High intensity aerobic interval training (HAIT) increases maximal oxygen uptake (VO₂max) more effectively than moderate-intensity continuous training (MCT) in patients with coronary heart disease (CHD). However, even within the same category of high intensity interval training protocols, higher intensity might be better for improving VO₂max. The purpose of this study is to assess the effect for increasing VO₂max and the safety of maximal-intensity aerobic interval training (MAIT) compared to HAIT.

Patients receiving percutaneous coronary intervention and attended cardiac rehabilitation within two weeks after acute coronary syndrome (ACS) were recruited. Participants were randomly assigned to either a MAIT or a HAIT protocol three times a week for six weeks. The MAIT protocol was set up for four cycles of maximal-intensity (95–100% of HRR, four minutes/cycle) walking with three cycles of active pause with low intensity intervals walking alternatively for every session. In contrast, the HAIT protocol was composed of three cycles of high intensity (85% of HRR, eight minutes/cycle) walking training and two cycles of active pause with low intensity intervals walking alternatively for every session. The change of VO₂max, rate pressure product, echocardiographic findings, body mass index, Borg's rate of perceived exertion scale were examined before and after training.

After completion of six-week aerobic interval training, there were significant increase of VO_2peak in both groups. But the increment of VO_2peak in MAIT group was significantly greater than HAIT group (P<0.05). The percentage increases for the MAIT and HAIT were 31% and 17%, respectively. And a total of 670.5 exercise-hours during MAIT and HAIT, we found no major cardiovascular complication and musculoskeletal complication.

The results of the current study indicate that six-week supervised MAIT is significantly more effective than HAIT in improving VO_2peak in ACS patients. Also it appeared safe after both MAIT and HAIT in a CR setting.