Friday
Dec092011
The Most Effective Ways to Utilize a Power Meter in your Ironman Training and Racing
Friday, December 9, 2011 at 02:17PM Click Here to Subscribe to Coach Kyle's Blog
In order to utilize the most effective methods of training and racing with power it is important to understand the critical principles of Ironman racing. Extensive endurance and muscular endurance (for more advanced athletes) are the most important components when preparing for the bike leg of an Ironman triathlon. The key to success is specificity. Becoming extremely efficient at the intensity you will race at, roughly 60%-80% of your Functional Threshold Power (FTP – The average power an athlete can sustain for one hour), must be the focus of your training.
Pacing
Nearly all record breaking times are set with negative splits. This means that the second half of the race is faster than the first, which obviously has to do with pacing. A power meter is by far the most accurate way to gauge your intensity (output) on the bike. Your speed on the bike is highly affected by wind, heat, hills etc. but when you have a power meter, you are able to roll along at the prescribed intensity and no longer need to guess at how hard you should be going. An Ironman athlete completing the bike leg in less than 5 hours can usually sustain a power output of 70%-80% of their Functional Threshold Power (FTP). Athletes finishing in the 5 to 8 hour range should stay between 60%-70% of their FTP and the 8+ hour rider will be somewhere between 50%-60% of their FTP. Being able to accurately ride at the correct intensity enables your training to become much more efficient and allows you to race much more effectively. The first half of the bike in an Ironman race may be the most critical part of the entire race and a power meter will help you keep your pacing under control.
Decoupling
The most critical component of endurance racing (specifically Ironman racing) is aerobic endurance. An athlete’s aerobic system composed of the heart, lungs, blood and the muscles’ aerobic enzymes must be fully developed. But how do you know if your aerobic endurance is progressing and how do you know when you’ve reached an optimal aerobic endurance fitness level? The parallel relationship between input (heart rate) and output (power) is referred to as coupling. When they are no longer parallel in a workout (e.g. one variable remains steady while the other drifts) the relationship is said to have decoupled. As aerobic endurance improves, there is a reduced rate of heart rate drift relative to constant power output. In determining your decoupling you can use software such as Training Peaks, WKO+ or perform the following calculation:
Pacing
Nearly all record breaking times are set with negative splits. This means that the second half of the race is faster than the first, which obviously has to do with pacing. A power meter is by far the most accurate way to gauge your intensity (output) on the bike. Your speed on the bike is highly affected by wind, heat, hills etc. but when you have a power meter, you are able to roll along at the prescribed intensity and no longer need to guess at how hard you should be going. An Ironman athlete completing the bike leg in less than 5 hours can usually sustain a power output of 70%-80% of their Functional Threshold Power (FTP). Athletes finishing in the 5 to 8 hour range should stay between 60%-70% of their FTP and the 8+ hour rider will be somewhere between 50%-60% of their FTP. Being able to accurately ride at the correct intensity enables your training to become much more efficient and allows you to race much more effectively. The first half of the bike in an Ironman race may be the most critical part of the entire race and a power meter will help you keep your pacing under control.
Decoupling
The most critical component of endurance racing (specifically Ironman racing) is aerobic endurance. An athlete’s aerobic system composed of the heart, lungs, blood and the muscles’ aerobic enzymes must be fully developed. But how do you know if your aerobic endurance is progressing and how do you know when you’ve reached an optimal aerobic endurance fitness level? The parallel relationship between input (heart rate) and output (power) is referred to as coupling. When they are no longer parallel in a workout (e.g. one variable remains steady while the other drifts) the relationship is said to have decoupled. As aerobic endurance improves, there is a reduced rate of heart rate drift relative to constant power output. In determining your decoupling you can use software such as Training Peaks, WKO+ or perform the following calculation:
Divide the workout into even halves. For each half the normalized power is divided by the average heart rate to establish two ratios. The ratios are then compared by subtracting the first half ratio from the second half ratio and dividing the remainder by the first half ratio. This produces a power- to- heart rate-ratio percentage of change from the first half to the second half of the aerobic threshold ride.
For Ironman racing the goal should be too keep decoupling on the bike to less than 5% for a minimum of 4 hours. Once an athlete’s aerobic system is fully developed it will make training at higher intensities more effective.
Variability Index (VI)
The variability Index is a measure of how smooth or consistent an athlete’s power output was during a workout or race. The VI is found by simply taking the normalized power and dividing it by the average power. The normalized power (easily calculated by your cycling computer or software) can be thought of as your average power without the “zeros” or “spikes”. A high VI is an indication that there was a lot of surging taking place. This can be instances such as heading into a head wind, going up and down small hills, being passed or passing someone else etc. Surges can zap your energy very quickly and wreak havoc on your body as it is trying to process fluid and fuel. Steady state pacing, especially in Ironman racing, is a far more efficient use of energy. A pacing strategy of a smooth and consistent power delivery will reduce fatigue and pay dividends on the run.
Reader Comments (8)
This is great... so regarding setting up your year's training, would you focus on creating a base period where you developed your aerobic engine by keying in on the minimization of decoupling and then shift emphasis towards high intensity work paired with aerobic maintenance for your build up to ironman?
Thanks for posing this Topic/Question John Paul!
Precisely, once you can show that your decouple is consistently under 5% (duration depends on the event) then the emphasis should shift towards higher intensity workouts.
What's your protocol for FTP testing? Most coaches and power-based athletes will not actually perform an all out 1 hour bike test, but use shorter tests to provide a reasonable estimate of FTP, such as average power one can achieve in a 2 x 20min interval test. Also, do you or have you considered utilizing Training Stress Score (TSS) as a means to quantify a workout's physiological stress load?
Hi David,
I like to use Joe Friel's method which consists of a 30min time trial to estimate FTP described on his blog: http://www.trainingbible.com/joesblog/2008/01/ftp-and-power.html
Andrew Coggan also describes several methods for estimating FTP in his book Training and Racing with a Power Meter. No matter which field test you use the key is to be consistent throughout the season.
Yes, I use TSS to quantify individual workouts as well as Fitness and Fatigue trends over the course of a training period. It can be very useful tool. By definition a TTS of 100 is a power output equal to your FTP for one hour.
Thanks Kyle -
The TSS concept is interesting. Over the last few years it has allowed me to really gauge the value, as in physiological training stress value, on my different cycling rides. 5-6 hour ride in Z1/Z2 versus a 2-3 Hr ride Z3 where both create about the same TSS. In a way TSS is a time management tool for the average time-crunched age a grouper allowing one to obtain the training stress in shorter durations. Your thoughts ?
Also, with my own experience, as well as access to hundreds of other power-based athlete's power data use for IM distance triathlons, as well as the subsequent run data, the information leads to support that if one accumulates in excess of 300 TSS during the bike leg of an Ironman,, that the odds are very likely the athlete will have a sub-par run performance, I think I saw you talk about pacing, which is awesome. Too many coaches do very well at training folks, but spend very little resources teaching folks how to actually race and perform on race day. Racing with a power meter is a big advantage, if used correctly to assist with pacing decisions that will present itself during the race. I like what your programi is bringing to the community -- good stuff. Congrats.
Why TSS is so valuable is that it allows us to quantify the physiological stress on the body. It allows us to take into account both intensity and duration and we no longer half to look at them as separate entities. A 5-6 hour ride might not produce exactly the same results as a 2-3 hour ride done at a higher intensity but as you stated both will produces a similar stress on the body. And yes this can be an effective to maximize the potential in an athlete with a given amount of hours to train.
The other great thing about TSS is that it has a direct relation to Intensity Factor (IF). TSS = (IF^2*hours*100) IF = Normalized Power / Functional Threshold Power. So when I say an athlete who plans to finish the bike leg of an ironman around 5 hours should be at 70% to 80% of their FTP what I’m really referring to is Intensity Factor (.70-.80). You’ll notice that if you plug in .75 for intensity factor (75% of FTP) and 5 hours you get a TSS of 281. At that same intensity athlete finishing in 6.5 hours will experience a TSS of 366. If that athlete were to go at an intensity of .65 (65%) for 6.5 hours they would have a TSS of 275.
So yes I agree with you that a TSS of over 300 would most likely have a sup-par run performance. TTS is a great metric to use in analysis (after a workout or race) but is not effective during a workout or race. It’s very hard to pace yourself off TSS but very easy to pace yourself off of IF. If you do the math right you can simply ride a prescribed average power and your TSS score will fall directly into the range it should be.
Kyle - Good stuff and nice to hear from one with knowledge about training with power who I can exchange comments with. I have been using power for about three years now and download everything into WKO software, including runs and swims. I will stop this thread after a few more questions.
I'm curious of your thoughts. (1) While technically a watt is a watt, from my perspective from a physiological standpoint a watt not always equal to a watt. For example, increasing one's power by 10 watts while cycling from 150 to 160 watts is much different than 10 watts going from 260 to 270. The physiological stress of watts increasing is not linear but takes on more of an exponential curve shape; and (2) similarly, 200w with a cadence of 90RPMs versus 200w with a cadence of 60RPMs, also from my perspective, though one is generating identical watts and identical TSS for a said duration, are very different from a physiological standpoint.
Anyway, I'll say hello to you and introduce myself next time I see you. We do not actually know each other officially, but have many common acquaintances, both in SBTC and RTC.
Happy to exchange thoughts and ideas!
(1) A watt is equal to a Joule per second, which IS a direct correlation to a energy expenditure. 4.184KJ ≈ 1 kCal (calorie). Most humans are 20-25% efficient so if you output one watt you are burning roughly 1 calorie (efficiency does NOT change much with intensity).The physiological energy expenditure IS a linear relationship and it takes the same amount of energy to increase from 150-160 as it does to increase from 260-270.
What you've observed is that the physiological STRESS on the body does not seem to follow the same linear relationship that energy expenditure does. As I'm sure you know your body utilizes several different energy systems (aerobic vs. aerobic) which "stress" your body very differently and when you cross from one regime to the other it becomes non linear. Why TSS is effective for endurance athletes is that your Functional Threshold (which is very close to your Lactate or anaerobic threshold) is point in the curve becomes non linear. We do the vast majority of our training under our FTP so our TSS scores are fairly accurate. A TSS score for a sprinter for example (someone who spends a lot of time above their FTP) will not be as accurate.
(2) When you output the same amount of watts at different cadences you are effectively changing how efficient your body is working. You hear people talk about finding the most efficient cadence all the time. What they are really talking about is finding the maximum output (watts) for a given input.
I know we have a lot of mutual friends as well.... look forward to meeting you!