Assessing the Influence of Reclined Vehicle Seatback Configurations with and Without a Belt-Positioning Booster on Child Posture Via Pressure Mapping

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 degrees, 45 degrees, and 60 degrees). 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 degrees (131.1 +/- 17.5 mm) and 60 degrees (125.5 +/- 16.7 mm) conditions compared to 25 degrees (148.7 +/- 17.4 mm). Without the booster, the center of force also became more aft in the 45 degrees (197.7 +/- 31.1 mm) condition compared to the 25 degrees condition (204.6 +/- 29.1 mm), but the position in the 60 degrees (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 degrees 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.