They are not direct force. They use electrical impedance as a proxy for force. Math seems to be one of your hang-ups, so it might be helpful to know a little more about what goes on with bike power meters. Direct force measurement would be something like a measuring a spring’s compression or deflection under force. But, no one wants a spring in their drivetrain, so bike power meters do not use direct force. Instead, they measure impedance changes in metal subject to the force. The problem is impedance is not directional or linear. So, they combine that with temperature and accelerometer data and complex algorithms to determine a force vector. Then more math is applied to calculate torque and again combined with accelerometer rotational data to arrive at power. The math is pretty freakin’ complex because it is non-linear. But it is relatively accurate in the end. The math for running power is actually easier. If you know an objects movement in 3D space and it’s mass, then power is a breeze to calculate.

It sounds like you are convinced of your training and racing methods that have been highly successful for you. The math and science behind the running power meters are valid and sound. And, it is proving to be very beneficial for many others.

Semantics. Bike power meters are measuring force through the strain gauge, as I said. Sorry for being an asterisk*** off with the rest of it. The fact is that bike power meters are taking an reading of your actual power output via the pedals/crank arm/hub. That's why they are consistent and accurate. You know exactly what I'm saying and are deciding to be an asshat about it.

And clearly, accurate running power isn't easier to calculate properly. If it was, we wouldn't have 20% variances with different companies and varying tracking during an activity. Sure, the math might be easier since you remove the force measurement that you get with a strain gauge, but simpler doesn't seem to make it any more accurate. Accuracy and consistency is needed is what is truly needed if you plan on using it for training. This pretty much means that the math and science behind running power meters isn't completely sound at this point and they have a ways to go. If it was as sound and valid as you say, then we'd see consistency between the systems. Which we don't.

Also, the only 2 benefits I've seen listed thus far are that Stryd is more accurate for measuring instant pace and that running power (assuming accurate and consistence) can help those who don't understand their body limits and pacing to hold back.

As far as long term adoption? I don't see it happening for the masses any more than the masses care about ground contact time, stride length, etc. It will be like HR training. Some people live and dye by HR training and HR zones. Power will be the same way. Small groups of people here and there that will do it. The rest of us will stick with traditional time/pace method that's worked for decades. Not only is the training easier for the masses to understand, but it's a hell of a lot easier to train with when I need to do mile repeats on the track at 7:30 vs 300W for your average runner. It's also a lot easier to tailor training to pace. It's pretty easy to look at a person's recent 5K time and see their interval paces for a workout and adjust paces from there. OTOH, you'd need a lot more data and time to even be able to analyze power. It's not as simple as "hey John, nice PR last week. Let's drop those 400m repeats down from 85 to 83 this week" to match their current fitness level.

You have to remember triathletes represent only a tiny fraction of runners/cyclists. Even there, only a small fraction of cyclists are anything beyond recreational. Hell, probably 90% of the people in the groups I've biked with have never entered an actual bike race before - usually just "Bike MS" or "Ride the Rockies" or something which are more or less just extended training rides for them. So while power meters might be popular for cycling races (say 80% of crit riders have a power meter) and maybe 25% of triathletes at your average race have one, I'm guessing maybe only 1-2% of those who ran Boston or Chicago or NYC run with HR or Power. And I honestly don't see that number going higher than 5%, ever.

I can tell you he does use run power. We use it a lot in his training and in his long course racing. We use it especially to dial in tempo intervals, training intensities to make sure we are not over doing, or going by some arbitrary pace value.

Post race in short course racing, we use it to evaluate how he did, how he paced, how the performance equates with the training we saw. And pacing at that level is a fine line between doing very well and blowing up.

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Jim Vance
http://TodaysPlan.com.au (Disclosure: I am contracted with Today's Plan)
http://www.CoachVance.com/
Twitter @jimvance