Biomedical subjects
Publications and source records attributed to A R Morton.
With running speed held constant, exercise durations of between two and 32 minutes all provoke significant asthma. However, the severity and length of the bronchoconstriction is less following exercise of two minutes duration. Exercise durations ranging from eight to 32 minutes show no difference in either incidence or severity of EIA.
Pulmonary function was evaluated in 11 female cross country runners before and after maximal treadmill exercise. Hydrostatic weighing was also performed post exercise. Significant increases were found in both residual lung volume (X delta + 210 ml, 20.6%) and total lung capacity (X delta + 170 ml, 3.4%). These changes were not correlated to the intensity of the exercise. The magnitude of the change in residual lung volume resulted in a mean error of 12.1% in body composition prediction. Standardized testing orders are recommended.
With total work constant, continuous running has been found to provoke more severe asthma than any of four different intermittent running regimes. This constitutes the first definite support for the clinical impression that exercise is better tolerated by asthmatics when broken into brief periods separated by intervals of recovery.
The purpose of this study was to determine and follow the effect of an acute bout of exercise on residual volume (RV) and other pulmonary function measurements over a 24-h post-exercise period, and to evaluate the effect on subsequent body composition calculations. Selected pulmonary function measurements of 12 male college students were collected prior to exercise at 5, 15, and 30 min, and at 1, 2, and 24 h post-exercise. RV was significantly (P less than 0.01) increased 20.8% (260 ml), 16.8% (210 ml) and 12.0% (150 ml) at 5, 15, and 30 min post-exercise, respectively. Total lung capacity (TLC) was significantly (P less than 0.01) increased 2.7% (190 ml) and 2.3% (160 ml) at 5 and 15 min post-exercise, respectively. Subsequent body composition calculations, using the post-exercise RV data, resulted in significantly (P less than 0.01) lower relative body fat measures, as compared to the pre-exercise value, through 30 min of recovery. In conclusion, our data demonstrate apparent increases in RV and TLC immediately following maximal treadmill exercise; these measurements remained significantly increased over pre-exercise values, through 30 and 15 min of recovery, respectively. It is recommended that the RV measurement and the actual hydrostatic weighing procedure not be separated by an acute bout of exercise, and that protocols for long-term studies be standardized.
To determine the effect of "warm-up" on exercise-induced asthma (EIA) 18 subjects ( mean age 19.7 years) performed five minutes of submaximal treadmill running to achieve a heart rate (HR) of 85% of predicted maximum for age. One such exercise test was preceded by "warm-up" and one was not. "Warm-up" consisted of three minutes of treadmill walking or jogging to attain 60% of predicted maximun HR for age. An identical incidence (77.8%) and severity (38.1% mean decrease in FEV1) of EIA was recorded after treadmill running whether preceded by "warm-up" or not. While this study does not support the concept that "warm-up" could reduce the likelihood of EIA, it is recommended that a longer, more intense "warm-up" involving interval exercise should be evaluated before rejecting the view that "warm-up" ameliorates EIA.
The total and alactic oxygen debts were measured in eight subjects following supramaximal treadmill running (14.5--16.1 km/h, 20% grade) to exhaustion, on two duplicate tests separated by 48 h. Mean total oxygen debts on the two trials were 5.28 +/- 0.42 1 and 4.57 +/- 0.46 1, (r = 0.34). Mean alactic oxygen debts were 2.81 +/- 0.21 1 and 2.74 +/- 0.121 (r = 0.89). Values for maximal total and alactic oxygen debts in this study were in close agreement to those found in the literature. The inability of the subjects to adequately reproduce an exhausting supramaximal effort was the major factor preventing reliable measurement of total oxygen debt. It is concluded that the method developed for the measurement of oxygen debt is both reliable and valid for the alactic portion of the debt.
We studied the effects of a 2-h exposure to ozone (0.5 ppm) in 14 nonsmoking males under four environmental conditions (WBGT (wet bulb-globe temperature index) = 64.4, 80.0, 85.2, and 92.0 degrees F). The subjects were divided into two groups, A (n = 8) and B (n = 6). Thirty minutes of exercise at 40% Vo2 max was performed from 60 to 90 min for group A and 30 to 60 min for group B. Pulmonary function changes, determined throughout exposure, were greatest immediately after exercise in both groups. Few changes occurred before the exercise period. However, the decrease in FVC (826 ml) and FEV1.0 (937 ml) following exercise was more than twice as large as the decrement seen at end exosure (388 and 423 ml, respectively). Measures of maximum expiratory flow (FEF 25-75%, FEF 50% FEF 75%) showed similar reductions. In many cases, reversal of these changes occurred during the remainder of the exposure period. The greatest decrease in FVC occurred when heat and ozone exposures were combined (WBGT = 92.0 degrees F). We conclude that the effects of ozone are most severe immediately after exercise and that heat stress may modify the overall effect of ozone on pulmonary function.
Statistically significant rises in serum glutamic oxalacetic transaminase and lactic dehydrogenase determinations occurred at exposures to TNT of 0.8 mg/m3 and persisted at exposures of 0.6 mg/m3. Based on these findings, the adequacy of the current threshold limit value for TNT (1.5 mg/m3) is questioned.
The purpose of this study was to construct tables and nomograms of spirometric norms for Perth children aged between six and 12 years. These norms were to be based on anthropometric measurements and age. A sample of 623 children was tested of which 556 were analysed and comprised 289 boys and 267 girls. All testing was carried out in the child's own school. The spirograms were recorded with a dry spirometer from which the FVC, FEV1, and FMF were measured. Correlation coefficients were established between each of these ventilatory parameters and anthropometric measurements of height, mass, arm span and age. The findings of the study revealed high correlations for both boys and girls between ventilatory parameters of FVC and FEV1 and height, mass, arm span and age. Moderately high correlations were found for both sexes between FMF and height, mass, arm span and age. Height correlated best with each of these ventilatory measures. It was also established that significant improvement in some correlations was obtained when anthropometric values were used in multiple correlation analysis. The use of height plus mass proved to be best when predicting FVC and FEV, for boys and girls, and for predicting FMF of girls. FMF for boys could be best predicted by using height alone. The limits of normality for ventilatory parameters of FVC, FEV1 and FMF were found to be best defined by the per cent standard error of the estimate. Tables and nomograms were established from regression and multiple regression equations in order to predict normal values in children. The findings of this study revealed that little difference existed between the ventilatory values of children tested in Perth, Europe and the Eastern States of Australia. However, the differences that were found to exist could be due to the age group which was sampled or possible environmental and genetic differences.
In a programme to examine the effect of 5 months of swimming training on school-children with asthma, 46 children swam a total distance of 3608 km (2242 miles) during 2806 training sessions. On post-training re-examination, nonspecific effects of physical conditioning were detected including improved posture and fitness, reduced fat folds, and enhanced swimming ability. Continuous monitoring of asthma and medication showed significant decreases in both parameters during the final phases of the study between children who continued to swim regularly and those who did not. The frequency and severity of exercise-induced asthma (after running) was unchanged by swimming training. Post-training questionnaires indicated a high degree of enthusiasm and acceptance of the programme by children and parents. No significant adverse effects were observed or reported during the study.
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Ventilatory function after three types of exercise-running, cycling, and swimming-was studied in 10 control subjects and 40 asthmatic patients. All performed eight minutes of submaximal aerobic exercise during each of the programmes, which were conducted in a randomly selected order. Biotelemetric monitoring of heart rates was used to equate the intensity of the exertion undertaken during the three systems of exercise. No control subject showed any significant variation in ventilatory capacity after exercise, and the responses after the three forms of exercise did not differ.In asthmatics exercise-induced asthma was observed after 72.5% of running tests, 65% of cycling tests, and 35% of swimming tests. In addition, those patients who developed exercise-induced asthma after swimming were noted to have significantly smaller falls in FEV(1) levels than were recorded after running and cycling. These results were statistically significant (P <0.01).The unexplained aetiology of increased airways resistance after exercise in asthmatics is discussed. This study indicates that swimming should be recommended in preference to running or cycling as an exercise programme for adults and children with asthma.
The growth of coagulase negative staphylococci (CNS) in spent and unspent peritoneal dialysate of physiologic (1.25 mmol/l) and standard (1.62 mmol/l) [Ca2++] was studied. Dialysate was prepared by filter sterilization and pH and iCa were measured. Three isolates of CNS grown in unsupplemented Mueller Hinton broth for 18 to 20 hr at 37 degrees C were adjusted to a density of 1.5 x 10(8) CFU/ml. The dialysate (5.4 ml) was inoculated with 0.6 ml of a 10(-4) dilution and then incubated aerobically at 35 degrees C. Plates were made at 0, 6, and 24 hr, and CFU/100 microliters were counted after 24 hr. In a larger study, 10 isolates of CNS were examined. Coagulase negative staphylococcal growth was inhibited by unspent dialysate (P = 0.000; unpaired t-test). Growth was greater in spent physiologic [Ca++] dialysate (iCa -0.76 mmol/l) at 6 hr (P = 0.007) and at 24 hr (P = 0.000) than in standard dialysate (iCa = 0.86 mmol/l) for two of three strains in the pilot study. Similar findings were noted for 4 of 8 strains in the larger study. There was an overall trend for greater growth in physiologic [Ca++] dialysate (P = 0.09). Some strains of CNS grow better in lower [Ca++] dialysate, perhaps representing clinically relevant trophism.
Current markers of myocardial injury lack specificity in patients with end-stage renal disease (ESRD). In particular, a false positive creatine kinase-MB (CKMB) elevation occurs in 5-10% of patients with ESRD. The aim of this study was to ascertain the relationship between CKMB and cardiac troponin I (cTnI), a new, highly sensitive and specific marker for myocardial injury, in the authors' dialysis population and compare their specificities. Blood samples were obtained from 112 dialysis patients (35 in peritoneal dialysis; 77 in hemodialysis). Patients were asymptomatic for cardiac ischemia and skeletal muscle injury. Mean +/- SD CKMB mass was 3.16 +/- 2.26 microg/L (range, 0.34-13.62), and cTnI was 0.025 +/- 0.061 ng/ml (range, 0.001-0.496). CKMB and cTnI levels did not correlate (r2 = 0.002; p = 0.61). CKMB mass concentration was significantly higher in men and in diabetics. No patient had a cTnI level greater than 1.5 microg/L, and eight asymptomatic patients had a CKMB mass greater than 6.7 microg/L. These data suggest a specificity of 100% for cTnI vs 94.6% for CKMB at these cutoff values. It is suggested that cTnI replace CKMB as a marker of myocardial injury in patients with ESRD.