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At least 757 records · Page 42Linked to original sources
PubMed2002

The effect of mouthguard design on stresses in the tooth-bone complex.

PURPOSE: Mouthguards protect the tooth-bone complex from impact loads that occur during sporting activity. The aim of this study is to investigate the effects of varying mouthguard thickness and stiffness on the magnitude of tensile stresses in the tooth-bone-complex. METHODS: A two-dimensional, plane stress, finite element representation of a central maxillary incisor (CMI) is created. For validation purposes, displacements of the incisal edge of the unprotected tooth model are compared with in vivo displacements under similar loads. A protective mouthguard is then superimposed over the model with varied labial thickness (1-6 mm) and stiffness (9-900MPa) representing a range of designs available. A large horizontal static load of 500N is then applied to the anterior surface of the mouthguard and the resulting stresses in the tooth-bone complex are presented. It is suggested that this loading condition most accurately represent the situation occurring when a guarded tooth collides with a soft object (e.g. boxing glove). RESULTS: It is generally found that mouthguard thickness and stiffness are both desirable in terms of reducing stresses. However, the protection offered by the low-stiffness guards, regardless of thickness, is minimal. Since this low-stiffness (9MPa) is representative of the most common choice of material in mouthguard fabrication, such findings may cast doubt on the ability of popular mouthguards to redistribute stress. CONCLUSION: While few would disagree that these low-stiffness guards absorb shock during hard-object collisions (e.g. baseballs), they may not protect the tooth-bone during soft-object collisions (e.g. boxing gloves). In order to optimize their protective capabilities for a range of loads, the range of materials used in mouthguard construction may have to be reconsidered.

Equipment Design↗
PubMed2002

Physiological responses to high-speed, open-wheel racecar driving.

UNLABELLED: High-speed auto racing has been demonstrated to produce accelerated heart rate (HR) during competition. However, it has not been determined whether the increase in HR was due to physical work efforts or a result of emotional stress. PURPOSE: The purpose of this investigation was to examine the physiological responses associated with open-wheel automobile driving at competitive speeds. METHODS: Oxygen consumption and HR were assessed in seven professional automobile racing drivers during two incrementally paced driving sessions. A portable metabolic analyzer and EKG were directly attached to the subjects as they participated in driving tests on an oval speedway and a roadway course. Maximal physiological responses of the subjects were also determined during a graded treadmill test. RESULTS: During treadmill testing, maximal oxygen consumption (VO2max) ranged from of 42.0 to 59.7 mL x kg(-1) x min(-1) (mean +/- SD = 47.6+/-8.1). The road course and oval speedway testing at competitive speeds elicited mean VO2 values of 38.5 and 21.9 mL x kg(-1) x min(-1), respectively, which correspond to 79% and 45% of VO2max. Road course driving produced mean HR values of 152 beats x min(-1) with 142 beats x min(-1) recorded when driving at competitive speed on the speedway course. CONCLUSIONS: Professional open-wheel race drivers possess cardiorespiratory capacity similar to athletes participating in sports such as basketball, football, and baseball. The VO2 and HR responses to road course driving were similar to those previously reported in traditional sports settings. The findings of this study suggest that professional open-wheel racing drivers should be regarded as athletes that encounter significant physiological stresses.(2)

Adaptation, Physiological↗
PubMed1984

Acute prolapsed lumbar intervertebral disc. An epidemiologic study with special reference to driving automobiles and cigarette smoking.

An epidemiologic case-control study to identify risk factors for acute prolapsed lumbar intervertebral disc was undertaken in Connecticut during 1979-1981. This paper focuses on nonoccupational factors of possible etiologic significance. Persons in their 30s were affected most frequently. Among surgical cases, the ratio of men to women was 1.5 to 1, while among probable and possible cases not undergoing surgery, the male to female ratio was about 1 to 1. Cigarette smoking in the past year was associated with an increased risk for prolapsed disc. The greater the number of hours spent in a motor vehicle, the higher the risk. Use of Swedish and Japanese cars was associated with a lower-than-average risk, while use of other cars was associated with a higher-than-average risk. For each type of car, older cars were associated with higher risks than newer cars. Variables that did not affect the risk for prolapsed lumbar disc in this study included height, weight, number of pregnancies, number of children, frequency of wearing shoes with high heels, smoking cigars or pipes, and participation in baseball or softball, golf, bowling, swimming, diving from a board, tennis, bicycling or jogging.

Acute Disease↗
PubMed2001

Cervical spinal stenosis and sports-related cervical cord neurapraxia in children.

STUDY DESIGN: Congenital spinal stenosis has been demonstrated to contribute to cervical cord neurapraxia after cervical spinal cord injury in adult athletes. A sagittal canal diameter <14 mm and/or a Torg ratio (sagittal diameter of the spinal canal: midcervical sagittal vertebral body diameter) of <0.8 are indicative of significant cervical spinal stenosis. Although sports-related cervical spine injuries are common in children, the role of congenital cervical stenosis in the etiology of these injuries remains unclear. OBJECTIVES: The authors measured the sagittal canal diameter and the Torg ratio in children presenting with cervical cord neurapraxia resulting from sports-related cervical spinal cord injuries to determine the presence of congenital spinal stenosis. METHODS: A total of 13 children (9 male, 4 female) presented with cervical cord neurapraxia after a sports-related cervical spinal cord injury. Age ranged from 7 to 15 years (mean +/- SD, 11.5 +/- 2.7 years). The sports involved were football (n = 4), wrestling (n = 2), hockey (n = 2), and soccer, gymnastics, baseball, kickball, and pogosticking (n = 1 each). Lateral cervical spine radiographs were used to determine the sagittal canal diameter and the Torg ratio at C4. RESULTS: The sagittal canal diameter (mean +/- SD, 17.58 +/- 1.63 mm) and the Torg ratio (mean +/- SD, 1.20 +/- 0.24) were normal in all of these children. CONCLUSION: Using the sagittal canal diameter and the Torg ratio as a measurement of congenital spinal stenosis, the authors did not find evidence of congenital cervical spinal stenosis in a group of children with sports-related cervical spinal cord neurapraxia. The occurrence of cervical cord neurapraxia in pediatric patients can be attributed to the mobility of the pediatric spine rather than to congenital cervical spinal stenosis.

Adolescent↗
PubMed2003

The role of hip arthroscopy in the elite athlete.

Intraarticular hip disorders in the elite athlete are a relatively rare but serious potential consequence of high-level competition. Axial and torsional forces involving the hips of elite athletes place them at potentially higher risk for chondral injuries, labral injuries, or both. Ten patients (13 hips) had arthroscopy. Of the 10 patients, the average age was 24 years. Nine patients were men and one was a woman. Of the 13 (10 patients) arthroscopies done two cases were bilateral, and one patient had the same hip operated on twice. Seven of the patients were professional hockey players, one patient was a football player, one patient was a baseball player, and one patient was a golfer. All 13 hips (10 patients) had anterior labral tears, whereas two hips had anterior and posterior labral tears. Two hips had an average of four loose bodies, four had evidence of chondral lesions, and one had an anterior margin acetabular fracture. Twelve of 13 arthroscopies were successful; however, one patient had recurrent symptoms. There were no surgical complications. Hip arthroscopy is a safe and reproducible method to diagnose and treat intraarticular hip disorders in athletes, which facilitates earlier return to their respective sport.

Adolescent↗
PubMed2004

The development of intelligent, triage-based, mass-gathering emergency medical service PDA support systems.

The support systems for the Emergency Medical Services (EMS) at mass gatherings, such as the local marathon or large international baseball games, are underdeveloped. The purposes of this study were to extend well-developed, triage-based, EMS Personal Digital Assistant (PDA) support systems to cover pre-hospital emergency medical services and onsite evaluation forms for the mass gatherings, and to evaluate users ' perceived ease of use and usefulness of the systems in terms of Davis ' Technology Acceptance Model (TAM). The systems were developed based on an established intelligent triage PDA support system and two other forms the general EMS form from the Taipei EMT and the customer-made Mass Gathering Medical form used by a medical center. Twenty-three nurses and six physicians in the medical center, who had served at mass gatherings, were invited to examine the new systems and answer the TAM questionnaire. The PDA systems were composed of 450 information items within 42 screens in 6 categories. The results supported the potential for using triage-based PDA systems at mass gatherings. Overall, most of the subjects agreed that the systems were easy to use and useful for mass gatherings, and they were willing to accept the systems.

Adult↗
PubMed2003

Kidney and testicle injuries in team and individual sports: data from the national pediatric trauma registry.

PURPOSE: We define the risk of kidney or testicle injury in children who play contact sports. MATERIALS AND METHODS: National Pediatric Trauma Registry data from 50 United States pediatric trauma centers for 1990 to 1999 were analyzed. The data were from age groups 5 to 11, 12 to 14 and 15 to 18 years. Major abdominal injuries, injuries due to team and individual contact sports, and the site of injury were examined. RESULTS: Of the 81,923 cases 5,439 were sports related. Abdominal injuries occurred in 459 patients (0.56%), and were due to contact sports in 191. Team sports were involved in 184 cases, including football in 44%, hockey in 19%, baseball in 15%, soccer in 12% and basketball in 6%. Abdominal injury rate by age was 16% for 5 to 11-year olds, 42% for 12 to 14-year-olds and 42% for 15 to 18-year-olds. Most common was splenic injury at 50% of cases, kidney injuries occurred in 22% and no testicle injuries were reported. Football accounted for the most kidney injuries (62%). Kidney injuries were more common among older teenagers. No injuries led to nephrectomy. CONCLUSIONS: Abdominal injuries are rare in children who play team and individual contact sports. No testicular injuries were reported. Kidneys are most at risk in football. Splenic injuries are most common overall, although the risk to kidney and spleen is equal in basketball. No kidneys were reported as lost. These data should help families and schools when assessing risk to genitourinary organs during these activities.

Abdominal Injuries↗
PubMed2005

Athletic pubalgia: definition and surgical treatment.

INTRODUCTION: Athletic pubalgia, or "sports hernia," affects people actively engaged in sports. Previously described in high-performance athletes, it can occur in recreational athletes. It presents with inguinal pain exacerbated with physical activity. Examination reveals absence of a hernia with pubic point tenderness accentuated by resisted adduction of the hip. Diagnosis is by history and physical findings. Treatment with an internal oblique flap reinforced with mesh alleviates symptoms. METHODS: A retrospective review from December 1998 to November 2004 for patients with athletic pubalgia who underwent operative repair was performed. Descriptive variables included age, gender, laterality, sport, time to presentation, outcome, anatomy, and length of follow-up. RESULTS: Twelve patients, 1 female, with median age 25 years were evaluated. Activities included running (33%), basketball (25%), soccer (17%), football (17%), and baseball (8%). The majority were recreational athletes (50%). Median time to presentation was 9 months, with a median 4 months of follow-up. The most common intraoperative findings were nonspecific attenuation of the inguinal floor and cord lipomas. All underwent open inguinal repair, with 9 being reinforced with mesh. Four had adductor tenotomy. Results were 83.3% excellent and 16.7% satisfactory. All returned to sports. CONCLUSION: Diagnosis of athletic pubalgia can be elusive, but is established by history and physical examination. It can be found in recreational athletes. An open approach using mesh relieves the pain and restores activity.

Adolescent↗
PubMed2005

Surface-enhanced plasmon splitting in a liquid-crystal-coated gold nanoparticle.

We show that, when a gold nanoparticle is coated by a thin layer of nematic liquid crystal, the nanoparticle surface has a strong effect on the director orientation, but, surprisingly, this deformation can enhance the surface plasmon splitting. We consider three plausible liquid crystal director configurations in zero electric field: boojum pair (north-south pole configuration), baseball (tetrahedral), and homogeneous. From the discrete dipole approximation, we find that the surface plasmon splitting is largest for the boojum pair, and this result is in good agreement with experiment.

Journal Article↗
PubMed1995

Computer-assisted three-dimensional reconstruction of human dermal dendrocytes.

We attempted to characterize the three-dimensional structure of dermal dendrocytes and to clarify the spatial relationships between dermal dendrocytes and mast cells, macrophages, and nerves. Normal human adult skin (breast, n = 2) was routinely processed for electron microscopy. Every other section (about 50 per data set) was collected at 80-nm intervals traversing about 8 microns of tissue. Grids showing the same cells were photographed by electron microscopy at a magnification of 4000x. Based on the 10-20 photographs per data set, cell outlines were digitized into the reconstruction program at appropriate layers and aligned. Thin, elongated cytoplasmic "dendrites" of dermal dendrocytes in two-dimensional micrographs proved to be thin, membrane-bound flaps in three-dimensional reconstruction. For dermal dendrocytes concentrated about superficial vessels (perivascular dendrocytes), the flaps enshrouded the vessel wall, and for dermal dendrocytes directly beneath the epidermis (subepidermal dendrocytes), these flaps were aligned parallel to the dermal-epidermal junction. The three-dimensional feature of dermal dendrocytes (perivascular and subepidermal) is quite similar to that of perivascular adventitial veil cells, suggesting ultrastructurally identified perivascular dendrocytes and veil cells must be identical cells. In conventional ultrathin sections, 20-40% of perivascular dendrocytes and occasional subepidermal dendrocytes were closely associated with mast cells. When viewed by computer-assisted three-dimensional reconstruction, membrane flaps of dermal dendrocytes consistently shrouded mast cell membranes for 50-90% of their perimeter; mast cells resembled a ball in a baseball glove (dermal dendrocytes). Occasional dermal dendrocytes surrounded non-myelinated nerves in the superficial dermis. Membrane flaps also enabled dermal dendrocytes to present extensive areas to the plasma membranes of adjacent monocyte/macrophages. These findings indicate that dermal dendrocytes are non-dendritic cells that are spatially related to mast cells, monocyte/macrophages, microvessels, and nerves by their membranous flaps. This suggests the need for further study of functional interactions between these cells.

Adult↗
PubMed2004

How dogs navigate to catch frisbees.

Using micro-video cameras attached to the heads of 2 dogs, we examined their optical behavior while catching Frisbees. Our findings reveal that dogs use the same viewer-based navigational heuristics previously found with baseball players (i.e., maintaining the target along a linear optical trajectory, LOT, with optical speed constancy). On trials in which the Frisbee dramatically changed direction, the dog maintained an LOT with speed constancy until it apparently could no longer do so and then simply established a new LOT and optical speed until interception. This work demonstrates the use of simple control mechanisms that utilize invariant geometric properties to accomplish interceptive tasks. It confirms a common interception strategy that extends both across species and to complex target trajectories.

Animals↗
PubMed1992

Sun protection with hats.

The degree of sun protection provided by various styles of hat at different anatomical sites on the head was measured using model headforms and ultraviolet-sensitive film badges. It was found that hats with a small brim, such as the flat cap favoured by elderly male photosensitive patients, provided negligible protection at all sites apart from the vertex and forehead. Peaked baseball-style caps offer good protection to the nose but are relatively ineffective at other sites on the face. Hats with a wide (greater than 7.5 cm) brim are necessary in order to provide reasonable protection factors (greater than 3) around the nose and cheeks.

Face↗
PubMed2007

Commotio cordis--sudden cardiac death with chest wall impact.

Commotio cordis (CC), sudden death as a result of a blunt, often innocent-appearing chest wall blow, is being reported with increasing frequency. The clinical spectrum is diverse; however, a substantial number of cases occur in youth athletics. In events that occur during sport, victims are struck by projectiles regarded as standard implements of the game. Sudden death is instantaneous and victims are most often found in ventricular fibrillation (VF). Overall survival is poor; however, successful resuscitation can be achieved with early defibrillation. Autopsy is notable for the absence of any significant cardiac or thoracic injury. Development of an experimental model has allowed for substantial insights into the underlying mechanisms of sudden death. In anesthetized juvenile swine, induction of VF is instantaneous following chest wall blows occurring during a vulnerable window before the T wave peak. Crucial variables including the velocity of impact, impact location, and hardness of the impact object have been identified. Rapid left ventricular (LV) pressure rise following chest impact likely results in activation of ion channels via mechano-electric coupling. The generation of inward current via mechano-sensitive ion channels likely results in augmentation of repolarization and nonuniform myocardial activation, and is the cause of premature ventricular depolarizations that are triggers of VF in CC. While softer-than-standard safety baseballs reduce the risk of CC, commercially available chest protectors are ineffective in preventing CC. The development of more effective chest protectors and more widespread use of automated external defibrillators at youth sporting events are needed.

Death, Sudden, Cardiac↗
PubMed2000

Sports-related injuries in children.

OBJECTIVE: To describe the demographics and types of sports-related injuries (SRIs) in children. METHODS: The authors performed a retrospective chart review of children 5-18 years of age diagnosed as having an SRI in a pediatric emergency department (ED) during a two-year period. Patients were identified by ICD-9 codes. Data collected were age, sex, sport, ED interventions, consultations, mechanism, location, and injury type. Pairwise comparisons were reported as odds ratios with 95% confidence intervals. RESULTS: Six hundred seventy-seven SRIs fit the inclusion criteria; 480 of the patients were male (71%). The mean ages of the males and females were 13.0 years (SD +/- 3.0 yr) and 12.4 years (SD +/- 2.9 yr), respectively. The six most common sports implicated were basketball (19.5%), football (17.1%), baseball/softball (14.9%), soccer (14.2%), in-line skating (Rollerblading)/skating (5.7%), and hockey (4.6%). Sprains/strains (32.0%), fractures (29.4%), contusions/abrasions (19. 3%), and lacerations (9.7%) accounted for 90% of injury types. Pairwise comparison of the four injury types in the six sports listed showed significant associations for contusions/abrasions in baseball, sprains/strains in basketball, fractures in Rollerblading/skating, and lacerations in hockey. Age variance, including all sports, of the younger group (5-11 yr) in fractures and the older group (12-18 yr) in sprains was significant. The most common injury location was wrist/hand (28%), followed by head/face (22%) and ankle/foot (18%). Each had significant sport-specific predilections. Contact with person or object was the mechanism for >50% of the SRIs. Sport-specific mechanisms followed lines drawn from the sport-specific injury types and locations. CONCLUSIONS: The pediatric age group incurs a variety of injuries in numerous sports with diverse sex, age, mechanism, location, injury type, and sport-specific differences.

Adolescent↗
PubMed1984

Prevalence and distribution of traumatic injuries to the permanent teeth of Dominican children from private schools.

The purpose of this study was to describe by age and sex, the prevalence, etiology, distribution and type of injury to permanent incisors of children from private schools of Santo Domingo, Dominican Republic, located in the Caribbean archipelago. The sample consisted of 1633 children, 5-14 yr enrolled in several private schools of Santo Domingo. The prevalence of injury was 10.0% (5.0% in boys and 5.1% in girls). The largest number of injuries was found in the 5- and 6-yr-old children, followed by the 7- and 8-yr-olds. There was no significant difference in the number of teeth injured in both sexes (0.1%). The most common type of injury in both sexes was concussion (42.7%) with no significant difference between sexes (5.7%). The most common cause of injury in both sexes was falling against an object (77.8% in boys and 78.3% in girls). Most boys injured their teeth playing baseball (86.4%) and most girls playing on roller skates (72.3%). More girls suffered injuries (not significantly) with the ratio of boys to girls being 0.91 to 1.

Adolescent↗
PubMed2003

Assessing physical activity in adolescents: common activities of children in 6th-8th grades.

OBJECTIVES: To provide data for physical activity assessment in practice by describing the leisure time activities of adolescents and determining if the activities and the metabolic equivalents (MET levels) of those activities differ for boys and girls. DATA SOURCES: The study was conducted in five middle schools in three rural counties in North Carolina. Subjects were 1,211 6th, 7th, and 8th graders aged 11-14 (mean 12.2) years. Half (52.5%) were girls. The sample was 64% white, 24% African-American and 12% other races. RESULTS: The top five activities of boys were football, basketball, bicycling, running, and baseball; the top five activities of girls were talking, running, walking, bicycling, and dancing. The average MET was 5.3 for boys and 4.3 for girls (p = 0.000). By grade levels, 6th graders had an average MET of 4.9 and the MET of 8th graders was 4.5 (p < 0.05). Older youth, girls, and children of parents with more education reported significantly more sedentary activities than the other youth. IMPLICATIONS FOR PRACTICE: Physical activity is an integral component of overall health. Once activities and activity levels are known, current practices can be augmented or changed to accommodate improved understanding of physical activity. Because an active lifestyle is important in preventing obesity and other chronic conditions and for general health, nurse practitioners (NPs) should ask adolescents about their common activities and encourage them to continue the more vigorous activities and reduce time spent in sedentary pursuits. Prescriptive physical activity can be included for primary, secondary, or even tertiary prevention, thus crossing all levels of NP practice.

Adolescent↗
PubMed1997

The structure of nitric oxide synthase oxygenase domain and inhibitor complexes.

The nitric oxide synthase oxygenase domain (NOSox) oxidizes arginine to synthesize the cellular signal and defensive cytotoxin nitric oxide (NO). Crystal structures determined for cytokine-inducible NOSox reveal an unusual fold and heme environment for stabilization of activated oxygen intermediates key for catalysis. A winged beta sheet engenders a curved alpha-beta domain resembling a baseball catcher's mitt with heme clasped in the palm. The location of exposed hydrophobic residues and the results of mutational analysis place the dimer interface adjacent to the heme-binding pocket. Juxtaposed hydrophobic O2- and polar L-arginine-binding sites occupied by imidazole and aminoguanidine, respectively, provide a template for designing dual-function inhibitors and imply substrate-assisted catalysis.

Amino Acid Sequence↗
PubMed1988

Behavioral neurophysiology: insights into seeing and grasping.

One marvels at a batter's ability to hit a baseball traveling at 150 kilometers per hour or a monkey's skill in snatching a flying insect. Indeed, the ability of many animals to reach out, grasp, and manipulate objects is a feat of biological engineering unmatched by even state-of-the-art robots. But how are the objects of our attention chosen and how are the eyes and hands directed to it? Recent progress in behavioral neurophysiology has clarified some of the brain mechanisms at work.

Animals↗