The Regulation of Human Skeletal Muscle Mass by Contractile Perturbation

Not Applicable

Completed

• Conditions: Disuse Atrophy (Muscle) of Lower Leg; Muscle Atrophy
• Interventions: Other: Unilateral Resistance Exercise; Procedure: Immobilization

• Registration Number: NCT03046095
• Lead Sponsor: McMaster University

Brief Summary

It is well known that periods of weight training lead to increases in skeletal muscle size and strength. In contrast, periods of inactivity such as bed rest or immobilization result in losses of skeletal muscle size and strength. However, individuals experience variable magnitudes of muscle size change in response to changes in mechanical tension, such that certain individuals experience large changes in muscle mass whereas others do not. What is not currently known, and will be the primary goal of the present investigation, is to determine whether individuals who gain the most muscle mass with exercise training also lose the most muscle when they are immobilized. The investigators hypothesize that individuals who gain the most muscle with training will also lose the most with immobilization.

Detailed Description

Resistance exercise, paired with protein ingestion, leads to the accretion of muscle proteins that over time results in the augmentation of muscle size and muscle strength. By virtue of its ability to stimulate increases in muscle size and strength, resistance exercise is an effective method that can be used by healthcare practitioners to promote the recovery of lost muscle mass resulting from a period of immobilization (resulting from broken bones, elective surgery, etc.). However, while exercise in general is an effective therapeutic strategy to combat muscle loss and frailty, the extent to which individuals respond to resistance exercise is highly variable. Some individuals exhibit large changes in muscle size (high responders) whereas other exhibit little to no change (low responders). Thus, where as one resistance exercise program might be an appropriate treatment for one individual following disuse, another individual might require a greater stimulus and/or pharmaceutical assistance in order to fully recover. What is currently unknown is whether individuals who experience the most profound increases in skeletal muscle mass following resistance exercise also lose the most muscle upon limb immobilization. Answering this gap in our knowledge will be the primary goal of this study. The procurement of this knowledge will hopefully permit the development of individualized exercise programs that can be used to influence the recovery of skeletal muscle that is lost with inactivity and immobilization.

Basic Information
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Recruitment & Eligibility
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Study & Design
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Trial Locations

Study Timeline

• Study First Submitted: 2017-02-02
• Study First Submitted QC: 2017-02-04
• Study First Posted: 2017-02-08
• Study Start: 2017-05-01
• Primary Completion: 2018-05-01
• Study Completion: 2018-09-01
• Status Verified: 2019-06
• Last Update Submitted: 2019-06-17
• Last Update Posted: 2019-06-18

Recruitment & Eligibility

• Status: COMPLETED
• Sex: Male
• Target Recruitment: 14

Inclusion Criteria

• Healthy
• Non-Smoker
• Do not heavily consume alcohol

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Exclusion Criteria

• Female
• Younger than 18, or older than 30 years
• use of anti-inflammatory or analgesic medication
• history of neuromuscular disorders
• family history of deep vein thrombosis
• regularly take part in structured physical exercise (greater than 2 days per week)
• take any medications known to influence protein metabolism

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Study & Design

• Study Type: INTERVENTIONAL
• Study Design: SINGLE_GROUP

Arm && Interventions

Group	Intervention	Description
Unilateral Resistance Exercise	Unilateral Resistance Exercise	One of the participant's legs will be randomized to a unilateral resistance training arm for 10 weeks in duration. The leg chosen to be trained will undergo resistance exercise three days per week (Monday, Wednesday, and Friday) for the entirety of the study.
Immobilization	Immobilization	One of the participant's legs will be chosen to be immobilized during the last two weeks of the study. Therefore, one leg will be resistance exercising from week 0-10 whereas the other leg will be immobilized during weeks 8-10.

Primary Outcome Measures

Name	Time	Method
Muscle Cross Sectional Area	May 2017 - Dec 2017	The changes in muscle cross sectional area will be assessed pre-training (week 0) and post training/immobilization (week 10) using magnetic resonance imaging (MRI). Muscle cross-sectional area will be assessed over a continuous period of 7 months.
Leg Lean Mass	May 2017 - Dec 2017	The changes in leg lean mass will be assessed pre-training (week 0) and post-training/immobilization using dual energy x-ray absorptiometry. Leg lean mass measurements will be made over a continuous period of 7 months.

Secondary Outcome Measures

Name	Time	Method
Skeletal Muscle Gene Expression	May 2017 - Dec 2017	Gene expression will be quantified pre-training (week 0) and post-training/immobilization from muscle tissue samples obtained via muscle biopsies in both legs. Gene expression assessment will take place over a continuous period of 7 months.

Trial Locations

Locations (1)

Exercise Metabolism Research Laboratory, McMaster Univeristy; 🇨🇦 Hamilton, Ontario, Canada