The pathophysiology of critical illness myopathy is thought to involve the following mechanisms: 1) impairment of muscular membrane excitability, secondary to an dysregulation of sodium channel gating, 2) mitochondrial dysfunction leading to bioenergetic failure and oxidative stress and 3) proteolysis, mainly related an activation of the ubiquitin-proteasome pathway. These mechanisms can be triggered by various factors, notably systemic inflammatory mediators, endocrine dysfunction, immobilization, some drugs and electrolyte disturbances. The protracted functional consequences of ICU-AW indicate that muscle regeneration is also impaired. Surprisingly, muscle regeneration, which essentially depends on the muscle stem cells (also called satellite cells), has not been well investigated in the context of critical illness. The satellite cells (SC), that are located at the periphery of the muscle fiber, are activated in response to any muscle injury and then proliferate and differentiate to repair or replace the damaged fibers, but also self-renew to replenish the muscle stem cells reservoir.