Ultrasound reveals negligible cocontraction during isometric plantar flexion and dorsiflexion despite the presence of antagonist electromyographic activity

Raiteri, Brent J., Cresswell, Andrew G. and Lichtwark, Glen A. (2015) Ultrasound reveals negligible cocontraction during isometric plantar flexion and dorsiflexion despite the presence of antagonist electromyographic activity. Journal of Applied Physiology, 118 10: 1193-1199. doi:10.1152/japplphysiol.00825.2014

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Author Raiteri, Brent J.
Cresswell, Andrew G.
Lichtwark, Glen A.
Title Ultrasound reveals negligible cocontraction during isometric plantar flexion and dorsiflexion despite the presence of antagonist electromyographic activity
Journal name Journal of Applied Physiology   Check publisher's open access policy
ISSN 8750-7587
0021-8987
Publication date 2015-05-01
Year available 2015
Sub-type Article (original research)
DOI 10.1152/japplphysiol.00825.2014
Open Access Status Not yet assessed
Volume 118
Issue 10
Start page 1193
End page 1199
Total pages 7
Place of publication Bethesda, MD, United States
Publisher American Physiological Society
Language eng
Subject 1314 Physiology
2737 Physiology (medical)
Abstract Because of the approximate linear relationship between muscle force and muscle activity, muscle forces are often estimated during maximal voluntary isometric contractions (MVICs) from torque and surface electromyography (sEMG) measurements. However, sEMG recordings from a target muscle may contain cross-talk originating from nearby muscles, which could lead to erroneous force estimates. Here we used ultrasound imaging to measure in vivo muscle fascicle length (L-f) changes and sEMG to measure muscle activity of the tibialis anterior, medial gastrocnemius, lateral gastrocnemius, and soleus muscles during ramp MVICs in plantar and dorsiflexion directions (n = 8). After correcting longitudinal L-f changes for ankle rotation, the antagonist L-f at peak antagonist root-mean-square (RMS) amplitude were significantly longer than the agonist L-f at this sEMG-matched level. On average, L-f shortened from resting length by 1.29 to 2.90 mm when muscles acted as agonists and lengthened from resting length by 0.43 to 1.16 mm when muscles acted as antagonists (depending on the muscle of interest). The lack of fascicle shortening when muscles acted as antagonists indicates that cocontraction was likely to be negligible, despite cocontraction as determined by sEMG of between 7 and 23% MVIC across all muscles. Different interelectrode distances (IEDs) over the plantar flexors revealed significantly higher antagonist RMS amplitudes for the 4-cm IEDs compared with the 2-cm IEDs, which further indicates that cross-talk was present. Consequently, investigators should be wary about performing agonist torque corrections for isometric plantar flexion and dorsiflexion based on the antagonist sEMG trace and predicted antagonist moment.
Formatted abstract
Because of the approximate linear relationship between muscle force and muscle activity, muscle forces are often estimated during maximal voluntary isometric contractions (MVICs) from torque and surface electromyography (sEMG) measurements. However, sEMG recordings from a target muscle may contain cross-talk originating from nearby muscles, which could lead to erroneous force estimates. Here we used ultrasound imaging to measure in vivo muscle fascicle length (L-f) changes and sEMG to measure muscle activity of the tibialis anterior, medial gastrocnemius, lateral gastrocnemius, and soleus muscles during ramp MVICs in plantar and dorsiflexion directions (n = 8). After correcting longitudinal L-f changes for ankle rotation, the antagonist L-f at peak antagonist root-mean-square (RMS) amplitude were significantly longer than the agonist L-f at this sEMG-matched level. On average, L-f shortened from resting length by 1.29 to 2.90 mm when muscles acted as agonists and lengthened from resting length by 0.43 to 1.16 mm when muscles acted as antagonists (depending on the muscle of interest). The lack of fascicle shortening when muscles acted as antagonists indicates that cocontraction was likely to be negligible, despite cocontraction as determined by sEMG of between 7 and 23% MVIC across all muscles. Different interelectrode distances (IEDs) over the plantar flexors revealed significantly higher antagonist RMS amplitudes for the 4-cm IEDs compared with the 2-cm IEDs, which further indicates that cross-talk was present. Consequently, investigators should be wary about performing agonist torque corrections for isometric plantar flexion and dorsiflexion based on the antagonist sEMG trace and predicted antagonist moment.
Keyword EMG
Cross-talk
Torque correction
Tibialis anterior
Gastrocnemius
Soleus
In-Vivo Observations
Tendon Moment Arm
Surface Emg
Cerebral-Palsy
Ankle-Joint
Cross-Talk
Maximal Plantarflexion
Electrode Geometry
Fascicle Length
Strain Patterns
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2016 Collection
School of Human Movement and Nutrition Sciences Publications
 
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