Bolus size and unilateral chewing cycle kinematics

Area of Science:

• Biomechanics
• Human Physiology
• Mastication Science

Background:

• Chewing is a complex motor task essential for food processing.
• Understanding how jaw movements adapt to varying food properties is crucial for masticatory function.
• Previous research has not fully elucidated the kinematic adaptations to different bolus sizes.

Purpose of the Study:

• To investigate the impact of varying bolus sizes on human chewing cycle kinematics.
• To quantify changes in jaw movement patterns in response to different food volumes.

Main Methods:

• Prospective within-subject design involving 38 young adults.
• Optoelectric jaw tracking system to record chin movements during unilateral gum chewing.
• Analysis of 10 representative chewing cycles for four bolus sizes (1, 2, 4, 8 g) using multilevel statistical procedures.

Main Results:

• Bolus size did not significantly affect chewing cycle duration (opening, closing, or total).
• Chewing cycle excursions (range of motion) increased significantly with larger bolus sizes (52-115%) across three axes.
• Jaw velocities increased significantly to accommodate larger excursions while maintaining cycle shape and duration.

Conclusions:

• Humans adapt to larger bolus sizes by increasing the perimeter and speed of the chewing cycle.
• Jaw kinematics adjust proportionally, preserving the overall shape and duration of the chewing cycle.
• These findings provide insight into the adaptive strategies of human mastication.