A heavy training load with inadequate rest can lead to a form of chronic fatigue in overtrained athletes. It can take many months of rest and gradual return to be back to normal.
Athletes often attribute symptoms to a viral infection, or simple nutrient deficiency, but it is rarely that simple.
Testing is available for Ferritin, Iron, Vitamin D, Magnesium, Viral infection, Thyroid etc.
It is also important to consider sleep, recovery, nutrition, stress
