Small Steps for Big Changes

Study Overview
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Brief Summary
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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
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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.

Official Title
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Time-efficient High-intensity Interval Training Versus Moderate-intensity Continuous Aerobic Training for Promoting Exercise Adherence: A Randomized-controlled Trial

Conditions
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Physical Activity

Intervention / Treatment
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* Behavioral: High-Intensity Interval Training


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Aged 30-65 Physically inactive (engaging in 2 or less aerobic exercise bouts per week in the last 6 months) BMI between 24-40 kg/m2 Cleared to engage in vigorous exercise (via PARQ+ and, if advised by this validated tool further clearance by their family physician) Exclusion Criteria: Any contraindications to exercise (e.g., musculoskeletal injury) Failure to obtain medical clearance to engage in vigorous intensity exercise following a positive PARQ+ screening Prior history of cardio- or cerebrovascular disease or myocardial infarction Diagnosed with type 2 diabetes Currently taking glucose-lowering medications (e.g., metformin), Hypertension that is not controlled by medication (systolic blood pressure (BP) >160 mmHg and/or diastolic BP >99 mmHg) Change in cardiovascular medications (e.g., statins) in the previous 6 months Class III obesity (BMI >40 kg/m2).

Ages Eligible for Study
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Minimum Age: 30 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: High-Intensity Interval Training (HIIT)<br>Participants will perform a series of high-intensity intervals with an interval length of 60-seconds at 90% of peak aerobic capacity workload, and a rest length of 60-seconds. | Behavioral: High-Intensity Interval Training<br>* 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.<br>|
| Active Comparator: Moderate-Intensity Continuous Exercise<br>Participants will engage in exercise at 45% of peak aerobic capacity workload. | Behavioral: High-Intensity Interval Training<br>* 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.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change from baseline in cardiorespiratory fitness (VO2peak) at 6 and 12-month follow-up | Changes in cardiorespiratory fitness (VO2peak), an objective measure of fitness and habitual activity, will be used as an integrative measure of exercise adherence (and overall health) at 6-month and 12-month follow-up. Specifically, peak oxygen uptake (VO2peak) will be assessed by a maximal cycling exercise test. Power output will begin at 30 W and increase by 15 W/min until volitional exhaustion. Expired gas samples will be collected continuously and VO2 measured by a metabolic cart (Parvomedics TrueOne 2400). The mean of the two highest 30 s average values will define VO2peak. VO2peak will be confirmed using standard criteria110. A Polar chest strap, which is integrated to the metabolic cart and cycle ergometer (Lode Excalibur), will capture Heart Rate. Peak power output will be recorded as the highest value attained. | Baseline, 6-month follow-up and 12-month follow-up | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Self reported adherence to exercise prescription | Self-reported adherence will be measuring using an online exercise log book, which participants will be asked to fill in following each exercise session. Adherence will be measured using raw exercise prescription bouts completed. Proportion achieved based on the amount prescription will also be calculated. | Exercise log book filled in for a 12-month duration | 
| Changes from baseline in objectively measured moderate-to-vigorous physical activity in bouts ≥10 minutes (MVPA10+) at 3-, 6-, 9-, and 12-months follow-up | Changes in total time spent in moderate-to-vigorous physical activity in bouts ≥10 minutes (MVPA10+) will be assessed over 7 days using tri-axial accelerometers at baseline and 3, 6-, 9- and 12-month follow-up. | Baseline, 3-, 6-, 9-, 12-month follow-up | 
| Changes in efficacy beliefs | Changes in participants exercise efficacy beliefs, self-regulatory efficacy beliefs, concurrent self-regulatory efficacy beliefs, and self-monitoring efficacy beliefs will be measured at baseline, post-intervention, 6-month follow-up and 12-month follow-up. Efficacy measures will be context specific and will utilize a confidence scale ranging from 0%-100%. | Baseline, Post-Intervention, 6-, 12-month follow-up | 
| Changes in body composition | Body composition will be assessed using the Hologic Discovery A device. DXA is a standard tool in the measurement of body composition and bone density in adults and children throughout multiple institutions. | Baseline, post Intervention, 12-month follow-up |