Tuesday, January 22, 2008

Active Spokes

Did you ever see an invention and wonder, “Why didn’t I think of that?” I’ll tell you about my experience with that thought last summer after I was approached by a triathlete from New York who asked me to take a look at his new concept.

It wasn’t the first time someone had asked me to do this. But there had only been one previous invention I thought had any promise. That one was ten years ago and it became the PowerTap™ power meter. It has done pretty well. None of the others I’ve been shown made it to market. They didn’t have any real merit and it was obvious.

So when this triathlete asked me to sign a non-disclosure agreement before seeing his invention I was highly skeptical and was already trying to come up with excuses for why I couldn’t be involved in the project. But when I saw the concept it was like the V-8 commercial where the guy dummy slaps his forehead, only now it was, “I could’ve thought of that!” The concept is quite simple but it contradicts traditional thinking about bicycle wheels. That’s probably the reason no one else, including me, dreamed it up.

The traditional way of viewing race wheels is that they need to be light, especially near the rim, as heavy rims make acceleration more difficult. And since climbing a hill on a bike is essentially a series of alternating decelerations and accelerations with every pedal stroke, we certainly don’t want heavy rims when climbing a hill. Nor do we want heavy rims on a course with a lot of corners. I once did a 30k bike leg in a duathlon that had 36 turns. A heavy rim would have been a disaster for this race with all of the accelerations coming out of each corner.

But there are times when a heavy rim would be advantageous. Nobody ever talks about this, but it’s true. When coming down a hill, starting up the next hill at the bottom of a descent, or riding on a flat course a heavy rim has certain advantages. You’ve probably experienced what I’m describing here if you’ve ever ridden a bike at your gym or health club that has a heavy flywheel. You know how difficult it is to decelerate or stop the thing without using the brake. The wheel just wants to keep on going even without you adding any more energy to the system. If some how your rim could be heavier going down hills and on flat terrain when acceleration is not necessary and light when climbing or coming out of a turn you’d have an advantage. So you have a choice to use either a heavy-rimmed wheel or a light-rimmed wheel when racing. I’ve never known anyone to opt for a heavy race wheel.

We’re pretty much brainwashed by marketing and common practice to believe that a light wheel is the only way to go for all situations. No one goes out and looks for heavy-rimmed wheels when making a purchase. Even if you did decide you wanted to use a heavy rim in a certain race it would require you to buy a second pair of race wheels—if you could find a manufacturer who made an aerodynamic, heavy-rimmed wheel. Good luck.

These thoughts passed through the mind of the inventor I mentioned above during a tough interval training session he was in early last year. His name is Russ Kalil. He's an Ironman. During the session Russ wished he had a heavier rim for the downhills and flats and a lighter one for the uphills and corners. Then it dawned on him—why not make a wheel that changes from a light rim to a heavy rim during the race? So when he got home he went straight to his basement and began toying with the concept he had dreamed up during the workout—a wheel with small weights that move along the spokes back and forth between the hub and the rim. At slow speeds they would be next to the hub. At high speeds they would move to the rim. And when you slow down they’d move back to the hub again. His prototype was made with rubber bands and fishing weights. It worked, at least in his basement on a work bench. So he began to refine it. That’s about when he contacted me.

He wanted to conduct a study to see how it would work in the real world and needed an athlete to test it on. I immediately enlisted my son, Dirk Friel, to be the test subject. Russ also brought Joseph Voelkel, PhD, from the Rochester Institute of Technology, onboard to conduct the testing. So Dirk and Dr. Volekel spent the summer conducting field tests on the 5-mile, rolling course for the Boulder Time Trial Series. What they found was a two- to five-percent improvement in Dirk’s times at a given power with the moving weights compared with the same wheel without the weights. In fact, Dirk went on to have his fastest time ever in one of the races in the series using the invention, which is now called the Active Spoke™.

Now as a much more refined and elegant device Russ has figured out how to calibrate the weights so they move to the rim at a specified speed. So you can customize the wheel to your typical race speeds and the course you’ll be racing on. The device can be installed on your existing race wheels (see photos). Look for a manufacturer’s wheel with this technology built in to also be available soon.

This past weekend the website where you can find out more details and purchase an Active Spoke™ kit to customize your own wheels went online at http://active-spoke.com/. The concept is currently being examined by the ITU for use in multisport racing and appears, as of this writing, to have met their standards for use in sanctioned races. The UCI has yet to review it. It is being rolled out at the SICI convention in Denver the end of this month (www.serottacyclinginstitute.com).

The bottom line is that the concept works. You’ll race faster on certain courses using Active Spokes™. When you see the simple concept in action you’ll probably do the same dummy slap I did and wonder why you didn’t think of it.

Tuesday, January 15, 2008

Saturday Talk In San Diego area

I'll be speaking this Saturday, January 19, at the Solana Beach B&L Bike shop at 2pm. The store is located at 211 N. Highway 101, Solana Beach, CA 92075. I'll be talking about training for cycling events, especially the San Diego Century. For more information call (858) 481-4148. It is free.

FTP and Power

Training with a power meter is much like training with a heart rate monitor. You need a reference point and, based on that reference, personal zones are set up. Then workouts are prescribed using those zones. With a heart rate monitor the reference point is your lactate threshold heart rate. I describe how to find this heart rate reference point in my books, especially the latest--Total Heart Rate Training.

The reference point for power comes from the work of Andy Coggan, PhD. He calls it Functional Threshold Power (FTP). FTP is the power you would average with your highest possible effort during a 60-minute race. Once you know your personal FTP you simply use Andy's system to find your zones as described in Hunter Allen's and Coggan's book, Training and Racing With a Power Meter:

Zone 1 <55% (active recovery)
Zone 2 56-75% of FTP (endurance)
Zone 3 76-90% of FTP (tempo)
Zone 4 91-105% of FTP (lactate threshold)
Zone 5 106-120% of FTP (VO2max)
Zone 6 121-150% of FTP (anaerobic capacity)
Zone 7 >150% of FTP (neuromuscular power)

The key to all of this is discovering your FTP, and making sure it's current as your power changes relatively quickly, at least as compared with heart rate which hardly changes at all over the course of a season. Expect FTP to change about every four to eight weeks as your training load increases or decreases.

There are many ways to find your FTP. My favorite is simply to have the athlete complete an all-out, solo 30-minute time trial which is NOT part of a race. I've found the average power for this 30-minute, solo effort to be quite close to what the athlete does in a 60-minute race, such as a 40k time trial. The reason is that when riding alone you'll feel sorry for yourself and not go as hard as you would should it be a 30-minute race where you are held accountable to the world for your results and motivation is therefore considerably higher.

Allen's and Coggan's book describes several other ways of finding your FTP. And it's a great reference for understanding other aspects of power-based training.

Friday, January 4, 2008

Climbing Power Formula

I came across an interesting formula yesterday that may be used to predict how much power is necessary to climb a given hill on a bike. It's from Allen Lim, PhD. Allen has a long list of accomplishments related to power-based cycling the most notable of which is consulting with Floyd Landis. Floyd credits Allen with determining what he would have to do powerwise to win the now infamous stage 17 of the 2006 Tour de France. I haven't talked with Allen in some time and no longer have his email address after a computer crash this past fall so I haven't been able to confirm what I'm about to show you. But it seems to work so I suspect it's right.

Dr. Lim's formula to estimate the power necessary to climb a hill:

bike + rider weight (kg) x 9.8 x elevation gain (meters) / time (seconds) = power (watts). Add 10% for rolling and air resistance.

So yesterday I tested it. I climbed a known one-mile hill and captured the data on my power meter. Here are my metrics from that climb:

Weight of my Cervelo Soloist with 1 water bottle - 8.18kg
Body weight with winter clothes, shoes, etc - 74.55kg
Elevation gain (est based on average 5% grade) - 78.87m
Time to climb hill - 312 seconds

Plugging all of these into the formula and adding 10% predicts that it would take me 225 watts to climb this hill. The actual was 218. Remarkably close, especially when you consider that I am estimating the elevation gain and there is some variation between power meter readings.

Of course this formula could be used to figure out how long it would take you to climb a given hill in a race at a certain power output by simply rearranging the formula components. You could also use it to figure out how much faster you would climb a hill if you reduced your total system weight by a given amount but kept power the same.

Interesting stuff. If Allen sees this I hope he comments.