A novel assessment of spontaneous laughter under free-living condition based on heart rate, acceleration, and autonomic nerve activity

Abstract

The present investigation aimed to develop a novel method of spontaneous laughter (SL) assessment based on heart rate variability (HRV) and lumbar accelerometry under free-living conditions. The subjects of the present investigation were ten healthy young men. The investigation consisted of three 15-min experimental periods after the resting period and 5 h of free-living conditions. The three experimental periods included light-intensity aerobic exercise (LAE), moderate-intensity aerobic exercise (MAE), or watching comedy movie inducing SL (SLA), and were randomly ordered across three separate days. During SLA, the subjects watched comedy movies. The autonomic nervous system (ANS) activity was measured using continuous heart rate (HR) responses over the investigation period; the total power, low frequency (LF: 0.035 to 0.15 Hz), and high frequency (HF: 0.15 to 0.4) components were obtained using frequency analysis. The LF and HF were normalized by total power (nHF, nLF), and the LF was divided by HF to obtain a sympathetic activity index (LF/HF). SLA increased sympathetic nerve activity without an increase in heart rate compared to the resting state. The results of the preset investigation suggested that the combination of acceleration with heart rate and the autonomic nerve activity can improve the accuracy for estimating the SLA under the free-living condition.