We performed three-dimensional vector measurement of exercise-induced magnetocardiograms (MCGs) for normal subjects with a wooden and brass-based bicycle ergometer. MCGs were measured by a three-dimensional second-order gradiometer connected to 39-channel SQUIDs, which can detect magnetic field components perpendicular to the chest wall (Bz) and tangential to the chest wall (Bx, By) simultaneously. Time-frequency analysis was applied to rest times and exercise-induced MCG data. The power spectrum of the ST segment at 6, 8, and 10 Hz was differed between rest times and the exercise-induced MCGs. In order to compare ST segments between rest times and exercise-induced MCG data, singular value decomposition (SVD) was also applied to the MCG data. We found that the time course of singular values in the ST segment differed between rest times and exercise-induced MCG data compared with the QRS segment.
