An athlete improved his VO2max by 40% after changing his distribution of training intensities. In yellow is his old (bad) distribution. In red is his new (improved) distribution.
In the first post in this series, I made the argument that all of the most common measures of ride intensity: heart rate, power, blood lactate, oxygen consumption, even relative perceived exertion; were all different ways of measuring calories burned per hour. Perhaps one of the most direct measures of the rate of calories burned is oxygen consumption. Because oxygen is a gas, usually the best way to measure it is by volume, how many liters of oxygen are consumed per minute, a metric known as VO2 which stands for the Volume of O2, with 02 being the chemical symbol for the gaseous form of oxygen that we breathe. At rest, one consumes less oxygen and fewer calories per minute than when exercising. Of particular interest has been the maximum amount of oxygen it is possible for an athlete to consume when they are exercising as vigorously as possible. In the exercise community, this metric is named VO2max. In the scientific community, this exact same metric is sometimes referred to as VO2peak. This reflects the rigor of the scientific community, it recognizes that the value for VO2 measured can depend on how the measurement is made so that it is not really possible to know the maximum oxygen consumption but only the peak oxygen consumption measured in a particular experiment. (The MET, a metric popular in the health community, is more or less the same thing as VO2 and the equivalent of VO2max is max METs.) In the exercise community VO2max is often interpreted as “engine size”, the higher the VO2max an athlete has, the larger an “engine” they have. While it certainly is the case that an endurance athlete with a relatively low value of VO2max is unlikely to be competitive at the highest levels of their sport, it is also the case that the athlete with the highest VO2max will not necessarily win the race, other factors matter as well. In fact, more recent discussions deprecate the importance of VO2max in favor of other parameters such as threshold power, ability to quickly recover from a hard effort, etc.. In the health community, VO2max (aka VO2peak aka max METs) is often used as a stand-in for aerobic fitness; e.g. to conclude that subjects with higher VO2max live longer than those with lower VO2max.
Given the importance of VO2max, it has been a source of discouragement to the exercise community that it seemed very difficult to significantly improve VO2max by training. It seemed that every athlete was born with more or less the level of VO2max they are going to have throughout their lives. There is some variability from athlete to athlete in the trainability of VO2max . Some athletes cannot improve their VO2max at all, others can, but it is rare to find an athlete who can improve their basic VO2max by more than 15% or so. But how is this trainability determined? In my last post in this series, I mentioned the intensity of exercise traditionally used to improve various skills that an athlete might want to improve. According to the coach I used as an example, Coach John Hughes, Zone 6 of his 7 zone system is the intensity he recommends for improving VO2max. Specifically, he recommends working up to 2 to 4 repeats of 2 to 3 minutes at a heart rate greater than 105% of an athlete’s lactate threshold heart rate as a routine for improving VO2max. Thus, a typical experiment used to determine the trainability of VO2max is to measure VO2max on all subjects, have them engage in a training routine like that recommended by Coach Hughes for 6 weeks or so, and then measure it again. And this brings us to the very anecdotal, very problematic report which is the subject of this post.
Simplifaster is a company that makes exercise equipment. It stands to reason that they would prefer that athletes believe that training, in particular, training with Simplifaster’s equipment, improves performance. If it did not, why would anyone buy their equipment? Thus, a report on their website claiming that, with the right training, VO2max can be increased not just by 15% but by 40% would appear to present a conflict of interest. And yet, such a report is just what I am going to talk about. Worse yet, it describes an experiment on just one athlete, what would be called a “case study” in the medical community. Given these reservations, why am I blogging about it? It is because it is thought-provoking. Maybe we should not believe this report without confirmation, but maybe we should be inspired by it to question the conventional wisdom about the trainability of VO2max more than we have to date. The article is here.
The author of the article, Alan Couzens, is both an exercise scientist and a coach. Most of the article is a case study of one athlete he coached with the rest being some discussion about how typical this one athlete might have been. This athlete’s event was the Ironman Triathlon. His goal was to qualify for the Ironman World Championships. Qualifiers for that event typically have a VO2max of 65-70 ml/kg/min. This athlete trained by doing a lot of high intensity interval training at the intensity normally recommended for improving VO2max, and fully trained, he never exceeded a VO2max of 53 ml/kg/min. It might be argued that no further increase in VO2max was possible since he was already fully trained, but even assuming an improvement was possible by changing his exercise plan, a 15% increase, normally considered the maximum possible, would only give him a VO2max of 61, below typical qualifiers. At this point I want to be clear as to the relevant question. To the athlete, it is ‘Can I qualify for the World Championships?’ However, for the purposes of this post, the relevant question is ‘How much can this athlete improve his VO2max?’ This is a related but different question. What this coach did is exactly what most coaches would do, to replace some of this athlete's high intensity VO2max training with a large volume of relatively low intensity aerobic training and to maintain this program for three years. In year 1, his VO2max improved by 22%. In year 2, his VO2max improved by an additional 12%. In year 3, his VO2max improved by an additional 6% for a total improvement in his VO2max of 40% over three years. His final VO2max was 74.6 ml/kg/min, higher than the typical triathlon national champion, and in fact, he was able to qualify for the national championships. Finally, the author of this study noted that this athlete was not average, very few of the athletes he has coached improved their VO2max by 40%, but on average, they improved their VO2max by 24%, still significantly more than the 5-15% conventional wisdom would predict.
So, is Coach Hughes wrong about the benefit of Zone 6 training for VO2max? The author does not say that. Rather, he says that after an athlete has completed a long period of high volume/low intensity training, a small additional increase in VO2max can result from a brief period of high intensity (e.g. Zone 6) training. For the athlete who was the subject of this case study, the author suggests that the first 32% of improvement came from the large volume of low intensity training and the remaining 8% came from the small volume of high intensity training which was only done at the very end, after the low intensity training.
There is nothing new about the training plan that Couzens recommends, it is basically the same plan that every coach I have ever read recommends. Is it polarized training? For some time now, I have been following Stephen Seiler, the exercise scientist who coined the term polarized training, and I get the sense from him that what is of proven value in polarized training is less the high intensity side of that polarization and more the low intensity side. Thus, both polarized training and the training plan recommended in this report mostly just support the conventional wisdom of the coaching community that large amounts of low intensity exercise are an essential part of training for endurance sports.
Before switching focus from Fitness to Health, I need to insert a caveat. Everything up to this point has considered athletes whose current training program may not be optimal but who are relatively fit to begin with. This is very different from the situation faced by the public health community who are interested in the benefits of exercise for health. Their studies are often on subjects who start out not exercising at all. Might such a person, one starting from a much lower level of fitness, have a greater potential for increasing their VO2max? I don’t have an answer to that question, but I do think about it while I am considering these health-oriented studies.
One health oriented study I have considered multiple times on this blog is one I call Gillen et al. This study claimed that the health benefits of 1 minute of high intensity interval training (Zone 7) was equal to those of 45 minutes of low intensity aerobic exercise (Zone 2.) At the time I first reviewed this publication I had the following reservation:
“Am I convinced that HIIT [High Intensity Interval Training] provides as much benefit as moderate exercise in extending longevity and improving health? … Not yet [because, although] after twelve weeks, HIIT and moderate exercise produce the same changes in VO2max, glucose tolerance, and muscle mitochondria, ... would these changes be equally maintained if the experiment were extended to a year or ten years?”
The report which is the subject of this post would argue that my concerns are very justified, that if the experiment had been extended from 12 weeks to 3 years the results might have been very different, the low intensity group might have increased their VO2max much more than the high intensity group.
This report has different implications for another study I reviewed. This study compared over 100,000 patients who had taken treadmill “stress tests” as part of their medical care. These subjects were grouped by their max MET scores (equivalent to VO2max) and their risk of dying was followed over the next 4 to 13 years. The astounding result obtained was that the fittest 2.3% of the patients had a greater than 5-fold lower risk of dying than the least fit 25%. Compare this to the decrease in risk obtained by not smoking which is only 1.4-fold. Because this was an observational study, it was not possible to determine how much of that fitness was genetic and thus is out of the patient’s control and how much was the result of exercise. One hint as to the answer to that question came from a second paper I considered in that post which also looked at over 100,000 subjects and which was also an observational study but which asks its subjects how much they exercised. In this study, those who exercised the most had a 1.5-fold lower risk of dying, suggesting that much of fitness is genetic. Another way to ask this same question is to assume that VO2max can typically be increased by about 25% by exercising. How much would that help the treadmill scores of subjects with low fitness? In the treadmill study patients were put into five groups; the 25% with the lowest fitness, the next 25% with below average fitness, the next 25% with above average fitness, the top 25% with high fitness, and then a subset of this last group, the 2.3% with the highest fitness. In general, improving VO2max/max METs by 25% would move a subject up 1 group. This would decrease their risk of dying by about 1.4-fold. Thus, both of these approaches, an observational study that looked at exercise rather than fitness and a theoretical approach based on studies which measure how much VO2max can be improved provided very similar results; exercise can reduce risk of death about 1.5-fold whereas genetic factors that impact fitness can reduce risk of death by about 3-fold. This is a very weak conclusion based on a shaky chain of logic, but it is intriguing and to my mind begs for follow-up.
In the final post in this series I am going to look at the major competing theory to Polarized Training, and that is Sweet Spot training, a theory that seems to recommend the exact opposite to Polarized Training. Rather than avoid exercise which is in between low intensity and high intensity, such medium intensity training is the focus of Sweet Spot. Stay tuned.
