RecruitingACTRN12609000181202

The effects of tendon vibration on quadriceps muscle activation in anterior cruciate ligament reconstructed and arthritic populations.

Sponsor

Health Research Council

Enrollment

60 participants

Start Date

Dec 5, 2008

Study Type

Interventional

Conditions

Anterior cruciate ligament (ACL) reconstruction

Summary

Joint disease often leads to an ongoing, reflex weakness of muscles acting across the damaged joint. This process is thought to occur at a spinal cord level and is called Arthrogenic Muscle Inhibition (AMI). Several neural pathways may contribute to AMI, one of which is the gamma loop. To investigate the functional significance of the gamma loop, a number of authors have used prolonged muscle or tendon vibration to experimentally attenuate the excitability of muscle spindle nerve fibres. Vibration artificially enhances muscle spindle activity for short periods but when vibration is sustained for longer than 10-20 seconds spindle firing is progressively diminished, reducing the transmission of Ia afferent input to the spinal cord. With a 20 minute period of vibration, transmission of Ia afferent input is blocked for 10-20 minutes after vibration ceases. In healthy subjects, prolonged tendon vibration has been shown to cause a reduction in muscle activity, motor unit firing rates and contraction force during maximum strength contractions. However, in patients who have ruptured their ACL, prolonged vibration has no effect on quadriceps force output or muscle activity, suggesting a pre-existing deficit in the transmission of muscle spindle input to quadriceps alpha motoneurons in the spinal cord. This deficit has been termed gamma loop dysfunction and has been shown to persist after ACL reconstruction, contributing to quadriceps AMI that is often observed in these patients. However, it remains unknown whether gamma-loop dysfunction contributes to quadriceps AMI in patients with knee osteoarthritis. This study will explore the effects of prolonged (20 minutes) vibration (Part A) and short-duration (5 second) vibration on quadriceps and hamstrings muscle activation. It is hypothesised that immediately after prolonged tendon vibration quadriceps torque and electromyography will be significantly reduced in the healthy control subjects but not in the ACL reconstructed and osteoarthritis groups, indicating gamma-loop dysfunction. It is further hypothesised that short duration tendon vibration will significantly enhance quadriceps torque and electromyography in the ACL reconstructed and osteoarthritis groups but not in healthy control subjects.

Eligibility

Sex: Both males and femalesMin Age: 16 Yearss

Plain Language Summary

Simplified for easier understanding

This study is investigating a nerve-related muscle weakness problem that occurs after knee injury or arthritis, where the muscles around the knee (especially the quadriceps at the front of the thigh) become automatically weakened. Researchers are using a technique called tendon vibration — where a vibrating device is applied to the tendon — to test and potentially stimulate these muscles. The study will compare people who have had ACL knee reconstructions, people with knee osteoarthritis, and healthy volunteers, to learn more about the underlying nerve pathways involved. You may be eligible if: - You are 16 years or older - You are either: a healthy volunteer with no known knee problems, OR someone who has had an ACL reconstruction in the past 4 to 24 months using a specific type of graft, OR someone with knee osteoarthritis confirmed by X-ray (Kellgren-Lawrence score 2 or higher) You may NOT be eligible if: - You have a history of spinal surgery - You have had low back pain with nerve symptoms in the past 6 months - You have a systemic condition that prevents maximum strength testing - (For healthy controls) You have had any prior knee injury or pathology Talk to your doctor about whether this trial might be right for you.

This is a simplified summary. Always discuss eligibility with your doctor before enrolling in a clinical trial.

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Interventions

Part A. 15 ACL reconstructed and 15 age and gender matched controls and 15 subjects with knee osteoarthritis and 15 age and gender matched controls will have their infrapatellar tendon vibrated (50Hz) for 20 minutes while seated in a chair. Three maximum voluntary contractions of the quadriceps and three maximum voluntary contractions of the hamstrings will be performed before and then again after vibration. Part B. 3-7 days later, the same subjects will have their infrapatellar tendon vibrated at 4 different frequencies (0Hz, 5Hz, 80Hz, 200Hz) during maximum voluntary contractions of their quadriceps. Three maximum voluntary contractions will be performed at each frequency, in a random order. A 2 minute rest period will be given between each contraction.

Locations(1)

Auckland, New Zealand

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ACTRN12609000181202