Low Work Capacity Research Articles

Physical and chemical characteristics of polymer-based spherical activated carbon and its ability to adsorb organics

The characterization of a polymeric spherical activated carbon (PAC) was performed by comparing its adsorption, porosity, functional groups and some of the physical properties with a commercial spherical activated carbon (CAC). The PAC was about 4 times superior to the CAC with respect to the mechanical strength. The micropore volume of the PAC was about 5% smaller than that of the CAC. The maximum methylene blue adsorption values of the PAC and the CAC were 32 and 14 mgg−1, respectively, which indicated low mesopore volumes as consistent with the values of BJH volume. This resulted in the low butane working capacity values for both activated carbons. Adsorption parameters for the Langmuir and the Freundlich isotherm models were determined for all organic substances tested. Both isotherms were suitable models to analyze the equilibrium data for the removal of all organics. However, the Langmuir model fitted better than the Freundlich model and the adsorption capacities of the PAC were somewhat higher than those of the CAC. The chemical properties of the activated carbons, the pH of solutions and the substituents on absorbates have an effect on adsorption of the organics tested.

6-Minute Walk Work for Assessment of Functional Capacity in Patients With COPD

The 6-min walk (6MW) test is commonly used to assess exercise capacity in patients with COPD and to track functional change resulting from disease progression or therapeutic intervention. Not surprisingly, distance covered has been the preferred outcome for this test. However, distance walked does not account for differences in body weight that are known to influence exercise capacity. The aim of this study was to evaluate the 6-min distance x body weight product (6MWORK) as an improved outcome measure with a solid physiologic foundation. One hundred twenty-four men and women with moderate-to-severe COPD volunteered and completed the testing sequence, which included pulmonary function, a peak effort ramp cardiopulmonary exercise study with gas exchange, and the 6MW. Means and SD were generated for the variables of interest. Differences were analyzed using analysis of variance techniques. Correlation coefficients and receiver operating characteristic (ROC) curves were calculated for the 6-min walk distance (6MWD) and 6MWORK with indexes of pulmonary function, work performance, and Borg scores for dyspnea and effort. Men and women presented with a significant smoking history that also differed by gender (48 vs 66 pack-years, respectively; p < 0.01). The mean (+/- SD) FEV(1) values were 45 +/- 12.6% and 48 +/- 12.1%, respectively (not significant), while the diffusing capacity of the lung for carbon monoxide (DLCO) was 14.7 +/- 6.1 vs 10.3 +/- 3.9 mL/min/mm Hg, respectively (p < 0.001), for men and women. The 6MWD averaged 416.8 +/- 79.0 m for men and 367.8 +/- 78.6 m for women, and these differences were significant (p < 0.002). When 6MWD was compared as the percent predicted of normal values, each gender presented with a similar reduction of 78.6 +/- 14.5% vs 79.9 +/- 17.5% (p > 0.05), respectively. 6MWORK averaged 35,370 +/- 9,482 kg/m and 25,643 +/- 9,080 kg/m (p < 0.0001) for men and women, respectively. 6MWORK yielded higher correlation coefficients than did 6MWD when correlated with DLCO, lung diffusion for alveolar ventilation, FEV(1), FEV(1)/FVC ratio, watts, peak oxygen uptake, peak minute ventilation, and peak tidal volume. The ROC curve demonstrated that 6MWORK had a significantly larger calculated area under the curve (p < 0.05) [plot of 100-sensitivity to specificity for each variable of interest for all subjects] than 6MWD when differentiating an objectively selected definition of low work capacity vs high work capacity (bike ergometry work, < 55 vs > 55 W, respectively). We conclude that work calculated as the product of distance x body weight is an improved outcome measure for the 6MW. 6MWORK can be used whenever the 6MW is required to estimate a patient's functional capacity. This measure is also a common measure, which can be converted to indexes of caloric expenditure for direct cross-modality comparisons.

Skeletal muscle mitochondrial function and exercise capacity in HIV-infected patients with lipodystrophy and elevated p-lactate levels.

To investigate the skeletal muscle mitochondrial function in HIV-infected patients with lipodystrophy or elevated p-lactate levels. Eight HIV patients treated with highly active antiretroviral therapy, with lipodystrophy or elevated p-lactate, and eight healthy controls were exposed to incremental exercise until exhaustion. Blood samples and gas analysis were performed at rest, during exercise and in recovery. Oxygen consumption, workload and blood lactate were assessed. Before and immediately after exercise muscle biopsies were obtained, in which citrate synthase (CS), hydroxyacyl-coenzyme A dehydrogenase (HD), glycogen and nucleotides were measured. Maximal workload was significantly lower in patients compared with controls [171 Watt (88-206) versus 235 Watt (118-294) P = 0.05]. A trend towards lower maximal oxygen consumption (VO(2max)) was detected in patients [2136 ml/min (1221-2598) versus 2985 ml/min (1506-3959) P = 0.11]. Patients had significantly elevated levels of blood lactate at rest [1.55 mmol/l (1-2.5) versus 0.8 mmo/l (0.37-1.1) P < 0.01), but no significant difference in maximal blood-lactate values was found. The decline in blood lactate in the recovery period was similar between groups. There was no significant difference in CS, HD, glycogen or nucleotides. The significantly lower working capacity and the trend towards reduced VO(2max) in patients could be caused by mitochondrial dysfunction, but may also be caused by impaired physical fitness. The similar levels of nucleotides, CS, HD, and glycogen and the normal increase in blood lactate during exercise indicates a normal oxidative phosphorylation. No evidence of serious damage to skeletal muscle mitochondrial function was found.

RESPONSE

Dear Editor-in-Chief: We thank Dr. Shephard for his interest in our paper regarding compliance in the exercise participants of the National Exercise and Heart Disease Project (NEHDP) and commend him and his colleagues for their program’s exceptional success. The NEHDP was a multicenter randomized clinical trial, led by enthusiastic physicians, nurses, and exercise specialists. Volleyball and other recreational games were incorporated to increase camaraderie and improve attendance. The study was designed not only to test the effectiveness of exercise in reducing morbidity and mortality in myocardial infarction survivors but also the feasibility of such a long-term supervised program in a “real world” setting. A large part of the early planning and decision-making processes of the NEHDP focused specifically on having the best compliance possible. The randomized trial is considered the “gold standard” to test such hypotheses, in part because the methodological concern of selection bias, common in studies from select clinical centers or convenience samples, is reduced. Unfortunately, we are unable to determine as per Dr. Shephard’s suggestion whether randomization effected perception of therapeutic value of the program, thus reducing attendance at the supervised sessions. A more important difference between the two studies is the method used to define and measure compliance. In the Toronto Rehabilitation Program, by the third year, participants attended the supervised center once every 4–8 wk and kept an exercise log indicating their participation in a prescribed exercise program on their own (5). Based on the self-reported log and periodic center visits, 82.8% of the Toronto study participants were considered to be compliant in that they fulfilled their exercise prescription at least three times per week. In contrast, the NEHDP compliance measure was indicative of the percentage of available supervised sessions that were attended by the participants in the third year. Unfortunately, no data are available regarding the specifics of the NEHDP participants’ exercise performance outside of the program. However, in a previous publication (4), it was reported that by the end of year 2 of the clinical trial, 77% of the exercise group was attending the organized sessions or exercising on their own. At the end of 36 months, 74% of the participants who were attending fewer than half of the study exercise sessions were considered to be exercising in another program or on their own at home. Therefore, our 13% reported compliance measure at the end of the trial reflects the number of actual sessions participants were attending, rather than the percentage of participants who were compliant with their exercise prescription. We agree with Dr. Shephard that consideration should be given to making exercise convenient by fitting it into patients’ lifestyles and that, for some, home exercise may be more feasible than regular attendance at specific scheduled sessions. Since completion of the NEHDP and the original Toronto study, others have shown home-based exercise to be both safe and effective for cardiac patients (1–3). It is important to note that even when we included participation in outside exercise in our logistic regression analyses, the same factors predicted noncompliance (i.e., younger age, lower work capacity, higher BMI and body fat percentage, and cigarette smoking). Therefore, regardless of the measure used for compliance, the important point of our study is that certain factors can help predict individuals who will be less likely to take advantage of rehabilitation opportunities and that these characteristics should serve as markers for individuals who may need more encouragement or support to comply to the requirements of an exercise program. Joan Dorn John Naughton Dai Imamura Maurizio Trevisan

Longitudinal evaluation of cardiopulmonary performance during exercise after bone marrow transplantation in children

Objective: Abnormalities in cardiopulmonary performance during exercise have been reported in children after bone marrow transplantation (BMT). We sought to study changes in exercise performance over time in pediatric BMT survivors. Study design: We retrospectively reviewed the results of serial cardiopulmonary exercise tests performed by patients who had undergone BMT at our institution. Four measurements of cardiopulmonary function are reported: maximum cardiac index (MCI), maximal oxygen consumption (Max VO2), oxygen consumption at ventilatory threshold (VO2 at VT), and maximum work (Max Work) performed. A linear mixed-effects model was fitted to assess changes in these parameters over time. Results: Thirty-three patients performed 96 cardiopulmonary exercise tests. MCI and VO2 at VT were depressed at initial testing and did not change over time. Max VO2 increased by 4% per year to 69% predicted, and Max Work increased to 77% predicted at 6 years after BMT. Conclusions: In spite of an impaired cardiovascular response to exercise as indicated by the persistently low MCI, aerobic and physical working capacity increase. Improved Max VO2 suggests that oxygen extraction at the musculoskeletal level becomes more efficient with recovery from BMT. This may represent a compensatory response to an impaired ability to increase cardiac output. (J Pediatr 2000;136:311-7)

Maximal exercise systolic pressure, exercise training, and mortality in myocardial infarction patients

The relation of maximal exercise systolic pressure to physical conditioning and to mortality was determined in 641 men with ≥1 myocardial infarctions. Each performed a standardized multistage exercise test before randomized assignment either to an exercise group or a control group and at scheduled periodic intervals over 3 years. This study compares 123 men with maximal exercise systolic pressures (MESP) of ≤140 mm Hg with 518 men whose maximal exercise systolic pressure was ≥140 mm Hg. At baseline, the 2 groups were comparable for age, entry time since the occurrence of the qualifying cardiac event, and reported use of antihypertensive medications. Men with low MESP used more β blockers, had lower systolic pressure measurements at rest and by definition at maximal exercise, and lower work capacity than men with higher levels of MESP. Men with low MESP experienced: (1) no reduction in mortality with exercise conditioning (p <0.86), and (2) a significantly higher mortality rate over 3 years (p <0.003) compared with men with higher levels of MESP. The relation of a low MESP to mortality persisted: (1) whether MESP or work capacity increased from the baseline exercise test to the last performed exercise test, and (2) whether it was measured at low (<6 METs) or high (≥6 METs) levels of work capacity. We conclude that low maximal exercise systolic blood pressure is a predictor of mortality and is associated with an ineffective training response in men with myocardial infarction.

Prognostic significance of double product and inadequate double product response to maximal symptom-limited exercise stress testing after myocardial infarction in 6296 patients treated with thrombolytic agents

Background The aim of this study was to evaluate the prognostic significance of the pressure-rate product (PRP) obtained during exercise stress testing and of its change from rest to maximal exercise (dPRP) in a population of survivors of acute myocardial infarction treated with thrombolytic agents. Methods And Results Survivors of acute myocardial infarction (n = 6251) from the GISSI-2 database, who underwent a maximal symptom-limited exercise test with either bicycle ergometer or treadmill, were followed up for 6 months. PRP and dPRP values were dichotomized (≤21,700 and >21,700, ≤11,600 and >11,600, respectively) and analyzed in a multivariate Cox model individually and simultaneously with other ergometric variables. Six-month mortality rate was 0.8% in the high PRP group and 2.0% in the low PRP group. Low PRP was an independent predictor of 6-month mortality rate (relative risk [RR] 1.97, 95% confidence interval [CI] 1.24 to 3.13). Patients with low dPRP had mortality rates higher than patients with high dPRP (2.1% vs 0.8%). At the multivariate analysis, low dPRP showed negative predictive value (RR 1.97, 95% CI 1.23 to 3.16). A further multivariate analysis was performed with PRP and dPRP, also adjusting for low work capacity, abnormal systolic blood pressure response to exercise, and symptomatic-induced ischemia. The results showed that low work capacity, low PRP, and symptomatic exercise-induced ischemia were still significantly associated with higher 6-month mortality rate ( P = .04, .02, and .05; RR = 1.68, 1.71, and 1.78 respectively). Conclusions PRP is a predictive index to assess prognosis in survivors of acute myocardial infarction treated with thrombolytic agents able to perform an exercise test after acute myocardial infarction, but its usefulness appears to be limited, considering that these patients were at low risk. (Am Heart J 1999;137:443-52.)

The Nature of Child Malnutrition and Its Long-Term Implications

The problem of malnutrition in poor societies is best viewed as a “syndrome of developmental impairment,” which includes growth failure; delayed motor, cognitive, and behavioural development; diminished immunocompetence; and increased morbidity and mortality. Growth retardation is often found in association with other problems, such as vitamin A deficiency and anaemia. These clusters of nutritional problems flourish during periods of vulnerability, namely in utero and during the first three years of life, and affect at least a third of all young children in developing countries. Survivors of malnutrition in early childhood suffer functional disadvantages as adults, including diminished intellectual performance, low work capacity, and increased risk of delivery complications. the prevention of low birthweight and the promotion of adequate growth and development during early childhood will result in healthier, more productive adults. Such investments, because they build human capital, are best viewed as long-term economic strategies.

The remedying of iron deficiency: what priority should it have?

Fe deficiency is considered to be the commonest of nutritional deficiencies worldwide. Adverse effects are stated to include lower growth rate and impaired cognitive scores in children and poor pregnancy outcome and lower working capacity in adults. In the present review, Fe intake, stores of the element, the magnitude of deficiencies and the benefits from interventions, as reflected in the results of clinical trials, are discussed. Because of inadequacies of knowledge in numerous respects, more information is needed regarding the extent to which clinical trials relate to public health realities, before introducing regional or national supplementation programmes. While Fe supplements are needed in certain groups, and in particular regions, increased dietary intakes could be supplied by food fortification, as well as by individual improvements in intake.

Evaluation of the change in defectiveness of cellulose and acetate fibres in thermal aging with the scale dependence of the mechanical properties

The kinetics of the change in the mechanical properties (strength, elongation, and strain energy at break) of viscose, acetate, and triacetate fibres during thermal aging were investigated. The coefficients of variation and scale dependence of the fracture characteristics and their standardized values were calculated for evaluating the defectiveness of chemical fibres based on cellulose and its acetates. The data obtained demonstrate the lower work capacity of viscose fibres in comparison to acetate and triacetate fibres. The results of the study can be used to predict the operational reliability of textile materials fabricated from chemical fibres based on cellulose and its acetates in prolonged thermal effects.

Die voorkoms van lewenstylverwante koronêre risikofaktore by Suid-Afrikaanse bestuurslui

The presence of lifestyle related coronary risk factors among South African business executivesThe general health status of an employee often displays a direct relationship with his productivity. This phenomenon, to a large extent, initiated the trend in several companies to provide the so-called “employeesupporter programmes" which concentrate on a holistic approach towards total well-being. The lifestyle of the South African executive is to a large extent destructive of health and total well-being. In many cases this leads to premature retirement, serious illnesses and even death. Executives (388) of 20 companies representing the mining, steel, construction, financial and motor industry, were evaluated for the purpose of this article. The mean age of the respondents was 44,6 ± 0.6 years. In 74,3% of the cases a low physical working capacity was found (&lt;2,5 Watt kg-1), while 4,6% of the executives showed a percentage body fat of &gt;20% which is regarded as a coronary risk factor. In 38,7% a n d 58,2% of the cases elevated systolic a n d diastolic blood pressure values were respectively found. The following amount of respondents showed elevated values with regard to the biochemical parameters: total cholesterol(69,5%), low density lipoprotein cholesterol (64,8%), triglycerides (24,1%) and total cholesterol/HDL ratio (77,0%). In 42,2% of the cases an abnormally low level of high density lipoprotein was found.

Prognostic significance of maximal exercise testing after myocardial infarction treated with thrombolytic agents: the GISSI-2 data-base

SummaryExercise testing helped in diagnosing postinfarction patients in the prethrombolytic era. Over the past decade acute myocardial infarction treatment has changed because of new thrombolytic therapies and consequently, the value of exercise testing is under debate. The GISSI-2 database allowed us to reevaluate the prognostic role of exercise testing in thrombolysed patients.The exercise test was performed in 6296 patients, on average 28 days after randomisation. The test was not performed in 3923 patients because of contraindications. The test was judged positive for residual ischaemia in 26% of the patients, negative in 38%, and non-diagnostic in 36%. Among the patients with a positive stress test result, 33% had symptoms, whereas 67% had silent myocardial ischaemia. The mortality rate was 7·1% among patients who did not have an exercise test and 7·1% for those with a positive test, 0·9% for those who had a negative test, and 1·3% for those who did not have a diagnostic test. In the adjusted analysis, symptomatic induced ischaemia, submaximal positive result, low work capacity, and abnormal systolic blood pressure were independent predictors of 6-month mortality (relative risks [RR] 2·54, 95% Cl 1·27-5·08, 2·28, 1·17-4·45, 2·05, 1·23-3·42, and 1·86, 1·05-3·31, respectively). However, when these factors were tested simultaneously, only symptomatic induced ischaemia and low work capacity were confirmed as independent predictors of mortality (RR Cox 2·07, 95% Cl 1·02-4·23 and 1·78, 1·06-2·99, respectively). Patients with a normal exercise response have an excellent medium-term prognosis and do not need further investigation. However, more evaluation should be devoted to the patients who cannot undergo exercise testing, because the potential to influence outcome appears to be much greater.

Isolated Congenital Complete Atrioventricular Block in Adult Life

The prognosis of congenital complete atrioventricular block (CCHB) is usually considered favorable in adults. This belief is based on studies comprising a limited number of patients and with rather short observation times. In the present study, the natural history of the disease was investigated by a prospective follow-up through decades of adult life of patients with a large group having well-defined CCHB without structural heart disease. The diagnostic criteria of CCHB proposed by Yater were applied. Patients registered as having CCHB in 1964, supplemented by younger patients all without symptoms during their first 15 years of life, were selected. The study was limited to patients with isolated, complete, permanent block. An interview was conducted with all patients and clinical follow-up data obtained. There were finally 102 patients, 61 women and 41 men. In November 1994, the time of observation, after the age of 15 years in survivors, was between 7 and 30 years. The mean age at follow-up or at death was 38 years, median age 37 years, and range 16 to 66 years. Stokes-Adams (SA) attacks occurred in 27 patients, in 8 with a fatal outcome. The first attack was fatal in 6 of these 8 patients. Nineteen survived and a pacemaker (PM) was implanted thereafter. Another 8 patients received a PM because of repeated fainting spells, and 27 others have had a PM implanted for other reasons such as fatigue, effort dyspnea, dizziness, ectopies during exercise tests, mitral regurgitation, and a low ventricular rate (VR). VR decreased with age, with a mean rate at 15 years of 46 beats per minute (bpm), at 16 to 20 years of 43 bpm, at 21 to 30 years of 41 bpm, at 31 to 40 years of 40 bpm, and after 40 years of age of 39 bpm. SA attacks occurred in all 7 patients with prolonged QTc time. Low VR at rest or at work, presence of bundle-branch block pattern, low working capacity, and ectopies at rest and/or during effort were not statistically significant risk factors. SA attacks occurred in 6 patients without any of these signs. Mitral regurgitation developed in 16 patients and 4 died. A PM reduced the risk of death. A change to a lower degree of block occurred in 6 patients. Prophylactic PM treatment is recommended even for symptom-free adults with CCHB because of the high incidence of unpredictable SA attacks with considerable mortality from first attacks, a gradually decreasing VR, significant morbidity, and a high incidence of "acquired" mitral insufficiency.

Physical disability from knee osteoarthritis

Osteoarthritis (OA) of the knee is a common, nonfatal, chronic condition that causes pain and physical disability in older people. Persons with knee OA report difficulty with activities that require ambulation and transfer from the sitting to the standing position. Physical disability from knee OA is the result of a complex interplay among the severity of disease, pain, comorbid conditions, psychosocial factors, and deficits in physical capacity such as low aerobic work capacity and lower extremity muscle weakness. These deficits in physical capacity may be correctable with exercise training. Short-term studies indicate that persons with knee OA show gains in physical capacity and report less pain and disability with exercise training. However, the long-term effectiveness and safety of exercise in persons with knee OA remains unknown.

Dependence of maximum performance time on work intensity in patients with a hereditary myopathy with succinate dehydrogenase deficiency.

Patients with a hereditary mitochondrial myopathy with succinate dehydrogenase (SDH) deficiency and abnormal lactacidosis during physical exercise have a low work capacity when exercising for about 10-15 min. Their maximum voluntary muscular strength is fairly normal. The relationship between the time (t) and a constant workload (N) that a healthy subject can maximally sustain can be expressed as: log t = beta + alpha log N. For normal subjects the constant alpha is approximately -5 and the constant beta has a large interindividual variation. Of four myopathy patients alpha was determined from two or three maximum bicycle exercise tests of different duration (including ramp- and steady-state tests using a new application of the method of adding submaximal loads to the final maximum workload). The value of alpha varied between -1.0 and -1.81 and beta had low values, both significantly different from those of healthy subjects. The alpha values explain the divergent results that may be obtained with different types of exercise tests in some of these patients, i.e. a normal or moderately reduced capacity in exercise tests of short duration (for example a short Tornvall or a ramp type of test) and a very low exercise capacity in tests of longer duration (for example a steady state type of test with workloads chosen to allow at least two loads). The low absolute value of alpha may be related to the abnormally increased anaerobic metabolism of these patients during exercise, caused by the SDH deficiency.

Cardiovascular disease in systemic lupus erythematosus. A study of 75 patients form a defined population.

All patients with systemic lupus erythematosus in a prospective, epidemiologically based study within a defined area in southern Sweden were invited to participate in an investigation of cardiac function. From 1981 to 1988, 101 patients were included in the study, and 75 of them were investigated according to a fixed protocol by echocardiography, Doppler cardiography, electrocardiography (ECG) at rest and at exercise, and myocardial scintigraphy (in patients whose ECG became abnormal during exercise). IgG anticardiolipin antibodies (IgG aCL) were determined by ELISA. Twenty of the 75 patients (27%) had valvular disease and 12 of these (60%) had increased concentrations of IgG aCL, compared with 12 of 55 (22%) without valvular disease (p less than 0.01). Pericardial effusion was detected in 14 patients (19%) during the study period. Mild pulmonary hypertension was found in 11 patients (16%), who also had increased frequency of IgG aCL. Myocardial infarction had occurred in 7 patients, 3 of whom were women less than 40 years of age. Echocardiography revealed regional hypokinesis or akinesis in 5 of the patients with myocardial infarction. Exercise testing revealed low work capacity in 13 of 54 patients (24%), the limiting symptoms being mainly exhaustion or musculoskeletal pain. An abnormal resting ECG was found in 9 of the patients participating in the exercise test. During exercise, abnormal ST-depression was observed in 8 patients, 2 of whom developed angina. Myocardial scintigraphy was performed in 6 of these patients, revealing reversible uptake defects in all. Prolonged glucocorticoid treatment was associated with valvular abnormalities as well as myocardial infarction. Valvular abnormalities and IgG aCL appeared to be risk factors for cerebral infarction.

The low physical working capacity of thyrotoxic patients is not normalized by oral antithyroid treatment.

The low working capacity in thyrotoxic patients has not been quantified and its causes have not been clarified. We studied the working capacity in nine thyrotoxic patients at diagnosis (test 1), after 3 months of oral antithyroid medication (test 2), and in four of them again after 1 year (test 3). The maximum power output was low in thyrotoxic patients (1.65 +/- 0.15 W/kg-1) and was not significantly higher after 3 months of treatment (1.84 +/- 0.15), although plasma thyroid hormone concentrations had been normalized for approximately 3 months. After 1 year's treatment the maximum power output was still somewhat low in the four tested patients (2.75 +/- 0.34). The rate of oxygen uptake under maximum exercise was low (26 ml/min-1/kg-1) and was not significantly increased at test 2 and 3. The net mechanical efficiency was low at test 1 and 2 (18.9 +/- 2.1% and 20.1 +/- 1.8%, respectively), but was normal at test 3 (25.2%). At all three tests the blood lactate response upon maximum exercise attained only about 50% of normal concentration. Thus, low work capacity in thyrotoxic patients remained for a long period of time after euthyroid conditions had been attained. The low capacity was due to low aerobic and anaerobic capacities and initially also to a low mechanical efficiency.

Effect of prior working on the structure and deformation capacity of Mn−29.5% Al−0.5% C alloy

1. Alloy Mn−29.5%Al−0.5%C in the homogenized condition at temperatures below 650°C exhibits low working capacity, i.e., high flow stress and brittleness, which is due to presence in the alloy of lamellar τ-phase. Upsetting of the alloy is possible only in the temperature range 650–750°C and at deformation rates 5·10−3–10−2 sec−1. 2. As a result of extrusion at 700°C recrystallized fine τ-phase grains are formed with a size of 0.5–2 μm. With extrusion in the single-phase e-region (950°C) there is e-phase grain refinement, and then during subsequent cooling fine-grained τ-phase forms. Deformation by extrusion with e=80% promotes total transformation of lamellar τ-phase into granular phase which causes an improvement in the working capacity of alloy Mn−29.5%Al−0.5%C. 3. In alloy Mn−29.5%Al−0.5%C, containing τ-phase with a grain size of 0.5–2 μm the superplasticity effect is observed which is more clearly developed with t=650–750°C and vd=10−2–10−3 sec−1.

Usefulness of a branching treadmill protocol for evaluation of cardiac functional capacity

A branching treadmill protocol was designed to measure functional capacity in patients with low work capacity and varying ability to walk at speeds used in traditional protocols. A comfortable walking pace is first selected (2.0 to 3.5 mph, 0.25 mph increments) and the workload is then increased every 2 minutes in 1 MET increments (a multiple of the resting oxygen uptake [1 MET = 3.5 ml O 2/kg/ min]) by adjusting grade. Nine trained (maximal MET = 7.6 ± 1.6, mean ± standard deviation) male subjects (age 59 ± 7 years) with previous myocardial infarction and 9 trained (maximal MET = 11.7 ± 2.5) male control subjects (age 56 ± 8 years) completed submaximal and maximal workloads without handrail support. The measured oxygen consumption, volume of oxygen in ml/kg/min (VO 2), was compared with the predicted VO 2 cost of treadmill walking calculated from speed and grade. A linear regression analysis of predicted versus measured VO 2 was performed. There were no significant differences between myocardial infarction and control regression lines. Therefore, a simplified prediction equation for estimated VO 2 in myocardial infarction and control subjects is proposed. Overall VO 2 prediction = 1.61 + 0.99 x. The main advantage of the branching protocol format is the selection of a stable, brisk walking pace compatible with age and gait, which may improve mechanical efficiency through impedance matching. The protocol is adaptable enough in design so that most patients can complete the exercise test without use of handrails, which is essential for an accurate estimate of VO 2 from treadmill speed and grade.

Workplace injuries in the developing countries.

Transfer of technology and industrial development without consideration for the characteristics of the local users and the environmental conditions of the recipient countries has proved to be not only socially destructive but economically expensive in terms of human suffering and material losses Most developing countries (DC) are paying an unacceptably high price in terms of suffering, sickness and also loss of production due to work-related accidents Poor working conditions and non-existence of an effective injury prevention programme in many DCs has resulted in a very high sickness and accident rate. In such circumstances, the salary and social benefits of the worker are low, because productivity is well below its capacity. This vicious cycle also results in the worker's malnutrition and low working capacity, resulting in turn in greater vulnerability to disease and job-related accidents A greater awareness is needed among employers and the workforce of such common problems as increased health hazards, ...