What is the trigger mechanism for changes of the oxidative potential in skeletal muscle?

It is known that the long-duration decline of high-energy phosphates(HP) level in skeletal muscles, induced by administration of beta-guanidinpropionic acid (beta-GPA), is followed by the increase of mitochondrial enzyme activities (MEA). The same increase of MEA was observed in the course of physical exercise training. The decrease of MEA and at the same time the increase of HP levels were found under gravitational unloading. If changes in HP level are believed to trigger on the alterations in MEA, the increase of HP levels in muscles should lead to decline of MEA as well. The present work was purposed to reveal if the changes in HP level under different contractile activity levels are associated with the changes of oxidative potential in the skeletal muscles.