Does Biological Sex Influence Insulin Sensitivity and Muscle Metabolism Following High-intensity Interval Exercise?

Study Overview
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Brief Summary
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High-intensity interval exercise (HIIE) is a type of exercise that involves alternating periods of intense exercise with periods of rest. HIIE has been shown to improve many aspects of cardiovascular and metabolic health in a time-efficient manner (e.g., only 20 minutes per exercise session). An important health benefit of exercise is improved blood sugar control, which can help reduce the risk of metabolic diseases like type 2 diabetes. A single session of HIIE has been shown to improve blood sugar in males, but it is unknown if females achieve the same health benefit. It is also not fully understood how exercise improves blood sugar in males and females. Therefore, the purpose of this project is 1) to determine if a single session of HIIE improves blood sugar control in males and females, and 2) to evaluate if changes in skeletal muscle can explain the beneficial effects of HIIE on blood sugar.

Detailed Description
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The primary purpose of this study is to determine if biological sex influences the effects of high-intensity interval exercise (HIIE) on insulin sensitivity and muscle mechanisms. The investigators will measure insulin sensitivity and muscle outcomes of participants on two separate occasions: 1) Following 30 minutes of sitting in the lab; and 2) Following a single session of HIIE on a stationary bike. Insulin sensitivity will be measured by taking blood samples after participants consume a sugary drink. Muscle outcomes will be measured by taking a small amount of muscle from the vastus lateralis (thigh) muscle. Groups of male and female participants will be recruited and tested using best practice guidelines for sex-based comparisons of exercise responses. The study will advance knowledge regarding the potential for biological sex to influence the metabolic responses high-intensity exercise.

Official Title
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Does Biological Sex Influence Insulin Sensitivity and Muscle Metabolism Following High-intensity Interval Exercise?

Conditions
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Exercise

Intervention / Treatment
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* Other: Seated Rest (Non-exercise control)
* Other: High-intensity interval exercise


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: 18-35 yrs VO2peak considered recreationally active as defined as 'fair' or 'good' (males: 41.6- 50.5ml/kg/min; females: 35-41.9 ml/kg/min) based on Canadian Society for Exercise Physiology (CSEP) normative fitness values. BMI between 18-27 kg/m2 1-3 structured exercise sessions/week, and not training for any specific sport Weight stable (within ± 2kg for at least 6 months) Eumenorrheic (female only), defined as menstrual cycle lengths ≥ 21 days and ≤ 35 days resulting in 9 or more consecutive periods per year) Non-smoker Exclusion Criteria: Diagnosed with cardiovascular or metabolic disease, hyper- or hypogonadism, and/or polycystic ovarian syndrome (PCOS) The use of medication for managing blood glucose or lipid metabolism Current use of oral contraceptives or use within the last 3 months Irregular menstrual cycles (<21 days or >35 days) Pregnant, lactating, or menopausal Recreational smoking of any kind Inability to perform the study exercise protocols or follow the pre-trial dietary or physical activity controls Taking medications affecting substrate metabolism (corticosteroids or nSAIDs) Actively engaging in a low-carbohydrate diet (e.g., ketogenic, Atkins)

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 35 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: Basic Science
Allocation: Non-Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Females<br>Female participant group | Other: Seated Rest (Non-exercise control)<br>* Sitting for 30 minutes<br>Other: High-intensity interval exercise<br>* Performing a single session of high-intensity interval exercise on a cycle ergometer<br>|
| Experimental: Males<br>Male participant group | Other: Seated Rest (Non-exercise control)<br>* Sitting for 30 minutes<br>Other: High-intensity interval exercise<br>* Performing a single session of high-intensity interval exercise on a cycle ergometer<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Insulin area under the curve | Insulin area under the curve measured during glucose tolerance test | 3 hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Glucose area under the curve | Glucose area under the curve measured during glucose tolerance test | 3 hours | 
| Mean insulin concentration | Mean insulin concentration measured during glucose tolerance test | 3 hours | 
| Mean glucose concentration | Mean glucose concentration measured during glucose tolerance test | 3 hours | 
| Peak insulin concentration | Peak insulin concentration measured during the glucose tolerance test | 3 hours | 
| Peak glucose concentration | Peak insulin concentration measured during the glucose tolerance test | 3 hours | 
| Insulin:glucose ratio | Insulin to glucose ration measured during the glucose tolerance test | 3 hours | 
| Postprandial glucose oxidation | Postprandial glucose oxidation measured with a metabolic tracer | 3 hours | 
| Skeletal muscle glycogen content | Muscle glycogen use during exercise | immediately before and after exercise | 
| Skeletal muscle contractile signaling protein content | Measured via western blotting | immediately before and after exercise | 
| Skeletal muscle insulin signaling | Measured via western blotting | 1hr into glucose tolerance test | 
| Mitochondrial gene expression | Measured via Reverse transcription polymerase chain reaction | Change from pre-exercise to 3hr post-exercise | 
| Muscle protein synthesis rates | Muscle protein synthesis rates assessed by incorporation of oral stable isotope tracer following exercise | 3hr post-exercise | 
| Local muscle oxygenation | Muscle oxygenation (vastus lateralis) assessed with near-infrared spectroscopy (NIRS) | During exercise | 
| Local muscle oxygenation | Muscle oxygenation (vastus lateralis) assessed with NIRS during and following thigh cuff inflation | Pre-exercise, immediately post-exercise and 2 hrs post-exercise |