The Regulation of Human Skeletal Muscle Mass by Contractile Perturbation
Condition: Muscle Atrophy; Disuse Atrophy (Muscle) of Lower Leg
MeSH terms: Muscular Disorders, Atrophic; Muscular Atrophy; Atrophy
Study type: Interventional

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.
    

Intervention name(s): Unilateral Resistance Exercise; Immobilization
Intervention type(s): Other; Procedure
Intervention description(s): Unilateral Resistance exercise will include training three days per week and each session will include 3 sets of leg extension and 3 sets of leg press. In each set, the participant will complete a maximum of 12 repetitions.; During the last two weeks of the study (week 8-10), a Don Joy adjustable knee brace will be applied to the participant's leg randomized to immobilization. The brace will be applied at a 40 degree angle relative to complete extension.
Other intervention name(s): Resistance training; Knee Bracing
Allocation: Randomized
Intervention model: Single Group Assignment
Intervention model description: The model will be a within-subject intervention. Each subject will have one leg randomized to unilateral resistance exercise (for 10 weeks) and the other to immobilization (for the last 2 weeks of the study).
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: Muscle Hypertrophy; Muscle Atrophy; Resistance Training; Immobilization