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Figure 1 Study protocol. Patients were divided into two groups: isolated early preconditioning (IEP) and second window of protection (SWOP). In the IEP group, serial exercise tests were performed at least 14 days before elective percutaneous coronary intervention for single-vessel left anterior descending coronary artery disease. In the SWOP group, exercise was 24 h and 4 h before PCI. Solid rectangle = treadmill exercise tolerance test. Cross-hatched rectangle = 180-s intracoronary balloon inflation.