Trunk flexion in healthy children aged 3 to 7 years.

I tested 80 male and 80 female subjects between the ages of 3 and 7 years on two exercises of isometric trunk flexor muscle strength (half-hold hooklying position and supine flexion position) and one exercise of isotonic trunk flexor muscle strength (hooklying sit-ups) to establish normative data for trunk flexor musculature capabilities. Measurements included the length of time the half-hold hooklying and supine flexion positions were maintained and the number of repetitions of sit-ups. I found no significant differences between the sexes in performance of the isometric tests. I did find, however, a significant difference between age groups for half-hold hooklying and supine flexion tests (p less than .0001), indicating that the ability to perform isometric trunk flexion improves with age. Height was another significant variable contributing to test results (p less than .0001). Children were able to perform sit-ups consistently at age 6 years only; the male subjects performed an average of 20 more sit-ups than the female subjects (p less than .04). I discuss in this article the possible contribution of neuromuscular maturation and physical growth to the development of normal trunk flexion. The results may be useful to clinicians to assess abnormal trunk flexion accurately in children aged 3 to 7 years.