Vascular Inflammation as a Therapeutic Target in COVID-19 “Long Haulers”: HIITing the Spot?

In the wake of the first wave of the ongoing global pandemic, it has become imminently clear that coronavirus disease 2019 (COVID-19) has brought with it a whole new clinical syndrome: "long COVID" (1, 2).Hence, after recovery from the acute viral infection, a remarkably large proportion of patients, who initially coined themselves "long haulers" in social media-based patient communities for COVID-19 survivors suffer from persistent and often invalidating symptoms, including dyspnoea, chest pain, tachycardia, post-viral brain fog, exercise intolerance, and extreme fatigue to mention a few (3, 4).According to recent studies ∼10% of all individuals infected with the causative acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), and as many as nine out of 10 patients that have required hospitalization because of COVID-19 develop long COVID that persists for at least 4 months, according to the currently available data (4).Time will tell whether the symptoms associated with long COVID are transient or ever-lasting phenomena.Long COVID will expectedly have a huge impact on the morbidity burden and quality of life in many COVID-19 survivors in the future, and when considering the extent of the global pandemic with currently more than 40 million verified cases, it will expectedly have substantial consequences, both in terms of economic cost and health care capacity throughout the world.It is thus widely recognized that there is an impending need for implementing evidence-based patient-tailored safe and effective rehabilitation schemes, but due to the paucity of data on this, the structure and specificity of such schemes remain obscure.While it is widely recognized that some exercise is better than none and more intense exercise is superior to less intense exercise, opinion papers and guidelines published over the past year have consistently refuted high-intensity interval training (HIIT) as an option for rehabilitation after COVID-19 (5-10).On the basis of the known pathophysiology of COVID-19 and the physiological effects of HIIT, we will however argue in favor of the opposite stand, that is, that HIIT should be considered as one of the rehabilitation interventions of choice for alleviating or even reversing the symptoms of long COVID. COVID-19 IS (ALSO) A VASCULAR DISEASEEven though COVID-19 is primarily a viral pneumonia, its multiorgan involvement, both in the acute phase and when considering the persistent systems in long COVID, stresses that this is far from the whole story.Over the past months, several studies have highlighted the presence of a substantial vascular component in the pathophysiology of the disease (11-14).Indeed, COVID-19 is associated with severe vascular inflammation, both in the