C2 static watts vs NK Empower Oarlock watts – A personal comparison

Just a short post on some findings using the Empower Oarlock – I am working on a review and I promise I will try and get it out as soon as possible! In testing the gate I had been wanting to compare two  equivalent workouts on a concept 2 ergo and the water to see whether it is possible to use the information on one to use the other – for example if you have set training wattages on the erg, could you use the same wattages on the water? To test this I decided to run a common FTP test to see how each compares to the other.

For those of you that aren’t aware of FTP (functional threshold Power) – it is basically an invented value that is described as the power that you are able to hold for an hour, and is closely correlated to a 4mmol blood lactate level (read about lactate testing here) but as it doesn’t require the costly blood testing method so is a cheap way of getting a similar result and to then be able to set training zones.

A workout for an hour flat out doesn’t sound like much fun however, and so in cycling it is common to run a 20” test and to then use 95% of the power for your FTP – rowing however is slightly different, I don’t know about you but I know my 6K score and my hour score are not 95% of each other! More commonly its around 80-85% and so one recommendation is to do a 20” at rate 20 and use 100% of that value to get your FTP.

Below is the table which shows the outcome of the two tests


As you can see I averaged 30 watts more on the water than on the erg which I wasn’t expecting – the conditions for the water workout were challenging (head wind and chop) so I thought I would see an impact on power with me battling the conditions as well as the workout, also interestingly other users of the Empower gate are seeing lower values on the water than they are seeing on the erg


As a side note the difference in wattage between on the water and on the erg that I am seeing is a similar value to the difference I used to see when I was comparing rowperfect and static ergo scores – so using lactate testing an sticking to 2mmol I would see 20-30 watts more on the dynamic than the static


It is too early to conclude what this means as of yet – just from my data and Rod Siegal’s it does seem to suggest that the comparability between the empower watts and ergo watts varies person to person so you can’t use training zones set on the erg on the water (and vice versa), it would be recommended to run the tests on both to work them out.

EDIT: another thing to add is that as I am sculling and the NK is recording one side power only (bow side in my case) and then doubling it then this could be skewing the results I favour if the water session – i.e. If I am putting more power out on bowside then I could be getting a false high result for the overall

My previous experiences do seem to suggest that the rowperfect may be a better tool for hitting the same watts as you would see on the water. Of course the only way to test this is to repeat the 20 min test on the rowperfect….. great….


About stelph82

I am a rower who is a lot of a technology geek as well!
This entry was posted in Biomechanics, Rowing software, Rowing Telemetry. Bookmark the permalink.

12 Responses to C2 static watts vs NK Empower Oarlock watts – A personal comparison

  1. Interesting. So far I seem to be in the “lower” camp but I have only done 2 outings on a twisty river where I don’t know the course very well.

    As I argue in this post http://wp.me/p8g86e-3t one of the thing we need badly is to establish how power (and other metrics) is measured and reported across manufacturers and devices.

    • stelph82 says:

      All my outings have shown a higher power at similar perceived effort/HR to erg so far – this was the first time I’d compared the two however

      One other thing I need to add as I’ve just remembered – I also need to investigate power imbalance – as the NK is one side only (left only on my case) this does mean there is a potential that if I am left unbalanced that that is skewing the result in favour of the water

  2. Tom, what’s with the spiky wattage on the erg test? Were you throwing some power strokes? This comparison is really interesting to me. I’ll try to duplicate it as soon as I get back on the water.

    • stelph82 says:

      Yes it’s where I tried to drag the splits down – equally the big dip on the water towards the end was where I had to shoot under the narrow HENLEY bridge!

      • tim says:

        the spikes look massive to me but maybe that’s just for a single stroke? eg: cruising at sub-300 watt average but the spikes are around 400w?

        also its very interesting that the water watts were higher…that surely is worth doing the test at least a couple more times? 🙂

      • stelph82 says:

        Yes they are unusual – I’ll keep an eye out for them with other workouts

        More tests? Meanie…

  3. Boris says:

    In cycling it’s quite common to have a lower indoor FTP, compared to outdoor FTP. For some reason it has to do with cooling, but also with motivation (no motivational thrill through movement).

    About cooling… body’s efficiency is only about 21-23% (for very well trained athletes). To turn the cranks one hour long @ 350W (=350W FTP) a well trained body needs to generate about 1520-1660 watts, depending on the personal efficiency. Under extreme/emergency conditions the humans body is able to generate up to 3L of sweat for 1h to keep the body temperature down. 1L of sweat (which needs to evaporate from the skin, no drips, no wipe off) would be worth about ~650W of cooling power. Adding some additional watts for body temp. buffering capacity, loosing heat through breathing, and so on… well, at the end for 350W the body has to deal with more than 1kW (!!!) of heat. From data I have seen, it seems that efficiency in rowing (at least for high output rowing) seems to be lower than in cycling. A good high volume fan and open windows is always good for a intense indoor erg session. 🙂

    About indoor… let’s face it. Sliding up and down on this on this rail is no fun at all. Sitting on a indoor bike turning the crank feels like “welcome to zombieland”. If you get out on the water (or the road) you get tactile feedback, you feel the water/road, you feel the wind, the movement… that helps a lot to keep pushing, especially when you left the comfort zone. 😉

    Just my 2cents.

    • stelph82 says:

      Thanks Boris – all very valid points – I think overheating is less of an issue for Erging than it is on a bike as the setup of the fan means you’re getting blasted by the fan throughout, and it doesn’t really explain why others are seeing the inverse of on erg watts being higher than on water

      Agree with the boredom tho, I defiantly agree it’s easier to motivate on the water against Oppo than it is on the erg

      • Boris says:

        I had more heat issues on the C2 Rowing machine, than on the indoor bike – same room. I know few people who are indoor better than outdoor. I guess you’ll double check your boat powermeter – just in case.

      • stelph82 says:

        Yes -hoping to get another companies power meter to be able to check the readout of the NK – although I believe NK have validated their gate using bio row so if there’s any gate out there that I would trust it would be this one!

    • Mel Harbour says:

      Motivation is a very weird thing in terms of these sort of pieces. The different scenario can cause big differences. Look at all the odd results you can get from things like putting a person on a stationary bike with a speedo set wrongly! Obviously up Henley Reach, you’ve got plenty of landmarks that you know well, and can structure your thinking to help you push hard for a long time. Whether that’s the same on the erg is anyone’s guess!

  4. rowperfect says:

    Thanks for your note about the Rowperfect data comparability to on-water. This is what I would expect because
    1 – the RP algorithm was set up to be directly comparable to world best times and directly proportional to body mass [see this article when it was re-verified https://www.rowperfect.co.uk/rowperfect-software-verified-against-world-best-times/ ]
    2 – The RP Android app defaults to an “ergo” setting which is broadly based on 95kg men in 4- which equates closely to Concept2 scores.
    3 – the RP data allows you to select boat class and input your body weight to get an adjusted score which equates to your “ideal best possible” on water score given flat water, no stream, no wind and perfect blade work [something for you to work on Tom!!]


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