INTRODUCTION
Intensive care unit (ICU)-acquired weakness is a devastating complication of critical illness. With time in ICU, the incidence increases and its presence is associated with increased short-term and long-term mortality.1,2 In ICU survivors, ICU-acquired weakness often does not recover completely, even years after ICU admission.3 Persistent ICU-acquired weakness is considered to be part of the postintensive care syndrome, which encompasses a spectrum of persistent physical, mental, and cognitive impairment seen in survivors of critical illness, especially after prolonged and/or severe critical illnesses.4 The mechanisms underlying ICU-acquired weakness are complex and involve structural and functional alterations in both muscles and nerves.5 Attained myofibers show signs of atrophy, which may be triggered by inflammation, immobilization, endocrine and metabolic alterations, impaired microcirculation, denervation, and certain drugs.5 Apart from that, relative starvation may also play a role. Indeed, a considerable number of patients have a nutritional deficit on ICU admission and/or cannot receive normal feeding. In healthy volunteers, prolonged underfeeding mimics the severe muscle atrophy as typically observed in prolonged critically ill patients. In these otherwise healthy people, this condition obviously can be reversed by giving nutrition.
