Older patients often suffer from multiple illnesses that require acute hospitalization. The goal of medical work is not only to save lives and heal acutely ill people but also to maintain physical fitness and self-sufficiency. In acutely hospitalized patients, the investigators often observe a decrease in muscle mass and strength, a deterioration in overall fitness with the need for long follow-up care, and sometimes permanent help with normal daily activities. An important part of the treatment of every acute patient is the emphasis on adequate nutrition and physical activity. The aim of this study is to determine the most appropriate intensity of exercise and diet that will be best for acute patients and will lead to the maintenance/improvement of physical fitness and thus shorten the length of hospitalization.

The goal of daily medical work is not only to save lives and cure acutely ill patients but also to maintain quality of life, minimize the risk of complications, and, in the ever-growing population of geriatric patients, to maintain functional ability and self-sufficiency. Acute diseases of the internal type are almost always associated with catabolism leading to proteolysis and exacerbation of malnutrition. Patients are then often observed to have loss of muscle strength and muscle mass, deterioration of fitness, and in geriatric patients, who often have limited functional reserve and loss of self-sufficiency with the need for long follow-up care and sometimes permanent assistance with activities of daily living.

In addition to treating the disease itself, it is important to provide adequate nutrition and to maintain muscle strength and subsequent self-sufficiency by activating patients and providing optimally targeted physiotherapy. Studies demonstrating the effect of intensive rehabilitation are very heterogeneous and often performed on a relatively small number of subjects. Also, the results of these studies and their meta-analyses are inconclusive. It cannot be clearly stated based on the current scientific knowledge that intensive rehabilitation influences important endpoints such as in-hospital mortality, length of hospital stay, or the incidence of nosocomial infections. Early rehabilitation in acutely ill patients does influence muscle mass, but these effects are rather short-term.3 The effect of nutrition itself, or of individual nutrients (vitamin D, hydroxymethyl butyrate, etc.) is well known, and recommendations for nutrition have been developed based on this scientific knowledge. There is very limited evidence for the benefit of combining intensive rehabilitation and nutrition at the same time. The investigators know from available work that this intervention increases muscle mass and improves self-sufficiency.

A very important and still evolving area of medicine is the gut microbiome. The number of bacteria in our digestive tract is approximately the same as the number of cells in our entire body. Some authors speak of the gut microbiome as a separate organ. Intestinal bacteria and their products have a proven effect on the immune system locally and systemically and influence a variety of metabolic processes (insulin sensitivity, appetite, lipid metabolism and storage, oxidative stress, influence on inflammation, etc.). Today, it is possible to talk about the gut-muscle axis and know that the composition of the gut microbiome influences muscle tissue and, conversely, physical activity has been shown to have a benefit on the gut microbiome.

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