Impact of Prehabilitation Components on Oxygen Uptake of People Undergoing Major Abdominal and Cardiothoracic Surgery: A Network Meta-Analysis of Randomized Controlled Trials

<b>Background/Objectives:</b> Patient preoperative cardiorespiratory physical fitness measured by maximal oxygen consumption (VO2max) is highly relevant to postoperative outcomes, with low VO2max associated with a greater symptom burden and a greater prevalence of long-term treatment-related cardiovascular disease risk factors in patients undergoing surgery. A network meta-analysis (NMA) was conducted to determine the effects of different components of prehabilitation, including exercise, nutrition, psychological intervention, and different combinations of the aforementioned interventions, on oxygen consumption in people undergoing major abdominal or cardiothoracic surgery. <b>Methods:</b> A literature search was conducted from inception to December 2025. Randomized controlled trials on the effectiveness of prehabilitation programmes on pre-surgery VO2max were included. The risk of bias was assessed via the Cochrane risk of bias (RoB 2.0) tool, and the quality of evidence was assessed via the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) tool. Pairwise meta-analyses and NMAs were conducted for direct and indirect evidence. <b>Results:</b> Fourteen studies were included in this NMA. The highest effect (ES) for VO2max scores was for the exercise group versus the control group (ES: 0.44; 95% CI: 0.11, 0.78). When exercise was categorized according to intensity, the highest effect was for high-intensity interval training (HIIT) versus the control (ES: 0.51; 95% CI: 0.04, 0.97). <b>Conclusions:</b> Exercise HIIT should be considered the most effective strategy for improving exercise capacity in patients undergoing major abdominal or cardiothoracic surgery. Given the importance of VO2 as a predictor of morbidity, mortality, and the potential occurrence of adverse events after the procedure in surgical patients, it is essential to include its measurement in future studies to estimate both the risk of procedures and the effect of prehabilitation programmes.