In addition, simvastatin attenuates the exercise-induced increase in cardiorespiratory fitness, and reduces the skeletal muscle mitochondrial content and oxidative capacity in humans. Impaired cardiorespiratory fitness and mitochondrial function is possibly due to reduction in Coenzyme Q10, which is a component of the electron transport chain and is indispensable for generation of adenosine triphosphate (ATP) during oxidative phosphorylation in mitochondria. Statins or hydroxyl-methylglutaryl coenzyme A (HMA CoA) reductase inhibitors interfere with the production of mevalonic acid, which is a precursor in the synthesis of coenzyme Q10.