STOCKHOLM – A cardiac rehabilitation program built around supervised high-intensity treadmill aerobic interval workouts improves peak oxygen uptake to a greater degree than does standard moderate-intensity cardiac rehab, according to a randomized trial.
Moreover, the advantage favoring aerobic interval training remained significant at follow-up 30 months after patients completed their formal 12-week cardiac rehab program, Dr. Trine T. Moholdt reported at the congress.
“One of the biggest challenges in cardiac rehabilitation is how to make patients continue with a healthier lifestyle after ending the rehab program. There are no long-term effects of exercise training; that is, you have to keep on doing it to get the benefit from it,” observed Dr. Moholdt of the Norwegian University of Science and Technology, Trondheim.
The group assigned to the aerobic interval cardiac rehab program reported exercising more regularly and at considerably higher intensity than did the standard rehab group during the 30 months after their structured program ended. That's the likely explanation for why their peak oxygen uptake (VO2max) at 30 months remained significantly higher than in the control group, although VO2max declined over time in both groups, she said.
Her study comprised 107 MI patients undergoing 12 weeks of cardiac rehab at three Norwegian hospitals. They were randomized to aerobic interval training or conventional cardiac rehab entailing two physical therapist-led group sessions per week, each lasting about 60 minutes and performed at 70%-80% of an individual's maximum heart rate.
The aerobic interval regimen consisted of a 10-minute warm-up followed by 40 minutes of uphill treadmill walking or jogging intervals. The workout consisted of four 4-minute-long high-intensity intervals at 85%-95% of a patient's individually determined maximum heart rate, followed by a 3-minute recovery, then a cool down. The high-intensity intervals were designed to be just challenging enough so that patients could say only a few words while doing them but would not experience pain in the chest or legs.
Subjects in both study arms were encouraged to do one additional workout per week at home.
Eighteen patients dropped out of the 12-week cardiac rehab program. Among completers, the aerobic interval group showed a mean improvement in VO2max from 31.6 mL/kg per minute at baseline to 36.2 at 12 weeks. This was a significantly greater gain than that seen in the moderate-intensity rehab group, which improved from 32.2 to 34.7 mL/kg per minute.
Follow-up assessments were conducted at 6 and 30 months after completion of the rehab program. VO2max declined over time in both groups. By 30 months VO2max in the aerobic interval training group was back to baseline; however, VO2max in the standard cardiac rehab group had declined to significantly below baseline. Thus, the aerobic interval training group retained a significant relative advantage, although it seems clear that some sort of refresher intervention needs to be developed.
In terms of secondary study end points, flow-mediated dilatation of the brachial artery increased significantly in both groups after the rehab program, with no between-group difference. So did quality of life scores and increases in plasma adiponectin, a hormone with multiple beneficial metabolic effects. Only the aerobic interval program graduates experienced a significant increase in HDL levels, which rose from 49.9 mg/dL at baseline to 51.5 mg/dL after 12 weeks.
In the 69 subjects who presented at 30 months post rehab, self-reported physical activity varied markedly between the two study groups. Fully 20% of the standard-rehab patients reported being physically inactive, compared with 4% in the aerobic interval group. Fifteen percent in the standard-rehab group indicated they engaged in high-intensity exercise, compared with 46% of graduates of the aerobic interval-based program – and therein lies the explanation for the significant long-term difference between the two groups in VO2max, according to Dr. Moholdt.
She noted that these results are consistent with an earlier randomized study she and her coworkers conducted in coronary artery bypass graft surgery patients followed for 6 months after completing cardiac rehab emphasizing either aerobic interval training or continuous moderate exercise (Am. Heart J. 2009;158:1031-7).
Attendees at the session devoted to research in cardiac rehab were generally enthusiastic about the Trondheim study findings and found the data convincing. One attendee said that the aerobic interval training program was as much a psychological as a physiological intervention.
“You've proved that a different self-reported behavior pattern was created. You've shown the patients that they could dare to perform high-level exercise,” he said.
“I do agree,” Dr. Moholdt replied. “Many patients quickly realized, often after the very first session, that it's not dangerous to become exhausted.”