In this pilot study a group of older adults undergoing midline laparotomy for gastrointestinal malignancy will participate in a mobility and activity training (MAT) program. MAT is designed to advance functional mobility and physical activity and spans the pre-operative, inpatient, and post-operative period. Patients undergoing abdominal surgery will be randomized to MAT versus control usual care and evaluated at their first appointment 4 weeks preoperatively (baseline), immediately prior to surgery, on hospital discharge, and 6 weeks post operatively. We hope to prove that abdominal surgery patients undergoing MAT will show less decline and earlier recovery in functional activity, and trunk and thigh muscle strength mass. This study is uniquely innovative in that it links functional activity assessment and training and analysis of trunk morphomics (muscle mass) in exploring mechanisms of post-operative recovery. Results from this pilot will be used to determine an effect size for the recruitment of a larger cohort and to study key surgical outcomes, including surgical complications, operative symptoms, hospital length of stay, and cost of care.