Correlated neurocardiologic and fitness changes in athletes interrupting training - Frederiks, J.; Swenne, C. A.; Bruschke, A. V.; Van der Velde, E. T.; Maan, A. C.; Tenvoorde, B. J.; Vanrooijen, M. G.; Mosterd, W. L.; Schiereck, P. (Medicine & Science in Sports & Exercise, 2000)