The purpose of this study is to investigate the effect of high and moderate intensity exercise training after coronary bypass surgery. The subjects are randomised to training at either 60-70% or 85-95% of their maximal capacity daily for four weeks. Primary outcome measure is change in maximal aerobic capacity, measured as change in maximal oxygen consumption, after the training period. Secondary outcome measures are change in quality of life, heart rate variability, ultrasound measures of the heart and blood variables, including endothelian markers.