title: Heart rate at 4 s after the onset of exercise in endurance-trained men.
abstract: It has been suggested that the increase in heart rate (HR) at the onset of exercise is caused by vagal withdrawal. In fact, endurance runners show a lower HR in maximum aerobic tests. However, it is still unknown whether endurance runners have a lower HR at 4 s after the onset of exercise (4th-sec-HR). We sought to measure the HR at the onset of the 4 s exercise test (4-sET), clarifying its relationship to heart rate variability (HRV), spectral indices, and cardiac vagal index (CVI) in endurance runners (ER) and healthy untrained controls (CON). HR at 4th-sec-HR, CVI, and percent HR increase during exercise were analyzed in the 4-sET. High frequency spectrum (HF-nu), low frequency spectrum (LF-nu), and low frequency/high frequency band ratio (LF/HF) were analyzed from the HRV. ER showed a significantly higher HF, and both a lower LF and LF/HF ratio compared with the CON. ER presented a significantly lower 4th-sec-HR, although neither CVI nor HR increases during exercise were statistically different from the CON. In conclusion, ER presented a lower 4th-sec-HR secondary to increased vagal influence over the sinus node. CVI seems to be too weak to use for discriminating individuals with respect to the magnitude of HR vagal control.
authors.affiliation: a Department of Physiological Sciences, Federal University of Espírito Santo, Avenida Marechal Campos 1468, Maruipe, Vitoria, Espirito Santo 29042-751, Brazil.
authors.forename: Divanei
authors.initials: D
authors.lastname: Zaniqueli
authors.forename: Elis Aguiar
authors.initials: EA
authors.lastname: Morra
authors.forename: Eduardo Miranda
authors.initials: EM
authors.lastname: Dantas
authors.forename: Marcelo Perim
authors.initials: MP
authors.lastname: Baldo
authors.forename: Luciana
authors.initials: L
authors.lastname: Carletti
authors.forename: Anselmo José
authors.initials: AJ
authors.lastname: Perez
authors.forename: Sérgio Lamêgo
authors.initials: SL
authors.lastname: Rodrigues
authors.forename: José Geraldo
authors.initials: JG
authors.lastname: Mill
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D010807:Physical Endurance / Q000502:physiology*; D013997:Time Factors; D014630:Vagus Nerve / Q000502:physiology
keywords: 4 s exercise test; coureurs de fond; endurance runners; exercice physique; heart rate; heart rate variability; physical exercise; retrait vagal; rythme cardiaque; test de l’exercice de 4 secondes; vagal withdrawal; variabilité du rythme cardiaque