Quantitative interpretation of lumbar muscle myoelectric signals during rapid cyclic attempted trunk flexions and extensions

doi:10.1016/0021-9290(94)90204-6

Journal of Biomechanics

Volume 27, Issue 2, February 1994, Pages 157-167

https://doi.org/10.1016/0021-9290(94)90204-6 Get rights and content

Abstract

The quantitative relationship between lumbar myoelectric signals (MES) and rapidly varying isometric trunk muscle forces was investigated. Ten young adult males were asked to cycle harmonically between attempted trunk flexion and attempted trunk extension in an upright position at rates of 0.33, 0.67 and 1.0 Hz to peak efforts of 20, 40 and 60% of maximum voluntary exertion levels. The forces voluntarily exerted against a load cell were measured and used along with acquired kinematic data to calculate the time course of the net sagittal moment at the level of the third lumbar vertebra during task performances. A 22 muscle double linear programming biomechanical model was used to predict the lumbar trunk muscle contraction forces from the calculated moments. Rectified and bidirectionally low-pass filtered myoelectric activities were acquired at the L3 level from four abdominal muscles and four back muscles. The processed MES were found to be well correlated (r>0.90) with predicted muscle forces when the MES were time-shifted to account for electromechanical delay as well as the dynamic phase shift between muscle electrical activity and contraction force. Mean time shifts that maximized the linear MES-force relationship ranged from 111 to 218 ms, were greater for the trunk extensors than the trunk flexors and generally exhibited lateral symmetry. The corresponding approximate phase angles averaged 20° at the slowest rate and 50° at the fastest rate. MES-force phase angles decreased as effort level was increased indicating that the dynamic MES-force relationship is nonlinear. These results illustrate the importance of accounting for the phase lag between muscle electrical activity and force when using MES to quantify muscle loads during rapidly varying exertions.

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Cited by (31)

Predicting the influence of hip and lumbar flexibility on lifting motions using optimal control
2018, Journal of Biomechanics
Computational models of the human body coupled with optimization can be used to predict the influence of variables that cannot be experimentally manipulated. Here, we present a study that predicts the motion of the human body while lifting a box, as a function of flexibility of the hip and lumbar joints in the sagittal plane. We modeled the human body in the sagittal plane with joints actuated by pairs of agonist-antagonist muscle torque generators, and a passive hamstring muscle. The characteristics of a stiff, average and flexible person were represented by co-varying the lumbar range-of-motion, lumbar passive extensor-torque and the hamstring passive muscle-force. We used optimal control to solve for motions that simulated lifting a 10 kg box from a 0.3 m height. The solution minimized the total sum of the normalized squared active and passive muscle torques and the normalized passive hamstring muscle forces, over the duration of the motion. The predicted motion of the average lifter agreed well with experimental data in the literature. The change in model flexibility affected the predicted joint angles, with the stiffer models flexing more at the hip and knee, and less at the lumbar joint, to complete the lift. Stiffer models produced similar passive lumbar torque and higher hamstring muscle force components than the more flexible models. The variation between the motion characteristics of the models suggest that flexibility may play an important role in determining lifting technique.
Relationship between neck acceleration and muscle activation in people with chronic neck pain: Implications for functional disability
2016, Clinical Biomechanics
Citation Excerpt :
This method is frequently used in sports performance analysis, as it helps review the quantitative relationship between the motions of one particular segment of the human body and the muscles involved (Glazier et al., 2003; Li and Caldwell, 1999). Furthermore, the phase shift data obtained from cross-correlation analysis inform of the phasic relationship of the development of force relative to EMG onset, which is defined as the electromechanical coupling of muscle contraction (Cavanagh and Komi, 1979; Thelen and Schultz, 1994). In addition, it is crucial to examine whether the electromechanical coupling as indicated by the relationship between the spinal acceleration/deceleration and the muscle activation found in individuals with NP is associated with the extent of functional limitation.
Previous study has found that people with chronic neck pain moved with a consistently compromised acceleration/deceleration at their cervical and thoracic spines. This study examined the strength of the association between the electromyographic activities and the acceleration/deceleration of the cervical and thoracic spine, and its correlation with the functional disabilities in individuals with neck pain.
Time history of the cervical and thoracic acceleration/deceleration and EMG activity was acquired in thirty-four subjects with chronic neck pain and thirty-four age- and gender-matched asymptomatic subjects during active neck movements. The strength of the association between the electromyographic activity of spinal muscles and the cervical and thoracic acceleration/deceleration was determined using cross-correlation method. Relationship between the strength of this association and the severity of the functional disabilities in neck pain group was examined using correlation analysis.
The strength of the association between cervical and thoracic acceleration/deceleration and electromyographic activities was significantly lower in neck pain group. Significant negative correlations were found between the functional disability level and the strength of this defined association in the symptomatic group.
The compromised capability of the spinal muscles to produce acceleration/deceleration in the neck pain group may imply an impaired electromechanical coupling of these spinal muscles when performing neck movements. Significant negative correlation of the degree of functional disabilities suggests that the present approach can be used as an objective and specific evaluation of the dynamic performance of the spinal muscles and its relationship with the functional disabilities in neck pain subjects.
Trunk active response and spinal forces in sudden forward loading - analysis of the role of perturbation load and pre-perturbation conditions by a kinematics-driven model
2015, Journal of Biomechanics
Citation Excerpt :
Any muscle activation on the other hand translates to a mechanical force only after an additional delay period called electromechanical delay (EMD). The rate of muscle force development during voluntary contractions was found to have inverse relation with EMD (Thelen et al., 1994; van Dieen et al., 1991). In addition, larger trunk flexion angles were reported to prolong EMD (Marras, 1987).
Understanding the central nervous system (CNS) response strategy to trunk perturbations could help in prevention of back injuries and development of rehabilitation and treatment programs. This study aimed to investigate biomechanical response of the trunk musculoskeletal system under sudden forward loads, accounting for pre-perturbation conditions (preloading, initial posture and abdominal antagonistic coactivation) and perturbation magnitudes. Using a trunk kinematics-driven iterative finite element (FE) model, temporal profiles of measured kinematics and external load along with subjects’ weights were prescribed to predict thoracolumbar muscle forces/latencies and spinal loads for twelve healthy subjects when tested in six conditions during pre- and post-perturbation periods. Results demonstrated that preloading the trunk significantly (i.e., p<0.05) increased pre-perturbation back muscle forces but significantly decreased post-perturbation peak muscle active forces and muscle latencies. Initial trunk flexion significantly increased muscle active and passive forces before the perturbation and their peak values after the perturbation, which in turn caused much larger spinal loads. Abdominal muscles antagonistic pre-activation did not alter the internal variables investigated in this study. Increase in sudden applied load increased muscle reflex activities and spinal forces; a 50 N increase in sudden load (i.e., when comparing 50 N to 100 N) increased the L5-S1 compression force by 1327 N under 5 N preload and by 1374 N under 50 N preload. Overall, forces on the spine and hence risk of failure substantially increased in sudden forward loading when the magnitude of sudden load increased and when the trunk was initially in a flexed posture. In contrast, a higher initial preload diminished reflex latencies and compression forces.
Obtaining maximum muscle excitation for normalizing shoulder electromyography in dynamic contractions
2013, Journal of Electromyography and Kinesiology
Citation Excerpt :
However, to avoid misinterpretation with percent maximum force, or torque, the term “MVE” has been adopted. MVE has been defined as maximal voluntary effort (Shirasawa et al., 2009), exertion (Fischer et al., 2011; Granata and Gottipati, 2008; Thelan et al., 1994), electrical activity (Madill and McLean, 2006; Mogk and Keir, 2003; Balogh et al., 1999) or excitation (Hodder and Keir, 2012; Chopp et al., 2010; Meyers and Keir, 2003). In the current communication, we differentiate between the maximum voluntary contraction (e.g. MVC) elicited by muscle excitation and the maximum voluntary excitation (e.g. MVE) itself.
Muscle specific maximal voluntary isometric contractions (MVIC) are commonly used to elicit reference amplitudes to normalize electromyographic signals (EMG). It has been questioned whether this is appropriate for normalizing EMG from dynamic contractions. This study compares EMG amplitude when shoulder muscle activity from dynamic contractions is normalized to isometric and isokinetic maximal excitation as well as a hybrid approach currently used in our laboratory. Anterior, middle and posterior deltoid, upper and lower trapezius, pectoralis major, latissimus dorsi and infraspinatus were monitored during (1) manually resisted MVICs, and (2) maximum voluntary dynamic concentric contractions (MVDC) on an isokinetic dynamometer. Dynamic contractions were performed (a) at 30°/s about the longitudinal, frontal and sagittal axes of the shoulder, and (b) during manual bi-rotation of a tilted wheel at 120°/s. EMG from the wheel task was normalized to the maximum excitation from (i) the muscle specific MVIC, (ii) from any MVIC (MVIC_ALL), (iii) for any MVDC, (iv) from any exertion (maximum experimental excitation, MEE). Mean EMG from the wheel task was up to 45% greater when normalized to muscle specific isometric contractions (method i) than when normalized to MEE (method iv). Seventy-five percent of MEE’s occurred during MVDCs. This study presents an 20 useful and effective process for obtaining the greatest excitation from the shoulder muscles when normalizing dynamic efforts.
A comparison of ultrasound and electromyography measures of force and activation to examine the mechanics of abdominal wall contraction
2010, Clinical Biomechanics
Citation Excerpt :
Proper activation and contraction of the abdominal wall is considered important for several reasons. First, abdominal muscles generate forces to produce moments in flexion, lateral bend and axial twist (Gatton et al., 2001; Marras and Mirka, 1990; McGill, 1991, 1996; Pope et al., 1986; Thelen et al., 1994). Second, properly coordinated abdominal muscle contraction is necessary to maintain a stable spinal column (Brown and Potvin, 2005; Brown et al., 2006; Cholewicki and McGill, 1996; Gardner-Morse and Stokes, 1998).
Ultrasound imaging is a valuable tool which, when applied appropriately, has the potential to provide information regarding the mechanics of abdominal muscle contraction. Typically, changes in muscle thickness are obtained and interpreted. However, the link between ultrasound measures of muscle thickening and EMG measures of activation is not clear.
Five healthy males performed a series of abdominal muscle contractions while surface EMG and trunk posture were monitored and ultrasound images of the internal oblique and external oblique were captured both at relaxation and upon contraction. Ramped isometric flexor and extensor moment contractions were also assessed and compared between EMG and ultrasound.
No definitive relationship between increases in muscle activation and corresponding measures of thickening was observed. Correlations between the two measures, across all contraction types, were 0.14 for internal oblique and −0.22 for external oblique.
The lack of clear association between abdominal muscle activation and thickening may be due to the composite laminate-like structure of the abdominal wall, with force being transmitted between obliquely oriented muscle layers. Thus, ultrasound alone may not be a valid measure of muscle activation or force in the unique architecture of the abdominal wall.
Activation Characteristics of Trunk Muscles During Cyclic Upper-Body Perturbations Caused by an Oscillating Pole
2008, Archives of Physical Medicine and Rehabilitation
Citation Excerpt :
The remaining time interval from the back muscles amplitude peak to the bottom inversion point stayed constant likewise: The resulting intervals were found to be 107ms at 3Hz, 97ms at 3.5Hz, and 98ms at 4.5Hz. These data are in accordance with data from the literature.37 Because the multifidus and erector spinae muscles are assigned to either the local (multifidus) or the global (erector spinae) systems,19 the similarities of multifidus and erector spinae coordination patterns are surprising.
Anders C, Wenzel B, Scholle HC. Activation characteristics of trunk muscles during cyclic upper-body perturbations caused by an oscillating pole.
To evaluate the effect of a new device on trunk muscle activation.
Cross-sectional survey of trunk muscle activation characteristics.
Physiologic laboratory at university institute.
Thirty healthy subjects (15 men, 15 women) were recruited from a university campus.
A simple flexible pole that applies rapidly alternating forces on the trunk when set into motion was used. The device was held horizontally in both hands, in front of the body. It was used at 3 different oscillation frequencies (3, 3.5, 4.5Hz), in horizontal and vertical plane, respectively.
Surface electromyography of 5 trunk muscles was measured and the data were normalized according to relative cycle time. Time dependent (amplitude curve) and time independent (mean amplitude over cycle) parameters were used for analysis.
Rectus abdominis and external oblique muscle amplitudes were directly proportional with oscillation frequency (analysis of variance), and these effects were independent of sex. Multifidus amplitude levels were subject to oscillation plane with increased levels for vertical oscillation in men but not in the women. All abdominal muscles exhibited continuous activation pattern, independent of oscillation plane. Back muscles changed from a continuous activation in horizontal plane into similarly phasic patterns in vertical oscillation plane. The occurring amplitude peak moved forward in relative cycle with increasing oscillation frequency.
Back muscle activation patterns were subject to oscillation plane. Abdominal muscle activation was independent from oscillation frequency and oscillation plane. These normative data may be used to identify disturbed trunk muscle coordination patterns and to control success of functional restoration during rehabilitation interventions of back pain patients.

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Journal of Biomechanics

Abstract

References (21)

Biomechanical model calculation of muscle contraction forces: a double linear programming method

J. Biomechanics

Least-squares identification of the dynamic relation between the electromyogram and joint moment

J. Biomechanics

Predictions of knee and ankle moments of force in walking from EMG and kinematic data

J. Biomechanics

The relationship between trunk muscle electromyography and lifting moments in the sagittal and frontal planes

J. Biomechanics

Electromechanical delay in human skeletal muscle under concentric and eccentric contractions

European J. appl. Physiol.

EMG-force dynamics in human skeletal muscle

Med. Biol. Engng

Use of surface electromyogram as a measure of dynamic force in human limb muscles

Med. Biol. Engng Comput.

Dynamic relationship between isometric muscle tension and the electromyogram in man

J. appl. Physiol.

In vivo registration of achilles tendon forces in man. I. methodological development

Int. J. Sports Med.

Cited by (31)

Predicting the influence of hip and lumbar flexibility on lifting motions using optimal control

Relationship between neck acceleration and muscle activation in people with chronic neck pain: Implications for functional disability

Trunk active response and spinal forces in sudden forward loading - analysis of the role of perturbation load and pre-perturbation conditions by a kinematics-driven model

Obtaining maximum muscle excitation for normalizing shoulder electromyography in dynamic contractions

A comparison of ultrasound and electromyography measures of force and activation to examine the mechanics of abdominal wall contraction

Activation Characteristics of Trunk Muscles During Cyclic Upper-Body Perturbations Caused by an Oscillating Pole