Researchers at the Guiyang Medical College in China conducted studies of 220 athletes and 30 average subjects using color DOPLER imaging. The study showed that just 30 minutes after receiving a dose of gypenosides, 100% of the test subjects showed positive effects. The effects measured included, increased stroke volume and cardiac output, decreased left ventricular end-systolic diameter and increased left ventricular end-diastolic diameter. The heart rate and blood pressure did not increase. This implies that Jiaogulan improved the efficiency of the pumping action of the heart such that the heart did not have to work as had to produce the same volume of blood flow.