<unk>  is the capacity to alter<unk> m in response to exercise or available fuel (especially fats and carbohydrates).<unk>  inflexibility was first described as the ability to generate energy through either aerobic or anaerobic respiration or as the inability of muscle to increase glucose oxidation in response to insulin. An organism can also be said to have<unk>  if it is capable of<unk> ing either carbohydrate or fat efficiency, depending on availability of those fuels. With aging there is a decrease in<unk>  due to a decline in pyruvate dehydrogenase activity which results in pyruvate increasingly being anaerobically converted to lactate rather than aerobically converted to acetyl-CoA. Similarly, a virus-induced cytokine storm can compromise<unk>  by inactivating the pyruvate dehydrogenase complex and other enzymes.
Metabolic flexibility
Respiratory compensation
Bodily integrity
Longevity
Tissue selectivity
Homeostasis
Cardiac rhythmicity
Human skin color