Ethan C. Hill, Terry J. Housh, Clayton L. Camic, Cory M. Smith, Kristen C. Cochrane, Nathaniel D.M. Jenkins, Joel T. Cramer, Richard J. Schmidt, Glen O. Johnson

The purposes of this study were to examine the effects of the velocity of repeated eccentric muscle actions on the torque and neuromuscular responses during maximal isometric and eccentric muscle actions. Twelve resistance trained men performed 30 repeated, maximal, eccentric, isokinetic muscle actions at randomly order velocities of 60, 120, or 180°·s¹ on separate days. Maximal voluntary isometric contractions (MVICs) were performed prior to (pretest) and following (posttest) the repeated eccentric muscle actions on each day. Eccentric isokinetic peak torque (EIPT) values were the averages of the first 3 and last 3 repetitions of the 30 repeated eccentric muscle actions. During the EIPT and MVIC muscle actions, electromyographic (EMG) and mechanomyographic (MMG) amplitude (EMG AMP and MMG AMP) and mean power frequency (EMG MPF and MMG MPF) values were assessed. The current results indicated that the repeated eccentric muscle actions had no effects on EIPT, or the EMG AMP, EMG MPF, or MMG MPF values assessed during the EIPT muscle actions, but decreased MMG AMP. The repeated eccentric muscle actions, however, decreased MVIC torque, as well as the EMG AMP and MMG MPF values assessed during the MVIC muscle actions, but increased MMG AMP. The results indicated that the velocity of the repeated eccentric muscle actions affected the MVIC torque responses, but not EIPT or any of the neuromuscular parameters. Furthermore, there are differences in the torque and neuromuscular responses for isometric versus eccentric muscle actions following repeated eccentric muscle actions.