In Deep: Power to the People

To complement Beta’s summer print issues’ stories on high-pivot full-suspension bikes, I was planning a saucy exposé about how inefficient they are. After spending two months on the absolutely stunning Forbidden Dreadnought, I theorized that there must be a cost associated with its idler pulley and chain tensioner. And my theory wasn’t just based on an assumption. It was based on fatigue that I could actually feel, though it took several thousand feet of climbing before I felt it. I was hitting the wall sooner than I was used to, but I couldn’t tell if it was in my head or in my bike. A power meter would be the only way to gather the data I needed, so I reached out to SRAM, owner of metrics gadgetsmith, Quarq. After a long call with power guru Nate Keck, I had a sound methodology, some basic knowledge, and a power-meter crank in the mail.

But after 20,000 feet of climbing a traditional but comparable bike to the Dreadnought that was of the same weight with same tires on the same trails in the same conditions, I found there actually wasn’t much efficiency lost at all. On average, it consistently took less than 1.2 percent more kilojoules of work to get the Dreadnought to the same peaks as my control bike. Interesting, sure, and not insignificant, so I went ahead and wrote a more detailed account of the process. But then something more interesting happened. The power meter, a tool for elite racers, competitive Zwifters and (overwhelmingly) roadies, suddenly became a vital part of my rides.

Power meters make it possible to quantify something that most of us have only ever measured by using pain or, at best, heart rate. The data that a power meter provides is instant, pure and far too valuable a tool to be used only for race training. That word “training” connotes an event. You train for something. That’s a noble pursuit, but not for most of us. What about bagging more trails in less time? Or more trails in more time?

Without needing to change every ride into a training ride, power meters present an opportunity to be strategic about fitness, and they do it in a remarkably intuitive way. To be clear this is not a primer on training with a power meter. I have one of those, and it’s 300 pages long. Nor is it a buyer’s guide or a value assessment. This is just an introduction to power meters through the eyes of someone who would otherwise never even consider using one, let alone read a 300-page book about it. 

First, let’s try and demystify the power meter. Whether they measure at the chainring, cranks, pedals or hub, they all rely on a mechanism called a strain gauge. That’s a thin piece of conductive metal affixed to an object that, under load, will deform a tiny bit. An electric current that is passed through the strain gauge then gets slightly disrupted. That disruption is measured, multiplied by the component’s angular velocity, and what results is a wattage value. So, even though power meters are predominantly on road and XC bikes, the components they’re attached to aren’t necessarily any less suited for aggressive riding.

Other than that basic knowledge, going blind into one’s  first ride with a power meter is probably the best approach. It’s like picking up an instrument you have no idea how to play. Sure, you’re not going to do it right at first, but that doesn’t mean it isn’t a good way to get comfortable with it. The moment you first settle into a familiar pace and look down at how many watts that pace produces, it’s pretty profound. You suddenly see a numerical representation of your effort. Effort you’ve been putting in since you  first got off your training wheels. Then, you ramp up that effort, and you have a reference for the delta between those efforts. Before you’ve done a moment of research, you can start developing a basic understanding of your upper and lower limits. You can even experiment with policing your power output to keep yourself from overdoing it, or perhaps to step it up when you’re underdoing it.

That data, and much more, is being compiled throughout your whole ride. And at the end of it, there are programs that will plot it on a graph for you. Before you even know what to do with those graphs, you’ll notice a pattern, or at least, I did. On my longer rides, I would look at the levels my power output would reach throughout each long climb. Consistently, those levels would get lower and lower as my ride went on until, in a few cases, I could pinpoint where I hit the wall and had to go into survival mode. It wouldn’t occur to me until I started doing more research, but things don’t have to be that way. 

A logical response is to simply use wattage readings to help set a more realistic pace. I actually saw some results using this method. But that was about when I started doing some real research to help me refine that method. I then realized the depth of what I’d gotten myself into and, surprisingly, it was not terrifying.

The dominant school of thought in power training was developed by Andrew Coggan, a co-author of the tome that’s been guiding me through this. It centers around seven “power zones,” which themselves center around a value called functional threshold power, or FTP. This is the average power a given rider can sustain for one hour. Each power zone is a different percentage of your FTP. Training plans involve rides that put you in and out of those power zones at strategic intervals. 

Of course, that’s easier to do in a road setting when you aren’t at the mercy of the trail. Training on a mountain bike involves some planning, some solo rides and, in my case, some flexibility to just ditch the plan sometimes and do the ride I wanted to do. 

Checking progress is done, in part, by regularly testing FTP. Usually every four weeks. As long as your body weight doesn’t  fluctuate, this is an accurate measure of the training’s effectiveness. After a couple months of learning the ropes and frequently wavering in my commitment, I wasn’t seeing much. But at my last FTP test, I’d improved by 13 watts, which I confirmed in another test a week later. That in turn steps up each of my zones and, in theory, I should expect to see similar gains at my next test. 

This all probably feels pretty nerdy, and you can expect it to get way nerdier once you start. But think back to the path you took toward understanding your suspension. First you learned about setting sag, and then rebound damping. You then started to grasp compression damping, followed by what happens when compression gets split into high-speed and low-speed.

Then there were spring curves and how they interact with leverage-rate curves. Once you’ve understood the outputs that result from a given input, each next step begins to feel inviting, not intimidating. For those who race downhill, suspension setup can get just as intense as developing a fitness training regimen, often involving just as many high-tech devices and analytics. Like power meters, that world is also becoming more accessible, and soon we’ll see 300-page books written about bottom-out metrics. What we do with it is up to us. Racers will use it for racing, because it makes racing better. But some of us will just use it for riding. Because it makes riding better.

Photo: Anthony Smith