None listed
Conditions
Brief 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.
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 vibrate
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.
Sponsors
Health Research Council
Study design
Allocation
Randomised controlled trial
Intervention model
Crossover
Primary purpose
Treatment
Masking
Blinded (masking used)
Eligibility
Sex/Gender
All
Age
16 Years to No maximum
Healthy volunteers
Yes
Inclusion criteria
Participants in the ACL reconstructed group should have had an ACL reconstruction in the last 4-24 months using a semitendinosus gracilis graft. Participants in the osteoarthritis group will have radiologically diagnosed osteoarthritis of the knee with a kellgren lawrence score of greater than or equal to 2.
Exclusion criteria
Control subjects who volunteer but have a history of injury or pathology in either knee joint may be excluded Participants from all groups may be excluded if they have a history of spinal surgery, low back pain in the last 6 months with associated neurological signs and symptoms or any systemic disease that prevents them from participating in maximum strength testing.
Outcome results
None listed