Table 3

Variation of differences between helmet and head measurements by age group

Characteristic*Young (2–6 years) (n=38)Medium (7–9 years) (n=44)Old (10–14 years) (n=44)Two tailed p value
*See accompanying protocol for measurement definitions based on the actual orientation of the helmet on the head.
Helmet minus head cast measurement (mean (SD) in cm and ml)
    Circumference at rim4.2 (2.4)5.3 (2.0)4.9 (2.8)0.22
    Anterior-posterior length0.7 (2.5)1.2 (1.2)1.0 (2.2)0.64
    Width1.6 (0.9)1.6 (0.7)0.7 (2.6)0.049
    Length of anterior-posterior arc3.6 (1.9)2.6 (1.7)3.1 (2.7)0.23
    Length of width arc2.3 (2.1)2.5 (2.4)2.0 (3.0)0.71
    Depth (helmet rim to top)1.2 (1.1)0.5 (1.0)0.5 (0.9)0.007
    Volume (helmet rim to top)551 (276)438 (303)436 (226)0.16