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Shrawan Kumar

Publications and source records attributed to Shrawan Kumar.

49 records · Page 3Linked to original sources
PubMed2003

EMG power spectra of cervical muscles in lateral flexion and comparison with sagittal and oblique plane activities.

The purpose of this study was to calculate electromyographic (EMG) power spectra of the sternocleidomastoid (SCM), the splenius capitis (SPL) and the trapezius (TRP) muscles from both sides of the body in bilateral lateral flexion and compare them with the EMG spectral characteristics of the same muscles in the sagittal and oblique planes recorded from the same subjects in the same experimental session but reported elsewhere in the literature. Forty normal and healthy young adults (21 males, 19 females) volunteered for the study. The subjects were prepared and positioned appropriately to exert linearly ramping isometric exertion aided by visual feedback against a rigid and load cell instrumental device. Exertions were carried out in a random order. The maximal voluntary contraction was reached within a 5-s test period. The torque and EMG from the SCM, SPL and TRP muscles were sampled bilaterally at a rate of 1 kHz. The EMG data were subjected to fast Fourier transform analysis. During lateral flexion, the torque generated by females was significantly lower than males ( P<0.01) and represented at 75% of male torque. Contrary to flexion/extension and oblique plane activities, the ipsilateral SCM was most active with highest power and up to four dominant frequencies demonstrating four distinct peaks. The bandwidth of this muscle progressively increased with the grade of contraction up to 400 Hz, similar to flexion/extension with median frequency (MF) spread between 21 and 109 Hz for males and 78 and 99 Hz for females. The ipsilateral SPL was the second most active muscle, which maintained a narrow bandwidth (200 Hz) and one dominant frequency, rising in power with increasing grade of contraction. Flexion and extension caused symmetrical activity bilaterally. The results of MANOVA revealed a significant main effect of gender, activity direction, grade of contraction and individual muscles ( P<0.001). There was a significant interaction between muscle and activity direction ( P<0.001) implying significantly different MF and mean power frequency if the direction of exertion was changed. Male and female subjects responded to direction differently ( P<0.001).

Adult↗
PubMed2003

Analysis of low velocity frontal impacts.

OBJECTIVES: The objectives of the study were to determine the phasic recruitment of cervical muscles with increasing magnitudes of low velocity frontal impacts, and to determine quantitative effects of awareness of impending impact in comparison to being impacted unawares. BACKGROUND: Biomechanics of low velocity frontal impact is poorly understood and requires more work. METHODS: Ten healthy young adults were subjected to frontal impacts causing accelerations of 5.3, 8.6, 11.0 and 14.0 m/s(2) (0.54, 0.88, 1.12 and 1.43 gs) while the subjects were unaware of the impending impact and after being told that they were going to be impacted. Electromyograph from sternocleidomastoids, splenius capitis and upper trapezius was recorded bilaterally. Triaxial accelerometers recorded the acceleration of the sled, torso and head of the subjects. RESULTS: The normalized electromyograph magnitude progressively rose with the level of acceleration whereas the time to onset generally decreased. At 14 m/s(2) sled acceleration the trapezius muscle generated 79% of their maximal voluntary contraction whereas the sternocleidomastoids generated 32% of their maximum voluntary contraction. The normalized peak electromyograph, the time to onset, the time of the peak electromyograph were significantly affected by the level of acceleration (P<0.01), the expectation of impact (P<0.01) and muscle group studied (P<0.01). The subject gender did not have a significant effect. The kinematic variables and the electromyograph regressed significantly on acceleration (P<0.01). CONCLUSIONS: The muscle responses were greater with higher levels of acceleration, particularly the trapezius in frontal impacts. Since the muscular components play a significant and central role in head/neck complex motion abatement at higher levels of acceleration, it may be a primary site of injury at low velocity whiplash phenomenon. RELEVANCE: An understanding of the pattern of biomechanical loading may assist in a more specific treatment of the patient injured in a low velocity frontal impact.

Acceleration↗
PubMed2002

An electromyographic study of low-velocity rear-end impacts.

STUDY DESIGN: Experimental analysis was performed to determine the effects of low-velocity rear-end impacts on phasic and magnitudinal activity of the cervical muscles in expected and unexpected conditions. OBJECTIVES: To determine the phasic response of the cervical muscles to increasing low-velocity rear-end impacts, and to compare the quantitative effects of awareness and unawareness of impending impact. SUMMARY OF BACKGROUND DATA: The literature contains little information on the etiology of whiplash injuries. Animal and cadaver studies have yielded some insight into the phenomenon. However, in vivo studies of the cervical muscular response and head-neck kinematics to low-velocity impacts are rare. METHODS: Seven healthy volunteers were subjected to rear-end impacts of 4.9, 8.8, 10.8, and 13.7 m/s2 acceleration at two levels of expectation: expected and unexpected. Bilateral electromyograms of the sternocleidomastoids, trapezii, and splenii capitis were recorded. Triaxial accelerometers recorded the acceleration of the chair, torso at the shoulder level, and head of the participant. RESULTS: At an acceleration of 13.7 m/s2, the sternocleidomastoids generated up to 179% of their maximal voluntary contraction electromyogram, whereas the splenii and trapezii did not exceed 35% of their maximal voluntary contraction in most of the experimental conditions. Electromyographic variables were significantly affected by the levels of acceleration and expectation (P < 0.001). The onset time and peak electromyogram time for the sternocleidomastoid progressively decreased with increasing levels of acceleration. The kinetic variables and the electromyographic variables regressed significantly on the acceleration (P < 0.01), explaining from 96% to 100% of the variability. CONCLUSIONS: Muscle responses were greater with higher levels of acceleration. Because the muscular component of the head-neck complex plays a central role in the abatement of higher acceleration levels, it may be a primary site of injury in the whiplash phenomenon.

Acceleration↗
PubMed2002

Isometric axial rotation of the human trunk from pre-rotated postures.

The purpose of this investigation was to study the torque and electromyogram (EMG) in axial rotation from pre-rotated postures. A group of 50 young adults (27 men and 23 women) volunteered for the study. These prepared subjects carried out axial rotation with pre-rotated postures in the direction of pre-rotation and away from it. Torque and EMG were recorded bilaterally from latissimus dorsi, erector spinae at L(3) and T(10) levels, pectoralis, rectus abdominis, external and internal oblique. In 15 degrees pre-rotated posture the axial rotation in the direction of pre-rotation reduced the torque by between 11% and 17% and away from it increased the torque by 12% to 16%. In 30 degrees pre-rotated posture the decrement in torque in the direction of pre-rotation was 24%-33%, and in the opposite direction the gain was between 21% and 32%. Even with decreased torque with rotation in the pre-rotation direction the EMG increased up to 123%. The EMG magnitude and slopes of EMG in these activities demonstrated significant increases while in the opposite direction slight decreases were observed. The EMG of each muscle was significantly different from all other muscles ( P<0.001). A significant ( P<0.01) but low correlation between EMG and torque was obtained. Significant linear regressions between torque and EMG of different muscles were obtained ( P<0.01; r=up to 0.70).

Adolescent↗
PubMed2002

Inner ear anomalies are frequent but nonobligatory features of the branchio-oto-renal syndrome.

OBJECTIVE: To summarize the syndromic features and evaluate the presence of inner ear anomalies in 35 patients with branchio-oto-renal (BOR) syndrome from 6 families. DESIGN: Retrospective evaluation of magnetic resonance imaging of the temporal bones and clinical features in patients with BOR syndrome. SETTING: Tertiary referral center. PATIENTS: The study population comprised 35 clinically affected patients with BOR syndrome from 6 families. Most of these families were followed for over 25 years. MAIN OUTCOME MEASURES: Twenty-four patients underwent high-resolution, heavily T2-weighted 3-dimensional magnetic resonance imaging of the temporal bones for evaluation of inner ear anomalies. Special attention was paid to the endolymphatic duct and sac. RESULTS: A total of 7 enlarged endolymphatic ducts and sacs (3 bilaterally and 4 unilaterally) and 5 enlarged endolymphatic ducts only (2 bilaterally and 3 unilaterally) were observed. Eight hypoplastic cochleas and 6 hypoplastic labyrinths were seen bilaterally. Seven family members had normal inner ears. CONCLUSION: These findings suggest that inner ear anomalies are frequent but nonobligatory features of BOR syndrome.

Adult↗
PubMed2002

Electromyography of superficial cervical muscles with exertion in the sagittal, coronal and oblique planes.

The purpose of the current study was twofold: (1) to determine the isometric force and electromyographic (EMG) relationship of the sternocleidomastoid, splenii and trapezii muscles bilaterally in graded and maximal exertions in the sagittal, coronal and oblique planes. and (2) to develop regression equations to predict force based on the EMG scores. A newly designed and validated cervical isometric strength testing device was used to measure the cervical muscle isometric strength and force/EMG relationship in cervical flexion, extension, bilateral lateral flexion, bilateral anterolateral flexion, and bilateral posterolateral extension, all beginning with an upright seated neutral posture. A group of 40 healthy subjects were asked to exert their cervical motions in the directions of interest, while the force output and EMG from the sternocleidomastoids, splenii, and trapezii were sampled bilaterally at 1 kHz. ANOVA, correlation, and regression analyses were carried out. The force and EMG scores were significantly different between the directions of effort (P<0.01). All regressions were significant (P<0.01). All subjects registered the highest forces in pure extension and the lowest in pure flexion, showing a gradual decrease from the posterior to anterior direction. There was a modest correlation between EMG of the investigated muscles and force (r=0.15-0.76, P<0.01). EMG output was, for example, approximately 66% higher in flexion than in extension (while force output was roughly 30% less in flexion than extension) - thus relatively more muscle activity was required in flexion than extension to generate a given force. The intermediate positions (i.e. anterolateral flexion) revealed force/EMG ratio scores that were intermediate in relation to the force/EMG ratios for pure flexion and pure extension. The cervical muscle strength and cervical muscle EMG are therefore dependent on the direction of effort.

Acceleration↗
PubMed2002

Electromyography of trunk muscles in isometric graded axial rotation.

This study was conducted to determine the pattern, magnitude, and phasic inter-relationship of the trunk muscles in maximal isometric and graded isometric axial rotational contractions and compare them with those previously observed from the same subjects in the same experimental session in dynamic conditions. In 50 normal young healthy subjects (27 male and 23 female), after a suitable skin preparation, bipolar silver-silver chloride recessed pregelled surface electrodes were placed on external oblique, internal oblique, rectus abdominis, pectoralis major, latissimus dorsi, erector spinae at T(10) and L(3) levels bilaterally with 2 cm interelectrode distance. EMG signals from grounded subjects were suitably preamplified and amplified by a fully isolated system. These subjects were stabilized in an upright-seated posture in the Axial Rotation Tester (AROT), which was placed in isometric mode for force and rotation output from the AROT. The 14 channels of EMG, the force and the rotation were sampled at 1 kHz. The subjects initially registered their isometric maximal voluntary contraction (MVC) on both sides which was used for reference and then performed their 25%, 50% and 75% of MVC bilaterally in an isometric mode in a random order. The EMG magnitude, the slope of the rise of the EMG, and the phasic interrelationship of muscles were analyzed. The results showed that female sample generated only 65% of torque of their male counterparts. There were no significant differences between the male and the female samples in the EMG variables. Exertions to the left and to the right were not significantly different from each other for the measured variables. However, the magnitude contribution of the muscles and the slope of rise of EMG were significantly different in two directions (p<0.001). The phasic interrelationship of the external obliques, the latissimus dorsi and the erector spinae were different from other muscles (p<0.01). With the increasing grades of contraction the latissimus dorsi and the external obliques increased their magnitude significantly whereas that of the erectores spinae underwent a decrease in proportionate terms (but not in absolute magnitude) suggesting their role as stabilizers but not as rotators.

Adult↗
PubMedDate not supplied

Cervical muscle response to head rotation in whiplash-type right lateral impacts.

OBJECTIVE: To determine the electromyogram (EMG) response of the cervical muscles to a right lateral impact whiplash-type perturbation when the head is rotated. METHODS: Twenty healthy volunteers were subjected to right lateral impacts of 4.2, 8.1, 10.3, and 12.5 m/s2 and were looking either left or right. Bilateral EMGs of the sternocleidomastoid, trapezius, and splenius capitis muscles were recorded. Triaxial accelerometers recorded the acceleration of the chair, torso at the shoulder level, and head of the participant. RESULTS: In a right lateral impact, muscle responses were of low magnitude with the head rotated to either the left or the right. At the highest acceleration of 12.5 m/s2, all generated less than 39% of their maximal voluntary contraction EMG. The sternocleidomastoid muscle showed a greater EMG response than its counterpart and the muscles contralateral to the direction of impact had higher EMG responses. The time to onset of the EMG for the splenii capitis and trapezii generally decreased with increasing levels of acceleration. As anticipated, an increase in applied acceleration resulted in an increase in accompanying head accelerations (P < .05), and when the head acceleration increased, so too did the force equivalent exertions by the various muscles. CONCLUSIONS: Overall, a right lateral impact with head rotation to either right or left appears to reduce the activity and thus the risk of muscle injury, perhaps because of "bracing" by muscles actively producing rotation or because of greater spinal stability from other structures when the head is in the rotated position.

Acceleration↗
PubMedDate not supplied

Electromyographic and kinematic exploration of whiplash-type rear impacts: effect of left offset impact.

BACKGROUND CONTEXT: Although there are some volunteer collision studies reporting the effects of rear impacts on head and neck kinematics, there are few studies detailing the cervical muscle electromyogram response. Moreover, the effect of a rear impact offset to the left on the resultant muscle responses is unknown. PURPOSE: The purpose of this study was to determine the response of the cervical muscles to increasing low-velocity rear impacts offset by 45 degrees to the subject's left, and to compare the quantitative effects of expected and unexpected impact. STUDY DESIGN/SETTING: Nine healthy volunteers were subjected to rear impacts, offset by 45 degrees to the subject's left, of 4.6, 8.7, 11.0 and 14.5 m/s2 acceleration, at two levels of expectation: expected and unexpected. METHODS: Bilateral electromyograms of the sternocleidomastoids, trapezii and splenii capitis were recorded. Triaxial accelerometers recorded the acceleration of the chair, torso at the shoulder level and head of the participant. RESULTS: At an acceleration of 14.5 m/s2, the left sternocleidomastoid generated 71% and the right sternocleidomastoid 82% of their maximal voluntary contraction electromyogram in the unexpected impact conditions. Under these conditions, the right splenius capitis (contralateral to the left offset rear impact) also generated 71% of its maximal voluntary contraction, whereas the left splenius capitis generated only 20% of this variable. The trapezii generated only 25% of their maximal voluntary contraction. Subjects exhibited lower levels of their maximal voluntary contraction electromyogram when the impact was expected. Electromyographic variables were significantly affected by the levels of acceleration and expectation (p<.001). The time to onset and time to peak electromyogram for all muscles progressively decreased with increasing levels of acceleration, in the unexpected condition. The kinetic variables and the electromyographic variables regressed significantly on the acceleration (p<.001). In response to rear impacts offset to the subject's left, muscle responses were greater with higher levels of acceleration, greater with unexpected impact conditions and greatest for both sternocleidomastoids and for the splenius capitis muscle contralateral to the side of impact. CONCLUSIONS: Because the muscular component of the head-neck complex plays a role in the abatement of impact at higher acceleration levels, they are likely a primary site of injury in the whiplash phenomenon in rear collisions. More specifically, when a rear impact is offset to the subject's left, it results in not only increased electromyographic generation in both sternocleidomastoids, but the splenius capitis contralateral to the direction of impact offset also bears part of the force of the neck perturbation. Expecting or being aware of imminent impact also plays a role in reducing muscle responses in low-velocity offset rear impacts.

Acceleration↗
PubMedDate not supplied

Effect of head rotation in whiplash-type rear impacts.

BACKGROUND CONTEXT: Knowledge is increasing about the electromyographic and kinematic response of the neck muscles to rear impact, and also recent information is available on the effect of a rear impact offset to the left (posterolateral). The effect of head rotation, however, at the time of rear impact is not known. PURPOSE: The purpose of this study was to examine the effects of head rotation to the left and right on the cervical muscle response to increasing low-velocity posterolateral impacts. STUDY DESIGN/SETTING: Twenty healthy volunteers were subjected to rear impacts of 4.7, 8.3, 10.9 and 13.7 m/s2 acceleration, offset by 45 degrees to the subject's left, with head rotation to right and left. METHODS: Bilateral electromyograms of the sternocleidomastoids, trapezii and splenii capitis were recorded. Triaxial accelerometers recorded the acceleration of the sled, torso at the shoulder level, and head of the participant. RESULTS: With the head rotated to the right, at an acceleration of 13.7 m/s2, the left sternocleidomastoid generated 59% and the right sternocleidomastoid 20% of their maximal voluntary contraction (MVC) electromyogram (EMG). Under these conditions, the remaining muscles (both splenii capitis and trapezius) generated 25% or less of their MVC. With the head rotated to the left, at an acceleration of 13.7 m/s2, the right sternocleidomastoid generated 65% and the left sternocleidomastoid only 11% of the MVC EMG. Under these conditions, again the remaining muscles had low EMG activity (27% or less) with the exception of the left trapezius which generated 47% of its MVC. Electromyographic variables were significantly affected by the levels of acceleration (p<.01). The time to onset and time to peak EMG for all muscles progressively decreased with increasing levels of acceleration, for both head rotation conditions. The kinetic variables and the electromyographic variables regressed significantly on the acceleration (p<.01). CONCLUSIONS: Direction of impact is a factor in determining the muscle response to whiplash, but head rotation at the time of impact is also important in this regard. More specifically, when a rear impact is left posterolateral, it results in increased EMG generation mainly in the contralateral sternocleidomastoid, as expected, but head rotation at the same time in this type of impact reduces the EMG response of the cervical muscles. Muscle injury seems less likely under these conditions in low-velocity impacts.

Acceleration↗
PubMedDate not supplied

An electromyographic study of isokinetic axial rotation in young adults.

BACKGROUND CONTEXT: Trunk rotation is associated with over 60% of all low back injuries. However, there are gaps in the knowledge about trunk rotation. PURPOSE: To study the axial rotation torque and electromyographs (EMGs) of seven trunk muscles bilaterally in static and isokinetic modes with increasing angular velocity to determine qualitative and quantitative muscle response. STUDY DESIGN: An electromyographic study of seven trunk muscles bilaterally was carried out in 50 normal subjects during static and isokinetic axial rotation at varying angular velocity. The qualitative and quantitative force and EMG measures were made and analyzed phenomenologically and statistically. METHODS: Fifty normal young adults (27 men, 23 women) performed an isometric maximal voluntary contraction (MVC) from the neutral upright-seated posture to their right and left. Also, these subjects performed isokinetic axial rotation from neutral seated position to right and left, and from prerotated right and left "end of range posture" toward the neutral at 10, 20 and 40 degrees per second angular velocity. All experimental trials were made on axial rotation tester designed for the study. EMG was recorded from the erector spinae at L3 and T10 vertebral levels, latissimus dorsi, pectoralis major, rectus abdominis and external and internal obliques bilaterally. The torque and EMG in isokinetic condition were normalized against those of isometric condition. Descriptive statistics were calculated. Data were subjected to analysis of variance, and torque was regressed on EMG. RESULTS: The peak isokinetic torques were significantly lower than the isometric torques (p<.01), but the EMGs of the isokinetic conditions were significantly higher than those of isometric trials (p<.01). The isokinetic axial rotation torque decreased by 1 Nm to 1.5 Nm with per degree increase in velocity of rotation, with the values for 10, 20 and 40 degrees per second angular velocities being significantly different (p<.01). There was a significant increase (p<.01) in percent EMG (up to 28%) per unit torque with increasing angular velocity of rotation. The rotation torque from prerotated position to neutral was significantly higher than that of rotation away from the neutral (p<.001). The EMG magnitude increased significantly with increasing velocity (2% to 17% at 10 degrees per second), 21% to 28% at 20 degrees per second, 30% to 36% at 40 degrees per second). Regression analysis revealed poor predictability of torque based on EMG. The latter was suggested because of the role and behavior of the ligaments and joint capsules of the spine. CONCLUSION: The axial rotation is initiated and maintained by the contralateral external obliques, ipsilateral latissimus dorsi and internal oblique. The ipsilateral erector spinae likely play a stabilizer role. The isometric torque is greater than the isokinetic, which decreases with increasing velocity. Even with decreasing torque, EMG progressively increases, indicating a disproportionally higher stress in the spinal connective tissues potentiating injury. The data presented here suggest that, for safety, load and velocity of rotation should be kept low.

Abdomen↗
PubMedDate not supplied

Power spectra of sternocleidomastoids, splenius capitis, and upper trapezius in oblique exertions.

BACKGROUND CONTEXT: There is relatively little known concerning the spectral profile of the cervical muscles, despite the fact that neck injury and pain are quite prevalent. PURPOSE: The objective of the study was to calculate and study the power spectral characteristics of the sternocleidomastoids, splenii capitis and upper trapezii in anterolateral flexion and posterolateral extension in a ramp contraction. STUDY DESIGN/SETTING: In a laboratory setting experiments were conducted to record surface electromyographic (EMG) data from six cervical muscles and power spectral variables obtained. PATIENT SAMPLE: Forty normal and healthy young adults (21 men, 19 women). OUTCOME MEASURES: Power spectral of EMG signals. METHODS: EMG data for the left and right isometric anterolateral flexion and posterolateral extension were acquired from the sternocleidomastoids, splenii capitis and upper trapezius bilaterally. The subjects were seated in an upright posture and exerted left and right anterolateral flexor and posterolateral extensor efforts from rest to their maximal voluntary contraction in a gradual linear ramp fashion using visual feedback as a guide. The force exerted and the surface EMG data were sampled at 1 kHz at every 10th percentile grade of contraction and the EMG data were subjected to the Fast-Fourier transform analysis. The median frequency (MF), mean power frequency (MPF), peak power and total power of all six cervical muscles were analyzed. RESULTS: In the anterolateral flexion the ipsilateral sternocleidomastoid and splenius capitis had a wider band of frequency, which further widened with increasing grade of contraction. The trapezius did not engage in the same manner or to the same magnitude. The MF of the sternocleidomastoid in the anterolateral flexion in both genders progressively increased, the splenius capitis remained relatively unchanged, and the upper trapezius declined with the increasing grades of contraction. CONCLUSIONS: There is no significant difference between the genders in spectral profile. There is a bilateral symmetry in spectral profile with reference to activity; however, they are significantly different in different activities for the same muscles. With increasing magnitude of contraction power, spectral density distribution increases and the median frequency decreases. These results can serve as a useful reference for painful necks. Restoration of power spectral characteristics may indicate normalcy, which cannot be gleaned by other EMG or force variables.

Adult↗