Are the exercise recommendations insane?

I try to stay fit. I lift weights. I do crossfit. I do judo, and I still practice at a fairly respectable level. Since I found the training diary Funbeat about two years ago I have been keeping a detailed training diary. Recently I went through my training statistics and came up with some interesting numbers. In the last two years I have trained 262 times for a total of 285h 29min. That comes out to about 23 minutes per day or 164min per week on average.

Now, let us have a look at the exercise recommendations from the World Health Organization, Centers for Disease Control, or the Swedish equivalent Folkhälsoinstitutet. Here follows the text from the WHO, the others are exactly the same.

Adults aged 18–64 should do at least 150 minutes of moderate-intensity aerobic physical activity throughout the week or do at least 75 minutes of vigorous-intensity aerobic physical activity throughout the week or an equivalent combination of moderate- and vigorous-intensity activity. Aerobic activity should be performed in bouts of at least 10 minutes duration. 

For additional health benefits, adults should increase their moderate-intensity aerobic physical activity to 300 minutes per week, or engage in 150 minutes of vigorous-intensity aerobic physical activity per week, or an equivalent combination of moderate- and vigorous-intensity activity. 

Muscle-strengthening activities should be done involving major muscle groups on 2 or more days a week.

We immediately notice that I follow the minimum guidelines of 75 minutes of vigorous-intensity aerobic activity, and two days with muscle-strengthening activities. But we cannot say that I fulfil the guidelines for additional health benefits. On average I do 164 minutes of exercise including strengthening activities. Of course, we might argue that I ride my bike to work, walk the dog, and go shopping so that I easily fulfil the quota. However, the guidelines specify at least ten minutes duration, and in the complete text specify that you should raise your heart rate and break a sweat. Even going as far as specifying that just shopping or walking the dog does not count for most people because the intensity is too low, so that argument does not work.

In the end we must find that I have a hard time keeping up with the guidelines. At the same time, with that activity level I am able to practice judo with our ten to twenty year younger elite and junior players. I am stronger than I ever was, and have as high endurance as I have had since I stopped swimming. For those (like me) who like numbers that means a 170kg dead-lift, a 90kg bench-press and a 124kg back-squat, and endurance-wise a VO2max of around 60ml/(min*kg). Nothing spectacular, but clearly very fit for a 35-year-old nephrophysiologist.

How can we possibly expect our patients, and the public in general to be able to train that much? And, would I actually increase my expected life-span and number of healthy days by more than doubling my training? For breast and colon cancer the guidelines say:

Data indicate that moderate- to vigorous-intensity physical activity performed at least 30–60 minutes per day is needed to see significantly lower risks of these cancers.

60 minutes per day? On average? For enough time to affect cancer mortality? Who the fuck even completed these studies?

Comparative physiology of aerobic scope

When surfing around looking for data on VO2max I found some interesting comparisons.

First we can have a look at different sports, you may remember that elite judo athletes had a maximal VO2 at around 60 ml/(min*kg). I guess most readers will have heard about the extremes of aerobic capacity. Who the best is depends on the unit used. Cross country skiers are the most extreme when compared to body weight. The highest ever published VO2max was Bjørn Dæhli, world champion from Norway. He had a VO2max over 90 ml/(min*kg), I have seen anything up to 96 ml/(min*kg), but cannot find the original publication.

If we ignore body weight, olympic rowers are reported with the highest oxygen consumption among athletes, but they can afford to be more massive than many other athletes and therefore get lower maximal uptake when related to body weight.

Then we can look at the real comparative physiology of endurance. Reported maximal oxygen consumption VO2max in running animals are quite a bit more impressive than humans. Note that these are extremes from non-original publications.

Human: 96 ml/(min*kg)

Horse, thoroughbred: 160 ml/(min*kg)

Dog, sledhound: 240 ml/(min*kg)

So, that's why I can run for an hour with my boxer, and when I am all done she wants to play fetch. For another hour.

Even more interesting than maximal aerobic capacity is the concept of aerobic scope. That is the difference between the rate of oxygen consumption at resting metabolic rate and at maximal aerobic exertion, i.e. VO2max.

Oxygen consumption at rest from original publications:

Human: 7.8 ml/(min*kg) (J Hum Kin vol 6, 2001, Andziulus et al)
Horse: 7.2 ml/(min*kg) (Am J Physiol vol 253, 1987, Weber et al)
Dog: 7.8 ml/(min*kg) (J Appl Physiol vol 19, 1961, Bailie et al)

This gives an aerobic scope of about 10 times in human endurance athletes, 20 times in racing horses and a whopping 30 times in racing dogs. This is not what is generally reported as aerobic scope because it is usually based on basal metabolic rate, which is a theoretical entity measured after sleep and fasting at a high ambient temperature. And, it is compared to popularly reported maxima for the different species. If you look at scaling and metabolic scope there are better articles with reproducible methods and averaged maxima e.g. Charles Bishop, Proc. R. Soc. Lond. B (1999) 266, 2275-2281.

In addition to being interesting, I am pretty satisfied to have combined science, dogs and photography in one post. 

Aerobic endurance

Today's post is about endurance. Physiologically, endurance is about energy delivery. In many ways the muscles are machines that can keep up a given amount of work for as long as there is sufficient energy. Chemically, fuel and oxygen is converted to carbon dioxide and water, which releases energy. This is the same thing that happens in a fire, but since we don't want to burn up, the energy release is very closely controlled by the use of the energy currency: adenosine triphosphate (ATP).

New ATP is produced through three basic mechanisms: nonaerobic metabolism, anaerobic metabolism and aerobic metabolism. The mechansims are listed in order of speed, that is the rate at which they can replenish ATP, which corresponds to the maximal level of effort that can be sustained by them.

Nonaerobic metabolism is the conversion adenosine diphosphate (ADP, with two phosphate groups), into ATP using creatine phosphate (CP). This is very fast and provides almost all energy the first 8-10 seconds of any exercise, and can produce around 1200 watt (Guyton & Hall, 10th ed.). It is limited by the intracellular stores of CP, which aren't that large.

Anaerobic metabolism is the breakdown of glucose or glycogen into lactic acid. The process is very fast, producing about 650 watt and can keep going for much longer than the CP-ATP conversion. However, it is limited by the acidity of lactate. All enzymes, including actin and myosin and the metabolic enzymes, have an optimal pH. When the pH varies from this they get less effective, and after about 60 seconds of pure anaerobic exercise the muscle pH will be far enough below the ideal for the process to be severely impaired and the muscle becomes fatigued. In judo, the combination of these first two kinds of metabolism is what provides energy during the intense parts of the workout.

Finally there is aerobic metabolism where glucose/glycogen, proteins, fat or lactate can be used to produce ATP through the Kreb's cycle, which requires oxygen. When burning glycogen, which is the most efficient, aerobic metabolism can produce about 280 watt. In judo this is what allows us to keep going for a full two hour session, and importantly what happens between the short periods of attack and defense to keep fatigue at bay. In the low intensity periods between bouts lactate can be removed from the muscle.

So, the most important part of endurance for judo training, and thus for keeping up with young elite athletes, is the aerobic capacity. The demands aren't as strenuous as for pure endurance sports like running or swimming, but you have to be fit enough to continuously recover from fatigue for a full two hours of training. Going back to our definition of endurance as energy delivery. This means the rate of oxygen consumption, which can be measured in ml/min. In order to be able to make comparisons between different athletes this in often normalised to body weight so that the most commonly used unit is ml/(min*kg).

According to the only english-language, judo-specific book on sports science I know of: "The sport science of elite judo athletes" by Wayland Pulkkinen, the maximal rate of oxygen uptake, or VO2max (that's "V" with a dot over it indicating volume over time, "O" with a "2" subscript as in oxygen, and max, as in max.), of judoka is around 60 ml/(min*kg).

The question then is: How do I measure up? To find out we have to find a way to measure VO2max, but actually measuring VO2max is impractical outside of a physiology laboratory. What remains is estimation from parameters we can easily measure. There are a number of more or less well validated methods to estimate VO2max. You can find them through your friendly, neighbourhood search engine (PubMed, not Google). Uth and co-workers presented their method in 2004 (Eur J Appl Physiol, 91(1), 111-115), so fairly recently, and they used well-trained men aged 21-51 years old by running while measuring their pulse.

The method by Uth et al calls for a resting heart rate, which I found to be about 50/min and a maximal heart rate which I found to be about 200/min. You then divide your maximum heart rate by your minimum heart rate and multiply by 15.3, let's say 15. That gives:

200 / 50 * 15 = 60 ml/(min*kg)

In conclusion, I can not blame my aerobic capacity for any of my shortcomings, but I did find out that I need to work on my running. My calves are killing me.

Fitness for judo

Physical fitness is a complex parameter that is not easily caught in any one number. As any role-playing gamer knows, there are three basic physical characteristics: constitution (CON), strength (STR) and dexterity (DEX).

In addition, judo competition is divided by weight categories so that each of the stats have to be optimised in relation to body weight. Some judoka have, apparently, rolled the perfect 18, 18, 18 and can beat everyone, but the rest of us will have to do with stats that aren't as stellar, and hopefully, bodies (and opponents) that aren't quite as large.

CON:

In judo constitution, or endurance, means that you have to be able to do two things: Control your opponent for at least five minutes, and launch your own attacks. The former is an inherently aerobic task because of it's length, but it is broken into shorter intervals by all sorts of breaks. At the same time the latter is anaerobic on the verge of nonaerobic. That is, during a match you use enormous amounts of energy very quickly, when attacking or defending, and then you have to re-coup this oxygen debt time and time again in the lulls of the fight.

STR:

For any given technical level, the stronger judoka always wins. The easiest way to get stronger is to increase muscle size, this increases the number of motor units and makes you stronger. It also makes you heavier. That's the reason for weight categories. Another way to become stronger is to learn how to activate as many muscle fibers as possible at the same time, while relaxing the opposing muscles as much as possible. This is an important reason for building strength using the movements that will actually be used in judo, and not only by lifting weights.

DEX:

Dexterity can be separated into speed and limberness, where speed is the most important. It is important to be limber enough to perform all techniques, but there are always techniques that require less flexibility. However, if you are faster than your opponent, he will be hard brought to avoid your attacks. Speed in judo means how quickly you can step and turn into your technique or out of your opponents. It also means how quickly you are able to notice and react to an opening in your opponent's defense. Both require very specific training, which is why years of recreational judo has surprisingly little impact on the ability to beat competitive judoka (not to mention that they have higher CON and STR as well, or do they?).

Next up will be a more detailed look at CON. How do competitive judoka perform, and how much do I have to catch up?

Judo!

I did include judo as something that the Nephrophysiologist blog would be about, but there hasn't been much about that. Actually, there hasn't been any judo here at all. It has been hard to find something sufficiently interesting to write about, something where I also feel I have enough to say that someone might find interesting.

So, what has changed? you might ask. My answer would be that my sights have been raised for me. As I moved home to Uppsala and changed labs and hospitals, I also changed clubs. From a small club with recent recruiting difficulties and therefore a clientele of slightly older, non-competetive judoka, to a large, competitive club with some recent successes. Anyway, while it is a lot of fun working out with the youngsters, they are in better shape than I am. It would be more fun if that wasn't the case.

To remedy the situation (so that I'm not that embarrassingly winded older guy) I started doing some supplemental training. At first I had the basic philosophy that anything is better than nothing (which is true). However, being a physiologist it's hard not to have a quick look at what the science says. The judo posts will try to handle the science of judo performance from a practical perspective as I play catch-up with elite judoka more than ten years younger than me.