HRV Biofeedback Calibration and Training
All participants received an ear sensor to measure their pulse and a small laptop with software to complete biofeedback sessions at the Week 2 lab visit. At lab visits, participants’ resting HRV (summarized as RMSSD [root mean square of successive differences]) was first measured which was followed by a short calibration session (for the full calibration description, see Nashiro et al., For Osc+ participants, biofeedback training was facilitated by the emWave Pro software (Heartmath, For Osc− participants, biofeedback training was facilitated by a custom-developed software (Feng, In general, the short calibration breathing sessions took place before the emotional memory task was administered, except for situations where there were scheduling challenges with the participant. After completing the emotional memory task, participants completed one 20-min biofeedback session at their resonance frequency. For Osc+ participants, 53% started this biofeedback session within 15 min of ending the emotional memory task. During the Week 4 session, none of the Osc+ participants completed the biofeedback before the emotional memory task, while one participant completed the memory task first before calibration. During the Week 5 session, three Osc+ participants completed the biofeedback before the memory task, while four participants completed the memory task first before calibration. For Osc− participants, 59% started the 20-min biofeedback session within 15 min of ending the emotional memory task. Due to errors in capturing timestamps for tasks, we were unable to calculate the number of minutes between the end of the memory task and start of the biofeedback session for 1% of participants. During the Week 4 session, three Osc− participants completed the biofeedback before the emotional memory task, while two participants completed the memory task first before calibration. During the Week 5 session, four Osc− participants completed the biofeedback before the memory task, while five participants completed the memory task first before calibration.