Interval Training Plus Creatine Effects on Performance and Glucose Tolerance
Condition: Healthy
Study type: Interventional

Summary: 
      Recent evidence suggests that high -intensity interval training (HIIT) may be an effective
      strategy to improve cardiorespiratory fitness, exercise performance, and insulin sensitivity.
      In addition, creatine (Cr), a nitrogen- containing compound, is widely used to enhance high
      intensity exercise performance. A seminal study demonstrated that the muscle content of Cr
      and phosphocreatine (PCr) can be elevated by exogenous Cr. Oral intake of Cr increases the
      concentration in blood and muscle, and part of the increased muscle Cr is transformed to PCr
      (a process catalyzed by Cr kinase). Cr supplementation increases total Cr (TCr = Cr + PCr) by
      ~20%, with the PCr component accounting for 10% of the increase.

      Combining HIIT and Cr is intriguing for two reasons; first, Cr supplementation improves
      performance through increasing PCr, PCr recovery, and muscle buffering which may facilitate
      higher training intensities and therefore greater training adaptations. Secondly, both Cr and
      HIIT have individually been shown to increase GLUT 4 and insulin sensitivity, suggesting that
      Cr supplementation may be an adjunct to HIIT for improving glucose control. To date, there
      have only been two studies investigating the performance effects of Cr combined with HIIT
      with preliminary positive results. No studies have examined the impact of combined Cr + HIIT
      on outcomes related to insulin sensitivity. Therefore, the purpose of this research is to
      examine the combined effects of Cr and HIIT on performance and insulin sensitivity as
      determined via an oral glucose tolerance test (OGTT) in young healthy adults.
    

Detailed description: 
      PURPOSE: To determine whether combining creatine with high intensity interval training (HIIT)
      results in better exercise performance and insulin sensitivity when compared to HIIT combined
      with placebo in healthy subjects.

      HYPOTHESES: a) Creatine + HIIT will result in improved exercise performance compared to
      placebo; b) Creatine + HIIT will result in improved insulin sensitivity compared to placebo.

      OBJECTIVES: To determine whether combining creatine with high intensity interval training
      (HIIT) results in better exercise performance and insulin sensitivity when compared to HIIT
      combined with placebo in healthy subjects.

      RESEARCH METHOD: A double blind placebo randomized controlled trial (RCT) in which 24 healthy
      young volunteers will participate in HIIT three times a week, for four weeks. Participants
      will be will be stratified for sex and randomized to one of two interventions; 1) HIIT plus
      Cr, or 2) HIIT plus placebo.

      STATISTICAL ANALYSES: A 2 (group) x 2 (time) way repeated measures ANOVA will be used to
      analyze all variables. Descriptive statistics (means, standard deviations [SD], and
      frequencies) will be calculated. Histograms will be used to identify any outliers and to test
      for normality. Data with skewed distributions will be log-transformed prior to statistical
      testing. Within group differences will be examined by paired t-test.

      24 participants will be included in this RCT. Sample size calculations were computed using
      means and standard deviations from a previous Cr + HIIT study [11] which showed an
      significant increase in cycling critical power with Cr + HIIT (6.72 +/- 2.54 % increase)
      compared to Placebo + HIIT (3.82 +/- 2.30 %). With 80% power at an alpha of 0.05 indicated
      that 11 participants per group are needed. To preserve power and account for potential
      drop-out we will recruit 12 per group.
    

Intervention name(s): Creatine; Placebo; High intensity interval training
Intervention type(s): Dietary Supplement; Dietary Supplement; Other
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Basic Science
Keywords: Creatine; interval training; effects on performance