title: The Acute Effect of Exercise Intensity on Vascular Function in Adolescents.
abstract: BACKGROUND
  Impairments in vascular function are present in asymptomatic youths with risk factors for cardiovascular disease. Exercise can promote vascular health in youth, but the effects of exercise intensity and the time course in response to acute exercise are unknown.
  
  
  METHODS
  Twenty adolescents (10 male, 14.1 ± 0.3 yr) performed the following on separate days in a counterbalanced order: 1) cycling at 90% of the gas exchange threshold (moderate-intensity exercise (MIE)) and 2) 8 × 1-min cycling at 90% peak power with 75-s recovery (high-intensity interval exercise (HIIE)). The duration of MIE (25.8 ± 2.1 min) was work-matched to HIIE (23.0 min). Macro- and microvascular functions were assessed before, immediately after, and 1 and 2 h after exercise by flow-mediated dilation (FMD) and laser Doppler imaging (total reactive hyperemia).
  
  
  RESULTS
  FMD was attenuated immediately after HIIE (P < 0.001, effect size (ES) = 1.20) but not after MIE (P = 0.28, ES = 0.26). Compared with that before exercise, FMD was elevated 1 and 2 h after HIIE (P < 0.001, ES = 1.33; P < 0.001, ES = 1.36) but unchanged in MIE (P = 0.67, ES = 0.10; P = 0.72, ES = 0.08). Changes in FMD were unrelated to shear or baseline arterial diameter. Compared with that in preexercise, total reactive hyperemia was always greater after MIE (P < 0.02, ES > 0.60 for all) and HIIE (P < 0.001, ES > 1.18 for all). Total reactive hyperemia was greater in HIIE compared with that in MIE immediately after (P = 0.03, ES = 0.67) and 1 h after (P = 0.01, ES = 0.62) exercise, with a trend to be greater 2 h after (P = 0.06, ES = 0.45).
  
  
  CONCLUSIONS
  Exercise intensity is positively associated with macro- and microvascular function 1 and 2 h after exercise. Performing HIIE may provide superior vascular benefits than MIE in adolescents.
authors.affiliation: Children's Health and Exercise Research Centre, Sport and Health Science, College of Life and Environmental Sciences, University of Exeter, Exeter, UNITED KINGDOM.
authors.forename: Bert
authors.initials: B
authors.lastname: Bond
authors.forename: Siobhan
authors.initials: S
authors.lastname: Hind
authors.forename: Craig A
authors.initials: CA
authors.lastname: Williams
authors.forename: Alan R
authors.initials: AR
authors.lastname: Barker
mesh_terms: D000293:Adolescent; D001916:Brachial Artery / Q000502:physiology; D002648:Child; D004730:Endothelium, Vascular / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008833:Microcirculation / Q000502:physiology; D005082:Physical Exertion / Q000502:physiology*; D012039:Regional Blood Flow; D014664:Vasodilation