Effects of a hybrid exercise on the activities of myogenic enzymes in plasma

Abstract

"Hybrid" exercise uses forces generated by an electrically stimulated muscle to resist the motion of a volitionally contracting agonist. This approach is effective in increasing muscle bulk and strength. Its safety, however, has not been studied and the purpose of this study was to address this lack by assessing the impact of a hybrid strengthening regimen on the serological markers of exercise associated muscle damage. Twelve healthy, sedentary men between the ages of 20 and 27 years were divided into two groups of 6. The members of each group completed an exercise session that consisted of 10 sets of 10 reciprocal elbow flexor and extensor contractions separated by 1-minute rest intervals. In one group, the subjects underwent a hybrid exercise protocol. Subjects in the second group underwent a conventional isometric electrical stimulation program with the same stimulation intensities. Plasma creatine kinase (CK), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH) activities were determined immediately before and after the exercise session as well as at follow-up 1, 2, and 7 days later. Secondary variables included active and passive range of motion and the subjects' perceived levels of "soreness". Evaluation revealed that neither enzymatic activities nor range of motion changed in a statistically significant manner with time within the groups or between the groups. In conclusion, the stimulation intensities involved in hybrid exercise programs of the upper extremity do not appear to be associated with either overt or covert signs of muscle injury.