title: Physical fitness as a determinant of vagal modulation.
abstract: The association between increasing age and decreasing vagal modulation is well known. However, the importance of fitness as a determinant of the decline in vagal modulation with age is not established. To test the hypothesis that decreasing vagal modulation is largely a function of declining fitness rather than increasing age, we studied a sample of healthy volunteers with a wide range of fitness levels, but a narrow age range. We assessed fitness by measuring the maximal oxygen uptake (VO2max) achieved during incremental bicycle exercise. Vagal modulation was assessed by calculating high frequency power (0.15-0.40 Hz) of the RR variability power spectrum from 24-h ECG recordings. We studied 37 healthy volunteers who were 22-44 yr old. In our sample, VO2max ranged from 25 to 70 mL.min-1.kg-1 (mean of 45 +/- 13). Age was not significantly related to high frequency power, but VO2max was highly correlated with high frequency power (r = 0.74, P = 0.0001), indicating that physical fitness is strongly associated with vagal modulation. Thus, the decline in vagal modulation often attributed to increasing age may, instead, be the result of a decline in fitness.
authors.affiliation: Division of Circulatory Physiology, Columbia University, College of Physicians and Surgeons, New York, NY, USA. rlg11@columbia.edu
authors.forename: R L
authors.initials: RL
authors.lastname: Goldsmith
authors.forename: J T
authors.initials: JT
authors.lastname: Bigger
authors.forename: D M
authors.initials: DM
authors.lastname: Bloomfield
authors.forename: R C
authors.initials: RC
authors.lastname: Steinman
mesh_terms: D000328:Adult; D015716:Electrocardiography, Ambulatory; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D010809:Physical Fitness; D014630:Vagus Nerve / Q000502:physiology*