Quadriceps Motor Unit Adaptation to Simulated Knee Injury

Not Applicable

Not yet recruiting

• Conditions: Muscle Inhibition; Knee Injury Simulation
• Interventions: Device: Joint Effusion via 60 mL Sterile Saline; Drug: Intra-articular Lidocaine; Other: Sham injection

• Registration Number: NCT06999057
• Lead Sponsor: University of Central Florida

Brief 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.

Detailed 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 neuromodulatory approaches in rehabilitation.

Study Timeline

• Status Verified: 2025-05
• Study First Submitted: 2025-05-20
• Study First Submitted QC: 2025-05-30
• Last Update Submitted: 2025-05-30
• Study First Posted: 2025-05-31
• Last Update Posted: 2025-05-31
• Study Start: 2025-08-01
• Primary Completion: 2026-06-01
• Study Completion: 2026-06-01

Recruitment & Eligibility

• Status: NOT_YET_RECRUITING
• Sex: All
• Target Recruitment: 45

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

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
Effusion Group	Joint Effusion via 60 mL Sterile Saline	60 mL sterile saline injected into knee
Deafferentation Group	Intra-articular Lidocaine	Lidocaine (single intra-articular dose)
Control Group	Sham injection	Sham procedure with fake needle

Primary Outcome Measures

Name	Time	Method
Motor Unit Recruitment (amplitude relative to recruitment threshold)	Baseline, 0, 30, and 60 minutes post-intervention	Measured via surface EMG decomposition
Motor Unit Recruitment (firing rate relative to recruitment threshold)	Baseline, 0, 30, and 60 minutes post-intervention	Measured via surface EMG decomposition

Secondary Outcome Measures

Name	Time	Method
Quadriceps Inhibition (Hoffmann Reflex)	Baseline, 0 and 60 minutes post-intervention	Measured with femoral nerve stimulation
Isometric Peak Torque (Quadriceps Strength)	Baseline and 60 minutes post-intervention	Measured with isokinetic dynamometer (Biodex)