Small Steps for Big Changes
Condition: Physical Activity
Study type: Interventional

Summary: 
      Exercise is a proven strategy for preventing type 2 diabetes. Traditionally individuals have
      been prescribed moderate-intensity continuous aerobic exercise but adherence to this standard
      exercise program is dismal. High-intensity interval training (HIIT) is a novel form of
      exercise that involves brief, repeated bursts of vigorous exercise separated by periods of
      recovery. HIIT elicits many favourable cardiometabolic adaptations that are similar to
      traditional exercise but does so with a lower amount of exercise and in substantially less
      time than moderate-intensity continuous exercise. Therefore, HIIT has been touted as a
      "time-efficient" exercise strategy for improving health. Whether overweight individuals at
      risk for pre diabetes will show greater adherence to HIIT than moderate-intensity continuous
      exercise over the long-term (12-months) has not been tested. Because exercise adherence
      requires complex self-regulation, interventions designed to improve adherence should include
      a behavioural component. The investigators will assess adherence to HIIT and
      moderate-intensity continuous exercise over 12 months following a short-term (2 week)
      intervention of either HIIT or moderate-intensity continuous exercise. Both conditions will
      include a self-regulatory component targeted to increase participants' confidence to engage
      in regular, independent exercise. The results will help determine whether HIIT is a more
      feasible option for promoting exercise adherence for pre diabetes prevention than the
      traditional moderate-intensity continuous exercise. The investigators hypothesize that a)
      over the 12 months follow-up subjects randomized to the HIIT will be more likely to adhere
      when compared to moderate-intensity continuous exercise, b) over the 12 months follow-up
      subjects randomized to HIIT will have higher rates of adherence and levels of total physical
      activity, c) greater increases in self-regulation (including goal setting, self-monitoring,
      and self-regulatory efficacy) following HIIT will mediate higher rates of adherence, d)
      10-days of HIIT and moderate-intensity continuous exercise will improve cardiorespiratory
      fitness, increase insulin sensitivity, reduce circulating inflammatory markers, and improve
      glucose control and e) Improvements in cardiometabolic health factors will be greater
      following HIIT compared to moderate-intensity continuous exercise.
    

Detailed description: 
      Eligible participants will be randomized to the HIIT or moderate-intensity continuous
      exercise conditions. Each condition will involve a two-week supervised exercise period
      consisting of ten sessions. Exercise prescriptions for each condition will be progressive in
      nature over the two week supervised period and will be matched for external work.
      Specifically, individuals randomized to HIIT will begin with four intervals lasting 1-minute
      each at ~85-90% peak oxygen uptake [VO2peak] and increased to 10 X 1-min intervals by day 10.
      Individuals randomized to moderate-intensity exercise condition will begin with 20 minutes of
      continuous activity at ~55-60% V02peak and gradually increase the duration to 50 minutes by
      day 10. Participants will self-select exercise modality (walking outdoors, elliptical
      machine, treadmill walking, or stationary cycling). One trainer will supervise participants
      during the 2-week training program. Participants will complete 3 of the 10 training days (day
      4, 7 and 9) at home unsupervised. Participants will wear a heart rate monitor during each
      exercise session (supervised and unsupervised) to monitor exercise intensity and ensure
      compliance. In addition, participants will record their exercise bouts in a logbook on both
      lab and home training days.

      Participants in both conditions received 10 minutes of behavioural counseling each day they
      trained in the lab (for a total of 70 minutes). Following the supervised training,
      participants will be instructed to maintain HIIT or moderate-intensity continuous exercise
      three days per week independently. Specifically, individuals randomized to HIIT will be
      prescribed three exercise sessions per week involving 10 X 1-minute intervals at ~85-90%
      VO2peak, while participants randomized to moderate-intensity continuous exercise will be
      prescribed three session per week of 50-minute continuous exercise at ~55-60% VO2peak.
      Training logs will be provided and participants will be instructed to estimate exercise
      intensity based on physiological cues taught during supervised training days.
    

Intervention name(s): High-Intensity Interval Training
Intervention type(s): Behavioral
Intervention description(s): Specifically, individuals randomized to HIIT will begin the intervention with four intervals lasting 1-minute each at ~85-90% peak oxygen uptake [VO2peak] and increasing to 10 X 1-min intervals by day 10 of the intervention. Individuals randomized to moderate-intensity exercise condition will begin the intervention with 20 minutes of continuous activity at ~55-60% V02peak and gradually increase the duration to 50 minutes by day 10 of the intervention.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Prevention