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.

The exercise part of cardiac rehabilitation today is often composed of low to moderate intensity training. Several studies have found interval training with high intensity to be more effective in improving physical capacity in healthy subjects and also in different patient populations. We therefore wish to compare high intensity interval training with moderate intensity training in patients operated with coronary bypass surgery. Maximal oxygen consumption is shown to be the best indicator of how many years you life, both in healthy persons and in cardiac patients.

The subjects in this study is attending a four week rehabilitation program at an residential institution in Norway. They are randomised to do either a moderate or a high intensity aerobic training session each day.

The hypothesis in advance, was that high intensity interval training lead to a greater improvement in maximal oxygen consumption than training with moderate intensity. We also hypothesised that there would be no difference between the two groups after 6 months, since then the patients had to administer their own exercise training.

Inclusion Criteria:

• Coronary Artery Grafting (4-12 weeks ago)

Exclusion Criteria:

• Not able to exercise on a treadmill
• Left ventricle ejection fraction < 30%
• hemodynamic significant valve deficit (> NYHA classification II)