Nutrition plan for long distance sport challenges. Part 5: The thermoregulation
Updated: Apr 9, 2018
Having closed the chapter on race fueling and energy supply, we can deal with a more "burning" problem. Thermoregulation! The "byproduct" of muscular activity is heat. The efficiency of muscular activity is only 20-25%, the remaining 75-80% is heat which needs to be managed, because the already mentioned enzymes, which are actually proteins, would end up as sunny side up eggs in the oven of muscles. The more intensive the muscular activity is the more intensive the heat production will be, the more heat we will have to dissipate to our environment.
Our heat dissipation "obligation" might reach 20 kcal per minute in case of intensive muscular activity, which works out at 1.200 kcal per hour. Even this would not mean a problem as long as the temperature of our environment is lower than our body temperature. The hotter it is, the smaller the difference between our body temperature and the temperature of the environment is, the tougher the challenge of the dissipation of the heat from muscular activity will be. Efficient thermoregulation is only possible via sweating. Almost 600kcal of excess heat can be dissipated by evaporating 1 litre of sweat. Taking the 20kcal per minute, equivalent to 1200kcal per hour, heat dissipation obligation into consideration, sweating due to intensive muscular activity might mean 1200/600 = 2 litres of fluid loss.
There is no endurance sport apart from gazing into the distance where two litres of fluid loss can be replenished. We are facing the impossible in this extreme case. The solution is planned and science-based fluid replenishment, the filling up of our body's fluid reserves, and not last but first, choosing an intensity and pace which involves a manageable heat production. It is just another reason for not rushing the race. The solution is to consume an extra 1,5 litres of drinks containing magnesium and sodium beside the regular 2 litres/day (day without training). Constant "sipping", intake of fluid containing Na+ during the race. Na+ is also the "catalyst" for water absorption. The place of water absorption is the first section of the small intestine where Na-cotransporters "pull" Na+ ions into intestinal epithelial cells from where they are thrusted into the extra cellular (ec) space by the sodium-potassium pump. Due to the increased sodium ion concentration in the extracellular space, water starts flowing rapidly from the small intestine towards our organs.
Then we do not have anything to do, just sweat the huge amount of ingested water. Modern sports drinks hydrate more effectively, are capable of delivering more water into our body, since their ion composition is optimal. Beside containing plenty of sodium, they do not stir up the delicate balance and proportion of ions. That is why they promote the indisputable fact: they indeed hydrate better than tapwater or mineral water.
Since replenishing the fluid loss caused by sweating is almost impossible in extreme heat, other cooling techniques have to be utilized: cold drinks can extract heat from our body, thus enabling heat dissipation. Evaporating water from the skin or head also cools. In this case, we have to be careful to allow only a little water to be poured on our socks or shoes. Sweat glands function better if we swipe off the drying salty sweat.
Training improves the efficiency of sweating as well. Trained sportspeople sweat more and more efficiently: bigger amount of fluid loss involves lower magnesium and calcium loss.
We can end our fable with this chapter: our friend has ruined his body's thermoregulation with one carelessly consumed gel. It is not that only insufficient amount, it is that no water could get into the sweat system from the small intestine. On top of that, the water his body contained was not directed towards sweating, but towards the stomach to dilute its dense content. The enzymes of the aerobic energy system went on strike due to the increased heat, so our friend could only crowl towards the finish line.
We can draw fine conclusions from fables and we might avoid the mistakes made by the heroes, or copy their feats. I hope, that conclusions from the fable I have presented prove to be useful and facilitate crossing the finish line.
The race is yor businness, leave refreshment with Enduraid!
Previous parts, here!