QUESTION: In a few months I will ride my first 300K (186-mile) brevet. A friend told me that the rule for pacing long rides is: Never go anaerobic. Sounds like smart advice, but how can I tell when I’m in danger of doing it? – Bud S.
RBR REPLIES: You’re talking about the “anaerobic threshold,” a phrase used for many years. Nowadays, the more common term is lactate threshold (LT).
To simplify the physiology, as you increase intensity, your body produces lactate. At relatively low workloads, the lactate is cleared readily. But at higher intensities, it builds up and you slow down rather dramatically.
The term “lactate threshold” refers to the intensity at which your body can no longer clear the lactate accumulation. Fit cyclists can sustain a threshold heart rate (about 90% of their maximum) for an hour. On longer rides, like your 300K, you’ll need to reduce your average heart rate considerably below that figure to last the distance.
You don’t need a heart monitor to do it. The trick is to ride at a pace that keeps your breathing regular. When breathing becomes forced it’s a sure sign you’re asking your system to clear a lot of excess lactate. Doing so uses muscle fuel and almost certainly means you’ll ride slower later in the event.
The trick is to keep your enthusiasm under control, especially on climbs or in pacelines where you might be forced to ride too hard.
That said, you can gain quite a bit of time on hills if you carefully elevate the pace to just below your LT and recover on the descents. But in a long event, you need to be extremely careful with this strategy because a foray or two over LT can cost you dearly.
Bottom line: If you’re breathing hard during a long ride, you’re probably in trouble – unless you’re so fit that extended efforts near your LT are possible. But riding that hard usually exacts a high price later in the event.
The only way to learn your maximum safe pace is to get experience in longer events. This is one of the educational benefits of a brevet series. With progressive distances of 200, 300, 400 and 600K, riders learn plenty about pacing and endurance.
Lots of us know what it’s like to push too hard early in a century or double century, then pay the price. But that’s actually an effective way to learn for sure where the limit is.
Fred, wouldn’t you also recommend a pace slow enough that the rider is primarily burning fat, rather than glucose? Standard wisdom (correct me if I’m wrong) is that none of us has enough glucose stores to last more than, oh, two hours. So for most of the ride, you need to burn fat. Since “fat burns in the flame of glucose,” and you need to burn some glucose throughout the ride, you don’t want to exhaust your glucose stores. Also, a rider who has gotten fit via hour-long training rides hasn’t trained his/her body to burn fat. I’d suggest that Bud S. ride a few really long training rides, certainly well over 100k and if possible 200k,, to introduce his body to heavy-duty fat burning. That will also give Bud first-hand experience of how his body feels at the end of such a ride, and that experience will inform his early-ride pace.
John, you can ride slow enough to rely mostly on fat, but that is a pretty slow pace. Fat does burn in a glucose fire and that is why you need to constantly eat during a long ride. While there is individual difference, you can absorb nearly 400 calories per hour of mixed carbohydrates (i.e. real food) and therefore need about 200 calories per hour from fat, which is about what a trained rider can burn. In this way you can ride “forever” at a reasonable pace as long as you keep eating.
Forty years ago, I did the qualifiers for P-B-P here in the States. At that time I could ride a sub-five century on a reasonably flat course (about 2000′ elevation). This was basically a TT ride, but there was some drafting. When I did the 600 Km brevet, my elapsed time was 27 1/2 hours. I would have failed the 1200 Km riding in this manner. I had to have someone unclip my feet (and this was in the days of toe-clips) and catch me when I finished. I could not dismount on my own.
A company called Xert has software that can be run on an Android, Apple and some Garmins that will give you a good estimate of the calories being burned by fat and carbs. If you stay below your LT, these will be approximately equal. This requires a power meter and HR monitor. You can ride almost forever at this pace. In my late 70’s now, but using the principle’s you described, and monitoring my power output, I recently did STP in 12 hours.
My experience is that anytime you go over your Lactic Threshold, you are burning matches. And when you burn the last one, you have to stop and recover. And in my experiment of one, my current lactic threshold is about 148 watts. If I keep my peak power output below 220 (and the 220 is for a brief period of time, say less than 2 minutes) and my average power between 138 and 142 watts, I can do a Century ride with 8000′ of climbing in just over 7 hours, and I clock in a approximately 200 lbs.