Seventy patients in cardiac rehabilitation with maximal exercise capacity less than 1.4 watt per kilogram bodyweight will be randomized 1:1 into either an intervention training (IN) group or usual care (UC). The IN patients will perform supervised endurance and resistance exercise for approximately 90 minutes once a week and traditional cardiac rehabilitation (TCR) once a week; the UC patients will perform TCR twice a week. The intervention is planned for six months with a follow-up of a further six months. The primary investigation is differences between IN and UC with regard to changes in exercise capacity (max watt/kgBW).

The DOPPELHERZ (The influence of individualized resistance-endurance exercise training on maximal power output in outpatient cardiac rehabilitation) randomized controlled trial was performed at the Department of Prevention and Sports Medicine, Klinikum rechts der Isar in Munich, Germany. 70 patients eligible for and/or participating in cardiac rehabilitation were randomized to six months in an individualized combined exercise group (ICE) or group- based cardiac rehabilitation (GCR), considered usual care in this patient population.

All patients gave written informed consent, the study protocol was approved by the local university hospital ethics committee, all procedures were conducted according to the Declaration of Helsinki.

Participants: All patients were American Heart Association Class "C" (moderate to high risk) based on the presence of cardiac disease and maximal power output of <5 METs (corresponding to <1.4 W/kg body weight), who met eligibility criteria for CR at the time of recruitment. Patients with decompensated or highly symptomatic (NYHA IV) heart failure, acute illness or injury, cardiac hospitalizations within six weeks of inclusion, drug abuse, unstable blood pressure or arrhythmias, high grade valve stenosis or instable diabetes mellitus were excluded.

Primary endpoint: The primary endpoint was change in maximal relative power output (W/kg) measured by CPX after six months.

Exercise training program In both the intervention and usual care arms of the study, exercise training was prescribed twice weekly over a period of six months, and all exercise sessions were led by certified exercise instructors and monitored by physicians.

Group-based cardiac rehabilitation (GCR): The GCR group performed regular exercise in a state-sanctioned cardiac rehabilitation group. This form of GCR is considered Phase III aftercare and has been described elsewhere9. Briefly, GCR patients received moderate-intensity heart rate targets from exercise cardiologists based on CPX results. The group-based program is offered for 90 minutes twice a week and is a combination of gymnastics (including endurance and resistance components), coordination and flexibility exercises, and includes educational components targeting diet and nutrition, stress and relaxation, methods for coping with CVD and behavioral and lifestyle change. The GCR sessions were conducted at a local university gymnasium and were performed in groups of up to 15 participants, as recommended by the German Federal Association for Rehabilitation.

Individualized combined exercise (ICE): The ICE group participated in once-weekly individualized combined resistance-endurance exercise training for 60 minutes and once-weekly traditional group-based cardiac rehabilitation as described above. The ICE intervention included 30 minutes of endurance exercise at 60-70% VO2peak and RPE 11-14 and five resistance exercises (chest press, leg press, lat pull-downs, shoulder press and seated cable row) following the recommendations of the German Federation for Cardiovascular Prevention and Rehabilitation (DGPR) and targeting the large muscle groups at an RPE<16. For the first three months, patients performed two sets of 12-25 repetitions at 30-50% 1RM; after three months patients were retested and thereafter performed two sets of 8-15 repetitions at 40-60% 1RM. The ICE sessions were located at the university sports medicine rehabilitation center and performed in groups of not more than four patients. They were instructed at a maximum 2:1 participant to therapist ratio.

Inclusion Criteria:

• participation in cardiac rehabilitation
• written consent
• < 1.4 watt/kgBW exercise capacity not more than 12 weeks before study begin

Exclusion Criteria:

• >= 1.4 watt/kgBW
• contraindications to exercise participation
• hospitalized for CVD within six weeks of inclusion
• acute illness/injury (e.g. fever)
• chronic drug abuse
• inability to understand study instructions
• unwillingness to participate