Heart rate variability in athletes and nonathletes at rest and during head-up tilt - Martinelli, F. S.; Chacon-Mikahil, Mara Patrícia Traina; Martins, L E B; Lima Filho, E C; Golfetti, R; Paschoal, M A; Gallo Júnior, Lourenço (Brazilian Journal of Medical and Biological Research, 2005)