Background.Developing adequate levels of muscular strength in the cardiac rehabilitation (CR) patient helps return the patient to an active lifestyle. This study evaluated the effects and safety of an 8-week high-intensity strength training (ST) program combined with a traditional aerobic-based CR program on the muscular strength of a diverse phase II CR population.Methods.Sixty-one phase II CR patients (age = 60.5 ± 10.6 years) stratified by risk (high risk:n= 18, ejection fraction = 23.6 ± 7.8%; intermediate risk:n= 19, ejection fraction = 40.0 ± 4.6%; low risk:n= 24, ejection fraction = 58.0 ± 7.7%) and gender (males = 46, females = 15) participated. One repetition maximum (1RM) testing was performed on the horizontal squat, shoulder press, leg extension, lat pulldown, and biceps curl. Patients performed two sets of each exercise 2 days per week at an intensity that started at 60% 1RM and progressed to 80% 1RM by week 4. Weeks 4 to 8 intensity was adjusted individually to maintain 8RM per set. Blood pressure and heart rate/rhythm responses to 1RM testing were monitored in high-risk patients. Muscle soreness and injury were monitored for all patients immediately after 1RM testing and on days 2 and 7.Results.All patient groups made significant gains (P< 0.05) in muscle strength (mean increase: lower body = 15.3%, upper body = 16.7%). No injury or significant muscle soreness occurred due to 1RM testing. No abnormal heart rate/rhythm or blood pressure responses occurred in high-risk patients.Conclusions.Diverse phase II CR patients can improve their strength significantly with a combination of high-intensity strength and aerobic training.