title: Sex differences in autonomic function following maximal exercise.
abstract: BACKGROUND
  Heart rate variability (HRV), blood pressure variability, (BPV) and heart rate recovery (HRR) are measures that provide insight regarding autonomic function. Maximal exercise can affect autonomic function, and it is unknown if there are sex differences in autonomic recovery following exercise. Therefore, the purpose of this study was to determine sex differences in several measures of autonomic function and the response following maximal exercise.
  
  
  METHODS
  Seventy-one (31 males and 40 females) healthy, nonsmoking, sedentary normotensive subjects between the ages of 18 and 35 underwent measurements of HRV and BPV at rest and following a maximal exercise bout. HRR was measured at minute one and two following maximal exercise.
  
  
  RESULTS
  Males have significantly greater HRR following maximal exercise at both minute one and two; however, the significance between sexes was eliminated when controlling for VO2 peak. Males had significantly higher resting BPV-low-frequency (LF) values compared to females and did not significantly change following exercise, whereas females had significantly increased BPV-LF values following acute maximal exercise. Although males and females exhibited a significant decrease in both HRV-LF and HRV-high frequency (HF) with exercise, females had significantly higher HRV-HF values following exercise. Males had a significantly higher HRV-LF/HF ratio at rest; however, both males and females significantly increased their HRV-LF/HF ratio following exercise.
  
  
  CONCLUSIONS
  Pre-menopausal females exhibit a cardioprotective autonomic profile compared to age-matched males due to lower resting sympathetic activity and faster vagal reactivation following maximal exercise. Acute maximal exercise is a sufficient autonomic stressor to demonstrate sex differences in the critical post-exercise recovery period.
authors.affiliation: Department of Health and Exercise Science, Appalachian State University, 111 Rivers Street, 038 HCC, Boone, NC 28608-2071 USA ; Department of Kinesiology, Nutrition, and Rehabilitation, University of Illinois at Chicago, Chicago, IL USA.
authors.forename: Rebecca M
authors.initials: RM
authors.lastname: Kappus
authors.affiliation: Department of Anesthesiology, Mayo Clinic, Rochester, MN USA.
authors.forename: Sushant M
authors.initials: SM
authors.lastname: Ranadive
authors.affiliation: Department of Kinesiology, East Carolina, Greensboro, NC USA.
authors.forename: Huimin
authors.initials: H
authors.lastname: Yan
authors.affiliation: Department Health and Human Physiology, University of Iowa, Iowa City, IA USA.
authors.forename: Abbi D
authors.initials: AD
authors.lastname: Lane-Cordova
authors.affiliation: Department of Kinesiology, Nutrition, and Rehabilitation, University of Illinois at Chicago, Chicago, IL USA.
authors.forename: Marc D
authors.initials: MD
authors.lastname: Cook
authors.affiliation: Key Laboratory of Adolescent Health Assessment and Exercise Intervention, Ministry of Education, East China Normal University, Shanghai, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Sun
authors.affiliation: Department of Health and Kinesiology, Texas A & M University, College Station, TX USA.
authors.forename: I Shevon
authors.initials: IS
authors.lastname: Harvey
authors.affiliation: Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, IL USA.
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Wilund
authors.affiliation: Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, IL USA.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Woods
authors.affiliation: Department of Kinesiology, Nutrition, and Rehabilitation, University of Illinois at Chicago, Chicago, IL USA.
authors.forename: Bo
authors.initials: B
authors.lastname: Fernhall
keywords: Blood pressure variability; Heart rate recovery; Heart rate variability; Sympathetic activity; Vagal modulation