Background Prolonged immobility in COVID-19 patients in mechanical ventilation combined with the infection-mediated harmful immune response can be responsible of peripheral nervous system complications, such as Intensive Care Unit Acquired Weakness (ICU-AW). We report preliminary findings of our monocentric prospective study. Method Prospective observational study of PCR-confirmed COVID-19 patients in mechanical ventilation in the Intensive Care Unit of Azienda Ospedaliero Universitaria Careggi (Firenze). We evaluated: 1. muscle power grading on motor response to nociceptive stimuli by means of MRC; 2. nerve conduction velocities, compound muscle action potentials (CMAP) and sensory nerve action potentials (SNAP) of six motor and four sensitive nerves in bilateral upper and lower limbs; 3. spontaneous muscle activity in bilateral tibialis anterior and biceps by needle. The presence of combined critical illness polyneuropathy and myopathy (CIPNM) was defined by very low amplitude of CMAP and/or SNAP on neurophysiological evaluation with normal or mildly reduced nerve conduction velocities, combined with myopathic features on needle electromyography. Data about pre-existing comorbidities such as diabetes and hypertension were also collected. Findings Between March 23 March 2020 to 10 April 2020, we performed ENG studies in 9 patients. Based on clinical examination ICU-AW (MRC score <48/60) was present in all 9 patients. Four of them had diagnosis of CIPNM at neurophysiological evaluation, and 3 of the remaining 5 patients presented neurophysiological findings consistent with common peroneal nerve compression Interpretation The present findings suggest that in critically ill patients affected by COVID-19 functional motor deficits are highly prevalent and should be searched for. ICU-AW have been found to negatively affect weaning from mechanical ventilation long-term outcome and increase in-hospital mortality of critical patients. Early recognition of these complications could help clinicians to plan an appropriate neuromotor rehabilitation (e.g. by early passive limbs mobilization and posture changes) for improving respiratory function and clinical outcome. Funding None