Rowing with a power meter and


As I wrote in this blog post, power measurement systems for on-the-water rowing are about to become mainstream. In fact, since the launch of NK’s Empower Oarlock, there is an affordable way to get started with measuring the power you put into rowing on the water. On the erg, we have always had power, but somehow it is rarely used. The entire rowing community has become addicted to a weird metric “pace”, expressed as the time it takes  to cross a virtual distance of 500m.

There is no real distance on the erg. All there is, is an accelerating and decelerating flywheel, and all metrics are measured from that. Power can be derived directly from the flywheel speed. On the water, there are external factors which make that you sometimes have to work harder to maintain the same pace, and do more physical work to cover the same distance. Headwind. Current. A bungee cord.

What is power? Power is the amount of work you do per unit of time, it is the rate at which you work. Also, it is the product of handle speed and handle force. And work is the product of force and distance. All these things are extremely important parameters in rowing. Think about it:

  • Handle force
  • Handle speed
  • Drive length
  • Strokes per minute

All these things are directly measured on the erg. They can be combined to measure the physical work you put into rowing. And training is about doing physical work (in a smart way) and recovering from that work, for your body to adapt itself and be able to do do more physical work, or sustain a higher power for longer, or do the same amount of work with a lower perceived exertion.

Rowing with a power meter can be used to

  1. Know your strengths and weaknesses
  2. Share row workout data with your trainer or team members, even if they trained at a different time, with different conditions
  3. Establish objective, measurable, quantitative goals to train to
  4. Tuning your training load to achieve optimum race performance

Some of these goals can also be achieved by training by heart rate or using lactate measurements. The disadvantage of using heart rate is that the external influences (caffeine, temperature, humidity, stress, fatigue, race adrenaline) can lead to huge heart rate swings. For example, I would never let my race pace be determined by heart rate. The disadvantage of using lactate measurements, is that it is cumbersome, expensive, and hard to do on the water. I am not dismissing these two methods, though. In fact, I think you should always measure your heart rate (because in combination with power it can tell you something about stress, fatigue, fitness) and using lactate measurements can be a really smart way to establish personalized training goals.

Rowing with a power meter (background reading)

This post is about how to use to use power to improve your training (and get faster). As preparatory work, you should probably read the following background material and introductions:

  1. Power Measuring in Rowing – my review of the book “Training and Racing with a Power Meter”.
  2. How to get started with training with power – A blog post by Hunter Allan, one of the authors of the above-mentioned book

Now that you have a basic idea of how triathletes and cyclists use their power meters, it’s time to get started with rowing. This is all you need:

  1. A Concept2 rower
  2. A way to extract your rowing data from the erg. See this blog post and this blog post. Personally, I recommend Painsled (for iOS) and BoatCoach (for Android) because they give you the most metrics
  3. A heart rate belt (we’re not ditching heart rate measurements)
  4. A login name on The basic registration is free. For a mere 5 EURO, you get all the full functionality, but the basic plan is good to get started.
  5. Optional: Power meter in your boat. is ready for the NK Empower Oarlock.

Also, take some time to get acquainted with the Concept2 monitor (the “PM”), especially how to set it to Watts. You’re going to use the Watt screen quite a lot.

How to use to improve your training with Power

Establish Power training zones and organize your training around them

Setting the Zones

First, head over to your settings page. On, you get there by clicking on the button with your name, on the top right of the navigation bar.

This is the Settings page:

If you read this in the future, the layout may have changed slightly, but the functionality should be roughly the same. There are three forms on this page.

  1. On the top left, you have the Heart Rate Zones. Here, we use the usual heart rate zones for rowing. On this page, you will find a nice calculator to figure out what the zones are for you. UT2 is light aerobic work, UT1 heavy aerobic work, AT the aerobic threshold, TR oxygen transportation zone and AN is the Anaerobic zone. The weight category settings is important for synchronizing your workouts to the Concept2 logbook. (I will probably reorganize this form a bit in the future, and make it look more like the Power Zones form on the top right, but for now this is what you have for Heart Rate zones.
  2. On the top right, you have the Power Zones. In the figure above, I use my own definition, but you are free to define your own zones, including their names. Just type the new names and hit “Save”.
Power Training Zones according to the guru

After updating the names and saving the form, I have the following:

So now I am all Cogganized. For new users, the zone boundaries are set to a default value, which follow the percentages in the table above, for a threshold power of 226W. You will want to change that soon, but for now don’t touch those boundary values yet. First you will want to set your FTP.

The third form is specially made for that. This is where you put your Functional Threshold Power (in Watts). How do you determine your Functional Threshold Power? It is basically the maximum average power that you can sustain over 60 minutes. Here are a few ways to obtain a value for your FTP:

  1. Dial up a one hour effort on the erg and row. Write down the average Power.
  2. Row a full out 20 minute effort. Write down the average Power. According to triathlon sources, your FTP is roughly 95% of this value. For rowing it looks a bit lower, somewhere in the 80% to 95% range. Actually, the famous “double the distance, add 5 seconds of split” rule suggests that FTP is 81% of the 20 minute power for heave Men, to 85% for lightweight Women.
  3. Row a full 30 minute effort, take 90% of the power. I derived this figure from Concept2 Rankings.
  4. Row a full out 2k, take 60% (Men) or 70% (Women). Guidance that I derived from Concept2 Rankings. Older men may be closer to 70%.
  5. Make a wild guess
  6. Use the Ranking Distances page on to estimate your maximum performance over 60 minute. More about this in the next section.

Now that you have (a guess of) your FTP, fill that in the third form and hit “Save”. You will notice that also the zones boundaries in the Power Zones form have changed. They have been recalculated based on your old FTP value and your new FTP value. So, for example, if the lower boundary of your Tempo zone was set to 169W for a FTP of 226W, and you changed your FTP to 200W, your new Tempo zone boundary will be proportionally lowered, to 149W.

If you want to adhere to the percentages rules for the zones in the table above, you’re good to go. But you may want to use a different definition of Power Zones. You can simply do that by calculating your zone boundaries according to your favorite equation or table, use the Power Zones form to adjust the naming and the values, and hit “Save”.

The cool thing is that when you train and get faster, your FTP will shift. You can use the FTP form to adjust all your zones in one go, by just updating the FTP value.

What was my training zone?

Now we’re all set up. Go and do a workout. Upload it to Head to the Workout Edit page:

On this page, I have highlighted the buttons you want to use first. They are

  1. Power Pie Chart (Power Zone based)
  2. Pie Chart (Heart Rate zone based)
  3. Distance Plot
  4. Time Plot

Every time you hit one of those buttons, the site gets busy generating a chart for you. Generating these charts takes a few seconds, so you have to be a little patient. Once you hit reload and the chart is ready, you will see a thumbnail on the top right, above Workout Summary. In the example above, I have already done this.

Clicking on the thumbnail opens the Chart Page, from where you can download the image file, or delete the chart if you don’t like it. Here is a Distance Plot:

We’re going to focus on the top and bottom of these charts. On the horizontal axis you see the distance you have covered in the workout (hence “Distance Plot”). In the top chart you see your heart rate as a bar chart, with the color of the bar representing the Zone you were working in. For clarity, the Zone names are indicated on the left. In the bottom graph, a similar thing is going on, but now with the Power you were working at, and the colors indicate the Power Zone. In this 4x4min workout, I was working in the Anaerobic Capacity Power Zone exclusively. Contrast that with the heart rate values, which are mainly in the TR zone, but because heart rate responds slowly, there is also substantial time spent in the AT and UT1 zones. The two middle charts show you your pace and the stroke rate. Compare pace to Power. The two are related, but I find it much easier to spot fast and slow sections (“power 10 strokes”) in the Watts chart. The reason is that the power you need to gain a 1 second pace improvement quickly increases with pace, so the faster you row, the harder it gets to speed up. The Watts chart really shows you how hard you have been working.

The Distance and Time charts are really nice to get a quick overview of the workout. I recommend creating these charts every time.

Here are a Power Pie chart (left) and a Heart Rate Pie Chart (right):

You can click on the images if you want to see a larger version. These Pie charts tell you per Zone how much time you have spent in that particular zone. So for example on the Heart Rate Pie chart, you can see 12:13 minutes (38.2% of the total workout duration) at a heart rate in the TR zone. If you are planning your training according to Power or Heart Rate zones, you can use these charts to see if you really have been working at the right level.

In the Advanced section, you can do a Flex Chart. The Flex Chart is worth a blog post in itself, so I won’t go into much detail, but you can basically plot any measured parameter against any other parameter in number of ways. Users of the free Basic plan have access to distance, time, power, pace, heart rate and stroke rate, and Premium users get a whole bunch of additional metrics. Here is just one example, but you can basically generate all the charts that I prototype in my book review:

Premium users also have a useful other plot, the Power Histogram:

In this plot you have Power on the horizontal axis and the percentage of strokes on the left vertical axis. This chart is interesting to see at a glance how your power was distributed. For this workout, the power was in a narrow band around 270W for the “work” intervals, and a broad band between 10W to 150W for the “rest” intervals. The narrow band in the work interval is a good thing. You want to pull flat and consistent.

Monitor your training load

This is an area where I expect to add more functionality, but currently we already have two very useful charts. You have to head over to the “Analysis” section of the site, using the button highlighted in the following picture:

Here, you currently have three buttons:

  1. Ranking Pieces (see next section)
  2. Stroke Analysis
  3. Power Histogram (Premium functionality)

Click on Stroke Analysis and you get the following page:

This is basically a Flex Chart again, and you can use the Blue buttons on the top left to select which parameters to plot on the axis. The dashed lines indicate the average values, which are also written out in the chart.

The default chart is Power vs Stroke Rate, and every data point is a stroke you took (across all erg workouts) in the date range that you can see on the top right. You can use that date range form to change the time period you are looking at.

The Distance slider lets you select strokes based on where in the workout they were done. It is interesting to see if the patterns in the chart change for higher distances (when you are getting tired). Talking about the patterns, the figure above shows my chart for the past 10 days and there are some interesting clusters of strokes there. Lots of data to think about.

The “Power Histogram” plot brings you to the following page:

This histogram is very similar to the one discussed above. The only difference is that this histogram represents ALL strokes you took (on the erg) in a time period, which you can define on the top right of the page. Personally, I use this plot in combination with a periodized training plan. I look at it to check if, for the given time period, I have the correct distribution of power zones. For example, in a certain week, I want to do 70% of the strokes in the UT1 zones, 20% in the AT zone, and 10% in the AN zone. Depending on your training plan, the exact values may differ, of course. To read the percentages, you can use the red line. Going from left to right, the red line shows the percentage of strokes recorded at that power or lower. So, for example, at the 200W level, the red line is at 73%. You can hover over the red line and read the value in the callout, or you can use the right-hand side vertical axis to read the value. 73% of strokes were done at 200W and lower. At the 300W level, the cumulative percentage is 96%. So that means that 23% (96-73) of my strokes were between 200W and 300W.

By the way, you can share this page with your friends (if they are also Premium members) by sending them the link on the top left of this page.

Know your strengths and weaknesses

Finally, the “Ranking Pieces” page (accessible from the “Analysis” page) allows you to assess your fitness and to start thinking about your strengths and weaknesses.

This is quite a complex page, and a lot of things are going on, so we’ll take it from the top to the bottom. The top of the page looks like this:

Basically, here are your best efforts at the Concept2 Ranking Pieces (500m, 1km, 2km, 5km, 6km, 10km, HM, 1 minute, 30 minute & 1 hour) from the database. For example, for a 500m effort, the best I recorded on (in the past 12 months) is 1:33.0. If I want to look at that piece in detail, I can click on the name “500m full out” in the table. I did this effort on April 25 and I didn’t record any heart rate data (unfortunately). If I select a different date range using the form on the top right, I may find a different 500m piece which was the fastest over that date range. Perhaps I was in good shape in April, but I don’t feel that 1:33.0 is representative for my current shape. In that case, I have to select a more recent time period.

The next part of the page is a scary-looking graph:

It is the Critical Power Plot. On the horizontal axis, we have the duration of the piece (in seconds), and on the vertical axis we have power (Watts). This is a very natural way to represent the data. The harder you work (higher on the vertical axis), the sooner you crash (more to the left). So plotting ranking pieces in this way will lead to a graph that roughly goes from the top left to the bottom right. The Duration axis is a logarithmic axis, just to allow to plot the very short pieces and the very long pieces in a visually pleasant way. Otherwise, you would have a bunch of points on the left, then a long empty plot, and finally a single point for your Half Marathon workout.

Each of the red dots is one of the ranking pieces from the table on the top of the page. You can hover over the point with your mouse to see which piece it is. Ignoring all the other lines and dots, you can already see that in my case the 5k and 2k pieces are “off”. They do not represent maximum efforts. Or if they did, the values from the other pieces suggest that I can go faster on these. Actually, that is also suggested by the small blue dots. The small blue dots are segments from one of your workouts. So I can see that I have a done a 20 minute segment at roughly 256W. Hovering over the point, I can see that I covered 5160 meters during that segment. That’s good evidence that I could do a 5k piece at 256W at least. Actually, 256W is probably not a bad power to start my next 5k attempt at.

The blue and green lines are curve fits to the data points. The blue line is the famous Paul’s Law (“double the distance, add 5 seconds of pace). The green line is a so-called “CP model“. CP stands for Critical Power and it is an established model in the field of Exercise Physiology. The beauty is that it is simple, mathematical, and yet is a good approximation of the processes in your body that limit your ability. Also, while the Paul’s law gives you higher and higher power as the duration shortens, the CP model is able to model a Maximum Power pretty well.

So looking at these models, if the red dots are above the curves, it means that I have done a better performance than expected from the fit, and vice versa. The way I use this is to look at the dot that is below the line and try to improve that piece. For example, the 2k and the 5k, in my case. When I improve my 2k, the red 2k dot will move up (and slightly to the left). This will change the curve fits, and improve the predictive power of the models.

Finally, at the bottom of the page are the pace predictions. Two tables for the two models discussed above. So, using the curve fits to the different models, the tables give you an estimated pace for the various ranking distances., for example, thinks that I could do a 100m in 17.1 seconds, and that my 2k is somewhere between 7:09 (Paul’s law) and 7:22 (CP model).

As I have polluted my data with a few bad performances, the 2k prediction is quite slow. I will try on Saturday, but I think I can get well below 7:09. A trick to remove those “bad” pieces is to change them. So, for example, make the 2000m a 1999m or 2001m workout using the Workout Edit page. This will prevent them from showing up on the Ranking Piece page. When I do that, here is the result:

By the way, you can also do this the other way. Sometimes the workout distance and duration on is not exactly equal to what you see on the PM. This is a limitation of the stroke-based CSV files. You can easily edit the values in the Workout Edit page and update them, so they show up on the Ranking Piece page. Anyway, here is my improved prediction:

So now I am suddenly looking at 6:54.9 (that would be a PB) or a 6:57.5 (almost a PB). Ouch! I think I will feel some pain, coming Saturday.

Finally, look at the bottom value in the chart. It read “1:00:00.0” (aka a full hour) and 205W. I could consider using this value as my FTP (see the section about Zone Settings above).


I hope you like what you see. Already now there is a lot on that will help you training by Power. And there is more to come. Feel free to suggest additional functionality through the comments. I have already received requests to calculate a “Suffer Score”, a single number that represents how hard a workout was. I will also work on implementing more power based functionality for OTW rowers (you need a NK Empower Oarlock for that).

Also, feel free to ask any questions, in case something wasn’t clear.

2 thoughts on “Rowing with a power meter and”

  1. I have added two more methods to estimate your FTP.

    – Row a full 30 minute effort, take 90% of the power. I derived this figure from Concept2 Rankings.

    – Row a full out 2k, take 60% (Men) or 70% (Women). Guidance that I derived from Concept2 Rankings. Older men may be closer to 70%.

    Both methods are rough estimates of course.

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