Date of Award


Document Type

Scholarly Project

Degree Name

Doctor of Physical Therapy (DPT)


Physical Therapy

First Advisor

Cindy Flom-Meland


Abdominal Muscles -- physiology; Exercise -- instruction


Purpose: The purpose of this study was to assess the benefit of instruction from a physical therapist in participant performance of an abdominal crunch on a Swiss ball, determined through electromyography (EMG) of the rectus abdominis.

Subjects: Our subjects included male (n=15) and female (n=15) college students between the ages of 18-50 years old. Exclusion criteria included a history of low back pain, prior spine surgery, pregnancy, previous formal instruction of crunches on a Swiss ball, and an allergic reaction to rubbing alcohol. Instrumentation: EMG biofeedback was used to test rectus abdominis muscle activity. This activity was transmitted by a Noraxon Telemy08 telemetry unit (Noraxan USA, 13430 North Scottsdale Rd., AZ 85254). Data was collected by the Noraxon Telemy08 receiver. The peak Notus5 system (Peak Performance, Englewood, CO) was used to store and analyze the EMG data. Procedure: Participants performed a manual muscle test of the rectus abdominis muscle and the EMG activity was recorded and used for base line data. The subjects were then asked to perform 10 abdominal crunches on the ball without any instruction. This data was recorded, and then verbal instruction on proper technique of an abdominal crunch on the ball was given. Following instruction, participants had one minute to rest, and then perform an additional 10 crunches using the new correct posture.

Data Analysis: For statistical analysis, a repeated-measures t-test was used with an alpha level of .05. Results: There was no significant difference when comparing the mean values of EMG muscle activity of the upper rectus abdominis pre and post instruction and lower rectus abdominis pre and post instruction. (78.05 and 76.14 --70.50 and 69.73 respectively)

Conclusions and Clinical Implications: In conclusion our study results did not support a significant difference in rectus abdominis muscle activity after instruction measured through EMG analysis. Injury due to over training, muscle imbalances or muscle strains could be avoided when patients are given instructions and demonstrate proper technique.