Positives

• A patient with Long Covid shared that practicing resonance frequency breathing helped them feel “considerably better” even when they couldn’t fully return to sleep, suggesting a calming effect on their nervous system Reddit.
  
  
• One person noted that reaching a calm baseline through this breathing technique not only made them “feel better” but also seemed to promote healing by reducing bodily stress Reddit.
  
  

Negatives

• Patients in HRV biofeedback for chronic disease commonly see no effect on time-domain HRV parameters, with researchers attributing the failure to participants not following the prescribed slow-breathing target ScienceDirect.
• The resonance frequency itself shifts between test and retest sessions in roughly two-thirds of participants, suggesting the personalized breathing rate is not as stable as protocols assume, which can blunt expected benefits Scientific Reports.

Hurdles & Side Effects

• HeartMath’s Inner Balance Coherence Plus sensor lists at $349, with the newer HeartMath app free for a 7-day trial then a recurring annual subscription (about $79 CAD) on top of the hardware.
• Patients pursuing higher-resolution HRV with a Polar H10 chest strap pay around $100 USD for the strap, and a compatible smartwatch or HRV app can add $350-$850 more depending on the model MDPI Sensors.