Inclusion Criteria:  male and female patient admitted to the Intensive Care Unit of the Department of Internal Medicine and Cardiology, University Hospital Ostrava, for an acute illness of an internal nature; patients admitted to another department of the hospital whose transfer to the above-mentioned ICU (intensive care unit) was carried out within 24 hours of the start of hospitalization may also be included assumption of a minimum length of hospital stay of 5 days ability to give informed consent the patient has both lower limbs the patient can receive fluids and liquid food orally  Exclusion Criteria:  patient admitted from another health care facility where he/she has been admitted for more than 48 hours terminal stage of disease (tumor or non-tumor) patient with neuromuscular disease (polymyositis, etc.) severe chronic disease associated with severe maldigestion (e.g., patient on parenteral home nutrition) patient is fully immobile for a long time