Date of Award


Document Type

Scholarly Project

Degree Name

Master of Physical Therapy (MPT)


Physical Therapy

First Advisor

Thomas Mohr




Purpose: Fitness Plus, Inc. has developed a series of exercise machines for strengthening of the trunk musculature. Their Low Back Unit is claimed to target the rectus abdominus (RA), gluteus maximus (GM), biceps femoris (BF), and erector spinae (ES) muscles, but there is no research to solidify these claims. The purpose of this study was to describe the electromyographic (EMG) activity during the use of the Fitness Plus, Inc. Low Back Unit.

Methods: Fifteen healthy, males (ages 20-30) volunteered to participate in this study. Surface EMG was used to assess the muscle activity in four trunk and hip muscles. The four muscles assessed were the RA, ES, BF, and GM. An electrogoniometer was used to monitor the trunk motion during the exercise. The EMG data for each muscle was analyzed using Norquest software and compared to each subject's maximal voluntary contraction (MVC) for that muscle. Descriptive statistics were used to describe the EMG activity and average percent of MVC for each muscle and under various loads.

Results: The results showed that the GM, BF, and ES all increased activity with an increase in weight, while the RA showed no consistent pattern of activity.

Conclusions: Although this researcher would not recommend the Fitness Plus, Inc. Low Back Unit for a patient with a prolapsed disc, it could be an effective tool for recreational GM, BF, and ES strength training or for patients where strength training is indicated.