High-Intensity Interval Exercise for Insulin Sensitivity

Overseen By Jenna Gillen, PhD

Age: 18 - 65

Sex: Any

Trial Phase: Academic

Sponsor: University of Toronto

Must not be taking: Blood glucose, Lipid metabolism, Corticosteroids, nSAIDs

Disqualifiers: Cardiovascular, Metabolic, PCOS, others

No Placebo Group All trial participants will receive the active study treatment (no placebo)

Compensation: Varies

Number of Visits: 3

What You Need to Know Before You Apply

What is the purpose of this trial?

This trial aims to determine if high-intensity interval exercise (HIIE), which combines short bursts of intense exercise with rest, helps control blood sugar in both males and females. Researchers seek to understand if this exercise type improves blood sugar levels in females similarly to males. They also aim to investigate whether changes in muscles can explain these benefits. Suitable participants exercise 1-3 times a week, maintain a stable weight, and have no diagnosed heart or metabolic diseases. As an unphased trial, this study offers participants the opportunity to contribute to groundbreaking research on exercise and blood sugar control.

Do I have to stop taking my current medications for the trial?

Yes, you must stop taking medications for managing blood glucose or lipid metabolism, oral contraceptives, and medications affecting substrate metabolism like corticosteroids or nSAIDs.

What prior data suggests that high-intensity interval exercise is safe?

Research has shown that high-intensity interval exercise (HIIE) is generally safe for most people. Studies have found that individuals can perform this exercise safely, even in short sessions, without needing long workouts to see benefits.

Regarding side effects, no major negative events have been reported for HIIE. This exercise has been proven to enhance the body's ability to use sugar and lower blood sugar levels. It also improves heart and lung health and can benefit the liver and fat tissue.

In summary, HIIE is well-tolerated with minimal risk, making it a safe option for improving overall health. ^{1 2 3 4 5}

Why are researchers excited about this trial?

Researchers are excited about high-intensity interval exercise (HIIT) for improving insulin sensitivity because it offers a dynamic and time-efficient alternative to traditional, longer-duration exercises. Unlike standard treatments for insulin resistance, such as medications like Metformin or lifestyle changes involving moderate-intensity continuous training, HIIT can achieve similar or even better results in a fraction of the time. This method involves short bursts of intense activity followed by rest, which may enhance metabolic health more effectively and could be more appealing to individuals who find it challenging to commit to longer exercise sessions.

What evidence suggests that high-intensity interval exercise is effective for improving blood sugar control?

Research has shown that high-intensity interval exercise (HIIE) can significantly help control blood sugar levels. Studies have found that HIIE improves the body's ability to use insulin, which helps lower blood sugar. These improvements can appear shortly after just one session and last for at least 24 hours. HIIE also benefits heart health, supporting overall body health. This trial will examine the effects of HIIE on both male and female participants to determine if women experience the same benefits as men. Overall, HIIE offers a promising way to manage blood sugar and reduce the risk of developing type 2 diabetes. ^{1 2 6 7 8}

Who Is on the Research Team?

Stephanie Estafanos, MSc

Principal Investigator

University of Toronto

Are You a Good Fit for This Trial?

This trial is for healthy, non-smoking men and women aged 18-35 with a BMI of 18-27 who are moderately active but not training for sports. Women must have regular menstrual cycles and can't be using oral contraceptives or be pregnant. Participants should not have metabolic diseases, be on blood glucose medications, or follow low-carb diets.

Inclusion Criteria

Your weight has stayed about the same (within 4.4 pounds) for the past 6 months.

You do exercise one to three times a week, and you are not training for a specific sport.

My menstrual cycles are regular, lasting 21 to 35 days.

Exclusion Criteria

I have been diagnosed with a heart, metabolic disease, hormone imbalance, or PCOS.

I am currently pregnant, breastfeeding, or going through menopause.

I am currently taking corticosteroids or NSAIDs.

Timeline for a Trial Participant

Screening

Participants are screened for eligibility to participate in the trial

2-4 weeks

Baseline Measurement

Participants' insulin sensitivity and muscle outcomes are measured following 30 minutes of sitting in the lab

1 day

1 visit (in-person)

Exercise Intervention

Participants undergo a single session of high-intensity interval exercise (HIIE) on a stationary bike

1 day

1 visit (in-person)

Post-exercise Measurement

Insulin sensitivity and muscle outcomes are measured after the exercise session

3 hours

1 visit (in-person)

Follow-up

Participants are monitored for safety and effectiveness after the exercise intervention

4 weeks

What Are the Treatments Tested in This Trial?

Interventions

• High-intensity interval exercise

Trial Overview The study aims to see if one session of high-intensity interval exercise (HIIE) improves blood sugar control in both males and females compared to just resting. It also investigates how HIIE affects muscle metabolism related to blood sugar improvements.

How Is the Trial Designed?

Group I: Males Experimental Treatment 2 Interventions

Male participant group

Group II: Females Experimental Treatment 2 Interventions

Female participant group

Who Is Running the Clinical Trial?

University of Toronto

Lead Sponsor

Trials

739

Recruited

1,125,000+

Published Research Related to This Trial

In a study of 42 overweight women, all three training methods (SIT, HIIT, and MICT) improved cardiorespiratory fitness (V̇O2peak) and reduced body mass by about 25% and 5%, respectively, over 12 weeks.

SIT and HIIT significantly enhanced insulin sensitivity, with improvements of approximately 26% and 39%, while MICT did not affect insulin sensitivity but did lower fasting glucose levels.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Twelve weeks of low volume sprint interval training improves cardio-metabolic health outcomes in overweight females. Sun, S., Zhang, H., Kong, Z., et al.[2019]

A single session of reduced-exertion high-intensity interval training (REHIT) led to significant physiological changes, including decreased muscle glycogen and increased activation of key metabolic pathways, suggesting it effectively stimulates muscle adaptation similar to traditional aerobic exercise.

REHIT resulted in more pronounced changes in oxygen consumption and metabolic markers compared to moderate aerobic exercise, indicating its potential as a time-efficient alternative for improving fitness and metabolic health.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Physiological and molecular responses to an acute bout of reduced-exertion high-intensity interval training (REHIT). Metcalfe, RS., Koumanov, F., Ruffino, JS., et al.[2022]

A systematic review of 11 studies involving 156 clinically stable patients with cardiometabolic diseases found that high-intensity interval exercise (HIIE) can lead to adverse responses in about 8% of individuals, indicating a higher risk compared to moderate-intensity exercise.

It is recommended that patients with cardiometabolic diseases who wish to engage in HIIE should be clinically stable, have prior experience with moderate-intensity exercise, and exercise under supervision to ensure safety.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

What Doesn't Kill You Makes You Fitter: A Systematic Review of High-Intensity Interval Exercise for Patients with Cardiovascular and Metabolic Diseases. Levinger, I., Shaw, CS., Stepto, NK., et al.[2022]

Sprint interval training (SIT) significantly improved insulin sensitivity and cardiovascular fitness in sedentary men, achieving similar results to traditional moderate-intensity continuous training (MICT) after 12 weeks, despite requiring only a fraction of the time (10 minutes vs. 50 minutes per session).

Both SIT and MICT led to a 19% increase in peak oxygen uptake and similar enhancements in skeletal muscle mitochondrial content, indicating that brief, intense exercise can be as effective as longer, moderate exercise for improving cardiometabolic health.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Twelve Weeks of Sprint Interval Training Improves Indices of Cardiometabolic Health Similar to Traditional Endurance Training despite a Five-Fold Lower Exercise Volume and Time Commitment. Gillen, JB., Martin, BJ., MacInnis, MJ., et al.[2022]

Sprint interval exercise (SIE) significantly improves insulin sensitivity more than continuous exercise (CELOW and CEHIGH) in young, healthy men, with the greatest effect observed 30 minutes post-exercise.

The improvement in insulin sensitivity after SIE may be due to increased post-exercise hyperinsulinemia and reduced lipolysis, indicating a unique mechanism of action compared to continuous exercise.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Higher insulin-sensitizing response after sprint interval compared to continuous exercise. Ortega, JF., Fernández-Elías, VE., Hamouti, N., et al.[2015]

A scoping review of 69 studies on high-intensity interval training (HIIT) in older adults found that HIIT protocols are generally well-tolerated and can provide significant health benefits, particularly in improving cardiorespiratory fitness.

Most research has focused on healthy older adults, highlighting a need for larger studies and more investigation into HIIT's effects on older adults with various health conditions.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

High-Intensity Interval Training in Older Adults: a Scoping Review. Marriott, CFS., Petrella, AFM., Marriott, ECS., et al.[2021]

High-intensity interval training (HIIT) is as effective, if not more so, than traditional moderate-intensity continuous training (MICT) for patients with cardiovascular disease, based on a systematic review of 23 studies involving 1117 participants.

The safety profile of HIIT in cardiac rehabilitation is promising, with only one major cardiovascular adverse event reported per 17,083 training sessions, indicating that HIIT can be safely implemented in this population.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

High-Intensity Interval Training for Patients With Cardiovascular Disease-Is It Safe? A Systematic Review. Wewege, MA., Ahn, D., Yu, J., et al.[2021]

High-intensity interval training (HIIT) and sprint interval training (SIT) can significantly improve glycemic control in individuals with metabolic syndrome (MetS) and type 2 diabetes (T2D), potentially more effectively than traditional aerobic exercise.

These interval training methods require less time commitment, addressing common barriers to regular exercise, making them a practical option for enhancing glucose metabolism in patients with MetS and T2D.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Impact of high-intensity interval training and sprint interval training on peripheral markers of glycemic control in metabolic syndrome and type 2 diabetes. Jiménez-Maldonado, A., García-Suárez, PC., Rentería, I., et al.[2022]

High-intensity interval exercise (HIIE) significantly improves glucose tolerance and insulin sensitivity in adolescent boys, showing a greater reduction in plasma glucose and insulin levels compared to a control group after exercise.

Both HIIE and moderate-intensity exercise (MIE) were equally enjoyable for participants, suggesting that HIIE can be a time-efficient and effective alternative to MIE for health benefits without sacrificing enjoyment.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

High intensity interval exercise is an effective alternative to moderate intensity exercise for improving glucose tolerance and insulin sensitivity in adolescent boys. Cockcroft, EJ., Williams, CA., Tomlinson, OW., et al.[2016]

A 6-week reduced-exertion high-intensity interval training (REHIT) program significantly improved insulin sensitivity by 28% in sedentary young men, demonstrating its potential for enhancing metabolic health.

Both male and female participants showed increased aerobic capacity, with improvements of 15% and 12% respectively, suggesting that REHIT is an effective and time-efficient alternative to traditional exercise for improving fitness and reducing diabetes risk.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Towards the minimal amount of exercise for improving metabolic health: beneficial effects of reduced-exertion high-intensity interval training. Metcalfe, RS., Babraj, JA., Fawkner, SG., et al.[2022]

A 12-week study involving 15 participants with type 2 diabetes showed that high intensity interval exercise (HI-IE) is as feasible as moderate intensity continuous exercise (MI-CE), with both groups maintaining high adherence rates of over 97%.

Both HI-IE and MI-CE effectively reduced total body fat and trunk fat, but neither intervention significantly changed glycated hemoglobin A1c (HbA1c) levels, indicating limited impact on blood sugar control in participants who were already well-managed.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Feasibility and preliminary efficacy of high intensity interval training in type 2 diabetes. Terada, T., Friesen, A., Chahal, BS., et al.[2022]

Citations

1. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC4334091/

Effectiveness and Safety of High-Intensity Interval Training ... Recent research has shown that high-intensity interval training (HIIT) can promote improvements in glucose control and cardiovascular health in individuals ...

2. sciencedirect.com sciencedirect.com/science/article/pii/S0925443920301654

Impact of high-intensity interval training and sprint ... HOMA-IR and HOMA-β% improved immediately after HIIT. Moreover, the beneficial effects of HIIT on HOMA-IR and β% effects were maintained 24 h following the ...

3. nature.com nature.com/articles/s41598-025-15432-8

High intensity interval training attenuate insulin resistance ... This study aimed to investigate the effect of 8 weeks of high intensity interval training (HIIT) on insulin resistance through liver ...

4. dom-pubs.onlinelibrary.wiley.com dom-pubs.onlinelibrary.wiley.com/doi/full/10.1111/dom.16220

Efficacy of high‐intensity interval training in individuals with ... The data indicated that HIIT significantly improves glycosylated haemoglobin and cardiorespiratory fitness compared with CON (weighted mean ...

5. dmsjournal.biomedcentral.com dmsjournal.biomedcentral.com/articles/10.1186/s13098-025-01909-z

Comparative effectiveness of high-intensity interval training ... The present findings indicate that HIIT significantly reduces FI and HOMA-IR compared to MICT, underscoring its superior efficacy in improving ...

6. frontiersin.org frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2025.1481200/full

Effects of practical models of low-volume high-intensity ... A positive value suggests a larger improvement in insulin sensitivity as a result of low-volume high-intensity interval training compared with ...

7. nature.com nature.com/articles/s41598-025-96703-2

The combined effects of high-intensity interval training and ... HIIT also improved insulin sensitivity and reduced hyperglycemia. HIIT significantly reduced hepatic glucose production, reduced fatty liver, ...

8. sciencedirect.com sciencedirect.com/science/article/pii/S2212877815001763

High intensity interval training improves liver and adipose ... These data indicate that HIIT lowers blood glucose levels by improving adipose and liver insulin sensitivity independently of changes in adiposity.