Consecutive patients aged >18 years who underwent elective surgery for gastrointestinal
cancer at VU University Medical Centre were included in this study. Patients who did not
give their informed consent, and patients who were severely deconditioned pre-operatively,
thus hindering their ability to perform measurements and mobilisation (according to the
treating surgeon), were excluded from the study. Patients were informed about this study
when their surgery was planned. They were asked to participate in the study on the day of admission