Positioning of the subject: A special device, consisting of a rigid padded wooden board resting on metal bar, which was attached to the metal framing of the hospital bed, held the knee joint at a 90-degree angle and secured firm support of the entire thigh (Fig. 1). The positioning was chosen to reduce unnecessary movement and minimize risk for mechanical ventilated ICU patients. Isometric knee extension forces were therefore measured while subjects were placed in a supine position in a hospital bed with a 30-degree incline of the head and torso.