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At least 577 records · Page 32Linked to original sources
PubMed1994

Evaluation of muscle force prediction models of the lumbar trunk using surface electromyography.

Optimization-based models for prediction of muscle forces in the lumbar region of the torso are used to estimate the forces acting on spinal motion segments, especially for asymmetric tasks. The objectives of this study were to determine (a) which of four torso model formulations best predicted the electromyographic data, (b) the difference in muscular contribution to spinal compression force for the four models, and (c) the effect of using the lowest possible muscle stress bound in the model formulation. An approach for the investigation of competing optimization model formulations was developed and was illustrated with electromyographic data from static asymmetric loading conditions. This method is based on (a) the choice of experimental conditions in which models predict decidedly different muscle forces, and (b) the ability to ensure that the experimental conditions are such that the minimum number of assumptions about the force-electromyogram relationship must be made in order to choose between competing model predictions. Of the four models analyzed, only the formulation with an objective function that was the sum of cubed muscle stresses predicted the electromyographic data acceptably. The muscular contribution to spinal compression force predicted by these models differed by as much as 160% for some experimental conditions. The use of the lowest possible muscle stress bound does not appear to predict muscle forces that are in agreement with electromyographic data.

Adult↗
PubMed2004

Novel RF coil geometry for lower extremity imaging.

A receive-only phased-array coil was designed to image the lower extremities. The array consists of four volume coils placed on two cylindrical formers. The coil array has the ability to image both legs simultaneously over a 40 cm longitudinal field of view (FOV). Experiments using phantoms show an increase in signal-to-noise ratio (SNR) in regions of interest through the center of the coil by an average factor of 2.8 over the body coil and 1.5 over the GE 4-channel torso array. In vivo data acquired from 10 subjects show that the X array provided similar SNR improvement in spin-echo images and more vascular details in angiographic images compared to the torso array.

Equipment Design↗
PubMed2006

32-element receiver-coil array for cardiac imaging.

A lightweight 32-element MRI receiver-coil array was designed and built for cardiac imaging. It comprises an anterior array of 21 copper rings (75 mm diameter) and a posterior array of 11 rings (107 mm diameter) that are arranged in hexagonal lattices so as to decouple nearest neighbors, and curved around the left side of the torso. Imaging experiments on phantoms and human volunteers show that it yields superior performance relative to an eight-element cardiac array as well as a 32-element whole-torso array for both traditional nonaccelerated cardiac imaging and 3D parallel imaging with acceleration factors as high as 16.

Algorithms↗
PubMed1986

Use of water pillows in reducing head shape distortion in preterm infants.

The purpose of this study was to determine the effectiveness of a water-pillow treatment in reducing bilateral head flattening of preterm infants. The subjects were 21 healthy infants of less than 36 weeks gestational+ age. Care of the experimental babies included supporting the head on a small water pillow and supporting the torso at the same level to avoid flexion or curvature of the spine; the control group received customary care. The ratios of the anterior-posterior diameter to the biparietal diameter were significantly different for the two groups (p less than .0005). The heads of the control infants became flattened on both sides, while those of the experimental babies maintained the round shape they had at admission to the unit. The findings support the use of a small water pillow, in combination with support for the torso, as a means of alleviating bilateral head flattening in preterm infants.

Beds↗
PubMed2001

Preoperative treatment with recombinant human growth hormone prevents ischemia reperfusion-induced diaphragmatic dysfunction.

BACKGROUND: Respiratory complications continue to be a major cause of morbidity and mortality following major vascular surgery. The recent UK Small Aneurysm Trial cited preoperative respiratory function as the major predictor of outcome following elective aortic surgery. AIM: The aim of this study was to investigate the effect of aortic clamping and revascularization on diaphragmatic muscle function in a small animal model and to evaluate the role of preoperative treatment with recombinant human growth hormone (rhGH) in preventing diaphragmatic muscle dysfunction. METHODS: Male Sprague-Dawley rats (n = 18) were randomized into one of three groups: control (n = 6) underwent laparotomy only; IR (n = 6) had a laparotomy with infrarenal cross-clamping for 30 min followed by lower torso revascularization for 2 h; IR + rhGH (n = 6) were treated with rhGH (Genotropin 0.3 IU/kg/day) for 5 days before laparotomy and aortic cross-clamping for 30 min followed by lower torso revascularization for 2 h. Diaphragmatic muscle contractile function was assessed ex vivo using electrical field stimulation in a tissue bath. RESULTS: Two hours of IR injury resulted in a significant impairment in diaphragmatic twitch (Control, 242.01 + 38.45 g; IR, 108.55 + 7.15 g). This impairment was prevented by pretreatment with rhGH (rhGH, 319.14 + 30.71 g; P < 0.01). Tetanic function was also significantly impaired by ischemia reperfusion injury (control, 605 + 77.63 g; IR, 228.12 + 14.38 g). Again, pretreatment with rhGH prevented this deterioration (IR + rhGH, 704.39 + 45.69 g; P < 0.05) compared with controls. CONCLUSION: The results of this study suggest that preoperative administration of rhGH may have a role in preventing the diaphragmatic dysfunction associated with infrarenal aortic cross-clamping and revascularization.

Animals↗
PubMedDate not supplied

How valid is adolescents' self-report as a way of assessing sun protection practices?

BACKGROUND: The accurate assessment of sun protective behaviors can assist in the effective targeting of preventive strategies. METHODS: This study explored the validity of self-report by adolescents in relation to parental/guardian reports using a scale to determine whether adolescents were accurately classified as adequately protected or not during the preceding weekend. The study sample was drawn from a school population and provided 53 matched adolescent and parental/guardian responses from 115 subjects (consent rate 46%). The validity of self-reports in relation to the level of protection afforded to a range of body parts (face, neck, shoulders, torso, etc.) was calculated. Calculations of sensitivity, which represented the proportion of cases in which the body part was classified as adequately protected by both the criterion reference and the self-report, and specificity, in which inadequate protection was confirmed by both the criterion reference and the self-report, were completed. In instances in which fewer than five observations fell into a cell, thereby limiting the accuracy of results, no measures were calculated. RESULTS: Measures of sensitivity for the use of sun protection were legs (59%), neck (79%), feet (79%), face (92%), and shoulders, torso, and upper arms (98%). In contrast measures of specificity were face (61%), legs (80%), and neck (87%). CONCLUSIONS: Although further studies of self-report methodologies with larger samples are required to verify these findings, the results suggest that adolescent self-report of solar protection is relatively valid and has the potential to be utilized with a degree of confidence to assess behavior.

Adolescent↗
PubMed1995

The topography of eccrine sweating in humans during exercise.

The purpose of this study was to investigate the distribution of steady-state sweating rates (msw), during stressful exercise and heat exposures. Six men completed 42-min trials: 2-min rest and 40-min cycling at 40% peak power in 36.6 degrees C (relative humidity 46.0%). The msw was monitored using ventilated capsules at the forehead, and at three additional sites. Repeat trials allowed monitoring from eleven skin surfaces. Auditory canal temperature (Tac) and 11 skin temperatures were measured. After normalising msw to the forehead response within subjects, differences in Tac and onset time thresholds, and transient and steady-state msw were examined. The pooled, lower torso msw onset [mean 45.5 (SEM 42.0) s] preceded that of the head [mean 126.5 (SEM 34.8) s, P < 0.05], but was not significantly different from the legs [mean 66.6 (SEM 25.7) s], upper torso [mean 80.2 (SEM 36.8) s] or arms [mean 108.6 (SEM 31.2) s]. Transient msw did not differ among regions (P = 0.16). Mean, steady-state forehead msw [3.20 (SEM 0.51) mg.cm-2.min-1] was not significantly greater than the scapula, forearm, hand, stomach and lower back msw (in descending order), but was greater than the chest [1.6 (SEM 0.2)], upperarm [1.6 (SEM 0.2)], calf [1.5 (SEM 0.3)] and thigh msw [1.0 (SEM 0.2), P < 0.05 for all comparisons]. The results did not support the caudal-to-rostral sweat onset evident during supine, resting heat stress. Equivalent Tac sweat thresholds existed between sites, while steady-state state msw topography varied among subjects and was not dominated by central regions.

Adult↗
PubMed1987

Changes in fitness and shipboard task performance following circuit weight training programs featuring continuous or interval running.

Pre- and post-physiological data were collected on 57 Navy men (mean age = 19.5 years) who participated in either circuit weight training/continuous run (CWT/CR) (N = 31) or circuit weight training/interval run (CWT/IR) (N = 26) programs. Measured variables included 4 measures of upper torso dynamic strength (one repetition maximum [1 RM] for arm curl, bench press, shoulder press, and lat pull-down); two measures of lower torso dynamic strength (1 RM) for knee extension and leg press); one measure of power (number of revolutions completed on an arm ergometer (Monark) at maximum drag); three measures of muscular endurance (number of repetitions at 60% 1 RM for bench press and leg press and maximal number of bent-knee sit-ups in 120 s); one stamina measure (time to exhaustion on a cycle ergometer (Monark) maximal work capacity [MWC] test; and three simulated shipboard tasks: manikin shoulder drag, open/secure a water tight door and paint bucket carry. Composite shipboard performance derived from the summed time (s) required to complete the three tasks was also calculated. Results show performance on the manikin shoulder drag and majority of evaluative fitness measures was significantly (p less than 0.05) enhanced following both circuit weight training/run formats. Significantly (p less than 0.05) higher values for shoulder press (F = 7.2), arm ergometer (F = 5.3), and sit-ups (F = 6.8) and lower values for leg press muscular endurance (F = 5.1) were observed in CWT/IR when compared to CWT/CR.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

A thermographic study of the effect of body composition and ambient temperature on the accuracy of mean skin temperature calculations.

The problem associated with using measurements from a small number of sites to determine mean skin temperature was investigated by studying variations in distributions of skin temperatures of the bare torsos of humans exposed to ambient temperatures of 18, 23, and 28 degrees C. Following a 60 minute equilibration period the temperatures of four regions (chest, abdomen, upper back, and lower back) were measured using both thermistors and an infra-red thermographic system. Regions of the torso usually represented by a single temperature exhibited significant point-to-point temperature variations especially in chilled subjects. Also an earlier finding was confirmed: in that larger variations in skin temperature distributions occur as body fat content increases. Caution must therefore be used in applying the concept of a mean skin temperature derived from a few select sites, especially with nude subjects who are chilled or have a high body fat content.

Adipose Tissue↗
PubMed2002

Body surface Laplacian mapping of atrial depolarization in healthy human subjects.

In the present study, we report body surface Laplacian mapping of atrial depolarization under sinus rhythm in 8 healthy male subjects. For each subject, 95 unipolar disk electrodes with inter-electrode distance of 2 cm were used to record simultaneously potential ECGs over the anterior chest. The Laplacian ECG was then estimated during the P wave using a novel spline Laplacian technique. The body surface potential map (BSPM) and body surface Laplacian map (BSLM) at different time instants or time intervals of the P wave were constructed and compared. The present results showed that the BSPMs during the P wave were characterized by the rotation of a pair of positive/negative potential distribution from right to left around the anterior torso. On the other hand, the corresponding BSLMs revealed more spatial details, including two positive activities (denoted as P1 and P2, appeared in all 8 subjects), and three negative activities (denoted as N1, N2, and N3, appeared in 7, 7, and 4 subjects, respectively). The separation of these activities and their evolving patterns were also compared and confirmed by computer simulation using a realistic geometry heart-torso model. The above findings may be directly related to the underlying activation sequence during atrial depolarization in healthy subjects, suggesting the potential clinical applications of the Laplacian ECG technique.

Adult↗
PubMedDate not supplied

The effects of acceleration on the mechanical impedance response of a primate model exposed to sinusoidal vibration.

Criteria for developing active and passive isolation mechanisms for reducing the effects of whole-body vibration exposure rely on a thorough understanding of the stiffness, damping, and resonance behaviors of the human or human surrogate body. Three Rhesus monkeys were exposed to seated whole-body sinusoidal vibration between 3 and 20 Hz at 0.69 and 3.47 msec-2 rms (0.1 and 0.5 g peak) accelerations. The mechanical impedance magnitude and phase were calculated as the ratio and phase relation between the transmitted force and input velocity, respectively, at the seat. The resultant profiles showed a significant decrease in the primary resonance frequency with increasing acceleration. At the lower acceleration level, a second lower impedance peak was observed at approximately 5 Hz. A three-mass, two degree-of-freedom model, which included upper torso and leg representation, was used to determine the mechanical parameters that best described the measured responses. The mean stiffness coefficients and the mean undamped natural frequencies associated with the upper torso and leg subsystems showed a significant decrease with increases in the acceleration level. The results of this study strongly suggested that nonlinear stiffness properties were responsible for the observed differences in the biodynamic response of the Rhesus monkey with acceleration level.

Acceleration↗
PubMedDate not supplied

Optimal placement of impedance epigastrography electrodes.

Impedance electrogastrography (IE) is a noninvasive method to assess gastric contractile activity. This indirect method uses a four-terminal impedance measuring method to determine impedance variations of the gastric region of the torso. These variations can be related to changes in the stomach shape and, therefore, to gastric contractions. Because the impedance variations are very small, the placement of the measuring electrodes on the skin is critical. In this study, a three-dimensional resistor model consisting of 4,466 resistors was used to simulate the human torso. The model was implemented on a personal computer, and the experimentally obtained optimal electrode locations were found to be superior to the commonly used ones. Measurements of volunteers confirmed these findings.

Body Mass Index↗
PubMed1996

Movement associated with high cerebral concentrations of isoflurane: no evidence of seizure activity.

PURPOSE: This study examined the effect of high cerebral concentrations of isoflurane on the electroencephalogram (EEG) and motor activity while using an experimental preparation in which isoflurane can be selectively delivered to the in situ goat brain. In a previous study we found that isoflurane (> 6%), when selectively delivered to the brain, was associated with spontaneous movement. METHODS: In each of six goats, the cerebral circulation was isolated and cannulae inserted into a carotid artery and the jugular veins to permit selective delivery of isoflurane using a bubble oxygenator-roller pump system. The EEG was measured while isoflurane (1.3%, 3% and 10-12%) was delivered to the brain; isoflurane concentration in the torso during these periods was 1.3%, 0.3% and 0.3% respectively. RESULTS: The EEG was active at isoflurane 1.3% but was isoelectric with spike activity at 3% and 10-12%; EEG power decreased from 32,249 +/- 15,241 microV2 (mean +/- sd) during the control period (isoflurane = 1.3%) to 1761 +/- 2435 microV2 when cranial isoflurane = 3%, and 3346 +/- 4780 microV2 when cranial isoflurane = 10-12% (P < 0.05). When cranial isoflurane concentration was 10-12%, with the torso isoflurane concentration at 0.3%, spontaneous motor activity occurred, including stiffening, extremity and jaw movement and blinking. The EEG returned to normal when isoflurane concentration was decreased to 1.3%. CONCLUSION: The presence of spontaneous movement with concomitant high cranial concentrations of isoflurane and isoelectric EEG is unexplained, but is consistent with a facilitatory effect of isoflurane on motor activity, presumably at a subcortical level.

Anesthetics, Inhalation↗
PubMed2005

Exposure to a rotating virtual environment during treadmill locomotion causes adaptation in heading direction.

The objective of this study was to investigate the adaptive effects of variation in the direction of optic flow, experienced during linear treadmill walking, on modifying locomotor trajectory. Subjects (n=30) walked on a motorized linear treadmill at 4.0 km h(-1) for 24 min while viewing the interior of a 3D virtual scene projected on to a screen 1.5 m in front of them. The virtual scene depicted constant self-motion equivalent to either (1) walking around the perimeter of a room to one's left (Rotating Room group) or (2) walking down the center of a hallway (Infinite Corridor group). The scene was static for the first 4 min and then constant rate self-motion was simulated for the remaining 20 min. Before and after the treadmill locomotion adaptation period subjects performed five stepping trials. In each trial they marched in place to the beat of a metronome at 90 steps min(-1) for a total of 100 steps while blindfolded in a quiet room. The subject's final heading direction (deg) and final X (fore-aft, cm) and final Y (medio-lateral, cm) positions were measured for each trial. During the treadmill locomotion adaptation period subjects' 3D torso position was measured. We found that subjects in the Rotating Room group, as compared with the Infinite Hallway group: (1) showed significantly greater deviation during post-exposure testing in the heading direction and Y position opposite to the direction of optic flow experienced during treadmill walking; and (2) showed a significant monotonically increasing torso yaw angular rotation bias in the direction of optic flow during the treadmill adaptation exposure period. Subjects in both groups showed greater forward translation (in the +X direction) during the post-treadmill stepping task that differed significantly from their pre-exposure performance. Subjects in both groups reported no perceptual deviation in position during the stepping tasks. We infer that viewing simulated rotary self-motion during treadmill locomotion causes adaptive modification of sensorimotor integration in the control of position and trajectory during locomotion, which functionally reflects adaptive changes in the integration of visual, vestibular, and proprioceptive cues. Such an adaptation in the control of position and heading direction during locomotion, because of the congruence of sensory information, demonstrates the potential for adaptive transfer between sensorimotor systems and suggests a common neural site for processing and self-motion perception and concurrent adaptation in motor output.

Adaptation, Physiological↗
PubMedDate not supplied

A new experimental hypertrophic scar model in guinea pigs.

Many aspects of the biology and effective therapy of proliferative scars remain undefined, in part due to a lack of an accurate, practical, reproducible, and economical animal model for systematically studying hypertrophic scars. This study was designed to investigate whether hypertrophic scar formation could be induced in guinea pigs by removal of the panniculus carnosus alone, and by a combination of the removal of the panniculus carnosus with application of coal tar afterwards. Whole thickness skin excision or deep partial thickness injury was used to create the lesions on intact skin. Different anatomic locations were tested in different groups. Scars thus developed were examined morphologically by light microscopy and electron microscopy (TEM and SEM) and biochemically by measuring the activity of glucose-6-phosphate dehydrogenase (G6PD) to check whether these scars had morphological and biochemical properties specific to hypertrophic scars. The albino guinea pigs used in this study were divided into three groups. Removal of the panniculus carnosus was performed from the ventral aspect of the torso in animals in groups I and II. On the skin overlying the area of panniculectomy, circular skin excision was performed in group I, and deep partial thickness burn injury was inflicted in group II, to see whether wounds would heal with hypertrophic scars. In group III, dorsal aspect of the torso were used and wounds were produced by circular skin excisions followed by panniculectomy on both sides but coal tar was applied to only one side. Tissue samples were taken from the scars that were hypertrophic in appearance, and from normal scars and normal skin for comparison. Light and electron microscopic examinations and G6PD activity measurements were performed on these samples. While hypertrophic scar development was not seen in group I and group II, scars with morphological and biochemical properties specific to hypertrophic scars developed in one third of animals in group III after healing of the wounds treated with coal tar. In conclusion, it is shown that it is possible to develop experimental hypertrophic scars in guinea pigs with morphological and biochemical properties similar to those of human proliferative scars. Therefore this model is a new, practical, and economical experimental animal model to study proliferative scars, although improvements are needed to increase yield.

Animals↗
PubMed2001

Sectional depiction of the pelvic floor by CT, MR imaging and sheet plastination: computer-aided correlation and 3D model.

The structures of the pelvic floor are clinically important but difficult to assess. To facilitate the understanding of the complicated pelvic floor anatomy on sectional images obtained by CT and MR imaging, and to make the representation more vivid, a computer-aided 3D model was created from a male and a female torso to develop a teaching tool. A male and a female cadaver torso were investigated by means of CT, MR imaging, and serial-section sheet plastination. A 3D reconstruction of the pelvic floor and adjacent structures was performed by fusion of CT and MR imaging data sets with sheet plastination sections. Corresponding sections from all three methods could be compared and visualized in their 3D context. Sheet plastination allows distinction of connective tissue, muscles, and pelvic organs down to a microscopic level. In combination with CT, MR imaging, and sheet plastination a 3D model of the pelvic floor offers a better understanding of the complex pelvic anatomy. This knowledge may be applied in the diagnostic imaging of urinary incontinence or prolapse and prior to prostate surgery.

Anatomy, Cross-Sectional↗
PubMed2002

Number of Langerhans immune cells in painful and non-painful human skin after shingles.

During injury or inflammation, paracrine sensitization of peripheral sensory neurons by immune cells contributes to the sensation of pain. It is less clear whether this neural sensitization contributes to neuropathic pain after neural injury as well. Shingles (herpes zoster) is a common disease that leaves some patients with prolonged neuropathic pain known as postherpetic neuralgia (PHN). Sensitization of cutaneous neurons has been hypothesized to contribute to PHN. Langerhans cells (LC), the Ia(+) macrophages of the skin, contact epidermal neurites and, when activated, synthesize molecules with the ability to sensitize axons. For these reasons, we examined morphological evidence for activation of LC in subjects with established PHN. We also evaluated the relationship between numbers of LC and nociceptive epidermal nerve endings; these are markedly reduced in PHN. We used design-based stereology to estimate the number of CD1a(+) LC in biopsies of painful and non-painful skin from ten adults with or without PHN after shingles on the torso. There were no differences in the number of LC in previously shingles-affected and normal-control skin biopsies. The number of LC also remained at normal levels in biopsies with near-loss of innervation from shingles. LC numbers were unrelated to the presence or severity of pain. These data suggest that neuropathic pain in established PHN is not associated with increased numbers of cutaneous macrophages, and that the number of cutaneous macrophages in skin from the human torso is independent of the number of epidermal nerve endings.

Aged↗
PubMed2001

Human body surface area: measurement and prediction using three dimensional body scans.

The development of three dimensional laser scanning technology and sophisticated graphics editing software have allowed an alternative and potentially more accurate determination of body surface area (BSA). Raw whole-body scans of 641 adults (395 men and 246 women) were obtained from the anthropometric data base of the Civilian American and European Surface Anthropometry Resource project. Following surface restoration of the scans (i.e. patching and smoothing), BSA was calculated. A representative subset of the entire sample population involving 12 men and 12 women (G24) was selected for detailed measurements of hand surface area (SAhand) and ratios of surface area to volume (SA/VOL) of various body segments. Regression equations involving wrist circumference and arm length were used to predict SAhand of the remaining population. The overall [mean (SD)] of BSA were 2.03 (0.19) and 1.73 (0.19) m2 for men and women, respectively. Various prediction equations were tested and although most predicted the measured BSA reasonably closely, residual analysis revealed an overprediction with increasing body size in most cases. Separate non-linear regressions for each sex yielded the following best-fit equations (with root mean square errors of about 1.3%): BSA (cm2) = 128.1 x m0.44 x h0.60 for men and BSA = 147.4 x m0.47 x h0.55 for women, where m, body mass, is in kilograms and h, height, is in centimetres. The SA/VOL ratios of the various body segments were higher for the women compared to the men of G24, significantly for the head plus neck (by 7%), torso (19%), upper arms (15%), forearms (20%), hands (18%), and feet (11%). The SA/VOL for both sexes ranged from approximately 12.m-1 for the pelvic region to 104-123.m-1 for the hands, and shape differences were a factor for the torso and lower leg.

Adult↗