Clinical Measures Predicting Knee Extensor Muscle Activation During a Maximal Voluntary Isometric Contraction

Gordon L Warren

doi:10.15226/2374-6904/2/4/00138

Abstract

Clinical Measures Predicting Knee Extensor Muscle Activation During a Maximal Voluntary Isometric Contraction

Highlights

Strength is determined by the anatomical properties of muscle and by its neurophysiological properties
A positive correlation means that greater knee extensor activation was associated with poorer hip flexibility
The positive coefficient for presence of active myofascial trigger points (MTrP) in the knee flexors indicates that knee extensor activation was higher if the subject had active MTrP in the knee flexors

Summary

Introduction

Strength is determined by the anatomical properties of muscle (e.g., number of muscle fibers, muscle fiber diameter, fiber pennation angle) and by its neurophysiological properties (e.g., motor unit recruitment, rate coding, motor unit synchronization). The inability to maximally activate the knee extensors in the absence of frank tissue damage can alter athletic performance, which often relies on optimal contraction of this lower-extremity muscle group [1]. The knee extensors have, on average, been observed to have a relatively low activation during a maximal voluntary isometric contraction (MVIC) compared to other muscles or muscle groups, including the biceps, brachialis, adductor pollicis, tibialis anterior, and ankle plantarflexors [5]. Activation of the knee extensor during a MVIC in otherwise healthy individuals has been reported on average to be in the 85-95% range, while the MVIC activation for other muscle groups exceeds 95%. The lower knee extensor activation levels observed in healthy individuals may not affect typical activities of daily living, but they could limit athletic performance and/or affect injury prevention

Methods

Results

Discussion

Conclusion