The figure above shows the Training Zones used by Coach John Hughes, the coach I more or less follow. What are Training Zones? It is obvious that it matters for a cyclist’s training how hard they exert themselves on a training ride. The same ride is harder if a cyclist completes it in 60 minutes by riding it as fast as they can as compared to if they take it easy and finish it in 80 minutes. This characteristic of a workout is named Intensity. The three most common ways Intensity is measured are:
- Subjectively, how hard a ride feels, a metric named Relative Perceived Exertion, labeled RPE on the above figure.
- How many watts of power as measured by a power meter in the bicycle's drive train, a metric labeled Power on the above diagram.
- How fast the athlete's heart is beating, labeled Heart Rate on the above figure.
As is shown in this figure, Coach Hughes believes that these measures are more or less interchangeable.
Although Intensity is a continuous value, for reasons of convenience Intensity is usually divided into discrete Training Zones. Different coaches divide Intensity into different numbers of zones and place the boundaries between zones at different points on the Intensity scale. Also, these boundaries have to be customized to the individual cyclist. Coach Hughes does so by defining the boundaries in terms of measured values for each cyclist, % LT and % FTP for heart rate and power, respectively. (RPE, being subjective, is automatically customized.) I won’t talk about power in this post, you can google the words “FTP power cycling” and find more than you would ever want to know about this topic. I track my intensity by RPE and Heart Rate, so that is what I will discuss. % LT (under Heart Rate in the figure) is short for Percent Lactate Threshold. Coach Hughes defines 100% LT as the heart rate measured during a one hour time trial. The boundary between Zone 4 and Zone 5 is defined to be 100% LT, and then Coach Hughes defines all other boundaries as fixed percentages of that value.
Besides following Coach Hughes, I’ve been trying to follow the principles of Polarized Training. Although Polarized Training has been interpreted differently by different people at different times, my current understanding of it is based on recent podcasts featuring the exercise scientist Dr. Stephen Seiler, the person who invented the term. Dr. Seiler says that Polarized Training means that 80% of training rides should be done below the aerobic threshold and that only 20% should be above it. When I started writing this blog, I believed that the aerobic threshold was the boundary of Training Zones 2 and 3 on Coach Hughes training zones so that if four of my rides each week were in Zone 1 or Zone 2 and if the fifth were ridden in a higher zone I would be following the principles of Polarized Training. Coach Hughes would appear to be a supporter of Polarized Training (see for example his article on Road Bike Rider entitled “Anti-Aging: The 80/20 Principle.”.) What inspired me to write this post is that, given Hughes’ support of Polarized Training and my belief that the aerobic threshold lay at the boundary between Zone 2 and Zone 3, I could not understand why Coach Hughes sometimes recommended riding above that boundary, in Zone 3, during the 80% of rides that ought to be ridden below the aerobic threshold. There are two possible explanations: either Coach Hughes’ zones are not designed such that an athlete’s aerobic threshold is at the boundary between Zone 2 and Zone 3 or Coach Hughes’ training plans do not always follow the principles of Polarized Training.
How do Coach Hughes Training Zones map onto the aerobic threshold of Polarized Training? To answer this question I once again turned to Dr. Seiler. Dr. Seiler uses a three zone system where the zones are named Low Intensity, Threshold Intensity, and High Intensity. These zones are defined by blood lactate concentration. Low Intensity is where Dr. Seiler says 80% of training rides should be ridden. The two boundaries between Seiler’s three zones are the aerobic and anaerobic thresholds. Seiler would say that neither Power nor Heart Rate can be used to locate these boundaries, he would argue that only blood lactate levels can do that, though Power and Heart Rate can be used as proxies after an athlete has calibrated them against lactate. Because both the aerobic and anaerobic thresholds increase with training, this calibration needs to be repeated periodically.
Unfortunately, most athletes, including me, don’t have access to the facilities needed for blood lactate measurements so we have to estimate these values some other way. Having said that aerobic threshold can only be determined by blood lactate, when interviewed in one podcast, Dr. Seiler did allow that for “many” athletes, their aerobic threshold would be somewhere near 80% of their maximum heart rate, which for me, translates into 144 beats per minute. Other coaches make different estimates. Coach Hughes does not explicitly offer an estimate of his own.
Besides just guessing at the translation between aerobic threshold and heart rate, there are other ways of estimating the aerobic threshold. One is to measure the ratio of oxygen inhaled and CO2 exhaled, a test as difficult as the blood lactate test. An easy test is the talk test - the aerobic threshold is the boundary between where an athlete can talk normally and where talking becomes erratic due to the need to breathe more deeply and often. Using the talk test, I estimate my aerobic threshold to be no more than 130 heartbeats per minute, quite a bit lower than the 144 bpm estimated from my maximum heart rate. Could it be that I am not one of the “many” athletes to which Seiler refers? It certainly could! Dr. Seiler mostly works with college age, elite athletes. I am much less talented, much less fit, and much older than those athletes. It is interesting in that context that the Polar Watch Company, maker of one of the most popular and respected sports watches, says specifically that the more fit you are, the higher the percentage of maximum heart rate your aerobic threshold will map to. For me, the range they gave ran from 108 bpm to 153 bpm assuming low fitness to high fitness, respectively. In that context, it seems quite plausible that if Seiler quotes a typical aerobic threshold of 144 bpm, mine would be below 130. This underlines Seiler’s original point that an athlete’s aerobic threshold should not be determined from their heart rate.
So at long last we have the foundation to ask the question “Why does Coach Hughes recommend Zone 3 training as part of the low Intensity training that the Polarized theory says should constitute 80% of workouts?” If my aerobic threshold were 144 bpm, what Dr. Seiler says is the case for “many” athletes, that would lie in Coach Hughes Zone 3. Thus, it would make sense for Coach Hughes to recommend Zone 3 training as part of the Low Intensity workouts that are critical for Polarized Training. If it is the 130 bpm I estimate from the talk test, then those Low Intensity workouts should be limited to Zones 1 and 2. Interestingly, Coach Hughes explicitly endorses the talk test as the boundary between Zones 2 and 3 when using RPE to determine training zones. There are two implications of that. First, it contradicts Coach Hughes’ implicit suggestion that the zones he defines using RPE, Heart Rate, and Power align - they do not necessarily do so. The second implication follows from the fact that for an athlete who uses the talk test to define their training zones, it must follow that by recommending Zone 3 as part of Low Intensity riding, he necessarily violates the principles of Polarized Training.
Where does all of this leave me? There are many things I like about the advice of Coach Hughes but his inconsistency is not one of them. In my last post, I discussed a weekly training plan from Coach Hughes. This plan includes four rides in Zone 1 or Zone 2 and one ride in Zone 3. This schedule is entirely consistent with Dr. Seiler’s Polarized Training ideas. In the post before that, I described Coach Hughes-derived annual training plan. That schedule includes five or six rides a week. Two of those rides are in Zone 1, which is fine from Dr. Seiler’s perspective, but one is a mixture of Zone 2 and Zone 3, and the last two to three are all in Zone 3 or higher, too Intense a schedule according to Dr. Seiler. Should I follow the advice of Coach Hughes, Dr. Seiler, or try to figure things out on my own? In fact, I am figuring things out on my own, using the advice of both Coach Hughes and Dr. Seiler, and writing this post has significantly helped me do that.
