Clinical Assessment of Trunk Flexor Muscle Strength in Healthy Girls ...

Fig. 2. Good (Grade 4) muscle test position.
trunk, as determined by palpation. 2 A Zero muscle test grade
was given to a subject if no abdominal muscle activity could
be palpated. Each subject was allowed a maximum of three
trials to complete the test for each muscle grade. We assigned
a muscle test grade after the first successful trial of each
muscle test.
Muscle tests were administered and graded for each child
by the researchers. We conducted a pilot study (N = 7) that
established interrater reliability at 100 percent.
Procedure
Each child removed her shirt. The child stood in relaxed
stance with her arms at her sides while we centered the
reference marker over the designated spinous process. We
positioned each child in supine on the mat with the hips
flexed to 90 degrees and the knees placed across the board in
approximately 120 degrees of flexion. We assessed each child's
ability to perform neck flexion through full range of motion
in the supine position because this movement is used for the
initiation of trunk flexion. Then one researcher demonstrated
to each subject the Fair trunk flexor muscle test procedure.
The child was allowed to practice the movement once. Each
child had three trials in which to complete the test successfully
in the Fair muscle test position. We gave a 30-second rest
period between all trials. After the first successfully completed
trial in the Fair test position, we demonstrated the Good
muscle test to the child and allowed one practice trial. If the
subject could complete the Good muscle test in one of the
three trials, we demonstrated the Normal muscle test procedure
for the subject to practice and attempt. If the child could
not pass the Fair muscle test, we tested the child according to
the Poor, Trace, and Zero test procedures and assigned a
grade according to level of test achievement.
Data Analysis
We assigned numerical values (0-5) to the muscle grades
for statistical analysis. We believed the assignment of numerical
values to ordinal data was appropriate for the statistical
analysis of this study because 1) numerical values allowed the
use of more flexible and powerful parametric tests and 2) the
RESEARCH
assignment of any numerical scale to such data seldom produces
marked differences in the conclusions drawn from the
analysis. 21
We performed a Pearson product-moment correlation to
determine the relationship of the variables height, weight, and
age to muscle grade, and a one-way analysis of variance
(ANOVA) to determine if significant differences existed
among the mean muscle grades of each age group. We also
performed a stepwise multiple regression analysis for the same
variables.
RESULTS
Table 1 records means and standard deviations for muscle
grade, age (in months), height, and weight by age group (in
years). As shown in Table 1, the mean muscle grade of 3- and
4-year-old subjects was in the Fair range (3.3 and 3.7) and
that of 5- and 6-year-old subjects was in the Good range (4.1
and 4.4). Seven-year-old girls had a mean muscle grade close
to Normal (4.8) strength.
Fig. 3. Fair (Grade 3) muscle test position.
Fig. 4. Poor (Grade 2) muscle test position.
Volume 64 / Number 8, August 1984 1205
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