Influence of Sedentary Time on Skeletal Muscle Protein Metabolism

Study Overview
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Brief Summary
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This study will investigate the influence of increased sedentary time on long-term measures of muscle protein synthesis and metabolic health. The investigators will test the hypothesis that increased time spent in sedentary behaviours will lead to a reduction in long-term measures of muscle protein synthesis and compromised metabolic health.

Detailed Description
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Sarcopenia, the loss of muscle mass with age, is thought to be accelerated by an inactive, sedentary lifestyle. Increased sedentary time has consistently been associated with lower muscle mass and compromised metabolic health. However, there is currently a lack of direct evidence to support these associations. Therefore, this study will investigate whether increased sedentary time (reduced step count and exercise cessation) directly influences long-term measures of muscle protein synthesis and metabolic health in young, active adults. Following a 7 day period of normal habitual physical activity, participants will undertake a 7 day period of step reduction and exercise cessation. It is hypothesised that 7 days of increased sedentary time will result in a reduction in long-term rates of muscle protein synthesis and a worsening of metabolic health.

Official Title
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Influence of Increased Sedentary Time on Long-term Rates of Skeletal Muscle Protein Synthesis in Young Adults

Conditions
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Sedentary Lifestyle

Intervention / Treatment
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* Behavioral: 7 days of habitual physical activity followed by 7 days of reduced physical activity


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Body mass index (18.5-29.99 kg/m2) Active - defined as: ≥ 7000 steps per day (assessed during screening) and taking part in regular exercise (defined as participation in ≥ 3 sessions of aerobic and/or resistance exercise type sessions a week for ≥ 6 months prior to recruitment) Good general health Exclusion Criteria: Lidocaine allergy Hypertension (≥140/90 mmHg) Current participation in another clinical study Previous participation in this study Bleeding disorder/s Current or recent smoker Past history of substance abuse and/or taking prescription or non-prescription medication (e.g., beta-blockers, insulin or thyroxine) or supplements that may influence normal metabolic responses. Participants who have previously (within 5 years of the present study) had 4 or more muscle biopsies obtained from the thigh quadriceps region will be ineligible.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 35 Years

Sexes Eligible for Study
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Male

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
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Physical inactivity<br>Study arm consisting of 7 days of habitual physical activity followed by 7 days of step reduction and exercise cessation. | Behavioral: 7 days of habitual physical activity followed by 7 days of reduced physical activity<br>* Young, active participants will undergo a 7 day period of habitual physical activity followed by a 7 day period of step reduction and exercise cessation.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Muscle protein synthesis (FSR %/day) | Long-term muscle protein synthesis (FSR %/day) will be determined using deuterium oxide (D2O) to compare muscle protein synthesis rates over the first 7 day period and the second 7 day period. | 0-14 days | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Rate of fat oxidation at rest (g/min) | Whole body oxygen consumption (VO2, L/min) and carbon dioxide production (VCO2, L/min) at rest will be measured using indirect calorimetry to calculate the rate of fat oxidation at rest (g/min). | For 20 minutes at day 7 and day 14 | 
| Rate of fat oxidation during an oral glucose tolerance test (g/min) | Whole body oxygen consumption (VO2, L/min) and carbon dioxide production (VCO2, L/min) following an oral glucose drink will be measured using indirect calorimetry to calculate the rate of fat oxidation during an oral glucose tolerance test (g/min). | At 0, 30, 60, 90 and 120min of the oral glucose tolerance test at day 7 and day 14 | 
| Rate of carbohydrate oxidation at rest (g/min) | Whole body oxygen consumption (VO2, L/min) and carbon dioxide production (VCO2, L/min) at rest will be measured using indirect calorimetry to calculate the rate of carbohydrate oxidation at rest (g/min). | For 20 minutes at day 7 and day 14 | 
| Rate of carbohydrate oxidation during an oral glucose tolerance test (g/min) | Whole body oxygen consumption (VO2, L/min) and carbon dioxide production (VCO2, L/min) following an oral glucose drink will be measured using indirect calorimetry to calculate the rate of carbohydrate oxidation during an oral glucose tolerance test (g/min). | At 0, 30, 60, 90 and 120min of the oral glucose tolerance test at day 7 and day 14 | 
| Blood glucose concentration | Blood glucose concentration will be assessed in blood samples taken during the oral glucose tolerance test. | At 0, 30, 60, 90 and 120min of the oral glucose tolerance test at day 7 and day 14 | 
| Blood insulin concentration | Blood insulin concentration will be assessed in blood samples taken during the oral glucose tolerance test. | At 0, 30, 60, 90 and 120min of the oral glucose tolerance test at day 7 and day 14 | 
| Blood fatty acid concentration | Blood fatty acid concentration will be assessed in blood samples taken during the oral glucose tolerance test. | At 0, 30, 60, 90 and 120min of the oral glucose tolerance test at day 7 and day 14 |