HEART Rate Variability Biofeedback in LOng COVID-19 (HEARTLOC)

Participants will be shown a paced breathing programme and instructed to implement this for 10 minutes twice daily for 4 weeks. During the 10 minute breathing exercises, the participant will need to wear the Polar H10 chest strap and can remove this when finished. The breathing will ideally be a breathing pattern of a 4 second nasal inhale, and 6 second nasal exhale using the 'resonance' programme in the 'biofeedback' section of EliteHRV app. Researchers will monitor the participant's comfort and ease during this breathing demonstration, if participants find this breathing rate too slow then it can be tailored to ensure a tolerable slow breathing rate with minimal impact on symptoms - most likely by reducing both inhale and exhale in 1 second increments until a more tolerable breathing rate and pattern is found. They will be advised to monitor the graph of HRV on EliteHRV which allows real-time assessment of HRV and to aim to breathe in and out deeply to raise the HRV graph reading as much as possible each time. Participant Information Sheet provides more clarification and instruction on this. They will be advised to perform the breathing programme lying down with minimal distractions on waking in the morning and just before bed in the evening, preferably in the same location each time. During this 4 week period researchers will make weekly contact by phone to check progress and help resolve any queries. The participant will also have contact details of the researchers in case of any technical issues with Polar H10 chest strap or app during the 4 week study period.