An electromyographical evaluation of the validity of the 2-minute sit-up section of the Army physical fitness test in measuring abdominal strength and endurance

Military Medicine, Nov 2002 by Szasz, Anna

The fourth investigator operated the electromyographic equipment. Before the surface electrodes were attached to the participant's skin, the investigator thoroughly cleansed the designated areas with an alcohol pad. Eight electrodes were attached to monitor the muscular activity of the rectus abdominus and rectus femoris. For the rectus abdominus, the investigator located the navel and measured 5 cm on either side. An electrode was placed one-half centimeter above and another onehalf centimeter below this site in parallel with the muscle fibers. For the rectus femoris, the investigator located the midpoint between the anterior superior iliac spine and the patella. The electrodes were placed on both thighs, one above the other with 1 cm between them. All electrodes were secured with an elastic band to prevent their movement throughout the test.

Results

Data Analysis

After obtaining measurements of the 2-minute EMG recordings for each participant, the researchers selected three groups of contractions for analysis: the first five contractions, the first five contractions after the 1-minute mark, and the final five contractions for each channel. The researchers manually marked the beginning point, peak, and terminating point for each contraction. Using the Myosoft computer software, the researchers analyzed the electrical activity of the muscles during each contraction in microvolts. The researchers used the area of each contraction as the parameter chosen to represent the electrical activity of the muscles and computed the average area of all 15 contractions. The program then used the mean to compute the percentage area of each contraction.

The researchers obtained an average of the percentage area for each group of five contractions for each channel for each participant. Then they obtained an average for the three groups of contractions for all participants (as seen in Tables I and II).

The researchers graphed the data for the right hip and abdominal channels in one graph and the left hip and abdominal channels in another graph. Figure 1 indicated the dramatic increase in hip flexor activity, especially near the end of the 2-minute period.

The researchers obtained the difference between the average area of the first and last five contractions for each channel. A paired sample t test was used to analyze the change in area for the left hip flexors and abdominal muscles and then the change in area for the right hip flexors and abdominal muscles (t = 5.951 for the right side and t = 5.025 for the left side; p

Assumptions

- The participants are physically fit.

- The participants understand and are familiar with the APFT's 2-minute sit-up test.

- The electrodes will pick up the activity of the specific muscles that the researchers are examining.

- The rectus abdominis and the rectus femoris are the proper muscles to be examined.

- The researchers' use of the area of the contraction is the most appropriate parameter to represent muscular activity of the rectus femoris and rectus abdominis.