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PubMed1998

Kinematics of the knee joint in deep flexion: a radiographic assessment.

The purpose of this study is to describe the kinematics of normal knees in vivo, assessed in deep flexion, using bi-planar radiographs. Antero-posterior and lateral views were obtained from five healthy males during three sequential positions of kneeling. In the first position, the subject knelt with the knees fully flexed (deep flexion between 150 and 165 degrees) and torso upright. In the second position, the subject bowed forward to an intermediate position (about 120 degrees of knee flexion). In the third position, the subject bowed further until his head touched the floor, supporting the upper torso with hands and with the knees flexed at about 90 degrees. The results show that past 135 degrees of knee flexion, the patella cleared the femoral groove and was in contact only with the condyles. For these particular postures, and during deep flexion, motion of the femur on the tibia did not reveal the classical femoral 'roll back'. Rather the lateral femoral condyle rolled further over the postero medial aspect of the lateral tibial plateau while contact of the medial femoral condyle occurred more anteriorly, but still in the posterior part of the medial plateau. This asymmetric rolling motion indicated an element of internal tibial rotation. Furthermore, the tibia was found to articulate with the femur at the most proximal points of the condyles in deep flexion. These data on the kinematics and contact characteristics of the tibio-femoral joint must be considered in any approach to design for a Deep Flexion Knee Implant.

Adult↗

PubMed2000

Attenuation smear: a 'paradoxical' increase in counts due to attenuation artifact.

BACKGROUND: Attenuation is a well recognized cause of reconstruction artifacts in SPECT imaging. Occasionally, we have noted an increase in activity extending from the apical septal portion of the ventricle in women with significant breast attenuation. Although the idea that attenuation can produce an increase in activity on the reconstructed images seems paradoxical at first, it is consistent with the process of filtered back projection. METHODS: We filled a cardiac phantom with 1 mCi of Technetium-99m, placed it in a water filled anthropomorphic torso phantom and imaged it over a 180 degree orbit. Next, a breast phantom designed to simulate a significant degree of breast attenuation was placed on the torso phantom and imaging was repeated. The images were reconstructed first using conventional filtered back projection then with maximum likelihood. RESULTS: When the phantoms with and without breast attenuation were reconstructed using filtered back projection and compared, the phantom with breast attenuation had a large 'smear' of activity extending anteriorly from the apical septal wall which was very similar to the abnormalities previously noted in clinical images; the phantom without breast attenuation had no such defect. This artifact was significantly less prominent when the images were reconstructed using the maximum likelihood technique. CONCLUSIONS: Attenuation artifact can also produce a seemingly paradoxical increase in counts on the reconstructed image but this phenomenon is consistent with the workings of filtered back projection.

Artifacts↗

PubMed2003

Detection of the fingerprint of the electrophysiological abnormalities that increase vulnerability to life-threatening ventricular arrhythmias.

Reduction of sudden death requires accurate identification of patients at risk for ventricular tachycardia (VT) and effective therapies. The Multicenter Unsustained Tachycardia Trial and Multicenter Automatic Defibrillator Implantation Trials demonstrate that the implantable cardioverter defibrillator impacts favorably on the incidence of VT in patients with myocardial infarction, underscoring the need to detect the electrophysiologic abnormalities required for the development of VT. Methods used for this purpose include: Holter monitoring, ejection fraction, signal-averaged ECG, heart rate variability, T-wave alternans, baroreflex sensitivity, and programmed stimulation. Performance of each method alone has demonstrated high-negative but low-positive predictive values. Recent studies confirm that their use in combination augments performance.A second approach for improving performance has been to reexamine how well each method detects the electrophysiological derangements that lead to VT. Our recent work has focused on the signal-averaged ECG. Judging from transmural maps of ventricular activation during VT and sinus rhythm obtained from patients, late potentials fail to detect completely signals from myocardium responsible for VT. To obviate this limitation we developed an approach based on inferred epicardial potentials in the frequency domain from 190-surface ECGs using individualized heart-torso models. Torso geometry and electrode positions are measured with a 3-armed digitizer. The location of cardiac structures is determined using echocardiography. The pericardial surface is approximated by a sphere that encloses the heart. Epicardial potentials are inferred using the boundary element method with zero-order Tikhonov regularization and the Composite Residual Smoothing Operator over the QRS complex. Studies are underway to determine if analysis of bioelectrical signals enveloping arrhythmogenic tissue improves identification of patients vulnerable to VT.

Arrhythmias, Cardiac↗

PubMed1998

The influence of a breakfast meal on the assessment of body composition using bioelectrical impedance.

OBJECTIVE: To investigate the effect of a breakfast meal on bioelectrical impedance (BI). DESIGN: Three separate interventions. SETTING: A university based study. SUBJECTS: Young, healthy volunteers recruited from staff. Twenty-nine subjects (11 men, 18 women), ten subjects (two men and eight women) and 13 subjects (2 men and 11 women) completed the first, second and third protocol, respectively. INTERVENTIONS: Total body BI (protocol 1) or both total body BI and segmental BI (namely arm, leg or torso BI); (protocol 3) was measured in the fasting state and for up to 5 h after the consumption of a breakfast meal containing 28% energy from fat. In the second protocol, total body BI was measured in the same way on two occasions after subjects consumed isocaloric meals containing either 28% energy or 4% energy from fat. RESULTS: Consumption of a 2300 kJ meal was followed by a significant (P = 0.0002) decrease in BI (95% confidence intervals 12.5 and 35.3), a change which occurred 2 h after the meal and continued until 5 h, irrespective of meal fat content. The fall in total body BI was accounted for primarily by a fall in the BI of the limbs, with virtually no contribution from the torso. CONCLUSION: To ensure consistency in the interpretation of BI for body composition analysis, it is important that measurements are made in the fasting state.

Adult↗

PubMed2001

Blunt trauma to scrotum in men with spinal cord injury after they had completed rehabilitation in a spinal unit.

STUDY DESIGN: A report of three men with spinal cord injury (SCI) who sustained blunt trauma to scrotum after they had completed rehabilitation in the spinal unit. OBJECTIVES: To raise awareness amongst health professionals regarding: (1) mechanism of scrotal trauma in men with SCI (2) need for prompt assessment of scrotal injury (3) measures to be taken by men with SCI and their carers to prevent injury to the scrotum. SETTING: Regional Spinal Injuries Centre, Southport, England. CASE REPORTS: (1) A 31-year-old with C-6 tetraplegia sustained traumatic haematocele as he squashed his right testis while he jumped on to a toilet seat in a hurry for bowel movement. (2) A 28-year-old male with T-7 paraplegia sat on his left testis while transferring on to a car seat. (3) A boxer dog jumped on to the scrotum of a 40-year-old male with T-8 paraplegia, while he was lying on his bed. CONCLUSIONS: Men with SCI are at high risk of sustaining trauma to scrotum during transfers. The scrotum may be squashed by the weight of the body during transfers, or the scrotum may be trapped between the thighs or under the torso. Men with SCI or their carers should check after each transfer that the scrotum is not trapped between the thighs or under the torso. The health professionals should encourage men with SCI to update their transfer skills at regular intervals in order to prevent trauma to the scrotum during transfers. Blunt trauma to scrotum requires prompt evaluation by ultrasonography so that appropriate treatment can be instituted without delay.

Accidents, Traffic↗

PubMed2001

Pro- and anti-inflammatory cytokine release in open versus endovascular repair of abdominal aortic aneurysm.

BACKGROUND: Pro- and anti-inflammatory cytokine release occurs with abdominal aortic aneurysm (AAA) repair although the relative contribution of each is currently poorly understood. Ischaemia-reperfusion injury is thought to play a greater role following open (OR) than endovascular (ER) repair, with resultant greater perioperative morbidity. METHODS: Thirty-two patients undergoing OR (n = 16) and ER (n = 16) of AAA were studied. Systemic venous (SV) blood was taken at induction (baseline), 0 h (last clamp off), 4, 24, 72 and 144 h, and femoral venous (FV) blood (indwelling catheter; lower torso venous effluent) at 0, 4 and 24 h. The cytokines interleukin (IL) 6, IL-8 and IL-10 were measured in these samples. RESULTS: In OR, SV and FV IL-6 increased from baseline to a peak at 24 h (SV 589 pg/ml (P = 0.001 versus baseline) and FV 848 pg/ml (P = 0.05)) before declining at 144 h. In ER, there was a similar pattern but the increase was smaller (24 h: SV 260 pg/ml (P = 0.003 versus baseline) and FV 319 pg/ml (P = 0.06)) at all equivalent timepoints compared with OR. IL-8 peaked earlier (4 h) from baseline in both groups before declining by 144 h, and significant differences between SV and FV were seen only in the OR group. IL-10 levels peaked in both groups at 24 h before declining at 144 h, and there were no significant locosystemic differences between the groups. CONCLUSION: Venous pro-inflammatory cytokine changes (IL-6) are consistent with significantly greater lower-torso reperfusion injury in patients undergoing OR. Smaller responses were seen after ER (IL-6 and IL-8), although both groups showed a similar anti-inflammatory response (IL-10); this pro- and anti-inflammatory imbalance may account for the increased morbidity associated with OR.

Aged↗

PubMed2004

What is the optimal device for carbon dioxide deairing of the cardiothoracic wound and how should it be positioned?

OBJECTIVES: To compare recently described insufflation devices for efficient carbon dioxide (CO(2)) deairing of the cardiothoracic wound and to determine the importance of their position. DESIGN: Experimental and clinical. SETTING: A cardiothoracic operating room at a university hospital. PARTICIPANTS: A full-size torso with a cardiothoracic wound and 10 patients undergoing cardiac surgery. INTERVENTIONS: Insufflation of CO(2) into the wound cavity at 2.5, 5, 7.5, and 10 L/min with a multiperforated catheter and a 2.5-mm tube with either a gauze sponge or a gas-diffuser of polyurethane foam at its end. The devices were tested when positioned at the level of the wound opening and 5 cm below and after exposure to fluid. MEASUREMENTS AND MAIN RESULTS: Deairing was assessed by measuring the remaining air content at the right atrium. With the multiperforated catheter, the gauze sponge, and the gas-diffuser, the lowest median air content in the torso was 8.4%, 2.5%, and 0.3%, respectively (p < 0.001), when positioned inside the wound cavity. When exposed to fluid, the gauze sponge and the multiperforated catheter immediately became inefficient (70% and 96% air, respectively), whereas the gas-diffuser remained efficient (0.4% air). During surgery, the gas-diffuser provided a median air content of 1.0% at 5 L/min, and 0.7% at 10 L/min. CONCLUSIONS: For efficient deairing, CO(2) has to be delivered from within the wound cavity. The gas-diffuser was the most efficient device. In contrast to a gas-diffuser, a multiperforated catheter or a gauze sponge is unsuitable for CO(2) deairing because they will stop functioning when they get wet in the wound.

Aged↗

PubMed2000

Effects of heart position on the body-surface electrocardiogram.

Previous studies have examined the influence of body position, respiration, and habitus on body surface potentials. However, the authors could only estimate the sources of the effects they documented. Among the proposed origin of changes in body surface potentials from those studies were the position of the heart, alterations in autonomic tone, differences in ventricular blood volume, and variations in torso resistivity. The goal of this study was to investigate specifically the role of geometric factors in altering body surface potentials and the electrocardiogram. For this, we used experiments with an isolated, perfused dog heart suspended in a realistically shaped electrolytic torso tank. The experimental preparation allowed us to measure epicardial and tank surface potentials simultaneously, and then reconstruct the geometry of both surfaces. Our results mimicked some of the features described by previous investigators. However, our results also showed differences that included considerably larger changes in the peak QRS and T-wave amplitudes with heart movement than those reported in human studies. We detected smaller values of root-mean-squared variability from heart movements than those reported in a human study comparing body surface potentials during change in inspiration and body position. There was better agreement with relative variability, which in these studies ranged from 0.11 to 0.42, agreeing well with an estimate from human studies of 0.40. Our results suggest that the isolated heart/torso tank preparation is a valuable tool for investigating the effects of geometric variation. Furthermore, the geometric position of the heart appears to be a large source of variation in body surface potentials. The size of these variations easily exceeded thresholds used to distinguish pathologic conditions and thus such variations could have important implications on the interpretation of the standard electrocardiogram.

Action Potentials↗

PubMed2001

From cell to body surface: a fully coupled approach.

Different types of equivalent cardiac sources are often used in the forward problem of electrocardiology. These may not be adequate to accurately reproduce the body surface potentials that are the result of cellular electrical activity, because they do not guarantee current conservation across the myocardial surfaces. Presented here are the outlines of 2 new coupling techniques that seek to overcome this problem by creating a continuous electrical pathway from the cellular level through to the body surface. The first technique directly couples the extracellular cardiac bidomain region to the surrounding passive torso regions creating a single system of equations without the need for matrix inversions. The second technique uses a fixed point iteration across each myocardial surface that has the goal of matching the potential fields and current flows across the cardiac boundaries into the neighbouring tissues. These techniques can be combined, directly coupling some regions and iterating across other region boundaries. Simulations on a transverse two-dimensional slice through a human male torso are presented, showing the convergence of these methods.

Body Surface Potential Mapping↗

PubMed2002

Electrocardiographic potential correlations: rationale and basis for lead selection and ECG estimation.

Einthoven gave to us the electrocardiogram. Electrocardiographic mapping demonstrated that localized electrophysiological events and phenomena have localized body surface electrocardiographic manifestations. Clinical electrocardiography has given us "reasonably good" means (criteria) with which to detect and characterize medically significant cardiac conditions, events, and diseases. However, clinical electrocardiography is imperfect, largely as a consequence of inadequate or redundant spatial sampling. This compromises the sensitivity and specificity of diagnosing cardiac diseases for which electrocardiographic manifestations are present but undetected due to imperfect sampling that results in a low signal-to-noise ratio for the specific abnormality. Correlation structure of body-surface potential distributions between and across populations or individuals provides important insight into and justification for the selection and use of "limited", "reduced", or "derived" lead systems aimed at improving the capture and use of electrocardiographic information. In this paper, we show the electrocardiographic voltage correlation relationships that occur on the body surface, across groups of subjects, either with or without cardiac disease. In addition, we demonstrate the correlation relationships between torso-surface and epicardial-surface potential distributions in experiments incorporating isolated canine hearts in a human-shaped torso tank. Analysis of these correlation relationships provides an explanation for the long-standing success of clinical electrocardiography but also suggests the means to improve its performance by incorporating new leads and/or their estimation from appropriately selected leads.

Body Surface Potential Mapping↗

PubMed2003

Tissue oxygen tension during regional low-flow perfusion in neonates.

OBJECTIVE: We examined cerebral cortical and peripheral organ tissue Po(2) values in a neonatal piglet model of regional low-flow perfusion. METHODS: Twenty-one neonatal piglets were placed on cardiopulmonary bypass, were cooled to 18 degrees C, then underwent either deep hypothermic circulatory arrest or regional low-flow perfusion at 20 or 40 mL/(kg x min) for 90 minutes. Regional low-flow perfusion was carried out by advancing the aortic cannula into the proximal innominate artery. Tissue mean Po(2) and Po(2) distribution were measured in the cerebral cortex, liver, small bowel, and skeletal muscle through the principle of oxygen-dependent quenching of phosphorescence. Measured quantities were compared by analysis of variance or the Fisher exact test. RESULTS: During regional low-flow perfusion, axillary and femoral arterial pressures, respectively, were 55 +/- 15 and 8 +/- 4 mm Hg at 40 mL/(kg x min) and 37 +/- 10 mm Hg (P =.04) and 17 +/- 5 mm Hg (P =.08) at 20 mL/(kg x min). Venous saturations were 95% +/- 6% at 40 mL/(kg x min) and 84% +/- 6% at 20 mL/(kg x min) (P =.03 at 15, 30, and 45 minutes). Cortical Po(2) was similar to prebypass values during regional low-flow perfusion at 40 mL/(kg x min) (53 +/- 5 mm Hg) but declined during reperfusion and recovery. Cortical Po(2) was lower than before bypass during low-flow perfusion at 20 mL/(kg x min) (38 +/- 7 mm Hg) but increased during reperfusion. Po(2) in liver and bowel was less than 10 mm Hg during low-flow perfusion at both 20 and 40 mL/(kg x min). Fraction of oxygen distribution with Po(2) lower than 15 mm Hg was less during perfusion at 40 mL/(kg x min) than at 20 mL/(kg x min) (P =.001). Three of 6 piglets that received a 40-mL/(kg x min) flow rate had significant upper torso edema, metabolic acidosis, and an unstable recovery period, whereas zero of 6 piglets that received a 20-mL/(kg x min) flow rate did. CONCLUSIONS: In a piglet model, regional low-flow perfusion at 20 mL/(kg x min) resulted in lower cortical tissue oxygenation but better recovery than did perfusion at 40 mL/(kg x min). Neither flow rate adequately oxygenated organs in the lower torso.

Acidosis↗

PubMed2000

Conserved and divergent aspects of terminal patterning in the beetle Tribolium castaneum.

To infer similarities and differences in terminal pattern formation in insects, we analyzed several of the key genes of this process in the beetle Tribolium castaneum. We cloned two genes of the terminal pattern cascade, namely tailless (tll) and forkhead (fkh), from Tribolium and studied their expression patterns. In addition, we analyzed the pattern of MAP kinase activation at blastoderm stage as a possible signature for torso-dependent signaling. Further, we analyzed the late expression of the previously cloned Tribolium caudal (Tc-cad) gene. Finally, we used the upstream region of Tc-tll to drive a reporter gene construct in Drosophila. We find that this construct is activated at the terminal regions in Drosophila, suggesting that the torso-dependent pathway is conserved between the species. We show that most of the expression patterns of the genes studied here are similar in Drosophila and Tribolium, suggesting conserved functions. There is, however, one exception, namely the early function of Tc-tll at the posterior pole. In Drosophila, the posterior tll expression is involved in the direct regulation of the target genes of the terminal pathway. In Tribolium, posterior Tc-tll expression occurs only for a short time and ceases before the target genes known from Drosophila are activated. Thus, we infer that Tc-tll does not function as a direct regulator of segmentation genes at the posterior end. It is more likely to be involved in the early specification of a group of "terminal" cells, which begin to differentiate only at a later stage of embryogenesis, when much of the abdominal segmentation process is complete. Thus, there appears to have been a major shift in tll function during the evolutionary transition from short germ to long germ embryogenesis.

Animals↗

PubMed1993

Perceived exertion and discomfort associated with driving screws at various work locations and at different work frequencies.

Eighteen subjects drove screws with air-powered tools into perforated sheet metal at three vertical and two horizontal work locations using three different work paces (8, 10, and 12 screws/min). Subjects drove screws with a pistol-shaped tool on the vertical orientation at knee, elbow, and shoulder height. They used an in-line tool to drive screws on the horizontal surface. A horizontal beam was placed just below each subject's elbow height and they drove screws into it with the lower arm perpendicular to the torso and with the arms fully extended. Subjects drove screws for 10 min at each work location and frequency combination before they assessed the condition using the Borg ten-point ratio rating scale. Subjects also ranked seven body areas according to discomfort for each work location. A two-factor ANOVA (and comparable non-parametric statistics) showed that both work location and frequency were significant factors in determining the Borg ratings. As work pace increased, so did the Borg ratings of perceived exertion for each work location. For each incremental increase in work pace, the Borg ratings of perceived exertion increased 12% to 25%, depending on the work location. Driving screws at elbow height on the vertical surface and with the lower arm close to the body on the horizontal surface were the work locations with the smallest ratings of perceived exertion. The ratings of perceived exertion for driving screws at elbow height on the vertical surface were 18% to 50% lower than the ratings for driving screws at knee or shoulder height and the ratings of perceived exertion for driving screws with the lower arm close to the body on the horizontal surface were 21% to 24% lower than driving screws with the arms fully extended. No significant difference was found among the discomfort ranks given to the various body parts for the two horizontal work locations. Differences were found among the body part discomfort rankings for the vertical work locations. While driving screws at knee height, the torso was most stressed; the wrist and hand were most stressed while driving screws at elbow height, and the shoulder and upper arm were the body parts that were stressed the most while driving screws at shoulder height.

Adult↗

PubMed1993

Trunk muscle activation and cocontraction while resisting applied moments in a twisted posture.

Previous studies of twisting have revealed substantial cocontraction of agonist and antagonist muscles within the torso when torsional moments are generated. The objective of the current study was to quantify the activations and cocontraction of eight trunk muscles as subjects maintained an axially rotated trunk posture and resisted external applied bending moments. Ten subjects twisted their torsos 25 degrees to the right (clockwise) and resisted 20 and 40 Nm bending moments from 12 directions. The moment directions were in a transverse plane and labelled clockwise as viewed from above, ranging from 0 degrees (mid-saggital, anterior) to 330 degrees, in 30 degrees increments. RMS EMG amplitude data were collected using surface electrodes and normalized to maximal voluntary contractions. Significant changes were observed in the muscle responses due to the interaction of the moment direction and moment magnitude for six of the eight muscles tested. Comparison of the present data with that collected previously in neutral postures indicated: (1) a large increase in the activation levels of the right erector spinae and the left external oblique muscles; and (2) a counter-clockwise shift in the moment direction at which the peak activation of these same muscles occurs. Analysis of the relative activation levels (RALs), constructed from the NEMG data to quantify the cocontraction, indicated that the changes in cocontraction were more robust in response to changes in the bending moment's direction as opposed to changes in bending moment's magnitude.

Adult↗

PubMed1994

The validity of visual observation to assess posture in a laboratory-simulated, manual material handling task.

A wide range of methods to evaluate posture in work situations relies on simple, unaided visual observation. In the present study the validity of visual observation to assess posture in a dynamic job was evaluated. Postural aspects were observed and recorded during a manual materials handling job simulated in a laboratory. The results from these observations, concerning gross body posture, torso flexion, arms and legs position, and load to be handled, were compared to the results obtained by direct opto-electronic recording. The agreement on a sample-to-sample basis (expressed by Cohen's kappa) was poor for the variables torso flexion (mean value for kappa = 0.38), position of arms (kappa = 0.43) and legs (kappa = 0.46) and load to be handled (kappa = 0.50) and acceptable only for the gross body posture (kappa = 0.79). Moreover, for each variable except gross body posture, the crude distributions of all observations and recordings across categories (irrespective of time) were significantly different. The results demonstrate that the observations are not valid. It is concluded that dynamic work situations require less simple, more time consuming methods (e.g., analyzing film or video records of the job) than a posture registration method based on direct visual observation.

Adult↗

PubMed1995

Loads on spinal tissues during simultaneous lifting and ventilatory challenge.

Muscles of the torso have been implicated to play a role in stabilization of the low back, and to assist in ventilation. This motivated an investigation to combine a load challenge to the low back with a breathing challenge, similar to that which a worker might experience when shovelling snow. Perhaps modulation of muscle activity needed to facilitate breathing may compromise the margin of safety of tissues that depend on constant muscle activity for support. Eight young healthy males dynamically lifted, and isometrically held, large loads (73-95 kg) and breathed a 10% CO2 gas mixture to elevate breathing (both with and without hand-held loads). Individual tissue forces were calculated using an anatomically detailed, dynamic model of the torso that was sensitive to individual variation by utilizing myoelectric signals, intra-abdominal pressure, ventilation rate and spine kinematics, obtained from each subject, as input. For large loads in the hands, most subjects appeared to stabilize the trunk with large muscle forces relegating the responsibility of creating lung air flow to the diaphragm. When reasonably small low-back demands were coupled with a breathing challenge and higher ventilation rates two out of eight subjects demonstrated entrainment of abdominal activity to breathing that resulted in additional cyclic low-back compressive loading of the order of 1000 N. Ergonomists should consider the additional tissue loading from physiologically demanding tasks and the related ventilation challenge, together with the tissue loads required to support external objects and maintain body posture.

Adult↗

PubMed1999

An ergonomics investigation into human thermal comfort using an automobile seat heated with encapsulated carbonized fabric (ECF).

This report presents the results of an ergonomics investigation into human thermal comfort using an automobile seat heated with an encapsulated carbonized fabric (ECF). Subjective and objective thermal comfort data were recorded while participants sat for 90 min in a heated and a non-heated automobile seat in an environmental chamber. Eight male participants each completed eight experimental sessions in a balanced order repeated measures experimental design. The conditions in the chamber were representative of a range of cool vehicle thermal environments (5, 10, 15 and 20 degrees C; in the 20 degrees C trial participants sat beside a 5 degrees C 'cold wall'). Participants in the heated seat condition used the heating controller with separate temperature control over the back of the seat (squab) and bottom of the seat (cushion) in an effort to maintain their thermal comfort while wearing the provided clothing, which had an estimated insulation value of 0.9 Clo. The trials showed that participants' overall sensations remained higher than 'slightly cool' in the heated seat at all temperatures. Participants' overall discomfort remained lower (i.e. more comfortable) than 'slightly uncomfortable' at temperatures ranging down to nearly 5 degrees C in the heated seat. Hand and foot comfort, sensation and temperature were similar in both seats. Asymmetric torso and thigh skin temperatures were higher in the heated seat although no significant discomfort was found in the front and back of the torso and thigh in either seat. Participants reported no significant difference in alertness between the control and heated seat.

Adult↗

PubMed1999

Multi-loop control of liquid cooling garment systems.

In this study the effects of multi-loop control of liquid cooling garments (LCGs) under exercise heat stress conditions were investigated by experiments and theoretical analysis. A triple-loop LCG, by which the torso, arms and legs could be independently cooled, was used in the two series of experiments carried out in a hot environment (35 degrees C/40% RH). The experiment consisted of rest, exercise on an ergometer at 70 W and exercise at 110 W. In the first experiment, each water inlet temperature (TWI) was adjusted according to the local thermal sensation. In the second experiment, TWI for the torso including arms and TWI for the legs were regulated by a skin temperature controller with set-point adjustment via heart rate. The experiments showed that a multi-loop LCG is more effective than a single-loop LCG in providing thermal sensation and comfort adjusted to the requirements of the different parts of the body, and that a skin temperature controller could be applied to a multi-loop system. The theoretical analysis was carried out using a mathematical model of thermoregulation. The results showed that a strong cooling of the surface over the working muscles (legs) provided the greatest thermoregulatory advantage during low body exercise, because most of the heat generated within the working muscles can be removed directly by heat conduction to the skin. Optimization of a human/LCG system could be attained by an optimal configuration and control. However, an optimal configuration always depends on the application purpose of an LCG system.

Adult↗