This study investigates how simulated knee injury-via artificial joint effusion or deafferentation-affects quadriceps motor unit behavior in healthy young adults. Participants will complete neuromuscular testing during a single 2-hour lab session. This research seeks to improve understanding of muscle inhibition and inform interventions after real-world knee trauma.
Using a controlled laboratory model, the investigators will simulate knee injury through two methods: (1) intra-articular saline injection to induce effusion, and (2) intra-articular lidocaine injection to induce sensory deafferentation. Healthy participants aged 18-30 will undergo surface and decomposition EMG, isometric strength testing, and reflex measurements before and after the intervention. The primary outcome is motor unit recruitment characteristics, with secondary outcomes including quadriceps inhibition (Hoffmann reflex) and isometric peak torque. The findings will inform future neuromodulatory approaches in rehabilitation.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
SINGLE
Enrollment
45
Injection of sterile saline into the knee joint to simulate joint swelling and induce quadriceps inhibition.
Injection of 7 mL lidocaine into the knee joint to simulate deafferentation by temporarily blocking sensory input.
Simulated knee injection using a stage needle without skin penetration, used to blind participants and serve as control.
Motor Unit Recruitment (amplitude relative to recruitment threshold)
Measured via surface EMG decomposition
Time frame: Baseline, 0, 30, and 60 minutes post-intervention
Motor Unit Recruitment (firing rate relative to recruitment threshold)
Measured via surface EMG decomposition
Time frame: Baseline, 0, 30, and 60 minutes post-intervention
Quadriceps Inhibition (Hoffmann Reflex)
Measured with femoral nerve stimulation
Time frame: Baseline, 0 and 60 minutes post-intervention
Isometric Peak Torque (Quadriceps Strength)
Measured with isokinetic dynamometer (Biodex)
Time frame: Baseline and 60 minutes post-intervention
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