1. John B. Pierce Laboratory and Department of Epidemiology and Public Health Yale University School of Medicine New Haven CT USA
2. Cardiac Arrhythmia Service & Cardiovascular Research Center Massachusetts General Hospital Boston MA USA
3. Department of Medicine Harvard Medical School Boston MA USA
4. Department of Health Physical Education & Recreation Western Michigan University Kalamazoo MI USA
5. Department of Exercise Sciences Brigham Young University Provo UT USA