Chewing Speed Does Not Follow Typical Patterns of Motor Slowing with Age

Aging adults experience gradual structural changes in nerve and muscle tissues that impair their ability to exploit speed as an effective movement strategy. The aim of the study was to examine whether chewing rates demonstrate a level of age-related neuromotor decline similar to other motor tasks. Fifteen young (20-40 years) and fifteen healthy older adults (60+ years) completed a battery of motor tasks including: walking, finger tapping, simple reaction time, postural sway, and chewing. Gait metrics were collected using a 20-foot pressure-sensitive walkway. All walking was performed at a preferred speed. Participants tapped an accelerometer affixed to a table at a preferred rate. Upper extremity reaction time was recorded by depressing a mouse button with an associated timing mechanism, whereas a similar foot pedal interface was used to measure lower extremity reaction time. Postural sway data was collected using a force plate. Surface electromyography of the masseter was used to record fast(2Hz), slow(1Hz), and preferred chewing rates. Fast and slow chewing rates were set using an auditory metronome which was switched off during recording. Age comparisons for each task were performed using general linear modeling, with additional considerations for chewing speed effects and interactions for the chewing task. The results reveal that older adults demonstrate a general slowing of movement with the exception of chewing speed which appears to be preserved with aging. Regardless of age, preferred chewing rates were nearly identical. Preservation of chewing rates compared to other motor tasks may be due to the difference in anatomical innervation between muscles of mastication and the limbs. Masticatory muscles receive bilateral innervation including ipsilateral and contralateral inputs from the motor cortices, whereas limb muscles receive mainly unilateral innervation from the contralateral cortex. The neural redundancy may preserve chewing rates despite age-related degradation of the system.https://digitalcommons.odu.edu/health_sciences/1009/thumbnail.jp