Objective: This study sought to implement pressure mapping
methodology to assess variation in children’s center of force positions in
reclined vehicle scenarios.
Methods: Thirty-four children between 4 and 12 y (8.1 ± 2.0 y) were
statically evaluated on a vehicle seat across two seating conditions (with and
without a backless booster) and three seatback recline conditions (25°, 45°, and
60°). Center of force was recorded using pressure sensors attached to the
seating surface. Average center of force fore/aft positions were calculated and
transformed into the vehicle coordinate system using 3D coordinate measurements.
Descriptive statistics and repeated measures ANOVA were used to assess variation
in center of force position across seating and recline conditions, with subject
included as a random effect.
Results: Center of force fore/aft position varied (p < 0.05) with
recline condition, seating condition, and the recline/seating condition
interaction term. On the booster, the average center of force position became
more aft in the 45° (131.1 ± 17.5 mm) and 60° (125.5 ± 16.7 mm) conditions
compared to 25° (148.7 ± 17.4 mm). Without the booster, the center of force also
became more aft in the 45° (197.7 ± 31.1 mm) condition compared to the 25°
condition (204.6 ± 29.1 mm), but the position in the 60° (206.1 ± 31.8 mm)
condition was similar. As children assumed more reclined postures, the center of
force became more aft, except for the no-booster 60° condition.
Discussion: Changes in center of force followed the same trends
observed in the pelvis and lower extremity position (became more aft) with
increasing seatback recline on the booster and smaller changes observed on the
no-booster condition. Future work should investigate additional vehicle/booster
geometries and longer seating durations. The changes in center of force observed
with seatback recline emphasize the importance of understanding how real
children modify their posture over time to different vehicle environments as
posture directly influences belt fit, occupant–restraint interaction, and injury
risk. Center of force data can inform the positioning of child surrogates in
future dynamic evaluations of reclined configurations.
