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Biomedical subjects

Shrawan Kumar

Publications and source records attributed to Shrawan Kumar.

At least 37 records · Page 2Linked to original sources
PubMed2005

Quantification of isometric cervical strength at different ranges of flexion and extension.

BACKGROUND: Studies have demonstrated that cervical strength is affected by injury to the neck. Cervical strength measurements are influenced by the protocol used for the measurements. Previous studies have determined the isometric cervical strength only at a few degrees of range of neck motion. The present study was aimed at quantifying cervical strength at neutral, 25%, 50% and 75% of flexion and extension. METHODS: Using a correlation study design, 39 volunteers in the age range of 18-30 years were recruited in two sessions, one for flexion and the other extension. Their sequence was randomized. The cervical strength was measured using a force measuring device. The device was firmly bolted in the floor. A rotating metal tube was pivoted, adjustably counterweighted and attached to the device at one end and an immovable object with a load cell in its path at the other. The neck was positioned in the desired posture and isometric efforts were exerted on the horizontal resistance arm. FINDINGS: Cervical strength was found to be highest in the neutral posture for both flexion (19.8 N females and 31.4 N males) and extension (39.5 females and 45.1 males) and significantly decreased with an increasing angular deviation of the neck (P<0.01). Males exerted significantly higher forces than females. The overall flexion-extension ratio was 1:1.7 (P<0.01). INTERPRETATION: The maximum force was exerted in the neutral posture of the neck and it was directionally dependent being less in flexion than extension (P<0.01). Males were stronger than females. The findings may assist in targeting rehabilitation goals.

Adolescent↗
PubMed2005

Turning away from whiplash. An EMG study of head rotation in whiplash impact.

OBJECTIVE: To determine the response of the cervical muscles to whiplash-type perturbations through low-velocity frontal impacts when the head is rotated to the right and left. METHODS: Twenty healthy volunteers were subjected to increasing acceleration in low-velocity frontal impacts, randomly with head rotated either left or right. Bilateral EMG of the sternocleidomastoids, trapezii, and splenii capitis and acceleration of the sled, torso, and head were recorded. RESULTS: With either direction of head rotation at the time of impact, the muscle responses increased with increasing levels of acceleration (p < 0.01). The time to onset and peak electromyogram for all muscles progressively decreased with increasing levels of acceleration. With the head rotated to the left, the left trapezius generated 77% of its maximal voluntary contraction (MVC) EMG (more than double the response of other muscles). In comparison, the right trapezius generated only 33% of its MVC. The right sternocleidomastoid (25%) and left splenius muscles (32%), the ones responsible for head rotation to the left, were more active than their counterparts (the left sternocleidomastoid generated only 5% of its MVC EMG and the right splenius 9%). On the other hand, with the head rotated to the right, the right trapezius generated 71% of its MVC EMG, while the left trapezius generated only 30% of this value. Again, the left sternocleidomastoid (27% of its MVC EMG) and right splenius (28% of its MVC EMG), being responsible for head rotation to the right, were more active than their counterparts (the right sternocleidomastoid generated only 4% of its MVC EMG and the left splenius 13%). CONCLUSIONS: Frontal impacts tend to generate the most muscle activity in the ipsilateral trapezius muscle, increasing the risk of their injury.

Acceleration↗
PubMed2005

Effect of trunk flexion on cervical muscle EMG to rear impacts.

OBJECTIVE: To determine the effect of occupant positioning on the response of the cervical muscles to whiplash-type posterolateral impacts. METHODS: Twenty healthy volunteers underwent left posterolateral whiplash-type impacts with the volunteers seated "out-of-position". Electromyograms of the cervical muscles were recorded. RESULTS: Whether having the trunk flexed to the left or right at the time of impact, the muscle responses were low in magnitude, showing a trend to increasing EMG responses with increasing acceleration (P>0.05). The time to onset and time to peak electromyogram for most muscles showed a trend to progressively decrease with increasing levels of acceleration. With the subject flexed to the left, all muscles generated 31% or less of the maximal voluntary contraction electromyogram. With the subject flexed to the right, all muscles generated 27% or less of their maximal electromyogram. In both positions, the trapezii were the most active (P<0.05). Thus, having the trunk flexed out of neutral posture at the time of impact produces a very low magnitude cervical muscle response compared to impacts with the trunk in neutral posture. CONCLUSIONS: In the absence of bodily impact, the flexed trunk posture appears to produce a biomechanical response that would probably decrease the likelihood of cervical muscle injury in low velocity posterolateral impacts.

Biomechanical Phenomena↗
PubMed2005

Effect of trunk flexion on the occupant neck response to anterolateral whiplash impacts.

OBJECTIVE: The purpose of this study was to determine the response of the cervical muscles to increasing low-velocity anterolateral impacts with the volunteer's trunk flexed to the right and left. METHODS: A total of 20 healthy volunteers were subjected to left anterolateral impacts of 4.0, 7.6, 10.7, and 13.4 m/sec and, sequentially, with trunk flexed either left or right. Bilateral electromyograms (EMGs) of the sternocleidomastoids, trapezii, and splenii capitis were recorded. DESIGN: At an acceleration of 13.4 m/sec, with the trunk flexed left, the left trapezius generated 48% of its maximal voluntary contraction EMG, whereas the right trapezius (contralateral to the left anterolateral impact) generated 38% of this variable. All other muscle generated </=23% of their maximal voluntary contraction EMG, a significant difference from the trapezii (P = 0.005). Similarly, with the trunk flexed to the right under these same conditions, the left trapezius generated 26% and the right trapezius 35% of their maximal voluntary contraction EMG. Again, all other muscles generated significantly less EMG activity, </=22% (P = 0.009). Overall, the EMG responses were of low magnitude compared with known data with the trunk in neutral posture in this direction of impact. CONCLUSIONS: When the subject sits with trunk flexed out of neutral posture at the time of an anterolateral impact, the cervical muscle response is reduced compared with anterolateral impacts with the trunk in neutral posture.

Acceleration↗
PubMed2004

Cervical muscle response to whiplash-type right lateral impacts.

STUDY DESIGN: Nine healthy volunteers were subjected to right lateral impacts of 4.9, 8.8, 10.8, and 13.7 m/sec acceleration at two levels of expectation: expected and unexpected. OBJECTIVES: To determine the response of the cervical muscles to increasing low-velocity right lateral impacts and compare the quantitative effects of expected and unexpected impact. SUMMARY OF BACKGROUND DATA: The literature contains little information on the etiology of whiplash injuries. In particular, in vivo studies of the cervical muscular response and head-neck kinematics to lateral impacts are rare. A previous study of left lateral impacts suggests that the burden of impact is borne primarily by the muscles contralateral to the side of impact. 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 13.7 m/sec2, both sternocleidomastoids, both trapezii, and the right splenius capitis generated on average around 40% or less of their maximal voluntary contraction electromyogram in both the expected and unexpected impact conditions. The left splenius capitis (i.e., contralateral to the right lateral impact), however, generated 84% of its maximal voluntary contraction electromyogram (double the response of other muscles). Electromyographic variables were affected significantly by the levels of acceleration (P < 0.01). The time to onset and time to peak electromyogram time for all muscles decreased progressively with increasing levels of acceleration. The kinetic variables and the electromyographic variables regressed significantly on the acceleration (P < 0.01), and the head acceleration was affected significantly by expectation (P < 0.01). In response to right lateral impacts, muscle responses were generally greater, with higher levels of acceleration, and greatest for the splenius capitis muscle contralateral to the side of impact (P < 0.01). CONCLUSIONS: Because the muscular component of the head-neck complex likely plays a central role in the abatement of higher acceleration levels, it may be a primary site of injury in the whiplash phenomenon in lateral collisions, and specifically, the splenius capitis muscle contralateral to the side of impact is most likely to be injured. Being aware of an impact may reduce the degree of head perturbation.

Acceleration↗
PubMed2004

SIX1 mutations cause branchio-oto-renal syndrome by disruption of EYA1-SIX1-DNA complexes.

Urinary tract malformations constitute the most frequent cause of chronic renal failure in the first two decades of life. Branchio-otic (BO) syndrome is an autosomal dominant developmental disorder characterized by hearing loss. In branchio-oto-renal (BOR) syndrome, malformations of the kidney or urinary tract are associated. Haploinsufficiency for the human gene EYA1, a homologue of the Drosophila gene eyes absent (eya), causes BOR and BO syndromes. We recently mapped a locus for BOR/BO syndrome (BOS3) to human chromosome 14q23.1. Within the 33-megabase critical genetic interval, we located the SIX1, SIX4, and SIX6 genes, which act within a genetic network of EYA and PAX genes to regulate organogenesis. These genes, therefore, represented excellent candidate genes for BOS3. By direct sequencing of exons, we identified three different SIX1 mutations in four BOR/BO kindreds, thus identifying SIX1 as a gene causing BOR and BO syndromes. To elucidate how these mutations cause disease, we analyzed the functional role of these SIX1 mutations with respect to protein-protein and protein-DNA interactions. We demonstrate that all three mutations are crucial for Eya1-Six1 interaction, and the two mutations within the homeodomain region are essential for specific Six1-DNA binding. Identification of SIX1 mutations as causing BOR/BO offers insights into the molecular basis of otic and renal developmental diseases in humans.

Amino Acid Sequence↗
PubMed2004

Cervical muscle response to whiplash-type right anterolateral impacts.

Frontal impacts are a common cause of whiplash injury. Yet, volunteer studies of the cervical muscular response and head-neck kinematics to frontal impacts are uncommon, and specifically, the effect of an offset (anterolateral) frontal impact on the resultant muscle responses is unknown. The purpose of this study was to determine the response of the cervical muscles to increasing low-velocity frontal impacts offset by 45 degrees to the right, and to compare the quantitative effects of expected and unexpected impact. Ten healthy volunteers were subjected to frontal impacts, offset by 45 degrees to the subject's right, of 5.1-, 8.7-, 12-, and 13.7-m/s(2) peak 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. At a peak acceleration of 13.7 m/s(2), with an unexpected impact, the contralateral trapezius (i.e., left trapezius in a right anterolateral impact) generated 83% of its maximal voluntary contraction electromyogram, whereas all other muscles generated 50% or less of this variable. Although it generated less EMG, the splenius capitis muscle also tended to show an asymmetric EMG response, with the left (contralateral) splenius capitis generating a higher percentage (46%) of its maximal voluntary contraction electromyogram than the ipsilateral (right) splenius capitis. In comparison, the sternocleidomastoid muscles behaved symmetrically and generated 25% or less of this variable under all impact conditions. Similarly, the times to onset and times to peak electromyogram for the contralateral (left) splenius capitis and (left) trapezius progressively decreased with increasing levels of acceleration (p<0.01). Subjects exhibited lower levels of their maximal voluntary contraction electromyogram when the impact was expected (p<0.01). The kinetic variables and the electromyographic variables regressed significantly on the acceleration (p<0.01). In response to right anterolateral impacts, muscle responses were greater with higher levels of acceleration, and more specifically, when a frontal impact is offset to the subject's right, it results in not only increased EMG generation in the contralateral trapezius, but the splenius capitis contralateral to the direction of impact also bears part of the force of the neck pertubation. Expecting or being aware of imminent impact plays a role in reducing muscle responses in low-velocity anterolateral impacts.

Acceleration↗
PubMed2004

Ergonomics and biology of spinal rotation.

Spinal rotation, though being a very common motion of the body, is poorly understood. Furthermore, this motion and the extent of its development is unique to the human. Beyond the extent of its need in common activities, spinal rotation is a destabilizating motion for an inherently unstable structure. Spinal rotation has been argued to be an essential feature for an efficient bipedal gait. Also, it provides leverage to the upper extremities in delivering a forceful impact. An artificial restriction/elimination of spinal rotation resulted in significantly shorter stride length, slower walking velocity, and higher energy consumption in walking (p < 0.05). Spinal rotation also decreases the amount of force the spinal muscles can generate (to 25% of spinal extension). However, its extensive employment in industrial activities has been associated with 60.4% of back injuries. It is further stated that the amount of scientific information currently available is inadequate to biomechanically model the spinal response in a working environment. For example, when the spine is pre-rotated, a further rotation in the direction of pre-rotation decreases the force production significantly (p < 0.01) and increases the EMG activity significantly (p < 0.01) but the pattern changes with effort in the opposite direction. This and other properties (described in the paper) render biomechanical models inadequate. Muscle activation pattern and neuromotor behaviour of spinal muscles in flexion/extension and rotation of the spine are significantly different from each other (p < 0.01). The localized fatigue in different spinal muscles in the same contraction is significantly different and has been called differential fatigue. Finally, the trunk rotation, being pivotal for bipedal locomotion has brought many back problems to the human race.

Abdominal Muscles↗
PubMed2004

Electromyographic and kinematic exploration of whiplash-type neck perturbations in left lateral collisions.

STUDY DESIGN: Seven healthy volunteers were subjected to left lateral impacts of 4.8, 7.9, 11, and 13.7 m/s acceleration at two levels of expectation: expected and unexpected. OBJECTIVES: The purpose of this study was to determine the response of the cervical muscles to increasing low-velocity left lateral impacts, and to compare the quantitative effects of expected and unexpected 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 lateral impacts are rare. METHODS: Bilateral electromyograms of the sternocleidomastoids, trapezii, and splenii capitis were recorded bilaterally. 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/s, the sternocleidomastoids and trapezii generated approximately <or=50% of their maximal voluntary contraction electromyogram in both the expected and unexpected impact conditions. Study participants exhibited lower levels of their maximal voluntary contraction electromyogram when the impact was expected. The splenius capitis behaved similar to these muscles in the expected condition, but when the impact was unexpected, the splenius capitis muscle contralateral to the impact (i.e., right splenius in a left lateral impact) generated 94% of its maximal voluntary contraction electromyogram. 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, splenii capitis, and trapezii on the side contralateral to the side of impact progressively decreased with increasing levels of acceleration. The onset time and peak electromyogram time for the sternocleidomastoid, splenii, and trapezii on the same side of impact progressively increased with increasing levels of acceleration. The kinetic variables and the electromyographic variables regressed significantly on the acceleration (P < 0.01). In response to left lateral impacts, muscle responses were greater with higher levels of acceleration, greater with unexpected impact conditions, and greatest for the splenius capitis muscle contralateral to the side of impact. CONCLUSIONS: 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 in lateral collisions. Expecting or being aware of imminent impact may play a role in reducing muscle responses in low-velocity impacts.

Acceleration↗
PubMed2004

Perceived physical stress at work and musculoskeletal discomfort in X-ray technologists.

A structured questionnaire/interview was designed to explore demographic, personal, occupational and occupational health factors as well as recreational physical activities which can affect X-ray technologists' musculoskeletal symptoms. This questionnaire was piloted for clarity and validity. Subsequently, a random sample of 20 volunteer participants (18 female, 2 male) from two University hospitals were administered the questionnaire in the presence of the investigators to ensure that questions were correctly understood. The data obtained were analysed for magnitude, duration and frequency of activities and for severity, duration and recurrence of morbidity. The X-ray technologists in the sample were found to be a young group of professionals ranging from between 20 - 54 years of age. Eighty-nine per cent of the technologists were physically active and 44% indulged in physical recreational activities. Despite the young age and active life style, the X-ray technologists had significant and diverse musculoskeletal problems; 83% of technologists had backache and 39% of the female technologists had neck pain and 28% shoulder pain. The majority of technologists had suffered multiple episodes of pain. Fifty per cent of the female sample and both male volunteers suffered from upper extremity pain.

Adult↗
PubMed2004

Vibration in operating heavy haul trucks in overburden mining.

The objective of this study was to determine if the vibration in sagittal (x), coronal (y) and vertical (z) axes of the seat pan of the heavy haul trucks used in overburden mining, and the vibration experienced by the drivers at the third lumbar and seventh cervical vertebral levels in operating these trucks exceeded the ISO standards, thereby posing threat to safety. A new and an old truck of two different makes and different carrying capacities (200 and 300 series) were instrumented with a triaxial accelerometer on the seat pan. Fourteen drivers (8 male and 6 female) were instrumented with a triaxial accelerometer at C7 and L3 spinous processes. The vibration at the seat pan, C7, and L3 levels were recorded using an onboard computer with PCMCIA card and, compared against the ISO standards. The vertical vibration of the seat pan in the entire sample ranged from a low of .37 m/s2 to a high of 11.73 m/s2. The vibration at the lumbar level in the sample ranged between .34 and 2.72 m/s2. The values for cervical level vertical vibration in the sample ranged between .2 and 2.22 m/s2. The gender of the driver, truck make, and it's carrying capacity did not have a significant effect on the vibration. However, the body weight of the driver, the segment of the truck and the site of measurement revealed significant differences in vibration (p < 0.001). Out of a total 36 combinations (4 trucks x 9 recording locations) the seat pan vertical vibration exceeded the ISO standards 8 times for males and 9 times for females. The lumbar vertebral vertical vibration in males exceeded ISO standards 12 times and in females 11 times. The cervical vertebral vertical vibration exceeded ISO standards once in females only. However, in sagittal and coronal planes the whole body vibration exceeded the ISO standards many times. Heavy haul trucks (240 and 320 ton capacity) frequently generated vibrations in excess of ISO standards in overburden mining operation representing a health hazard.

Adult↗
PubMed2004

Cervical muscle response to right posterolateral impacts.

OBJECTIVE: To test the hypothesis that the head kinematic and the cervical muscle EMG responses to unexpected impacts of increasing low-velocity in the posterolateral direction will be greater than to expected impacts. DESIGN: Ten healthy volunteers were subjected to right posterolateral of 5.0, 8.6, 12.2, and 15.4 m/s2 acceleration in expected and unexpected conditions. BACKGROUND: The effect of a posterolateral impact on the cervical muscle responses is unknown. METHODS: Bilateral EMG of the sternocleidomastoids, trapezii, and splenii capitis were recorded and compared. The acceleration of the chair, torso, and head was recorded and compared. RESULTS: At an acceleration of 15.4 m/s2, the sternocleidomastoids generated the highest EMG in the unexpected impact conditions with lower percentages for the expected impact (50% of their maximal voluntary contraction). The splenii exhibited between 30% and 40% EMG, the trapezii generated approximately 25%. The EMG was significantly affected by the levels of acceleration (P < 0.01) for the sternocleidomastoids and splenii. The time to onset and peak EMG for all muscles progressively decreased with increasing levels of acceleration and regressed significantly on it (P < 0.01). Head accelerations were greater in the unexpected impacts (P < 0.5). CONCLUSIONS: The cervical muscles play a primary role in posture control. They may be a at risk of injury in whiplash especially in unexpected impacts. In the case of the right posterolateral impacts the sternocleidomastoids and splenii show a differentially higher response compared to the trapezii (P < 0.5). This may suggest an increased risk of injury to these muscles. RELEVANCE: The results presented contribute to an understanding of head and neck responses in posterolateral impacts.

Acceleration↗
PubMed2004

Measurement of angular wrist neutral zone and forearm muscle activity.

OBJECTIVES: To determine the forearm muscles activity in different wrist deviated positions and wrist neutral zone, and to assess the self-selected resting position without visual feedback. BACKGROUND: Wrist deviation occurs in almost all industrial and office jobs. This has been deemed hazardous for carpal tunnel syndrome. Proper resting wrist position is likely to decrease the hazard for carpal tunnel pressure. METHODS: Twenty blindfolded subjects without history of hand/forearm musculoskeletal disorders participated in the study. The EMG of the forearm muscles (flexor carpi radialis, flexor carpi ulnaris, extensor carpi radialis and, extensor carpi ulnaris) in deviated and neutral wrist postures was recorded at a sampling rate of 1 kHz. Also, wrist neutral zone at rest was measured using a custom-made calibrated uniaxial electrogoniometer. One-way ANOVA with repeated measures was used in order to find the impact of wrist deviation on muscles activity. RESULTS: The participants positioned their wrist in rest at 7 degrees -9 degrees extension and 5 degrees -7 degrees ulnar deviation. Significantly higher EMG activity was recorded for each muscle in the wrist deviated postures when compared to neutral position (P < 0.001). CONCLUSIONS: Self selected wrist neutral posture decreased the muscle activity significantly. Placement of wrists in neutral zone is expected to reduce risk of injuries.

Adult↗
PubMed2004

Cervical muscle response to posterolateral impacts--effect of head rotation.

BACKGROUND: Rear impacts may be offset, and may also occur with the head rotated at impact. 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 right, but also with the head rotated either right or left. METHODS: Twenty healthy volunteers underwent right posterolateral impacts of 4.6, 8.0, 11.0, and 13.1 m/s2 acceleration with head turned right or left. Electromyograms of the sternocleidomastoids, trapezii, and splenii capitis were recorded, as were acceleration of the sled, torso, and head of the participant. FINDINGS: At an impact acceleration of 13.1 m/s2, with head rotated to the right, the left sternocleidomastoid and the contralateral (to rotation) trapezius and splenius capitis generated more electromyogram activity than their counterparts (P < 0.05). Following impacts with the head rotated to the right, the left sternocleidomastoid generated 67% of its maximal voluntary electromyogram, and the right sternocleidomastoid 5% of the maximal voluntary electromyogram, whereas the remaining muscles did not generate more than 31% of the maximal voluntary contraction electromyogram. In impacts with head rotated left, the right sternocleidomastoid generated 53% of its maximal voluntary electromyogram, and the left splenius capitis and left trapezius showed more electromyogram activity than their counterparts (P < 0.05). INTERPRETATION: Head rotation in a right posterolateral impact modifies the cervical response mainly by generating an asymmetry in the paired sternocleidomastoid electromyograms. This may asymmetrically affect the risk of injury to the sternocleidomastoids. An understanding of the muscular response to rear-impacts of different types and the effect of head rotation at the time of impact is relevant to understanding the mechanism of acute whiplash injury and may be helpful to develop targeted treatments and preventative measures.

Acceleration↗
PubMed2004

Working postures: a literature review.

Working postures are addressed in many papers in the ergonomics field but, surprisingly, scientific literature dealing with working posture itself is not common; knowledge has been elusive. This article reviews the working postures literature. Selected papers published in the English language before March 2003 including the phrase "working postures" in the title, abstract, or keywords were searched in the PubMed, Scirus, and Science Direct databases and reviewed. The literature provides evidence that working postures and musculoskeletal health are related. This relationship is supported by the overexertion, differential fatigue, and cumulative load theories of musculoskeletal injuries' precipitation. Goniometers, inclinometers, photographic techniques, electrogoniometers, and video recording systems are the means that are most often used to measure working postures. Information about working postures need to be collected and analyzed in a more systematic way in order to contribute for a deeper understanding of the relationship between working postures and work-related musculoskeletal disorders. This information will help to improve the control and rehabilitation of these highly prevalent disorders.

Cumulative Trauma Disorders↗
PubMed2004

Evidence of progression and fluctuation of hearing impairment in branchio-oto-renal syndrome.

We retrospectively analysed long-term serial audiometry data from patients with branchio-oto-renal (BOR) syndrome to show the features of progression and fluctuation in hearing impairment and relate the findings to age and magnetic resonance imaging (MRI) findings in the petrosal bones. Thirty-two clinically affected BOR patients from six Dutch families (A-F) were included. Audiograms were available in 24 cases, covering followup intervals of between 3 and 30 years, and suitable for individual statistical analysis in 16 cases: 14 cases also had MRI findings. Significant progression in hearing impairment was found in 10 cases, while findings of significant fluctuation were made in seven cases. These findings did not clearly correlate with MRI findings. Substantial fluctuation occurred only in cases followed at a relatively young age. Patients with an enlarged endolymphatic duct and/or sac showed significantly higher sensorineural hearing thresholds than those with either normal MRI findings or cochlear/labyrinthine hypoplasia with or without enlarged duct or sac. We conclude that progressive, fluctuant hearing loss occurred in some BOR patients; however, only young patients showed substantial threshold fluctuation. BOR patients with an enlarged endolymphatic duct and/or sac on MRI seemed to be predisposed to developing more severe hearing impairment.

Adolescent↗
PubMed2004

Electromyographic and kinematic exploration of whiplash-type left anterolateral impacts.

BACKGROUND: Volunteer studies of the cervical muscular response and head-neck kinematics in response to frontal impacts are uncommon. Moreover, the effect of a frontal impact offset to the left on the resultant muscle responses is unknown. OBJECTIVE: The purpose of this study was to determine the response of the cervical muscles to increasing low-velocity frontal impacts offset by 45 degrees to the left and to compare the quantitative effects of expected and unexpected impact. METHODS: Nine healthy volunteers were subjected to frontal impacts, offset by 45 degrees to the subject's left, of 5.0, 8.7, 11.3, and 15.6 m/s2 of acceleration at two levels of expectation: expected and unexpected. Bilateral electromyograms (EMGs) 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: Subjects tended to exhibit lower percentages of their maximal voluntary contraction EMG when the impact was expected. When the impact was unexpected, and at an acceleration of 15.6 m/s2, the splenius capitis muscle contralateral to the impact (ie, right splenius in a left anterolateral impact) generated 95% of its maximal voluntary contraction EMG, whereas the left splenius (ipsilateral to the left anterolateral impact) generated only 43% of this variable. Under these same conditions, the trapezii responded symmetrically, generating approximately 80% of their maximal voluntary contraction EMG. At an acceleration of 15.6 m/s2, the sternocleidomastoids generated approximately 37% of their maximal voluntary contraction EMG in both the expected and the unexpected impact conditions. EMG (such as time to peak EMG) and kinematic variables were significantly affected by the levels of acceleration (P < 0.001) and expectation status (P < 0.05). The time to onset of the EMG for the splenii capitis and trapezii progressively decreased with increasing levels of acceleration. In response to left anterolateral impacts, muscle responses were greater with higher levels of acceleration and greatest for the splenius capitis muscle contralateral to the side of impact. The head acceleration response was greater in the unexpected than in the expected condition (P < 0.05). CONCLUSIONS: Because the muscular component of the head-neck complex plays a central role in the abatement of higher acceleration levels, this is likely a primary site of injury in the whiplash phenomenon in frontal collisions. More specifically, when a frontal impact is offset to the subject's left, it not only results in increased EMG generation in both trapezii, but the splenius capitis contralateral to the direction of impact also bears part of the force of the neck perturbation. Expecting or being aware of imminent impact may play a role in reducing muscle responses in low-velocity anterolateral impacts.

Acceleration↗
PubMed2003

A biomechanical analysis of loads on x-ray technologists: a field study.

The aim of the study was to determine the biomechanical loads on radiographers in their occupation. Seven x-ray technologists (one male and six females with combined mean age 32.5 years, mean height 164.6 cm and mean weight 68.3 kg) volunteered to be videotaped while doing their jobs (same as normal and others in a simulated manner). X-ray technologists perform all these tasks regularly every day as part of their assignments. The magnitude of the load handled was measured on weighing scale and recorded. The videotape was played back in the laboratory and the initial and final frames of the tasks investigated were frozen for analysis. The joint angles, the height and weight of the technologist, and the load on their hands (weighed before the task was performed) were input into the 3-D Michigan static strength model for calculation of the lumbosacral load and loads on the joints of the extremities. The lumbosacral compression and shear loads were calculated for 16 tasks commonly performed by all x-ray technologists. The x-ray technologists' work was found to be biomechanically quite demanding. Tasks such as repositioning patients horizontally and lifting a patient from a wheelchair caused lumbosacral compression loads of 7,936N and 8,335N respectively, in which exceeded the maximum permissible limit set by NIOSH in 1981. The action limit defined by NIOSH was exceeded by other tasks. It is also of interest that the majority of the x-ray technologists were female.

Adult↗