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TL;DR
Obesity selectively altered posterior-area-elicited jaw-opening patterns and shortened digastric muscle contraction time without changing EMG amplitude or frequency.
Journal of Clinical Medicine · 10 authors, 1 centre
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Obesity selectively altered posterior-area-elicited jaw-opening patterns and shortened digastric muscle contraction time without changing EMG amplitude or frequency.
This preclinical study used seven obese and seven lean male Zucker rats (10 weeks old) to compare cortically evoked rhythmic jaw movements and masticatory muscle EMG. Repetitive intracortical micro-stimulation of the anterior and posterior cortical masticatory areas (A-area and P-area) was applied, and right anterior digastric (RAD) and masseter EMG plus jaw kinematics were recorded. P-area stimulation produced a more lateral-shifting, slower-opening pattern than A-area stimulation. Only P-area-elicited movements were affected by obesity: jaw-opening duration was significantly shorter in OZRs (24.3 ms) than LZRs (27.9 ms, p<0.01); jaw-opening speed was significantly faster in OZRs (67.5 mm/s) than LZRs (50.8 mm/s, p<0.05); and RAD EMG duration was significantly shorter in OZRs (5.2 ms) than LZRs (6.9 ms, p<0.01). EMG peak-to-peak amplitude and frequency parameters did not differ. The authors conclude that obesity alters coordinated masticatory movement, with functional change in the digastric muscle partly involved, though tongue movement and other factors are speculated to contribute.