Endurance athletes often mistakenly think that they need a full stomach before starting a race or an intense training session. Some athletes have the bad habit of not drinking, or, at least, not drinking enough...
Endurance athletes often mistakenly think that they need a full stomach before starting a race or an intense training session. When digestion is in full force it “steels” blood away from the other organs, starting with the brain (the well-known sleepiness after a large meal), and ending with the muscles which cannot receive enough oxygen for the activity through the blood. Faced with this difficulty, the body will try to get rid of the ingested food in a natural manner at a time close to the start and will reduce the performance. It will do the same in case of intestinal obstruction caused by the cold or intense emotions such as when we find ourselves unprotected, wet, or sweaty after having eaten. Those who might be vulnerable for this should therefore limit themselves to ingesting liquid sugars (easily digestible) without taking any solid foods.
Some athletes have the bad habit of not drinking, or, at least, not drinking enough. Remember that blood is made up for a large part of water. If we do not replenish our water reserves after sweating a lot, there is a real risk of undergoing a significant decrease in blood pressure and consequently no longer sending enough blood (and therefore oxygen) to the brain. When the body notices that some areas of the brain are not functioning correctly, the first thing it tries to do is to reduce the intensity of the effort. The slightest neurological problem can generate an alarm response of remarkable intensity.
The lack of iron is another important factor. There are two important blood values: serum iron (circulating iron) and ferritin (iron stores). Serum iron only changes in serious or chronic conditions, while low ferritin levels are easily identifiable by having a ferritin test. If your iron levels are low, and as such also your hemoglobin levels, you easily get tired and even light exercise costs a lot of energy. Therefore, even though the head might be ready to sustain a very intense effort, it is possible that the body might not keep up.
Some medicines, alone or in combination with others, can cause unusual tiredness. The list is long: antihypertensives, antihistamines, pump inhibitors (so-called "gastric protectors"), cortisone, chemotherapy, antibiotics etc. Some intoxicate the liver and kidneys; others have a more indirect effect. Our advice is to replace these (under the guidance of a doctor) with natural alternatives that do not intoxicate those organs that are important for performance.
Summarizing: do not let an inexplicable drop in performance just go on without taking any action. When it happens, you should examine with a doctor what the most likely cause is. It will then be easy to put together a therapy that can provide an efficient resolution of the problem.