Does preoperative intervention in people undergoing cardiac surgery reduce pulmonary complications, shorten length of stay in the intensive care unit (ICU) or hospital, or improve physical function?Systematic review with meta-analysis of (quasi) randomised trials.People undergoing coronary artery bypass grafts and/or valvular surgery.Any intervention, such as education, inspiratory muscle training, exercise training or relaxation, delivered prior to surgery to prevent/reduce postoperative pulmonary complications or to hasten recovery of function.Time to extubation, length of stay in ICU and hospital (reported in days). Postoperative pulmonary complications and physical function were measured as reported in the included trials.The 17 eligible trials reported data on 2689 participants. Preoperative intervention significantly reduced the time to extubation (MD -0.14 days, 95% CI -0.26 to -0.01) and the relative risk of developing postoperative pulmonary complications (RR 0.39, 95% CI 0.23 to 0.66). However, it did not significantly affect the length of stay in ICU (MD -0.15 days, 95% CI -0.37 to 0.08) or hospital (MD -0.55 days, 95% CI -1.32 to 0.23), except among older participants (MD -1.32 days, 95% CI -2.36 to -0.28). When the preoperative interventions were separately analysed, inspiratory muscle training significantly reduced postoperative pulmonary complications and the length of stay in hospital. Trial quality ranged from good to poor and considerable heterogeneity was present in the study features. Other outcomes did not significantly differ.For people undergoing cardiac surgery, preoperative intervention reduces the incidence of postoperative pulmonary complications and, in older patients, the length of stay in hospital.