title: Peak heart rates and sympathetic function in tetraplegic nonathletes and athletes.
abstract: OBJECTIVE
  To examine differences in peak heart rate (HR) and measures of sympathetic function between nonathletes and athletes with chronic, motor-complete, cervical spinal cord injury (SCI).
  
  
  METHODS
  Eight nonathletic men with SCI (C4-C7; age 47 ± 9 yr, with injury duration of 16 ± 9 yr) and 13 athletic men with SCI (C5-C8; age 37 ± 8 yr, with injury duration of 16 ± 6 yr) participated in the study. Measures of sympathetic function included palmar sympathetic skin responses (SSR) to median nerve stimulation, and systolic (SBP) and diastolic (DBP) blood pressure responses to a passive sit-up test. Peak HR responses were assessed during a maximal exercise test.
  
  
  RESULTS
  Compared to the athletic group, the nonathletic group exhibited lower peak HR (102 ± 34 vs 161 ± 20 bpm, P < 0.001) and average SSR scores (0.13 ± 0.35 vs 2.41 ± 1.97, P = 0.008), along with greater reductions in SBP and DBP in response to passive sit-up (SBP: -22 ± 10 vs -9 ± 12 mm Hg, P = 0.019; DBP: -18 ± 8 mm Hg vs -4 ± 9 mm Hg, P = 0.003). On the basis of the criteria for orthostatic hypotension (OH) (drop in SBP ≥ 20 mm Hg or DBP ≥ 10 mm Hg), 88% and 23% of nonathletes and athletes had OH.
  
  
  CONCLUSIONS
  Attenuated peak HR in nonathletic individuals with tetraplegia may be secondary to impairments in sympathetic function including absent SSR and OH. Furthermore, the degree of preserved sympathetic function documented in tetraplegic athletes may suggest a predisposition to engage in high-performance sports. Collectively, our findings provide novel insight into the importance of the sympathetic nervous system for exercise performance.
authors.affiliation: 1International Collaboration on Repair Discoveries, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, CANADA; 2Division of Physical Medicine and Rehabilitation, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, CANADA; 3G. F. Strong Rehabilitation Centre, Vancouver, British Columbia, CANADA.
authors.forename: Katharine D
authors.initials: KD
authors.lastname: Currie
authors.forename: Christopher R
authors.initials: CR
authors.lastname: West
authors.forename: Michéle
authors.initials: M
authors.lastname: Hubli
authors.forename: Cameron M
authors.initials: CM
authors.lastname: Gee
authors.forename: Andrei V
authors.initials: AV
authors.lastname: Krassioukov
mesh_terms: D000328:Adult; D056352:Athletes; D001794:Blood Pressure / Q000502:physiology; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007024:Hypotension, Orthostatic / Q000503:physiopathology; D008297:Male; D008475:Median Nerve / Q000503:physiopathology; D008875:Middle Aged; D011782:Quadriplegia / Q000503:physiopathology*; D013119:Spinal Cord Injuries / Q000503:physiopathology*; D013564:Sympathetic Nervous System / Q000503:physiopathology*