A case for mountain bike power meters
Guest post from PowerTap assistant engineer and PRO Mountain Biker, Joe Maloney.
Like most people who ride bikes, I didn't start with a power meter. Heck I didn't even start out with racing. I grew up riding with my dad and fell in love with pushing myself to the next level. 10 miles, then 20 miles, 30, 40, and so on. This was well before power became the standard for road training. As time passed, biking changed from hobby to obsession and I have been training seriously for a few years now. When racing and training on the road, power is the name of the game. So my road training has been power-based as I've gone from beginner to Cat1.
But I've always been one for the dirt. My favorite is XC mountain biking. Despite the dominance of power meters in road training and racing, power meters have only recently made their way to dirt. And even then there are many who think power meters have no place off-road. I used to be one of them — until I had a chance to ride one.
When you're hammering down the road, power training is a simple matter of how much power you create against the force of the wind and rise in the road, but off-road has many more dynamics. You're pedaling uphill sure, but there is so much coasting. So much pushing and pulling on the bike. Pumping the terrain and jumping. How could a power meter measure your effort when so much of it isn't going through the chain? I had the chance to bring a disc PowerTap with me to some races recently in Montana and Colorado and I asked myself this very question.
I wasn't sure what I was looking at when I downloaded the file. Like many people, the first thing I noticed was the average power. What felt like a hard ride had an average power of a recovery ride. Obviously you're coasting so much, on and off the gas, that all those efforts are offset by big chunks of zero power. But isn't the point of the point of the power meter to tell me how hard I was riding? Isn't it getting it wrong?
The problem was that I was looking at the file like it was a road ride. Looking at an off-road file as a road power file is like sticking a VHS tape into a DVD player. It doesn't make any sense. You need to look at the file differently. On the road it's about setting new power records, steady state, attacking and then throwing down big power to motor away. You'll see some steady efforts on a mountain bike, but mostly it's about the on and off — the surges.
When I realized this, the data started to make sense. I started to look at the files in terms of surges, time in power zones, and normalized power. Looking at off-road files with these tools has proven to be very informative for me. It has changed the way I train. After getting a few race files, I've been able to cook-up some new workouts that better prepare me for races. I've gone from looking at off-road power as an expensive toy to a critical component of training. Now if only we could come up with a meter that measures gnar shredding...
While racing on the Pro XCT circuit, I've found that having power data to go along with heart rate and GPS tells the whole story. Racing locally or nationally, I've found that my heart rate will go to max and stay there. Locally, I can win, nationally I can't...yet. The heart rate doesn't quiet tell the story. The power data shows just how much harder the big races are. I was commonly doing the same number of surges in the first 30 minutes of a national or UCI level race as I was in the an entire 2 hour local race.
That's information that can be used for training. That's information that can improve your performance. If that's not a case for power meters off road, I don't know what is.
Joseph Maloney is a recent UW-Madison graduate in engineering and now works as an engineer for Saris Cycling Group, primarily on PowerTap. He grew up in Milwaukee, WI where he discovered bikes while riding with is dad. He races as a Pro XC racer, Cat 1 in cyclocross and a lowly Cat 2 on the road. He spends his time trying to make it as an elite mountain biker, training and coaching to support his racing. You can check him out on Twitter @jhmaloney and his website for coaching and updates on his shenanigans, or on Facebook.