 Patients undergoing elective open and laparoscopic surgery of colon, rectum, stomach, pancreas and liver for any indication will be included. Further inclusion criteria are: age between 18-75 years, ASA score 4, and a signed informed consent. Patients are stratified into two subgroups laparoscopic and open surgery and will be randomized 1:1 for an autofeedback of their step-count using an activity tracker wristband or for the control group without autofeedback. Sample size n 29 patients in each of the four groups, overall n 119 is calculated on an assumed difference in step-count of 250 steps daily intervention versus control group. The primary study endpoint is the step-count during the first five postoperative days; secondary endpoints are the percentage of patients in the two groups, who master the predefined mobilization step-count targets, the assessment of additional activity data from the devices, the assessment of the preoperative mobility, length of hospital and intensive care unit stay, number of patients who receive physiotherapy, 30-day mortality, and the overall 30-day morbidity. 