Suunto Ambit 3 + Stryd – powerful combo for trail running

I have been collaborating with these two companies and I think there is a change happening with analyzing trail running training and races.

So let me run through the basics of the technology:

Suunto Ambit 3 Vertical

I have been trying out the Ambit 3 Vertical and don’t yet have a lot of experience with it. However, it seems like a small evolution of the usual smart GPS watch. I’m very happy to see focus on vertical training and this is a great watch for anyone interested in being able to easily measure their vertical training in any sport in a simple package. I emphasize the simplicity factor here, because there is so much complexity going on with the data and the User Experience (UX) of the technology today leaves quite a bit to be desired. The Vertical does a good job here and shows the vertical profile of any run on the watch screen after any run. It also shows monthly and yearly statistics of how much vertical training you have done. These key metrics are really at your fingertips.


Here’s the elevation profile of a short 5 km run from the house up and down a mountain and back. I also get my weekly totals, which are not that impressive in this example (I average about 2,500m+ weekly). Easy.

What the Ambit 3 also does, uniquely today, but I’m sure not very long is that it allows power meters to be connected with the watch in the running mode. Historically, power meters have really only existed for cycling, but now there is a new product that does this for running and the Ambit 3 has this data available in an easy format for you.

… so that brings me to Stryd.


Stryd – power meter for running

This is a ridiculously clever and seemingly simple device, but it works. What it does is that you put in your key body metrics and then the device measures your movements in 3D and calculates the power output you need to execute those. It then translates all this data into a single number: your running power. All you have to do is to wear the device using the chest strap that then also gives you HR. It’s just a little bit bigger than any normal HR sensor. There are no buttons, you just put it on, start your exercise in the Ambit 3 and go running.


The Stryd sensor and belt

Why does it matter? (for a mountain trail runner)

It matters a whole lot. As a mountain-athlete, I don’t have very many meaningful numbers to go with for training and racing. What most people have available is:

-Pace – almost completely meaningless in the mountain environment as even the slightest hill throws this off

-Distance – doesn’t mean much, because you can’t really correlate the same distance on flat asphalt to mountain trains at all. You can easily spend 2-3 the time doing the same distance. Last summer, I did some 30+ minute kilometers in some technical parts in the Pyrenees and I wasn’t slacking.

-Elevation – this is a key metric, but alone it doesn’t really tell you much

-Time – doesn’t tell you how hard you went

HR – this is normally the best available measurement, combined with time. I know that 150 BPM is about my ‘ultra race pace’ and 170 BPM is my ‘road half marathon race pace’. There are many flaws in going with just this metric however: it only responds with a significant lag, which is a big deal in the mountains as terrain is always changing. Your HR goes up in the uphills, but only after a time, so you’d find out too late that you’re going too hard and by the time you find out, the hill may be over and you risk going too slow by staring at your HR. Your pacing will be off. HR is also dependent on many things like how did you sleep last night, so it doesn’t really tell you what kind of output you’re getting out of yourself.

So power gives you the metric that is far more meaningful as a single metric than any of the above for evaluating your training and pacing for races.

I did a test earlier this week, running continuously for 10km @ 3:40 / km pace to test this pace for my half marathon this Sunday. I ran the half today at this page (3:39 avg/km, 1:17:03 total).

My HR and power for the training run:


My HR and power for the race:


Otherwise all stats are comparable… pace was the same, route very similar with almost no elevation change on smooth asphalt. I think it’s showing me very expected results: in the shorter training run, I was able to put out more power at a lower HR, so I guess I was running more efficiently than in the race. In the race, I managed to keep the same pace with slightly less power output, but higher HR, so I guess I paid more for it. The only meaningful outside bias for this is that the race was a bit more windy than the training run, which could explain some of the higher HR.

The key is to analyze and interpret this data and then take appropriate action in training and races. That is not going to be exactly easy (and I’ve simplified things for this article).

I’ll just leave it there for this post, but my initial reaction to these new tools is very positive and I will start analyzing this more and incorporating it into my training. This is after a long time of training without paying too much attention to any metrics and it is very interesting.

Anyone interested in hearing more, please reach out.



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