Introduction - The MicroBiome Run

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All living creatures try to satisfy two opposing natural driving forces

Animals are constantly at the highest level of physical fitness to avoid becoming food, or starving to death for lack of it. Survival requires fitness and the movement used to obtain food must be energy efficient. At the same time, the individual wants to survive at rest with as little energy sacrifice as possible. It stores and reserves for later exertion. The two principles operate as a continuous circular system: during the foraging cycle, energy is invested to obtain the food that is the source of energy, for subsequent processing and storage to provide the energy required for the next energy investment cycle. It is this duality that creates the balance that keeps the body at a high level of fitness and physical performance.

As humans, we have largely eliminated the physical effort required to obtain food by thinking, and now we do it facultatively, which we call sport. However, in most cases, its intensity, form and frequency do not meet the requirements that would make us physically capable of obtaining food. Today, survival in all circumstances is no longer the goal, and we have lost the natural feedback loop: we survive despite insufficient or inadequate physical fitness, but we pay for this with our quality of life.

The consequence of this imbalance is that the complex metabolic systems that provide the energy needed to sustain physical performance (such as running) simply collapse: there is no need for biochemical pathways and structures that provide the energy requirements for prolonged, low-intensity exercise, because the short-term energy requirements of most physical activities can be delivered by mechanisms (primarily carbohydrate metabolism) that are normally used by the animal kingdom only for temporary performance enhancement. The change in metabolism is due to the fact that it is easier - though undoubtedly more dangerous in the long term - for the body to use readily available carbohydrate than to rely constantly on, for example, fat metabolism.

The developed world is in a fever of "longevity", the prolongation of life at all costs, while quality of life at the individual level is much more important. In our university studies, we all encounter the physiological experiment of keeping the heart of a hollowed-out frog moving hang on a hook by applying various fluids. It was only later that I realised that this experiment had an important message: today, almost anyone can be kept alive for any length of time, it's just a question of where we draw the line of life.

Instead of longevity, the new goal should be called "Healthevity". This is what The MicroBiome Run is about.

Let's try to understand how we generate energy

To put it very simply, our bodies have a triple energy-producing system, best illustrated by a car analogy. The human body is capable of using fat, carbohydrate and, in extreme circumstances, protein to provide energy for its own functioning. Chemical energy is converted into kinetic energy to the greatest extent by skeletal muscle.

Skeletal muscles are able to operate as a high-torque, low-speed diesel engine, using fatty acids and cellular organella called a mitochondria in the cells to extract energy. The fuel source is fat stored in skeletal muscle or available in adipose tissue. Mobilisation, delivery to the site, processing and thus energy production takes time, the bottleneck of the system being the number and size of mitochondria and the speed of mobilisation, i.e. their processing capacity. This is the system that allows us to hike, run or cycle for hours.

The stability of the system is precisely provided by the feedback itself: the intensity of the motion is finite, and just as a diesel engine delivers maximum power at low revs. The intensity of the movement in which we rely on this system - very simply put - is called Z2 (Zone 2). In the lower part of the zone, we hardly exert any force (Z1 is the zone of regeneration, the "walk" that many people call for), and when we reach the top third, we start to use carbohydrate more and more: our respiration rate is rising and our heart rate is increasing. This is already a partial activation of another engine, but only with a signalling value. It is of course possible to gradually widen the zone, to run/cycle more and more by burning fat and at higher and higher intensities: but this requires an increase in the number and size of mitochondria, which is possible by training at the upper limit of the Z2 zone (careful balancing). It's a long-known principle, and it's how cyclists prepare for the Tour de France, using countless measurements.

So the second engine we have at our disposal runs on petrol: it can deliver huge power at high revs for a short time, but in return it has a tremendous energy demand that determines all its characteristics: it is a carbohydrate-based mechanism. The breakdown of glycogen stored in the skeletal muscles, in the liver, provides glucose to the muscle cells, which is metabolized in the cytoplasm and, if there is still free mitochondrial capacity, is also converted into carbon dioxide and water, releasing energy. The healthy body takes advantage of this when it needs to make a short burst of extra effort: you have to run up an incline, suddenly accelerate to get over the green light. If the mitochondria are saturated, lactic acid is produced, which the muscles first try to distribute and use at the cellular and then tissue level; if they can't, the lactic acid is released into the circulation.

For healthy athletes, this is when the third, exogenous engine kicks in

Bacteria in the gut microbiota use lactic acid and possibly convert it into propionate, which can be reused for muscle tissue. This system is an auxiliary power unit, a wood gasification boiler, designed to correct the system's insufficiency.

A few things follow immediately from the above for athletes:

Their performance can be enhanced in a number of ways, but a finely tuned combination of these is probably the most appropriate. Their aim is to widen the Z2, so that it can perform at increasing intensities almost exclusively by burning fat, as this will practically 'run you out of the world'. To increase the number of mitochondria, very mild overloading of the system is best, only increasing physical activity to a level that requires the muscles to increase the number of mitochondria, but not to the point of massive lactic acid production, which would saturate the system and then shut it down.
Another known fact is that during interval training (when a short, full-force run is interspersed between two slow bouts of training), the body is subjected to shock, inducing glycogen breakdown, which, in addition to shock tolerance, increases the number of enzymes that utilize glycogen, and is probably the reason why professional athletes have an increased glycogen storage capacity in both liver and muscle, with high efficiency of utilization.
But what was not clear until after the 2015 Boston Marathon experiments was that during this time another system, the Z2(bacteria) system, which sits at the Z2-Z3 boundary, is also expanded by the lactic acid in the circulation reaching the intestinal tract, creating conditions favourable for the proliferation of the bacteria Veillonella. The bacteria recycle the lactic acid, their numbers increase and the buffer capacity they provide in the event of lactic acid shock is widened.

In the light of the above, there are 3 sports that meet these requirements for many people and can be fine-tuned: running, cross-country skiing and cycling. And now let's look at what happens when the exercise we do is insufficient...

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