Low levels of anterior tibial loading enhance knee extensor reflex response characteristics

Document Type

Article

Publication Title

Journal of Electromyography and Kinesiology

Abstract

We examined whether neuromuscular reflexes were altered with anterior loads applied to the tibio-femoral joint. A ligament testing device was modified by attaching a reflex hammer to a steel mounted frame to illicit a patellar tendon tap, while anterior directed loads displaced the tibia on the femur. Five trials were acquired while anterior-directed loads (20, 50, 100 N; counterbalanced) were applied to the posterior tibia between 20 N pre (20 N Pre) and post (20 N Post) baseline conditions on two different days. Surface electromyography (sEMG) recorded mean quadriceps (Q) and hamstring (H) reflex time (R Time = ms) and reflex amplitude (R Amp = %MVIC). A load cell on the anterior tibia measured the timing (KE Time = ms) and amplitude (KE Amp = N) of the knee extension force, and was used to calculate electromechanical delay (EMD = ms) and peak knee extension moment (KE Mom = N m/kg). Data from 19 recreationally active subjects revealed good to excellent response consistency between test days and between baseline conditions for R Time, R Amp, KE Time and KE Amp. With anterior tibial loading, R Time was faster at 50 N vs. 20 N Post, and R Amp was greater at 20 N Pre vs. 20 N Post (Q and H) and at 50 N vs. 100 N (Q only). KE Mom was greater at 20 N Pre and 50 N vs. 20 N Post, and EMD was shorter at 50 N vs. 20 N, 20 N Pre and 20 N Post. These results suggest that knee extensor reflex responses are enhanced with low (50 N) but not moderate (100 N) anterior loading of the knee. © 2004 Elsevier Ltd. All rights reserved.

First Page

61

Last Page

71

DOI

10.1016/j.jelekin.2004.07.002

Publication Date

2-1-2005

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