To start out, I'll explain why power appeals to me. I began seriously training in 2010 and mostly trained by goal pace. Based on my marathon goals, I would find my target training paces (easy, tempo, 10k, etc...) from the McMillan calculator and work backward in training. For example, a 3:30 marathoner should be able to run sub-45 min 10k, or about 7:12 pace. If I encountered a workout that called for intervals at 10k pace in training, I'd aim to hit or exceed the pace given by the calculator. Easy enough, and relatively effective. I collected heart rate data on and off in these years and mostly used it to guide my pace.
Fast forward to my ultra years and I fell in love with volume, as do most ultra runners. In an effort to squeeze in volume, one typically has to give up on doing much intensity. I turned to Maffetone and an extreme focus -- I think obsession really -- on heart rate training. I gauged every run by heart rate intensity to the point where I was doing my hard sessions with heart rate targets in mind and graded every run by what my heart rate data told me. The most common thing my social group talks about on Strava is heart rate. I even tinkered with the idea of racing by heart rate. Fortunately, I quickly realized that wasn't such a great idea for me as it is extremely hard to predict with the terrain variation in mountain ultras. (I do think heart rate is a paramount thing to observe and measure in terms of fitness and health, but using it for the in the moment the decisions and to guide your training is a bit trickier.)
In 2016, I decided to try and qualify for the Boston Marathon and realized I'd need something a bit more solid than heart rate if I was going to narrow in on such a specific time goal and returned to training more by structure and pace. I continued to track heart rate of course, but tended to analyze it after the fact and less in the moment. Then I read Jason Koop's book and it changed the way I viewed ultra running -- it didn't need to all be LSD and Maffetone! His book encouraged me to change the focus back to training and fitness and not just volume. A return to pace and structure treated me well in 2016 as I did qualify for Boston and had a great year overall.
So, the reason to consider power? Other than wanting to tinker, I considered it primarily because I see the disadvantages in heart rate training. Heart rate training is only valuable if you have a very accurate understanding of your heart rate zones. And, truthfully, I find very few people do. This requires some good sample data -- threshold data the best -- and lots of experiments. Using heart rate guidelines like 180-age and such confuse the issue and remove any individuality. Another problem is that heart rate data can be influenced by lots of things -- life stress, caffeine, fatigue, alcohol, diet, etc... This can be a positive or negative, but definitely skews the definition of work. Finally, heart rate data tends to lag effort, so if you aren't paying attention to perceived effort, you can "blowout" your heart rate easily. Depending on the workout and your fitness, a heart rate "blowout" may be unrecoverable without full recovery, which I am not a fan of.
Power data aims to improve upon heart rate data by changing the definition of work being done. Instead of thinking of pace or heart beats, you think of force and work rate. However, by using power you can also analytically measure other areas like efficiency, training stress, and such with more precision. Power can actually measure the force you apply on multiple planes, which is valuable because any power applied any where other than forward is theoretically waste. Truthfully, it is just a more analytical, and perhaps accurate, way to measure what heart rate and pace already tell you. The difference is subtle because all of the metrics in this post measure work and stress, just in different ways. (And, TrainingPeaks is capable of using all three when analyzing fitness.)
The other advantage of power is that it isn't lagging like heart rate. If you start going uphill, power instantly increases. Of course, the reverse of that is that it can literally change with every stride, meaning you have to use a smoothed number (like 10 or 30 seconds) to avoid the noise. And, like heart rate or pace, you must know your threshold to properly set zones. So, testing and tinkering hasn't been eliminated. Like heart rate, power zones can theoretically change through the year with fitness.
So, enough with all the background and theory, I've used power data on a few dozen runs and finally am honing in on my "zones". My initial trial for threshold power was a bust due to training fatigue and wind, so I have reverse-engineered my zones by more experimentation. Someday soon I'll do my zones with a threshold test again, but those aren't very fun!
Advantages that I have found:
- I think the primary advantage I have found is in using it on a treadmill where I am often not sure if the machine is calibrated properly. Also, I prefer to run on treadmills with a slight grade, making a read on pace even more perplexing. Running indoors also wreaks havoc on my heart rate, due namely to heat, I think. So, power offers a more unbiased view of effort in these situations. You can see a slight increase in power after the first two intervals in the display below as I slightly increased the pace. Interestingly, power peaked in the fifth interval even though the 6th was my fastest. While though I wasn't looking at my power on my watch, I was making an effort to be efficient on that 6th interval.
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| Power data from a recent treadmill interval session I did. The data was captured in Movescount. |
- Power data is measuring power in all planes, so any loss of form due to fatigue will show up as an increase in power, meaning the runner needs to slow down or improve efficiency. Slowing down on a treadmill may be difficult whether due to a drastic need to button push or admit to yourself you cannot handle the pace. However, on a track, if you only had a smoothed power measure shown on your watch, this could be quite a good way to measure and target your effort.
- Related to the above, I think the efficiency measures that could be derived from power and loss of data on different planes could be quite powerful. However, I think the individual would need either a coach or be extremely geeky to enjoy this. And, other measures like stride rate, vertical oscillation, and ground contact time already exist.
- The integration of data with TrainingPeaks and their variety of other analytics is very useful.
Disadvantages that I have found:
- To use power, you must re-orient your entire view of how you train to power. This shouldn't be that complicated, but I equate it to someone learning a foreign language and only thinking in one language and translating to the other. A runner used to thinking in pace or heart rate will find themselves doing a lot of translation until power becomes second nature.
- The data is so accurate to the moment that it can be noisy, requiring the use of smoothed values to be useful. This calls into question which smoothed value is most useful -- 10 secs or 30 secs? More?
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| Power data from an "easy" non-structured run collected by Movescount. See how "noisy" it can be? But, my hill sprint stands out really well at the end! |
- *Data collection is only supported by a few watches and, at least for my Ambit 3 Run, you only get the power number, none of the other cool metrics collected by Stryd. Power is the most important number, but some of Stryd's advanced analytics would be useful as well. I don't like carrying my iPhone around when I run. Hopefully future versions of Ambit are able to capture all this data from Stryd. (The Stryd does support offline data caching so I can capture my data within the device even if not on my watch and sync with my mobile phone later.)
- *Likewise, only a few software programs allow you to dig deep into the analytics of power. Movescount collects the data, but only to graph it and display back the point values, which are quite noisy. Strava doesn't support power in their run profile yet. TrainingPeaks does support power and has quite a few good displays of the data. But, I'd like to see all the other data points the Stryd collects integrate in one place.
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| A comparison of power by zones and heart rate by zones from Training Peaks |
In summary, I like having power as a training tool and will continue to experiment with it. I will also likely get the new version at some point. But, I think I am a little ways away from exclusively training with it. I'd like to see the software and watches catch up quickly to really make this data more powerful! If inclined, I think a runner could gather very valuable information in regards to efficiency using this tool.
*Note to the reader: With the new Stryd footpod, it does sound like most of the data may actually make its way into Garmin Connect. Also, it stores the data on the pod so you can load it to their power center later.
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