Tour de Pink V

A selfie taken at our start of the 2015 Tour de Pink. The start/finish line is to the left of my head, marked by the pink and yellow decorations. There is nobody else there because we got there a bit late and everyone else had already left. This picture would have been better had we used a selfie-stick, but when I attempted to purchase one at Best Buy, I was told that I was over the legal age for purchasing this device.

This year, my wife and I rode in the Tour de Pink for the fifth year in a row. As in previous years¹, there were rides of 12, 23, 34, 47, 63, 81, and 100 miles. The routes were the same as for the previous four years and are shown on the map I posted in 2012. Because of my dad's illness and death, we were unable to train this year, so instead of our usual 63 miles, we rode the 34 mile route. I confess that it was discouraging to "go backwards", to have to decrease our mileage from previous years rather than increase it. On the other hand, because the 34 mile route goes over different roads than the 63 mile route, this change provided some much appreciated variety.

There were changes to the signup and fundraising aspects of the ride this year that I did not like. Since last year, the organizers had their website redone. Somehow, the developers who did that were not able to bring forward the membership information from the previous design so I had to re-enter all my information. Then, after I had committed to riding, I was informed that the fundraising schedule had been changed. In previous years, we had until one month after the ride to complete our fundraising. This year, I was informed, fundraising had to be completed before packets could be picked up, a few days before the ride. Honestly, I always self-fund so I really didn't care, but my wife enjoys getting some of her friends to support her ride, and this made it more difficult for her to do so. Compounding the problem, and another consequence of having had a rough year, we were signing up relatively late, not the organizers fault, but had we known about the tighter fundraising deadline, we might have pulled it together to sign up earlier. But the coup de grâce came when, in a last minute email, the organizers told us that although the deadline for fundraising was Thursday, they needed to "run the numbers" on the previous Monday, so the real deadline was not Thursday but Monday. At that point, we gave up on my wife being able to fundraise and I sat down to donate to both me and my wife. I did that the Sunday prior to the new deadline of Monday, since I had no idea what time on Monday they would "run the numbers." When I went to donate to myself, I was dismayed by the huge amount of information the organizers insisted they get from me before they would deign to take my money, but in the end, the donation was made. I then went to donate to my wife. After redundantly entering all the same information, I was told that "something had gone wrong" and that I had to "contact their fundraising department."  I would have hoped for a phone number for the fundraising department as part of this message, but it was not provided. Further, try as I may, nowhere on their website could I find any such thing as a fundraising department. I called their main number and left a message, hoping they would call me back before "running the numbers." The next day, my wife called them to resolve this issue, and they told her that this was a feature, not a bug. "The anti-fraud feature of our new website was triggered when two donations came in right after another from the same credit card." (Of course, nobody would ever want to make donations to more than one rider. Sheesh!) Next, they didn't want to take her money. "Just pay when you pick up the packet" they suggested. This didn't work for us because our team captain was picking up packets for the whole team, so when my wife insisted, they reluctantly took her credit card number. The final irony came when I went to my LBS to pick up some last minute parts and found that, coincidentally, they were the site of packet pickup. I asked the people giving out packets if our team captain had picked up our packets, and when they checked, they said he had not. "We had a very early deadline for registering teams for team pickups this year" the person behind the counter said. I am sure I am just projecting, but I could have sworn that person took perverse satisfaction in this inconvenience. When we got to the ride the following Sunday, it seemed to us that there were many fewer riders this year than previously. I wonder why (he asks sarcastically)?

So, bad year, discouraged at doing a shorter ride, annoyed at the organizers, getting up at 5 am to drive in the dark to the ride start, getting there a bit late and missing our team, this was not a good start. A few miles into the ride, we encountered an unfortunate stretch of road with a lovely wide shoulder ruined by a rumble strip. It looked like there might have been enough shoulder on the far side of the rumble strip to use, so I gave it a try. The rumble strip was brand new and especially aggressive, and riding over it caused my headlight to fall off and be ruined, and shook my cadence sensor to bits, both ruining it and preventing me from collecting stats for this ride. To top it all off, we got back to the finish early and lunch was not ready. We had the choice of sitting around and waiting for what in the past has been a mediocre lunch, or just blowing it off and going home. We chose the latter. I was all set to entitle this post "The Last Tour de Pink?" but as we were riding back to the car, my wife turned to me, graced me with her world-famous smile, and said "What a lovely ride!" All of a sudden, it was worth it. I guess we will be going back next year.

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1) We rode the Tour de Pink in 2011 before I started this blog, so that ride is described in my post for the 2013 ride. Here are the links for the rides we did in 2012, 2013, and 2014.

What Does Decoupling Mean?

This graph, taken from my Garmin cycle computer, recorded on the Rice Track, probably is recording something other than classic decoupling, except perhaps at the very end. Note the relatively constant reduction of speed at a constant heart rate over the entire time of the hour and a half ride. This is something I almost always observe, but it probably reflects something other than decoupling because it happens too soon; classic decoupling normally appears after a couple of hours of riding. The fall off in speed seems to accelerate at the very end of the ride, which might be decoupling. I do not know what the relatively constant fall off in speed vs heart rate is, but one guess is that it is due to heat. This ride, like many of my rides, starts early in the morning to avoid the heat, and the temperature rises significantly over the course of the ride.

A frustration I have reading the training literature is that it seems that nobody puts all the facts together in logical order in one place. I feel like I pick up a fact here, a fact there, and it is only months later that I can start putting all the pieces together and make sense of it. Such is the case with decoupling. A brief description of decoupling is as follows: My heart rate is normally determined by the intensity at which I exercise. If I ride my bicycle on a flat course (e.g. the Rice Track) with no wind, the faster I ride, the higher my heart rate is. If I ride at a steady speed, my heart rate stays constant, at least for a while. However, after some period of time at that steady pace, my heart rate will start to increase. This phenomenon is called decoupling. How quickly decoupling occurs is used as a measure of endurance. The longer I can ride before my heart rate increases, the more endurance I have. But, despite having read a number of well respected training manuals, it is only now, after years of research, I feel like I am beginning to get a sense of what causes it.

There a lot of indicators I can use while training to let me know if I am training at my intended level of intensity. I can monitor how I feel; if my legs feel sore or if I am breathing heavily, for example. This is sometimes referred to as Relative Perceived Exertion (RPE). I can monitor my speed using my Garmin cycle computer. Of course, the meaning of that speed is influenced by many factors: whether I are going uphill or downhill, the intensity and direction of the wind, and which bicycle I ride to name but a few. I could remove many of these variables by using the output of a power meter instead of speed to measure how much effort I am expending, but power meters cost more than I am willing to spend (in the ballpark of $1,000). And finally, I can monitor my heart rate.

Speed and heart rate are two different ways to measure the intensity of a ride. Both are affected by issues other than the intensity of the ride, so can be misleading. However, in both cases, if I stay aware of these other factors, I can allow for them and avoid being misled. Because heart rate and speed reflect somewhat different things, more information can be gathered by comparing them than by looking at either one by itself. In fact, I have used comparison of speed and heart rate many times on this blog. That is, after all, what a MAF test is. After warming up, I ride on the Rice Track which is flat and contains no traffic or stops, keeping my heart rate between 130 to 140 beats per minute, and measure my average speed over 45 minutes. If I am off the bike for two months or so, I return to a low level of fitness and that speed may be as low as 12 miles per hour. If I am at my peak fitness, that speed can be over 16 miles per hour. Another way I have used this comparison is to note not just the average speed, but how that average changes over time; is the average speed for the second half of a ride significantly slower than for the first, for example? If they are almost the same, then heart rate and speed are coupled. If they are significantly different, then heart rate and speed are decoupled. What would cause these two factors to become decoupled over the course of a ride?

Answering this question is difficult. It would seem that muscle fatigue must be involved, but much less is known about muscle fatigue than I would have expected. As recently as 2010, the our whole understanding of what limits aerobic exercise was turned upside down (European Journal of Applied Physiology (2010) Volume 109 Pages 763-770; explanation here.) I hope to return to this topic later, but for now, I suggest we consider some aspects of muscle fatigue to be an observation without explanation, it happens and we don't know why. However, one part of muscle fatigue is well understood, and that one is important; glycogen depletion. To to explain how this contributes to decoupling, I have to talk about two¹ different kinds of muscle fibers, fast twitch and slow twitch,and the fuels that they can use.

The names fast twitch and slow twitch refer to technical aspects of the electrophysiology of these different kinds of muscle fibers; it is only coincidence that fast twitch muscle fibers are used when I ride fast, and slow twitch when I ride slow. Fast twitch muscle fibers are very strong but tire quickly. They are used in a sprint, for example. Slow twitch muscle fibers are relatively weak, but can keep going for hours. They are used in a long bike ride. Both fast twitch and slow twitch muscle fibers can use glucose as a fuel. This glucose can either come from glycogen stored in the muscle fiber itself or from the blood, which mostly comes from food I eat. However, the glucose from glycogen can be provided much more quickly than glucose from blood; no matter how much I eat, I will have to slow down when my muscle glycogen is gone. In addition to glucose, slow twitch muscle fibers can use fat as fuel. (Fast twitch muscle fibers cannot use fat, they can only use glucose.) Again, this is a slower process and turns out not to be all that directly relevant to decoupling, but does have an indirect effect, discussed at the end of this post. The final, key point is that glycogen cannot be shared between muscle fibers. When fast twitch fibers run out of glycogen, they cannot borrow from slow twitch fibers, and vice versa.

It turns out that the rate of availability of different kinds of fuels is a major contributor to decoupling. If I am riding at a relatively slow pace, it will primarily be my slow twitch muscle fibers pushing the pedals. However, after a couple of hours, the glycogen in my slow twitch muscle fibers will be used up. These fibers can continue working using blood glucose or fat, but not at the same rate; fast twitch muscle fibers will have to make up the difference. The problem is, fast twitch muscle fibers are stronger but less efficient than slow twitch muscle fibers; my heart will have to beat faster to accomplish the same amount of work, resulting in decoupling.

I had always assumed that there are mechanisms for fatigue of slow twitch muscle fibers other than glycogen exhaustion, but truth be told, I do not know if there are or are not. However, if there are, they should play an almost identical role in decoupling as glycogen exhaustion. Once slow twitch muscles loose their ability to function at the same level, fast twitch fibers will be called upon to pick up the slack and their lower efficiency will result in decoupling.

The above explains "classic" decoupling, where after some period of riding, heart beat rises with no increase in effort. There are other situations where heartbeat is higher than expected for a given level of exercise. Three conditions, besides fatigue, that can cause this are emotional upset, dehydration, and heat. Heat turns out to be very important, as is the correct response to the decoupling created by heat. If one is competing in a race and attempts to maintain constant speed under conditions of high heat, one will "run out of steam" by the end of the race. Rather, one should maintain constant heart rate and allow speed to drop.

If "classic" decoupling is a measure of endurance, and endurance is something I am trying to train, what are the changes in my physiology that occur during training to improve my endurance, to delay decoupling? I'm think it is highly likely that these effects are not yet completely understood, but here are two that I think are fairly well established. First, the amount of glycogen stored in my slow twitch muscle fibers will increase. This will allow me to ride for a longer period of time before that glycogen is exhausted and decoupling begins. Second, my slow twitch muscle fibers will become "better" at using fat as a fuel. Fat will never be able to completely substitute for glycogen, but the more efficiently it can be used, the more it will slow down the use of glycogen, making it last longer.

So who cares? I do, but not because I expect any of this to improve my fitness. I care because I am curious. I like to understand why my body behaves the way it does when I ride and when I train. That said, I firmly believe that our current understanding of normal muscle physiology is woefully lacking, and that as a result, we are far from being able to design a training routine based on theoretical considerations. That is why I am such a fan of coaches like Joe Friel. I think the years of experience that the best coaches have provide a much better basis for designing a training program than the kinds of theoretical understandings discussed in this post. Finally, I think for the kind of cycling I want to do and the goals that I have, training is not all that complicated; "just ride" is probably pretty good advice. Still, trying to figure this stuff out, while not all that useful, I find to be a great deal of fun.

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1) There are more than two kinds of muscle fibers, there are at least three, but my simplified explanation is adequate for this post.