Effect of Multicomponent Prehabilitation on Early and Long-term Outcomes in Elderly Patients With Frailty After Digestive Surgery for Cancer: A Randomized-controlled Study

1. Indication for oral nutritional supplementation: Patients at risk of malnutrition (MNA-SF 8-11) or with malnutrition (MNA-SF 0-7). 2. Protocol of nutritional optimization: Enteral nutritional powder (Ensure for patients without diabetes and Glucerna for patients with diabetes) twice a day. The target protein intake is 1.5-1.8 g/kg/d. Patients with iron deficient anemia (hemoglobin \<130 g/L for men and \<120 g/L for women) will be given oral iron therapy. 3. The duration of nutritional optimization: The day admitted to the hospital to the surgery to one day prior to the surgery.

1. The respiratory training will be performed for at least 2-3 times per day. Respiratory training include thoracic breathing exercise and cough training. 2. Aerobic exercise will be performed for at least 1-2 times per day. Aerobic exercise includes jogging, walking or climbing stairs. Exercise intensity will be based on patients' tolerance. The goal of the training is to complete the training plan as far as possible. 3. Every training should be last for 45 minutes to 1 hour. If the patient can not tolerate, the training time should be reduce to 30 minutes. 4. The duration of exercise training: The day admitted to the hospital to the surgery to one day prior to the surgery.

1. Muscle strength training in the bedside and walking in the ward. 2. Aerobic exercise includes jogging, walking or climbing stairs. Exercise intensity will be based on patients' tolerance. The goal of the training is to complete the training plan as far as possible. 3. Exercise training is performed under the supervision of physiotherpists durign hospital stay, and is reminded by regular telephone calls and phone messages after hospital discharge.