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?

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.