Short Term Immobilization of the Lower Limb

University of Central Florida50 enrolled

Overview

The purpose of this study is to determine the effects of one week of knee-joint immobilization on muscle size, strength, neuromuscular function, and brain function. In addition, the effects of two different interventions (i.e., neuromuscular electrical stimulation and action observation/mental imagery) throughout immobilization will be determined. Following the immobilization period, participants that have lost strength will be rehabilitated with twice weekly resistance training sessions, and sex-based differences in rehabilitation timelines will be examined.

This study will utilize a repeated measures design in healthy adults aged 18-40 years. After a thorough familiarization visit, muscular size, strength, neuromuscular responses, and corticospinal excitability/inhibition will be measured before (PRE) and after (POST) one week of unilateral knee joint immobilization of the left leg. Four groups will be examined: 1) immobilization only, 2) immobilization + daily neuromuscular electrical stimulation, 3) immobilization + daily action observation/mental imagery training, 4) a control group. Throughout the immobilization period, participants will be in a leg brace locked at 90 degrees knee flexion. They will perform daily range of motion exercises and wear a compression sock at all times to mitigate the risk of blood clots. Following completion of the immobilization period, participants that have lost strength will complete a supervised rehabilitation program of twice weekly lower body resistance training sessions until they have returned to baseline levels of strength. Group assignment will be randomized and blocked on sex to ensure an equal number of participants within each group consisting of a relatively equal number of males and females.

Study Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

PREVENTION

Masking

NONE

Enrollment

Interventions

Neuromuscular Electrical StimulationOTHER

Participants in this group will perform twice daily neuromuscular electrical stimulation training sessions of the quadriceps muscles (specifically, the vastus lateralis and rectus femoris) or the immobilized left leg.

Action Observation + Mental ImageryOTHER

Participants in this group will perform daily action observation + mental imagery training via video and audio recordings.

Eligibility

Sex: ALLMin age: 18 YearsMax age: 40 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria: * Healthy men and women between the ages of 18-40 years * Body mass index \>20 kg/m2 or \< 35 kg/m2 Exclusion Criteria: * Body mass index \<20 kg/m2 or \> 35 c * Experience of major joint pain/discomfort of the upper or lower limbs, back, or neck within the previous six months. * History of major musculoskeletal injury or surgery * Neuromuscular disease (e.g., Parkinson's, MS, ALS) * Metabolic disease (e.g., diabetes, thyroid disorder, metabolic syndrome) * Personal or family history of blood clots * Trouble using or controlling one's muscles * History of cancer * History of stroke * History of heart attack * History of arthritis * Use of an assistive walking device or mobility aids within the past six months * Use of anabolic steroids within the past six months * History of convulsions, seizures, or syncope * History of concussion as diagnosed by a physician * Certain medications (e.g., muscle relaxants, benzodiazepines) * Very thick hair or certain hairstyles that would impede the TMS coil from making direct contact with the scalp * Allergy to rubbing alcohol * Lack of transportation to and from the laboratory * Implant of any kind * Pregnancy * Allergy to silver * Diagnosis of any psychiatric condition

Outcomes

Primary Outcomes

Muscular strength

Changes in muscular strength will be measured via maximal voluntary contraction torque

Time frame: 15 minutes

Muscular size

Changes in muscular size will be measured via ultrasonography of the quadriceps

Time frame: 10 minutes

Corticospinal responses

Corticospinal responses will be measured with transcranial magnetic stimulation targeting the lower limbs

Time frame: 30 minutes

Motor unit behavior

Motor unit recruitment threshold and firing rate will be measured with surface electromyography signals detected from the quadriceps

Time frame: 10 minutes

Voluntary activation

Voluntary activation will be measured using the interpolated twitch technique

Time frame: 15 minutes

Rate of recovery

The time taken to recover strength lost will be measured via number of resistance training sessions needed after immobilization

Time frame: 1.5 hours per session

Secondary Outcomes

Compliance

Compliance will be measured via the use of accelerometers around both ankles. Compliance will be calculated as the number of participants that following the crutch/brace protocol as described.

Time frame: one week

Physical activity (Step count)

Physical activity will be assessed via step counts and compared to changes in primary outcome measures via accelerometers around both ankles