power is too expensive" is virtually obsolete. Gone are the days that you could only get lab based results in the lab. Nowhere is this more present than with the new Pioneer crank based system, which offers so much data that developers are still trying to find applications for some of the biometrics! With all that said if you want an indepth review of the latest powermeters then stop reading and visit DC Rainmaker's Power Meter Buyers guide. If you want some answers to the laundry list of questions this article all started with......then keep reading.
Let's start simply by explaining what wattage is and how it relates to you the rider. Power or "watts" as it's commonly referred to is simply the measurement of the rate of work being done and can be thought of as INPUT. Where a powermeter measures the work being done...an HRM (heart rate monitor) measures your body's REACTION to the work being done or in other words your body's OUTPUT. The major difference is that one of those is uneffected by the environment (wattage) and the other can change virtually by the hour pending a host of environmental factors that can effect your bpm. Think about it....if you are at the start of a race with your HRM strap on and waiting for the green light your HR is high (mine will hit low tempo sometimes!). However in that same scenario your computer isn't reading 250w standing there....only is it going to read that if the work is being done...i.e pedaling. With that it can be said that HR is effected by environmental factors where as power or "wattage" is not. It's not to say you will produce the same power numbers on 3hrs of sleep a night vs. 8hrs but rather what you see is what you get un filtered vs. with an HRM you can reach 130bpm regardless. This has fueled the term "truth-o-meter". Another analogy for power vs. HRM is by thinking of things is terms of weights in a gym. Training with power is like walking in picking up a 20lb dumbell and doing 10 reps ...20lbx10reps=200lbs lifted (work measured) next time you up the weight to 25lbs and you net 250lbs of work done, the progression is measurable and you can validate it. Training with HR in contrast is like walking into the gym and all of the weights being unlabled, picking up a weight and doing 10reps.... weightx10=X. With heart rate we are able to track progression but it is more in nuances within a season rather than looking at your power and seeing your FTP (functional threshold power) increase quite tangibly. Both methods rely on objectively tracking progression through consistency of application. Just like the gym you stress recover stress recover and over time you can objectively see your power on the bike increasing. WIth power the progression and training stress applied is more tangible and objective vs. reliant more on subjective data (how do you feel) and correlating that with various other environmental factors like weather and temperature. Bottom line power enables more specificity.
Another beneficial application when training with power that can be found when trying to dial in your nutrition. It's accepted in the feild of exercise science that 1 kj is virtually equal to 1 kCal. Such that if you performed 800kj of work by the end of your training ride you can apply that as 800kCal's burned. Which should give you an idea of what you need to replace by subtracting what you fueled with on the ride. This will curb overeating and aid in safe gradual weight loss as the miles tack up.
Specificity within your workouts with power can't be emphasised enough. How many of you have gone out for a threshold interval and waited 1-2min for your HR to rise into the prescribed zone? With power there is no sprint needed to jack your heart rate because your powermeter reads your input (wattage) instantaneously....harder and/or faster you pedal the more watts you produce intantly with no lag! This makes critical peaking workouts like 1min anaerobic and 5min VO2max intervals extremely detailed and speciffic in workload and more importantly reflects a measurable progression or lack thereof. With HR these two workouts other than in duration will commonly be indistiguishable to the enthusiast and fall victim to MAX efforts vs.... 400-460W. One is ambiguos the other is speciffic...one is progressive and one can lead to overtraining fast if not careful. We as busy athletes want to be efficient and as Goldie Locks would say have our training stress be "not too much, not too little, but just right". This specificity allows you to not only do your workouts right but plan your workouts right! Below is a formula Dr. Allen Lim uses to estimate power needed to climb certain sections of major races to the likes of Team Garmin, BMC, Trek....and more. By figuring out what is required you can also train accordingly. For us enthusiasts that means looking at Strava and Garmin Connect and figuring out what kind of power is required to win our local or regional races by analyzing your competitors files! If you know that your Cat 4 crit in town requires numerous 15sec efforts at 450w+ and an average FTP of 3.2w/kg in order to be in contension, but you're dying after 3x15sec and have an FTP of 2.9w/kg then we now can employ the proper dosage of training in an effort to have the physiological adaptations required.
Dr. Lim's formula to estimate the power necessary to climb a hill:
bike + rider weight (kg) x 9.8 x elevation gain (meters) / time (seconds)=power (watts). Add 10% for rolling and air resistance.
So if you want to really get the most out of your cycling, buy a powermeter for half or less than half of those new fancy carbon goodies in the window that promise merely marginal gains.....and reap exponential gains with wattage based training. If you're not faster by the end of the season....then sell the powermeter for close to what you paid for it. Then go by some carbon aero parts, because it's a long ride home alone when you get dropped by the group..... and all those environmental factors we talked about....well they will be introducing themselves to you.