text: Hyperventilation A Possible Explanation for Long Lasting Exercise Intolerance in Mild COVID 19 Survivors Since the outbreak of the coronavirus COVID 19 pandemic most attention has focused on containing transmission and addressing the surge of critically ill patients in acute care settings As we enter the second phase of the pandemic emphasis must evolve to post acute care of COVID 19 survivors Persisting cardiorespiratory symptoms have been reported at several months after the onset of the infection Information is lacking on the pathophysiology of exercise intolerance after COVID 19 Previous outbreaks of coronaviruses have been associated with persistent dyspnea muscle weakness fatigue and reduced quality of life The extent of Covid 19 sequelae remains to be evaluated but persisting cardiorespiratory symptoms in COVID 19 survivors can be described as two distinct entities The first type of post Covid symptoms are directly related to organ injury in the acute phase or the complications of treatment The second type of persisting symptoms can affect patients even with mild initial disease presentation without evidence of organ damage The mechanisms are still poorly qualified to date There is a lack of correlation between initial symptom severity and residual symptoms at exertion We report exercise hyperventilation as a major limiting factor in COVID 19 survivors The origin of this hyperventilation may be related to an abnormality of ventilatory control by either hyperactivity of activator systems automatic and cortical ventilatory control peripheral afferents and sensory cortex or failure of inhibitory systems endorphins in the aftermath of pulmonary infection Hyperventilation induced hypocapnia can cause a multitude of extremely disabling symptoms such as dyspnea tachycardia chest pain fatigue dizziness and syncope at exertion 