Muscle force cannot be directly inferred from muscle activation: illustrated by the proposed imbalance of force between the vastus medialis and vastus lateralis in people with patellofemoral pain

Hug, Francois, Hodges, Paul W. and Tucker, Kylie (2015) Muscle force cannot be directly inferred from muscle activation: illustrated by the proposed imbalance of force between the vastus medialis and vastus lateralis in people with patellofemoral pain. Journal of Orthopaedic and Sports Physical Therapy, 45 5: 360-365. doi:10.2519/jospt.2015.5905


Author Hug, Francois
Hodges, Paul W.
Tucker, Kylie
Title Muscle force cannot be directly inferred from muscle activation: illustrated by the proposed imbalance of force between the vastus medialis and vastus lateralis in people with patellofemoral pain
Journal name Journal of Orthopaedic and Sports Physical Therapy   Check publisher's open access policy
ISSN 0190-6011
1938-1344
Publication date 2015-05-01
Year available 2015
Sub-type Critical review of research, literature review, critical commentary
DOI 10.2519/jospt.2015.5905
Open Access Status
Volume 45
Issue 5
Start page 360
End page 365
Total pages 6
Place of publication Alexandria, VA United States
Publisher American Physical Therapy Association * Orthopedic Section
Collection year 2016
Language eng
Abstract Muscle force cannot be directly inferred from neural drive assessed using electromyography (EMG). Although the limitations associated with inferring force from EMG are well known, this has received little attention in the clinical literature. This commentary discusses these limitations within the context of the imbalance of force production between the vastus medialis (VM) and vastus lateralis (VL) muscles, which has been speculated to contribute to the development and/or persistence of patellofemoral pain. The balance of neural drive between vasti muscles is most frequently measured with 2 approaches: (1) the onset of VM EMG relative to that of the VL, and (2) the ratio of the EMG signal amplitude of the VM and VL. Here, we demonstrate that this classical approach cannot determine whether an imbalance of force exists between the VM and VL. Considerations such as altered electromechanical delay (time between the onsets of muscle activation and patellar motion) in people with patellofemoral pain may lead to a reconsideration of the classical interpretation of the onset of VM EMG signal relative to that of the VL. Also, beyond the amplitude of the neural drive, muscle force depends on several biomechanical factors (eg, specific tension and physiological cross-sectional area). Therefore, the VL/VM activation ratio does not provide information about the VL/VM force ratio, which is ultimately the most important information from a clinical perspective. Although the literature includes defenses for both the existence and absence of this force imbalance in people with patellofemoral pain, a reconsideration of the methods used to assess this imbalance is needed.
Keyword Anterior knee pain
Biomechanics
Electromechanical delay
Electromyography
Force
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Critical review of research, literature review, critical commentary
Collections: Official 2016 Collection
School of Biomedical Sciences Publications
School of Human Movement and Nutrition Sciences Publications
 
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