Despite the controversy, on October 6, 2021, the World Health Organization (WHO)recognized Long Coronavirus disease (COVID) by officially defining it: " symptomsappeared 3 months after the onset of the primary infection by the Severe AcuteRespiratory Syndrome Coronavirus-2 (SARS-CoV-2), persisting for at least 2 months andwhich cannot be explained by any other condition ". Long COVID can affects any type ofpatient and has polymorphic and fluctuating symptoms over time.The Reunion Island is a French overseas department located in the Indian Ocean accountingmore than 860,000 inhabitants. It has recorded since March 11, 2020, nearly 491,825 casesof COVID-19 and 961 deaths of hospitalized patients. Reunion's population is multi-ethnicand younger than the metropolitan France's one. It also has a higher prevalence ofobesity and type 2 diabetes, two serious form factors of COVID-19. This specific contextmakes this island a particular study site for Severe Acute Respiratory SyndromeCoronavirus-2 (SARS-CoV-2) and Long COVID.In addition, some studies have confirmed the involvement of the autonomic nervous system(ANS) in the symptomatology of Long COVID and demonstrated that patients with a LongCOVID present a dysfunction of their ANS which is objectified by a reduced Heart RateVariability (HRV). The regulation of heart rate by the ANS is strongly favored byrespiration. A regular slow and deep breathing training helps to adjust the baroreflex,which connect heart rate, breathing and blood pressure. The result of this training is aninduced state called "cardiac coherence" (CC).The investigator therefore hypothesize that respiratory training to CC could "re-educate"the ANS and durably improve the symptomatology of patients with Long COVID.