Patients will receive usual care in Intensive Care Unit (prescription of a standard nutrition formula (at approximately 20 -25 kcal/ kg/day and protein intake 1.2 g/kg/day) once patients are hemodynamically stable.

patients will receive the amino acid intervention that is provided in addition to 'usual care' enteral and/or parenteral nutrition either enteral or parenteral to target a total protein delivery of 2.0g/kg/day. The physical exercise intervention will be delivered by trained nursing staff, and started as close to the time of randomization as feasible (within 24hours of randomization). The intervention group will receive exercise sessions, for up to 20 min duration (as tolerated by patient). The implementation of physical exercise intervention will be protocolized to provide passive exercise early before weaning and shift to active exercise after weaning and also graduated resistance during each session and between daily sessions.

Amino acid enteral and/or parenteral nutrition either enteral or parenteral to target a total protein delivery of 2.0g/kg/day.

Rectus femoris cross-sectional area (RFCSA) will be measured by B-mode ultrasonography using a 3 to 12 MHz transducer array. Patient will be positioned supine in 30° upper body elevation, with legs extended and muscles relaxed. The point that represented 60% of the distance from the anterior superior iliac spine to the superior border of the patella will be identified. The ultrasound probe will be positioned perpendicularly along the superior aspect of the right thigh and transverse images of the rectus femoris will be obtained. A copious amount of gel will be applied to minimize tissue compression. The inner echogenic line of the Rectus Femoris will be traced manually on a frozen image and RFCSA will be calculated by planimetric technique.

Ultrasound evaluation of the rectus femoris muscle

Duration of mechanical ventilation.