In this study, the investigators want to examine the impact of coronary artery bypass graft (CABG) surgery on skeletal muscle mass, muscle metabolism, and insulin sensitivity in 90 subjects. In extent, the impact of a subsequent exercise intervention will be examined, with a follow-up up to 12 months after surgery.

90 subjects undergoing elective CABG surgery will be included. These subjects are free from orthopedic limitations, will have no severe complications during surgery, and are willing to participate in a 12-week exercise training intervention.

At baseline (before surgery), following parameters will be assessed: blood parameters (glycemic control, lipid profile, anabolic/catabolic hormones, inflammatory markers), body composition (by dual x-ray absorptiometry), handgrip strength, and general subject features (medication, gender, age, etc.).

The first three days after surgery, blood samples will be collected for the analysis of glycemic control, lipid profile, anabolic/catabolic hormones, inflammatory markers.

Next, at the start of exercise intervention, after 6 and 12 weeks of exercise training, and after a 12-month follow-up, following parameters will be assessed: blood parameters (glycemic control, lipid profile, anabolic/catabolic hormones, inflammatory markers), body composition (by dual x-ray absorptiometry), handgrip strength, maximal exercise capacity (by ergospirometry testing), physical activity (by questionnaire), and quality of life ( by questionnaire).

At 12 months of follow-up, cardiovascular mortality and morbidity (re-occurrence of angina, acute myocardial infarction, need for surgery, death) will be assessed.

When initiating exercise intervention, subjects will randomly (n=30 in each group) be assigned to 12 weeks of standard exercise intervention (endurance exercise training), modified exercise intervention (endurance exercise training + strength training), or modified exercise intervention (endurance exercise training + strength training + oral protein supplements).

This will be a cluster randomized clinical trial. Investigators executing the measurements will be blinded for treatment allocation.

Inclusion Criteria:

• Elective CABG surgery
• Willing to participate in 12-week exercise intervention

Exclusion Criteria:

• Complicated surgery
• Severe complications during first days after CABG surgery
• Orthopedic limitations that interfere with proper exercise intervention participation