The final frontier: Oxygen flux into muscle at exercise onset

In humans at exercise onset, intramuscular phosphocreatine decreases immediately, whereas muscle oxygen (O-2) uptake seems to rise after a delay of up to 15 s which is inconsistent with models of metabolic control. Novel microcirculatory investigations reveal that elevated capillary-to-myocyte O-2 flux in rat muscle is, in fact, initiated simultaneously with contractions.