title: The Effect of Caffeine on Repeat-High-Intensity-Effort Performance in Rugby League Players.
abstract: BACKGROUND
  Repeat-high-intensity efforts (RHIEs) have recently been shown to occur at critical periods of rugby league matches.
  
  
  OBJECTIVE
  To examine the effect that caffeine has on RHIE performance in rugby league players.
  
  
  METHODS
  Using a double-blind, placebo-controlled, crossover design, 11 semiprofessional rugby league players (age 19.0 ± 0.5 y, body mass 87.4 ± 12.9 kg, height 178.9 ± 2.6 cm) completed 2 experimental trials that involved completing an RHIE test after either caffeine (300 mg caffeine) or placebo (vitamin H) ingestion. Each trial consisted of 3 sets of 20-m sprints interspersed with bouts of tackling. During the RHIE test, 20-m-sprint time, heart rate (HR), rating of perceived exertion (RPE), and blood lactate were measured.
  
  
  RESULTS
  Total time to complete the nine 20-m sprints during the caffeine condition was 1.0% faster (28.46 ± 1.4 s) than during the placebo condition (28.77 ± 1.7 s) (ES = 0.18, 90%CI -0.7 to 0.1 s). This resulted in a very likely chance of caffeine being of benefit to RHIE performance (99% likely to be beneficial). These improvements were more pronounced in the early stages of the test, with a 1.3%, 1.0%, and 0.9% improvement in sprint performance during sets 1, 2, and 3 respectively. There was no significant difference in RPE across the 3 sets (P = .47, 0.48, 1.00) or mean HR (P = .36), maximal HR (P = .74), or blood lactate (P = .50) between treatment conditions.
  
  
  CONCLUSIONS
  Preexercise ingestion of 300 mg caffeine produced practically meaningful improvements in RHIE performance in rugby league players.
authors.forename: Brandon M
authors.initials: BM
authors.lastname: Wellington
authors.forename: Michael D
authors.initials: MD
authors.lastname: Leveritt
authors.forename: Vincent G
authors.initials: VG
authors.lastname: Kelly
mesh_terms: D054874:Athletic Performance / Q000502:physiology*; D001628:Beverages; D002110:Caffeine / Q000008:administration & dosage*; D000697:Central Nervous System Stimulants / Q000008:administration & dosage*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005538:Football / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D010465:Perception; D005082:Physical Exertion / Q000502:physiology; D012420:Running / Q000502:physiology; D055815:Young Adult
chemical_list: D000697:Central Nervous System Stimulants; D019344:Lactic Acid; D002110:Caffeine
keywords: caffeine; collision; rugby league; sprint performance