Biofeedback for CHAMPS

"* 5 days of 3-min HRV readings to establish baseline HRV~* After meeting with study personnel to review HRV biofeedback (BF) practice with the app, participants will be asked to begin HRV BF training for 5 min a day~* Participants will increase the length of HRV BF training by 5 min every few days until they reach 20 min a day of HRV BF training~* Participants will aim for 20 min of daily HRV BF training for 6 consecutive wks out of the 8-wk total BF training protocol~* Study personnel will follow the participants' progress with training via the online portal provided through the Optimal HRV app and have brief (15-min) check-in appts. with participants to discuss how they are experiencing HRV BF, what they find helpful, and barriers to their practice if they are having difficulties~* After completing the 8-wks of BF training (including 2 wks of 5-min titrations to the full 20-min protocol), participants will be asked to take 3-min HRV readings for 5 days to assess post-intervention HRV"