The Irisin and Metabolic Exercise Training Study
Condition: Obesity
MeSH terms: Obesity
Study type: Interventional

Summary: 
      It has been established that greater amounts of vigorous intensity physical activity lead to
      improved health outcomes. Interestingly, the response of biologically active substances,
      called myokines, differs according to exercise intensity. As such, the current study aims to
      compare the difference in the response to irisin according to different exercise intensities
      in both normal weight subjects and individuals living with obesity. This study will compare
      continuous moderate intensity physical activity to high intensity physical activity against a
      control condition. Furthermore, this study will determine whether differences in exercise
      intensity are associated with better insulin sensitivity.
    

Detailed description: 
      Although exercise is recognized as a cornerstone in the management of obesity and diabetes,
      previous research has shown substantial inter-individual variability following an exercise
      intervention. As of now, the mechanisms underlying the cardio-metabolic response to exercise
      have not been fully elucidated. When accounting for genetic factors, only 20-30% of the
      response is explained, which indicates that other factors must contribute to this
      exercise-related cardio-metabolic response. Exercise stimulates the release of myokines,
      which have been shown to play a critical role in health. However, the contribution of these
      myokines to the cardio-metabolic response is unknown. Furthermore, the regulation of myokines
      according to different exercise stimuli (i.e., exercise intensity) is unclear. It is
      suggested that altering specific exercise parameters can reduce the variability in the
      response and increase the proportion of participants who obtain the expected physiological
      adaptations.

      The purpose of this project is to: 1) determine whether high intensity interval training
      (HIIT) generates a greater secretion of irisin compared to moderate (MOD) aerobic exercise in
      individuals living with obesity and in those with a normal weight; 2) investigate whether the
      increase in irisin during exercise is associated with insulin sensitivity in individuals
      living with obesity and in those with normal weight; and 3) determine whether differences
      exist between groups.

      Methods: The investigators will use a randomized controlled crossover design to perform this
      study in which 40 participants (aged 19-50) will be recruited into two groups (n = 20 obese,
      n = 20 normal weight). Each group will be randomized into three conditions: 1) an acute bout
      of MOD aerobic exercise: 35 minutes of cycling at 50% of heart rate reserve (HRR), 2) an
      acute bout of HIIT aerobic exercise: cycling at 50% of HRR for 5 minutes followed by 2
      minutes of cycling at 85-90% of HRR consecutively for a total of 35 minutes, and 3) a control
      condition: blood draws matched for exercise time will be taken while the participant remains
      seated. The primary outcome measure will be insulin sensitivity using the Matsuda Index. The
      primary exposure variable will be the acute secretion of irisin during exercise.

      Study hypothesis: It is hypothesized that: 1) an acute bout of HIIT aerobic exercise will
      generate a greater plasma irisin secretion compared an acute bout of continuous MOD aerobic
      exercise; 2) increased irisin will be positively associated with greater insulin sensitivity;
      and 3) differences will be observed between individuals living with obesity and those with a
      normal weight.
    

Intervention name(s): High Intensity Interval Aerobic Exercise (HIIT); Continuous Moderate Aerobic Exercise (MOD); Control Sitting Condition (C)
Intervention type(s): Behavioral; Behavioral; Behavioral
Intervention description(s): Cycling at 50-55% heart rate reserve for 5 minutes followed by 2 minutes of cycling at 85-90% heart rate reserve consecutively for a total of 35 minutes.
Blood draws will occur at 6 different time points during exercise (0min, 7min, 14min, 21min, 28min, 35min).; 35 minutes of cycling at 50-55% heart rate reserve. Blood draws will occur at 6 different time points during exercise (0min, 7min, 14min, 21min, 28min, 35min).; Blood draws matched for exercise time will be taken while participant remains seated for 35 minutes (0min, 7min, 14min, 21min, 28min, 35min).
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Prevention
Keywords: Exercise; Physical Activity; Cardio-metabolic Health; Myokines; Cardiorespiratory Fitness; Obesity; Type 2 Diabetes