exercise & environmental physiology, metabolism, lactate shuttle, crossover concept, lactate, lactic acidosis, traumatic brain injury, obesity, diabetes, the Warburg Effect in cancer, aging biology, isotope tracer technology, arterial-venous difference measurements, clamp technology, muscle biopsies, cell culture, mitochondrial biogenesis, energy substrate partitioning, carbohydrate metabolism, lipid metabolism, fatty acid reesterification, menopause