title: Ischemic preconditioning of one forearm enhances static and dynamic apnea.
abstract: BACKGROUND
  Ischemic preconditioning enhances ergometer cycling and swimming performance. We evaluated whether ischemic preconditioning of one forearm (four times for 5 min) also affects static breath hold and underwater swimming, whereas the effect of similar preconditioning on ergometer rowing served as control because the warm-up for rowing regularly encompasses intense exercise and therefore reduced muscle oxygenation.
  
  
  METHODS
  Six divers performed a dry static breath hold, 11 divers swam underwater in an indoor pool, and 14 oarsmen rowed "1000 m" on an ergometer.
  
  
  RESULTS
  Ischemic preconditioning reduced the forearm oxygen saturation from 65% ± 7% to 19% ± 7% (mean ± SD; P < 0.001), determined using spatially resolved near-infrared spectroscopy. During the breath hold (315 s, range = 280-375 s), forearm oxygenation decreased to 29% ± 10%; and in preparation for rowing, right thigh oxygenation decreased from 66% ± 7% to 33% ± 14% (P < 0.05). Ischemic preconditioning prolonged the breath hold from 279 ± 72 to 327 ± 39 s, and the underwater swimming distance from 110 ± 16 to 119 ± 14 m (P < 0.05) and also the rowing time was reduced (from 186.5 ± 3.6 to 185.7 ± 3.6 s; P < 0.05).
  
  
  CONCLUSIONS
  We conclude that while the effect of ischemic preconditioning (of one forearm) on ergometer rowing was minimal, probably because of reduced muscle oxygenation during the warm-up, ischemic preconditioning does enhance both static and dynamic apnea, supporting that muscle ischemia is an important preparation for physical activity.
authors.affiliation: The Copenhagen Muscle Research Center, Department of Anesthesia, Rigshospitalet, University of Copenhagen, Denmark.
authors.forename: Thomas
authors.initials: T
authors.lastname: Kjeld
authors.forename: Mads Reinholdt
authors.initials: MR
authors.lastname: Rasmussen
authors.forename: Timo
authors.initials: T
authors.lastname: Jattu
authors.forename: Henning Bay
authors.initials: HB
authors.lastname: Nielsen
authors.forename: Niels Henry
authors.initials: NH
authors.lastname: Secher
mesh_terms: D000293:Adolescent; D000328:Adult; D001049:Apnea / Q000503:physiopathology; D054874:Athletic Performance / Q000502:physiology*; D001794:Blood Pressure; D062485:Breath Holding; D004242:Diving / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D005542:Forearm / Q000098:blood supply* / Q000502:physiology; D006801:Humans; D019194:Ischemic Preconditioning; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000502:physiology; D010100:Oxygen / Q000097:blood*; D013318:Stroke Volume; D013848:Thigh / Q000098:blood supply; D014655:Vascular Resistance; D063996:Warm-Up Exercise / Q000502:physiology; D055815:Young Adult
chemical_list: D010100:Oxygen