(1) Coordination of chewing rhythm and heart rate Proposal of methods for analyzing heartbeat synchronicity and heart rate modulation Yutaka Yoshida (yyoshida@med.nagoya-cu.ac.jp), Emi Yuda(emi21@med.nagoya-cu.ac.jp), Hiroki Ogasawara(ogas@med.nagoya-cu.ac.jp), Junichiro Hayano (hayano@med.nagoya-cu.ac.jp) Nagoya City University Graduate School of Medical Sciences 1-Kawasumi, Mizuho-Cho, Mizuho-Ku, Nagoya Japan 467-8601 ABSTRACT In this paper, we analyzed coordination of chewing and heart rate in two healthy subjects to examine if chewing rhythm affects autonomic outflow. Results revealed no significant relationship between chewing rhythm and change of heart rate modulation. Future studies should investigate heart rate modulation by control of chewing rhythm. Keywords: heart rate modulation, chewing rhythm 1. Introduction Many earlier studies have reported on the relationship between chewing gum and cerebral blood flow. These suggest possible effects of chewing on autonomic regulations, but convincing evidence is lacking for the relationship between chewing and autonomic functions. In this paper, to examine if chewing rhythm affects autonomic outflow, we analyzed coordination of chewing and heart rate. For this purpose , we first developed a method for measuring chewing interval from electromyograms (EMG) of t h e masticatory muscles. Then, we developed methods for evaluating two different forms of coordination of chewing rhythm and heart rate, i.e., heartbeat synchronicity with and heart rate modulation by chewing. 2. Method We used taste-free gums for chewing for this study. Two healthy subjects in the sitting position at rest chewed the gum at their own pace for 5 min, during which electrocardiogram (ECG), EMG (masseter and temporalis muscles), and respiration curves were measured at a sampling frequency of 500 Hz. We detected all R waves in ECG signal and obtained beat-to-beat R-R interval time series. For EMG signals, after removing 60-Hz AC noise using an 8⅓-point moving average filter, we calculated upper and lower envelopes of the EMG signals and computed the distance between them as continuous functions of time. Then, we detected peaks as the time points of chewing and obtained chewing interval time series (Fig.1). To evaluate the heartbeat synchronicity with chewing , chewing intervals were standardized to a period of 2π a nd the distribution of heartbeat occurring within the peri od was analyzed (eq.1). To examine the modulation of heart rate by chewing, the changes in R-R interval with the relative temporal positions they occurred within the standardized period of chewing was analyzed. 742 人間工学 Vol.53, Supplement ('17) P-21