Date of Award


Document Type

Scholarly Project

Degree Name

Master of Physical Therapy (MPT)


Physical Therapy

First Advisor

Thomas Mohr


Electromyography; Muscles -- physiology


Strength training is a primary factor in athletics and rehabilitation. Lower extremity strength training has traditionally consisted of free weights, biomechanically designed weight machines, or plyometrics. The Plyo Press is a new machine that is currently being utilized in the Frappier Acceleration Program for athletes. It is specifically designed for lower extremity strength training in combination with plyometrics. The principle behind its design is to build strength in the most effective way to enhance speed and dynamic activity without the stress to the low back or legs that is present with the use of free weights.

Because the Plyo Press is newly designed there has been limited research conducted on the machine to validate the manufacturer's claims. Therefore, the purpose of this study was to compare muscle recruitment during a free weight squat lift, a leg press in the Plyo Press leg machine, and a plyojump in the Plyo Press machine. EMG analysis was performed on selected trunk and lower extremity muscles in order to provide information on the muscle activity and recruitment pattern evoked by the Plyo Press.

Fifteen healthy male subjects were loaded down with 80% of their previously determined 1 Repetition Maximum and performed three repetitions of each exercise. An analysis of the normalized EMG data was conducted using the Myosoft and Norquest software package.

The results of this study revealed that the Plyo Press appeared to specifically recruit the vastus lateralis muscle during each of the exercises. The Plyo Press appears to offer the advantage of specifically training the vastus lateralis muscle while minimizing the recruitment of other lower extremity and back muscles.