title: The effects of four weeks of creatine supplementation and high-intensity interval training on cardiorespiratory fitness: a randomized controlled trial.
abstract: BACKGROUND
  High-intensity interval training has been shown to be a time-efficient way to induce physiological adaptations similar to those of traditional endurance training. Creatine supplementation may enhance high-intensity interval training, leading to even greater physiological adaptations. The purpose of this study was to determine the effects of high-intensity interval training (HIIT) and creatine supplementation on cardiorespiratory fitness and endurance performance (maximal oxygen consumption (VO2PEAK), time-to-exhaustion (VO2PEAKTTE), ventilatory threshold (VT), and total work done (TWD)) in college-aged men.
  
  
  METHODS
  Forty-three recreationally active men completed a graded exercise test to determine VO2PEAK, VO2PEAKTTE, and VT. In addition, participants completed a time to exhaustion (TTE) ride at 110% of the maximum workload reached during the graded exercise test to determine TWD (TTE (sec) x W = J). Following testing, participants were randomly assigned to one of three groups: creatine (creatine citrate) (Cr; n = 16), placebo (PL; n = 17), or control (n = 10) groups. The Cr and PL groups completed four weeks of HIIT prior to post-testing.
  
  
  RESULTS
  Significant improvements in VO2PEAK and VO2PEAKTTE occurred in both training groups. Only the Cr group significantly improved VT (16% vs. 10% improvement in PL). No changes occurred in TWD in any group.
  
  
  CONCLUSIONS
  In conclusion, HIIT is an effective and time-efficient way to improve maximal endurance performance. The addition of Cr improved VT, but did not increase TWD. Therefore, 10 g of Cr per day for five days per week for four weeks does not seem to further augment maximal oxygen consumption, greater than HIIT alone; however, Cr supplementation may improve submaximal exercise performance.
authors.affiliation: Department of Health and Exercise Science, University of Oklahoma, Huston Huffman Center, 1401 Asp Avenue, Norman, OK 73019, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Graef
authors.affiliation: Department of Health and Exercise Science, University of Oklahoma, Huston Huffman Center, 1401 Asp Avenue, Norman, OK 73019, USA.
authors.forename: Abbie E
authors.initials: AE
authors.lastname: Smith
authors.affiliation: Department of Health and Exercise Science, University of Oklahoma, Huston Huffman Center, 1401 Asp Avenue, Norman, OK 73019, USA.
authors.forename: Kristina L
authors.initials: KL
authors.lastname: Kendall
authors.affiliation: Department of Health and Exercise Science, University of Oklahoma, Huston Huffman Center, 1401 Asp Avenue, Norman, OK 73019, USA.
authors.forename: David H
authors.initials: DH
authors.lastname: Fukuda
authors.affiliation: Department of Health and Exercise Science, University of Oklahoma, Huston Huffman Center, 1401 Asp Avenue, Norman, OK 73019, USA.
authors.forename: Jordan R
authors.initials: JR
authors.lastname: Moon
authors.affiliation: Department of Health and Exercise Science, University of Oklahoma, Huston Huffman Center, 1401 Asp Avenue, Norman, OK 73019, USA.
authors.forename: Travis W
authors.initials: TW
authors.lastname: Beck
authors.affiliation: Department of Health and Exercise Science, University of Oklahoma, Huston Huffman Center, 1401 Asp Avenue, Norman, OK 73019, USA.
authors.forename: Joel T
authors.initials: JT
authors.lastname: Cramer
authors.affiliation: Department of Health and Exercise Science, University of Oklahoma, Huston Huffman Center, 1401 Asp Avenue, Norman, OK 73019, USA.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Stout