Heart rate variability (HRV) is used to noninvasively assess the activity of the autonomic nervous system, in particular, its parts help to evaluate the cardiac sympathetic and parasympathetic activities. Increasing HRV may contribute to improving autonomic nervous system dysfunctions. In traditional medicine, acupuncture in the region of the vagus nerve distribution in the ear could increase parasympathetic activity and cause changes in HRV. Zero point located on the vagus nerve distribution is scientifically proven to enhance parasympathetic activity, however, the number of studies examining the effect of auricular acupressure at zero point on HRV is limited while this method is highly effective and convenient. In our study, we want to survey heart rate variability during auricular acupressure at Zero point on the left ear in healthy volunteers.

Participants and Methods: A randomized controlled trial is conducted by comparing the changes in HRV and elements of HRV during the auricular acupressure process at zero point on the left ear in healthy volunteers. A total of 114 participants were randomly assigned to 2 groups by computer GraphPad software and the allocation was 1:1. Participants in the experimental group received auricular acupressure at the left zero point, while the control group received placebo auricular acupressure by removing the ear seed but keeping the sticker attached in the left zero point. The primary outcome was the change in heart rate variability during auricular acupressure at zero point on the left ear. This trial will be performed as randomized, controlled, and single- blinded.

Inclusion Criteria:

• Healthy males and females were individuals aged between 20-29.

• Volunteers who agree to participate and sign the Informed Consent Form, following a detailed explanation of clinical trials.

• Vital signs within normal range:

  • Pulse, and regularly heart rate, go together.
  • Resting heart rate: 60 - 100 beats/min.
  • Resting blood pressure: 90/60 mmHg to ≤ 140/90 mmHg.
  • Breathing rate: 16 ± 3 times/minute.
  • emperature: 36.6-37.50C.
  • SpO2 ≥ 95%.

• Body mass index (BMI): 18.5 - 23 kg/m2 .

• Had no history of cardiovascular disease, diabetes, or thyroid.

• Had no psychiatric stress problem during acupuncture day (confirmed by answering the DASS 21 questionnaire with stress points less than 15 points).

• Not currently participating in other intervention studies.

• Have no acupuncture experience yet.

Exclusion Criteria:

• Used stimulants such as beer, alcohol, coffee, and tobacco within 24 hours before conducting the study.
• Played sports 2 hours before the study.
• Had skin injuries in the area of auricular acupressure.
• Women during menstruation period, pregnancy, or breastfeeding.
• People using drugs affecting blood pressure and heart rate within 1 month.

Demographic characteristic and outcome data will be shared