Quadriceps Motor Unit Adaptation to Simulated Knee Injury
University of Central Florida
Summary
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.
Description
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 neu…
Eligibility
- Age range
- 18–30 years
- Sex
- All
- Healthy volunteers
- Yes
Inclusion Criteria: 1. Age 18-30 years 2. Physically active (Tegner ≥ 5) 3. No prior lower-limb surgery or major injury Exclusion Criteria: 1. Lower limb surgery or significant injury in past 2 years 2. Cardiopulmonary, neurological, or psychiatric disorders 3. Needle/electrical stimulation anxiety 4. Medications affecting neuromuscular or psychological function 5. Pregnancy 6. Allergic to lidocaine 7. Inability to elicit Hoffmann reflex
Interventions
- DeviceJoint Effusion via 60 mL Sterile Saline
Injection of sterile saline into the knee joint to simulate joint swelling and induce quadriceps inhibition.
- DrugIntra-articular Lidocaine
Injection of 7 mL lidocaine into the knee joint to simulate deafferentation by temporarily blocking sensory input.
- OtherSham injection
Simulated knee injection using a stage needle without skin penetration, used to blind participants and serve as control.
Location
- University of Central FloridaOrlando, Florida