Evaluating Patterns of EMG Amplitudes for Trunk and
Neck Muscles of Patients and Controls
V. Reggie Edgerton, Steven L. Wolf, Daniel J. Levendowski and Roland R. Roy
KEYWORDS: surface electromyography, muscle dysfunction, muscle ratios, muscle patterns, back pain
We used ratios of EMG amplitudes to characterize neural strategies of motoneuron recruitment for seven bilateral muscle groups of the
back and neck during nine motor tasks to discriminate patients who sustained sprain/strain injuries (n=61) from a control population
(n=400). Compensatory relationships between muscle pairs improved the predictability of hypoactivity or hyperactivity based on the
probability distribution of muscle rations obtained from uninjured subjects. We defined severity of hypoactive or hyperactive EMG activity
by (a) the number of ratios that exceeded the normal range (95% confidence interval), (b) the compensatory relationship between these
muscle pairs during each motor task, and (c) the consistency and frequency of hypoactivity or hyperactivity across nine motor tasks.
Accuracy of the classification system was 88% with a specificity of 90% and a sensitivity of 70%. Between-session reliability for the
overall classification of 40 controls and 44 patients was 93%. These results indicate that muscle ratios can objectively quantify altered
strategies of motoneuron recruitment attributed to muscle trauma and pain common to sprain/strain injuries.
Theoretical Basis for Patterning EMG Amplitudes
to Assess Muscle Dysfunction
V. Reggie Edgerton, Steven L. Wolf, Daniel J. Levendowski and Roland R. Roy
KEYWORDS: surface electromyography, EMG, sprain/strain injuries, muscle dysfunction,
muscle EMG ratios, muscle recruitment patterns, back pain
A theoretical basis for assessing muscle dysfunction due to sprain/strain injuries is presented. We propose that muscle tissue trauma
results in an alteration in the patterns of neural recruitment, a reduction in the force-generating capability of the injured muscle, and/or pain
sensations. Furthermore, a lower than normal recruitment of motoneuron pools in the injured area can result in elevated recruitment levels
from compensating motoneuron pools for a given motor task. It is proposed that these changes in motoneuron recruitment can be readily
apparent in the rations of EMG amplitudes among multiple pairs of muscles associated kinesiologically with the affected muscle. Chronic
compensating actions, such as those resulting from faulty neural feedback of the force-length-velocity relationships for a stretched tendon
or muscle unit, could cause further injuries. It is proposed that consistent and valid measures of ratios of EMG amplitudes between many
muscle pairs acquired for well-defined motor tasks can be used to facilitate diagnoses and direct treatment strategies for sprain/strain
injuries and pain.
EMG Activity in Neck and Back Muscles During
Selected Static Postures in Adult Males and Females
V. Reggie Edgerton, Steven L. Wolf, Daniel J. Levendowski and Roland R. Roy
KEYWORDS: surface electromyography, EMG, sprain/strain injuries, muscle dysfunction,
muscle EMG ratios, muscle recruitment patterns, back pain
Surface electromyographic (EMG) amplitudes were gathered from 100 men and 100 women while maintaining the end range of nine motor
tasks. Ratios of EMG amplitudes were used to characterize the activation patterns of 14 muscle groups of the back and trunk during 10
motor tasks. Procedures to identify electrode placement sites were developed to ensure reliability of all EMG recordings. Subcutaneous
fat was estimated at each muscle site and a correction factor was used to account for signal attenuation due to the impedance attributable
to adipose tissue thickness. Logarithmic transformations were performed to obtain a Gaussian distribution of the EMG amplitudes and
muscle ratios. The transformed EMG amplitudes and transformed ratios were highly reliable between sessions across nine active motor
tasks (Pearson's r and intra-class correlations ranged form 0.74 to 0.96). Significant gender differences were observed in the transformed
EMG amplitudes and ratios of amplitudes in selected muscles and muscle pairs. It appears that the transformed EMG ratios represent a
reliable means of assessing muscle recruitment patterns in a series of well-defined motor tasks in a large population of presumable normal
adult male and female subjects. The acquisition of this large database under well-controlled conditions using defined criteria for each motor
task provides a template to which individuals with injuries involving the neck and trunk musculature can be compared.
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