The relationship between EMG activity and extensor moment generation in the erector spinae muscles during bending and lifting activities

The relationship between EMG activity and extensor moment generation in the erector spinae muscles was investigated under isometric and concentric conditions. The full-wave rectified and averaged EMG signal was recorded from skin-surface electrodes located over the belly of the erector spinae at the levels of T10 and L3, and compared with measurements of extensor moment. The effects of muscle length and contraction velocity were studied by measuring the overall curvature (theta) and rate of change of curvature (d theta/dt) of the lumbar spine in the sagittal plane, using the '3-Space Isotrak' system. Isometric contractions were investigated with the subjects pulling up on a load cell attached to the floor. Hand height was varied to produce different amounts of lumbar flexion, as indicated by changes in lumbar curvature. The extensor moment was found to be linearly related to EMG activity, and the 'gradient' and 'intercept' of the relationship were themselves dependent upon the lumbar curvature at the time of testing. Concentric contractions were investigated with the subjects extending from a seated toe-touching position, at various speeds, while the torque exerted on the arm of a Cybex dynamometer was continuously measured. Under these conditions the EMG signal (E) was higher than the isometric signal (E0) associated with the same torque. E and E0 were related as follows: E0 = E/(1 + A d theta/dt), where A = 0.0014 exp (0.045P) and P = percentage lumbar flexion. This equation was used to correct the EMG data for the effect of contraction velocity. The corrected data were then used, in conjunction with the results of the isometric calibrations, to calculate the extensor moment generated by the erector spinae muscles during bending and lifting activities. The extensor moment can itself be used to calculate the compressive force acting on the lumbar spine.     

Intramuscular pressure in the leg and thigh related to tensile strap force during knee brace wear. An experimental study in man

The role of mitochondria in the energy metabolism of Babesia microti and Babesia rodhaini was investigated. A variety of mitochondrial inhibitors showed greater sensitivity to B. microti than to B. rodhaini. Additionally, alpha-glycerophosphate- and succinate-cytochrome c reductase activities in the crude mitochondrial fraction from B. microti were substantially higher than those from B. rodhaini. Our results suggest that the mitochondria of these parasites possess a series of "classical" apparati for energy production and their relative functional role may be quantitatively greater in B. microti when compared with B. rodhaini.     

Sports injuries in footballers related to defects of posture and body mechanics

The objective of this study was to investigate possible relationships between the incidence of sports injury and the existence of body mechanics defects in players of various codes of football. Injuries were recorded prospectively over a 24 month period. Fifteen aspects of body mechanics were evaluated at the start of the study using a specially developed photogrammetric technique known to have high reliability and sensitivity. It was found that subjects who suffered from ankle injuries had lower mean scores for ankle mechanics than the non-injured players. Knee injuries were found to be associated with lumbar lordosis and sway back. Subjects who suffered from muscle strains had a higher incidence of lumbar lordosis, sway back and abnormal knee inter-space. Back injuries were associated with poor shoulder symmetry, scapulae abduction, back asymmetry, kyphosis, lordosis and scoliosis. Subjects who suffered from two or more injuries had lower overall body mechanics scores than the other subjects. In general, it was found that the incidence of ankle, back, knee and muscle injuries was influenced by the presence of defects of body mechanics. These results suggest that intervention to improve body mechanics would be likely to reduce the incidence of sports injuries in football.     

Comparison of surface EMG signals between electrode types, interelectrode distances and electrode orientations in isometric exercise of the erector spinae muscle

The influence of electrode type, interelectrode distance (IED) and electrode orientation on EMG signals from the paraspinal muscles was investigated. Bipolar electrodes were placed at distances 2, 3, 4, 6 and 8 cm over the erector spinae in the cranio-caudal direction ("in series") as well as in the direction perpendicular to it ("in parallel"). Ten subjects performed 5 s isometric contractions of the erector spinae at 20, 40, 60, 80 and 100% MVC by pulling upward on a handlebar attached to the floor. RMS EMG signals were analyzed for mean average amplitude (AA). Mean total power (TP) and mean median frequency (MF) of the raw EMG signal were determined using fast Fourier transform. In addition to graded loading, sustained fatiguing contractions were performed from which TP and MF were obtained. With increasing IED the AA and TP increased while MF decreased. Although a trend towards higher AA, TP and MF was found for electrodes "in series", as compared to those "in parallel", the difference never reached significance. It is concluded that consistent information about muscle activity was obtained with Miniature Biopotential Skin Electrodes and 14445C Hewlett-Packard electrodes independently from IED or orientation. Orientation "in parallel" prevented the electrodes from sliding during muscle contraction. The third tested type, electrodes developed in the Neuromuscular Research Center, Boston, proved extremely sensitive to movement.     

The role of intra-abdominal pressure in spinal unloading

Previous studies on how an increase in intra-abdominal pressure (IAP) effects the loading of the lumbar spine during back extension show diverging results. From a critical review of the literature we deduce a simplified, but consistent, model of the mechanisms involved in IAP-induced unloading of the lumbar spine. The model is then expanded by explicitly incorporating equilibrium equations for the pressurised abdomen and the abdominal wall. It is shown that the unloading effect of IAP can be viewed as that of a pressurised column of fixed cross-sectional area, between the rib cage and pelvis. Different abdominal forms are examined and a form with zero longitudinal curvature is found to have some important mechanical benefits for the generation of IAP-induced alleviation of compressive loading of the lumbar spine.     

Comparison of intrathoracic and intra-abdominal measurements of central venous pressure

BACKGROUND: Complications can arise from standard intrathoracic central venous pressure (CVP) measurements in critically ill, mechanically ventilated patients. We have assessed the feasibility of catheterisation by the femoral route to measure CVP in the abdomen (ACVP). We compared measurements by the standard jugular or subclavian route (TCVP) with simultaneous ACVP measurements by the femoral route. METHODS: Between June, 1994 and May, 1995, we recruited 20 critically ill adult patients with various disorders; all patients already had a TCVP line in situ. We placed a femoral catheter in the inferior vena cava close to the right atrium under electrocardiographic guidance. The catheter position was confirmed (and corrected if necessary) by chest radiography. CVP was measured from both sites hourly for 6 h. Positive end-expiratory pressure, mean airway pressure, and intra-abdominal pressure were recorded simultaneously. FINDINGS: One patient was excluded because radiography showed that the catheter position was incorrect. For 133 paired measurements of ACVP and TCVP in the remaining 19 patients, the mean difference was 0.45 mm Hg (SD 0.89: 95% Cl 0.30-0.60); the limits of agreement were -1.33 to 2.23 mm Hg (-1.63 to 2.53). We found a small tendency for the difference between ACVP and TCVP to increase as positive end-expiratory pressure and mean airway pressure increased; the difference was statistically, but not clinically, significant. INTERPRETATION: Our study showed that for clinical purposes CVP can be measured by a femoral catheter placed in the abdominal inferior vena cava near the right atrium. This approach can replace standard TCVP measurements in critically ill, mechanically ventilated patients.     

Carbon dioxide volume and intra-abdominal pressure determination before the creation of a pneumoperitoneum

The associated stress of an ostomy experience can threaten a patient's security and sense of control. One major stressor is the influence of uncertainty, when patients lack a clear perception of what will happen and are unable to define meaning or personally interpret information bombarding them from the complex health care system. Mishel's Uncertainty in Illness Theory offers the ET nurse a practical framework for understanding how the patient attaches meaning to illness cues and how the ET nurse can positively affect the desired adaptation process. Because the patient trusts the ET nurse's expertise and experience, the nurse can help the patient to understand the ostomy experience and perceive its structure. As a credible authority, the ET nurse has the expert power to facilitate patient coping and adaptation by minimizing ambiguity through individualized education, counseling, and support while simultaneously constructing a sense of order and predictability for both patient and family.     

Changes in the contractile and bioelectrical activities of the rat small intestine under increased intra-abdominal pressure

A relationship was established between the increased intra-abdominal pressure and decreased electrical and mechanical motor activity of the small intestine in rats. Possible pathophysiological mechanisms are discussed. A model was developed for estimation of the electrical and motor activity of the small intestine in rats, which can be used for experimental studies of conditions where intra-abdominal pressures can be elevated.     

Handwriting posture and cerebral organization: How are they related?

Since J. Levy and M. Reid (see PA, Vols 57:5149 and 61:12570) first reported an association between handwriting posture and cerebral lateralization, a number of studies related to this issue have appeared in the literature. There is currently a great deal of controversy regarding the nature of the association between handwriting posture and brain organization. It is argued that this controversy loses much of its force when clinical data regarding functional lateralization in left-handers are taken into account. The relevant background on brain organization in left-handers, Levy and Reid's findings and studies related to their findings, and Levy and Reid's speculations with respect to possible interpretations of their data and research bearing on those speculations are reviewed and discussed. (2 p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is blood pressure related to kidney size and shape?

OBJECTIVE: To examine the relationship between blood pressure and the size and shape of the kidneys in healthy volunteers from the community. DESIGN: A cross-sectional community-based study of normal volunteers in Portsmouth City, Hampshire, UK. SUBJECTS: Subjects numbered 185 (99 female), aged 19-66 years. RESULTS: Blood pressure was higher in men, and in those with higher body mass index. Both systolic and diastolic blood pressure were correlated with the derived kidney volume. However, when corrected for age, sex and BMI the relationship was not statistically significant. Blood pressure correlated inversely with the width : length ratio of the left kidney. CONCLUSIONS: Blood pressure was not correlated with kidney size in this group of adults.     

Familial and metabolic factors related to blood pressure in Pima Indian children

High blood pressure, abnormal glucose tolerance, and obesity are frequently associated with each other, but the mechanism of these associations is poorly understood. Studying them in children may help in understanding the pathogenesis of hypertension. Blood pressure, height, weight, and plasma glucose and serum insulin concentrations during a 75-g oral glucose tolerance test were measured in 1,698 Pima Indian children aged 6-17 years who participated in an ongoing epidemiologic study. Weight relative to height was used as an index of obesity. The parents of many of the children were also examined. Fasting and 2-hour glucose and insulin concentrations, adjusted for age, sex, and relative weight, were positively related to systolic blood pressure but not to diastolic blood pressure. Relative weight, 2-hour glucose, and fasting insulin concentrations were independently and significantly associated with systolic blood pressure in a stepwise regression analysis that included age and sex. After parental hypertension was taken into account, maternal but not paternal non-insulin-dependent diabetes mellitus, controlled for the child's relative weight and glucose and insulin concentrations, was significantly associated with higher blood pressure in children. The stronger association with maternal diabetes suggests a greater sharing of environmental factors between mother and child than between father and child, but familial similarities in obesity and glucose and insulin concentrations, the diabetic intrauterine milieu, and shared environmental factors probably all contribute to this association.     

Effects of intra-abdominal pressure on pharmacokinetics and tissue distribution of doxorubicin after intraperitoneal administration

Increased hydrostatic pressure in solid tumor nodules decreases the penetration of chemotherapy into cancerous tissue. This is true for both i.v. and i.p. chemotherapy. The purpose of this study was to determine the influence of increasing intra-abdominal pressures on the pharmacokinetics and tissue distribution of doxorubicin administered i.p. Four groups of 10 Sprague Dawley rats were given i.p. doxorubicin (4 mg/kg) during 60 min combined with no pressure (control), 10, 20 and 30 mm Hg pressures. During the course of i.p. chemotherapy, peritoneal fluid and blood were sampled. Two other groups of 10 rats received the same dose of i.p. doxorubicin during 10 min combined with no pressure and 30 mm Hg pressure. At the end of experiments animals were sacrificed and tissue samples were collected. Doxorubicin concentrations in peritoneal fluid, plasma and tissues were determined by HPLC. Pharmacokinetic studies showed that increased intra-abdominal pressures of 10, 20 and 30 mm Hg did not alter peritoneal fluid AUCs, the plasma AUCs and the peak ratios of i.p. doxorubicin when compared to the control group (no pressure). A subset analysis of high intra-abdominal pressure groups (20 and 30 mm Hg) versus control group showed statistically significant differences in peritoneal fluid AUCs, plasma AUCs and AUC (peritoneal fluid/plasma) ratios. For all groups, the highest tissue concentrations of doxorubicin were found in tissues associated with the parietal peritoneum: the bladder, the abdominal wall and the diaphragm. After 10 min of i.p. chemotherapy, the group treated with 30 mm Hg pressure showed a significant increase of doxorubicin concentrations in these tissues as compared to the control group. This significant increase of tissue doxorubicin concentrations was not found after 60 min of pressure with i.p. chemotherapy; prolonged intra-abdominal pressure was associated with a high incidence of intestinal ischemia. In conclusion, intra-abdominal pressure of 20 and 30 mm Hg significantly decreased the AUC ratios of i.p. doxorubicin but concomitantly increased tissue uptake of doxorubicin in bladder, diaphragm and abdominal wall during the first 10 min of i.p. administration. These findings may have significance in the design of improved strategies to increase tissue concentrations of chemotherapy delivered by an i.p. route.     

Experimental study of the effect of intra-abdominal pressure during laparoscopy on tumour growth and port site metastasis

BACKGROUND: The influence of raised intraperitoneal pressure during laparoscopy on tumour growth and port site metastasis is still unknown. METHODS: Tumour growth of colonic adenocarcinoma DHD/K12/TRb was measured after laparoscopy with carbon dioxide at different pressures (0, 5, 10 and 15 mmHg) in a rat model. Cell kinetics were determined after incubation with carbon dioxide (0, 5, 10 and 15 mmHg) in vitro (n=60). Additionally, tumour growth was measured subcutaneously and intraperitoneally 4 weeks after laparoscopy at different intraperitoneal pressures (5, 10 and 15 mmHg) (n=100). RESULTS: In vitro tumour growth decreased significantly after incubation with carbon dioxide at 10 and 15 mmHg compared with a pressure of 0 or 5 mmHg. In vivo, mean(s.d.) intraperitoneal tumour weight was significantly increased after laparoscopy at 5 mmHg (919(1085) mg) and at 10 mmHg (1274(1523) mg) (P< 0.05), but decreased again after laparoscopy with an intraperitoneal pressure of 15 mmHg (731(929) mg) compared with the control group (365(353) mg) (P=0.3). Mean(s.d.) subcutaneous tumour growth was promoted after laparoscopy at 5 mmHg (172(234) mg), at 10 mmHg (190(253) mg) and at 15 mmHg (178(194) mg) compared with controls (48(33) mg) (P < 0.05). CONCLUSION: In vitro, raised intraperitoneal pressure leads to suppression of tumour growth. In vivo, intraperitoneal tumour growth is suppressed only by higher pressure (15 mmHg). Subcutaneous tumour growth is stimulated by carbon dioxide independently of the intraperitoneal pressure.     

Efficacy of hyaluronidase in reducing increases in intraocular pressure related to the use of viscoelastic substances

OBJECTIVE: To evaluate the efficacy of hyaluronidase in preventing increases in intraocular pressure related to injections of hyaluronan-containing viscoelastic substances. METHODS: Twenty-five white rabbits were divided into 5 groups. In groups 1 through 4, 0.15 mL of aqueous humor was removed and replaced with 0.10 mL of a viscoelastic substance in both eyes. Additionally, 10 units of hyaluronidase (0.05 mL) was injected in the anterior chamber of the right eye, whereas the left eye was injected with a volumetrically equivalent dose of balanced saline solution. Viscoelastic substances tested were Healon and Healon GV (Pharmacia & Upjohn, Kalamazoo, Mich), Viscoat (Alcon Laboratories, Fort Worth, Tex), and Ocucoat (Storz Ophthalmics, Clearwater, Fla). In group 5, right eyes were injected with 10 units of hyaluronidase and the left eyes were treated with balanced saline solution. RESULTS: After injections of viscoelastic substance, intraocular pressure rose rapidly, reaching a peak at approximately 46 hours after injection and returning to preinjection levels within 24 hours. Hyaluronidase significantly decreased intraocular pressure when used with Healon, Healon GV, and Viscoat, but not with Ocucoat. When injected in the absence of viscoelastic, hyaluronidase appeared to decrease intraocular pressure, but this result was not statistically significant. CONCLUSIONS: Injections of hyaluronidase into the anterior chamber of rabbits effectively prevent increases in intraocular pressure induced by hyaluronan-containing viscoelastic substances. This effect may be related to the ability of hyaluronidase to cleave hyaluronan moieties.     

Is nondipping in 24 h ambulatory blood pressure related to cognitive dysfunction?

OBJECTIVE: Associations between the outcome of 24 h ambulatory monitoring and cognitive performance were studied in order to evaluate the potential relevance of ambulant blood pressure status to brain function. It was hypothesized that a small daytime-night-time difference in mean blood pressure (nondipping) is associated with reduced cognitive performance, in line with studies in hypertensive subjects that have reported associations between nondipping and target-organ damage. METHODS: The study followed a cross-sectional design and was part of a larger research programme on determinants of cognitive aging (Maastricht Aging Study, MAAS). A group of 115 community residents aged 28-82 years was recruited from a general practice population and screened for cardiovascular events and medication use. All underwent 24 h blood pressure monitoring. Cognitive performance was measured with tests of verbal memory, attention, simple speed and information processing speed. RESULTS: Mean daytime or night-time levels of both systolic and diastolic blood pressure were unrelated to cognitive outcome, when age, sex and educational level were controlled for. Differences between mean daytime and night-time blood pressure (based on both narrow and wide measurement intervals for day and night-time periods) were positively associated with memory function (5-9% of additional variance explained) and one sporadic positive association was found on the sensorimotor speed score (4%). Nondippers (n=15) showed lower levels of both memory and sensorimotor speed scores. CONCLUSIONS: Ambulatory blood pressure status was not associated with cognitive performance. A reduced nocturnal blood pressure drop was associated with quite specific cognitive deficits, but the underlying mechanism remains to be determined.     

Strategies to decrease the incidence of intra-abdominal recurrence in resectable gastric cancer

Two main approaches are suggested to improve treatment results in resectable gastric cancer: extended lymphadenectomy and adjuvant antitumour therapy. Progress is to some extent stalled by the perception of gastric cancer as a pathophysiologically uniform disease; it has been demonstrated, however, that there are variants of gastric cancer associated with predominantly intra-abdominal spread or with haematogenous metastases. Recent clinicopathological studies have provided information about the mechanisms of this metastatic diversity. A review of clinical trials suggests that no single method of treatment can efficiently address all variants of gastric cancer spread, but new treatment strategies may be based on defining the pathophysiological variant of gastric cancer and selecting adjuvant therapy according to the most probable mode of tumour spread. Treatment should start with surgery which includes a 'reasonably' extended lymphadenectomy aimed at achieving an increased rate of curative resection and more accurate staging. Risk factors for peritoneal spread of tumour require the perioperative use of intraperitoneal chemotherapy. Subsequent adjuvant therapy may be indicated in patients at high risk of further cancer spread or occult metastases, as determined by pathological examination of the resected specimen.     

Effect of posture, route of respiration, and negative pressure on palatal muscle activity in humans

Sleep apnea is worse in the supine posture and is associated with retropalatal airway narrowing or occlusion. We have, therefore, examined the effects of posture, negative pressure, and route of respiration on palatal muscle activity in 13 nonsnoring awake male subjects by using electromyography. Electromyographic activity of the levator palatini and palatoglossus was expressed as a percentage of maximum activity. Both the levator palatini (P = 0.002) and palatoglossus (P = 0.002) exhibited phasic inspiratory activity. Overall, posture did not affect the levator palatini (F = 1.58; P = 0.23) or palatoglossus (F = 0.98; P = 0.34) activity, but analysis by route of respiration showed the palatoglossus to be more active when the subjects were nose breathing supine (F = 6.64; P = 0.02). Levator palatini activity was lower when nose breathing was compared with mouth breathing in both the erect and supine postures (F = 6.67; P < 0.02). Nose breathing with the mouth held open caused an increase in palatoglossal activity (P = 0.04). Negative-pressure application (0 to -12.5 cmH2O) caused significant increases in levator palatini (P < 0.001) and palatoglossus (P < 0.001) activity, 100 ms after pressure stimulus, irrespective of route. However, the palatoglossus required significantly greater negative pressures to cause activation when applied via the nose compared with the mouth (P < 0.05). These observations indicate that the levator palatini and palatglossus have respiratory activity and are reflexly activated by negative pressure.     

Relationship of posture and age to urinary protein excretion

The influence of posture and age on urinary protein excretion was studied in 120 normal men volunteers. The supine excretion rate was less than 140 mug/min in all but two people (median value 38 mug/min) and tended to increase with age. The excretion rate decreased on quiet standing in 80% of people, which corresponded to a fall in creatinine-clearance. In the remaining 20% protein excretion increased on standing but generally remained within normal limits and was dissociated from changes in creatinine clearances. This increase was more prevalent in younger people and may represent a phenomenon analogous to orthostatic proteinuria, differing only quantitatively.