Differing structural properties of foods affect the development of mandibular control and muscle coordination in infants and young children

Abstract

The development of chewing is an essential motor skill that is continually refined throughout early childhood. From a motor control perspective, the advancement of textures is dependent upon the fit between a child's oral anatomic and motor system and food properties. The purpose of this exploratory study is to identify age-related changes in chewing motor coordination and control and to determine if these changes are associated with the differing structural properties of solid foods, as well as to explore the role of explanatory variables such as the emergence of teeth and bite force. The masticatory muscle coordination (i.e., coupling of synergistic and antagonistic muscle pairs) and control (i.e., speed, displacement, chewing rate, duration, and number of chews) of fifty children were assessed cross-sectionally at five ages: 9-, 12-, 18-, 24-, and 36-months using electromyography (EMG) and 3D optical motion capture while children ate three foods that had differing structural properties. The results of this study found that children made gains in their chewing motor control (decreased duration of chewing sequences and lateral jaw displacement) and coordination (improved jaw muscle coupling) throughout this period. The structural differences in foods also affected chewing performance at all ages. These preliminary findings suggest that some solid textures are better adapted for immature mandibular control than others and that the development of chewing is a protracted process that may be impacted by the emergence of teeth and changes to bite force.

Keywords: Development; Electromyography; Food structure; Kinematics; Mastication.

Figure 1

Panel A shows the placement of the markers used for the recording of jaw movements in 3-dimensions. The right jaw marker was used for analysis and the four head markers were used to create an anatomically based coordinate system. JR = jaw right; JC = jaw center; JL = jaw left; RTH = right top head; LTH = left top head; RBH = right bottom head; LBH = left bottom head. Panel B shows the placement of the EMG electrodes on the jaw elevators (left and right masseters) and depressor (ABD). ABD = anterior belly of the digastric.

Figure 2

Representative example of the post-processed EMG and kinematic signals from a 9-, 18-, and 36-month-old.

Figure 3

The mandibular vertical speed of children in the five age groups. Age groups with the different capital letters (A, B) represent statistically significant differences between age groups, p<0.05. Products with different lower case letters (a,b) represent significant differences between those products, p<0.05.

Figure 4

The lateral and vertical displacement of the jaw for the five age groups. Age groups with the different capital letters (A, B) represent statistically significant differences between age groups, p<0.05. Products with different lower case letters (a,b) represent significant differences between those products, p<0.05.

Figure 5

The chewing rate across the five age groups for each product. Age groups with the different capital letters (A, B) represent statistically significant differences between age groups, p<0.05. Products with different lower case letters (a,b) represent significant differences between those products, p<0.05.

Figure 6

The duration of the chewing sequence for the five age groups for each product. Age groups with the different capital letters (A, B) represent statistically significant differences between age groups, p<0.05. Products with different lower case letters (a,b) represent significant differences between those products, p<0.05.

Figure 7

The number of cycles in the chewing sequence for the five age groups for each product. Age groups with the different capital letters (A, B) represent statistically significant differences between age groups, p<0.05. Products with different lower case letters (a,b) represent significant differences between those products, p<0.05.

Figure 8

The synergistic and antagonistic coupling of muscle pairs. A higher coefficient represents muscle pairs that are more tightly coupled. Age groups with the different capital letters (A, B) represent statistically significant differences between age groups, p<0.05. Products with different lower case letters (a,b) represent significant differences between those products, p<0.05.