Biomedical subjects

A R Morton

Publications and source records attributed to A R Morton.

At least 37 records · Page 2Linked to original sources

PubMed1998

Classification of compressed breast shapes for the design of equalization filters in x-ray mammography.

We are developing an external filter method for equalizing the x-ray exposure in mammography. Each filter is specially designed to match the shape of the compressed breast border and to preferentially attenuate the x-ray beam in the peripheral region of the breast. To be practical, this method should require the use of only a limited number of custom built filters. It is hypothesized that this would be possible if compressed breasts can be classified into a finite number of shapes. A study was performed to determine the number of shapes. Based on the parabolic appearance of the outer borders of compressed breasts in mammograms, the borders were fit with the polynomial equations y = ax2 + bx3 and y = ax2 + bx3 + cx4. The goodness-of-fit of these equations was compared. The a,b and a,b,c coefficients were employed in a K-Means clustering procedure to classify 470 CC-view and 484 MLO-view borders into 2-10 clusters. The mean coefficients of the borders within a given cluster defined the "filter" shape, and the individual borders were translated and rotated to best match that filter shape. The average rms differences between the individual borders and the "filter" were computed as were the standard deviations of those differences. The optimally shifted and rotated borders were refit with the above polynomial equations, and plotted for visual evaluation of clustering success. Both polynomial fits were adequate with rms errors of about 2 mm for the 2-coefficient equation, and about 1 mm for the 3-coefficient equation. Although the fits to the original borders were superior for the 3-coefficient equation, the matches to the "filter" borders determined by clustering were not significantly improved. A variety of modified clustering methods were developed and utilized, but none produced major improvements in clustering. Results indicate that 3 or 4 filter shapes may be adequate for each mammographic projection (CC- and MLO-view). To account for the wide variations in exposures observed at the peripheral regions of breasts classified to be of a particular shape, it may be necessary to employ different filters for thin, medium and thick breasts. Even with this added requirement, it should be possible to use a small number of filters as desired.

Biophysical Phenomena↗

PubMed1998

The effects of learning on the ventilatory responses to inspiratory threshold loading.

Progressive threshold loading (PTL) is frequently used to assess inspiratory muscle endurance in health and disease. We and others have noted a systematic increase in endurance with the first few exposures to the task in subjects previously naïve to PTL, which may not be related to conditioning of the muscles themselves. The purpose of this study was to investigate the mechanisms responsible for this increased endurance by examining the ventilatory responses to 3 PTL tests, each > 24 h apart, in 18 healthy subjects. During PTL, threshold pressure (Pth) was increased by approximately 10% every 2 min until task failure. Subjects were allowed to adopt any breathing pattern. Respiratory muscle strength (maximal inspiratory pressure [PImax]) was unchanged over successive tests while maximal Pth (Pthmax) during PTL increased (69 +/- 17, 77 +/- 16, and 86 +/- 11% of PImax, respectively, p < 0.05) (mean +/- SD), indicating that the increased Pthmax could not be attributed to improved respiratory muscle strength. Breathing pattern changed with successive tests, so that for comparative loads inspiratory time (TI), respiratory frequency (f ), and duty cycle (TI/Ttot) decreased. This change in breathing pattern did not alter respiratory muscle efficiency (respiratory muscle V O2/work), which was similar in each test (2.4 +/- 2.2%), but perceived effort (Borg Score), which was maximal at task failure in each test, decreased at comparative loads with successive tests. Thus, Pthmax during initial tests appeared to be limited by discomfort rather than respiratory muscle function. These findings suggest that the increased Pthmax with successive tests is a consequence of differences in the breathing pattern adopted, reflecting neuropsychological rather than respiratory muscle conditioning. Measurements from PTL should only be used to assess respiratory muscle performance after allowing time for learning.

Adult↗

PubMed1998

The influence of exercise-induced plasma volume changes on the interpretation of biochemical parameters used for monitoring exercise, training and sport.

A number of studies have demonstrated considerable plasma volume changes during and after exposure to different environmental and physiological conditions. These changes are thought to result from transient fluid shifts into (haemodilution) and out of (haemoconcentration) the intravascular space. If the levels of plasma constituents are to be routinely measured for research purposes or used as indicators of training adaptation or the health of an athlete, then it is important to consider the dynamic nature of plasma volume. Controversy still exists over the relevance of plasma volume interactions with plasma constituent levels, and while some investigators have taken plasma volume shifts into account, others have chosen to ignore these changes. Bouts of acute exercise have been shown to produce a transient haemoconcentration immediately after long distance running, bicycle ergometry and both maximal and submaximal swimming exercise. While these changes are transient, lasting only a few hours, other studies have reported a longer term haemodilution following acute exercise. In addition, endurance training has been shown to cause long term expansion of the plasma volume. It would, therefore, seem important to consider the influence of plasma volume changes on plasma solutes routinely measured for research, and as markers of training adaptation, prior to arriving at conclusions and recommendations based purely on their measured plasma level. To further confound this issue, plasma volume changes are known to be associated with heat acclimatisation, hydration state, physical training and postural changes, all of which may differ from one experiment or exercise bout to the next, and should thus be taken into account.

Blood Chemical Analysis↗

PubMed1998

The influence of total, dialysis, and residual renal urea clearances on serum albumin in peritoneal dialysis.

Though serum albumin (SA) and Kt/V predict mortality in peritoneal dialysis (PD), the relationship between them remains unclear. We report a cross-sectional study of factors associated with SA in PD, and a prospective study of the effect of increasing dialysis dose on SA in hypoalbuminemic patients with Kt/V < 2.1. Multiple linear regression was performed in 56 subjects with dependent variable SA at 4 months after starting PD (SA2), and independent variables: age, sex, diabetes, 4h-D/Pcr, predialysis SA (SA1), nPCR, PD-duration, modality, Kt/V, Ccr, and daily volume excreted normalized to body water (Vt/V). Forward stepwise selection (alpha = 0.05) produced a model (r2 = 0.492, P < 0.001) containing predictors of SA2: SA1 and nPCR (positive), and Vt/V (negative). With Vt/V excluded, Kt/V became significant (negative). Broken into components, dialysate Kt/V was significant, but residual Kt/V was not significant. In 14 hypoalbuminemic patients with Kt/V < 2.1, PD prescription was changed, targeting a Kt/V > 2.1. After 3.3 months, Kt/V rose from 1.7 +/- 0.25 to 2.21 +/- 0.36 (P = 0.0001), and nPCR rose slightly, 0.71 +/- 0.13 to 0.78 +/- 0.19 (P = NS), with no significant change in SA, 30.5 +/- 3.0 g/L to 31.4 +/- 3.8 g/L (P = 0.268). Dialysate and urine volumes are negative predictors of SA. Volume-dependent dialysate-protein loss could account for poor correlation between Kt/V and SA, and lack of improvement in SA with increased Kt/V.

Adolescent↗

PubMed1997

Significance of prolonged left ventricular wall motion abnormalities after exercise echocardiography following non-Q-wave acute myocardial infarction.

Exercise echocardiography was used to assess myocardial ischemia after non-Q-wave acute myocardial infarction in 40 consecutive patients. Resting parasternal long- and short-axis views and apical 4- and 2-chamber views were recorded, digitized, and stored. A maximal symptom-limited exercise test was performed within 21 days (mean 17.7 +/- 3) using a cycle ergometer with continuous monitoring and the echocardiogram was repeated in the same views. Resting and exercise echocardiograms were then compared. Coronary angiography was performed in all patients within 21 days of exercise echocardiography. Stenosis in > or =50% of the lumen diameter was considered significant. Of the 40 patients studied, 29 (72%) had continuing angina and 11 (28%) had no angina. Eighteen patients (62%) with angina developed angina during exercise testing and 19 (65%) developed ST-segment depression. In patients without angina, 1 (9%) developed postexercise angina and 2 (18%) developed ST-segment depression. The mean wall motion score index after exercise increased from 1.2 +/- 0.3 to 1.8 +/- 0.4 in patients with continuing angina (p <0.001) and from 1.2 +/- 0.3 to 1.4 +/- 0.3 in patients without angina (p = NS). Prolonged wall motion abnormalities lasting >20 minutes persisted in > or =1 segment in 27 of 29 patients (93%) with angina or in 2 of 1 1 patients (18%) without angina (p <0.001). Patients with continued angina had predominantly 3-vessel coronary artery disease (22 of 29 [76%]) or 2-vessel disease (7 of 29 [24%]), and those without angina had 1-vessel disease (6 of 11 [55%]) or 2-vessel disease (4 of 11 [36%]). One patient had 3-vessel disease. The duration of wall motion abnormality demonstrated a significant relation to 2- and 3-vessel coronary artery disease (p <0.001). Thus, patients with non-Q-wave acute myocardial infarction had a high incidence of multivessel coronary disease not necessarily detected on routine exercise testing. There was also a significant incidence of prolonged wall motion abnormality.

Case-Control Studies↗

PubMed1997

Acute intensive interval training and in vitro t-lymphocyte function.

Five male endurance-trained runners completed an interval running session of 15 x 1-min intervals at 95% VO2 max. Venous blood samples were collected pre-exercise and then immediately, 30- and 60-minutes post-exercise. The response of cultures of total lymphocytes to mitogen (phytohaemagglutinin) were significantly reduced immediately after exercise, but returned to resting levels by 30-min of recovery. Conversely, the mitogen response of cultures of pure T-lymphocytes (CD4+ and CD8+ cells), separated using a magnetic separation technique, showed no significant change during the exercise and recovery periods. These data showed directly that there was no apparent change in the functional capability of T-lymphocytes following an intensive interval training session. Furthermore, there were significant changes in the composition of the total lymphocyte cultures immediately post-exercise; increased numbers of natural killer (NK) cells (CD56+) and T-suppressor cells (CD8+) and decreased numbers of T-helper cells (CD4+). There were also significant correlations between total mitogen response and the composition of the cultured lymphocytes. These data indicated that the large increases in NK cells, relative to T-cells, following intensive exercise, were the most likely cause of the reduced mitogen response of total lymphocyte cultures.

Adult↗

PubMed1997

The influence of blood volume changes on leucocyte and lymphocyte subpopulations in elite swimmers following interval training of varying intensities.

The effect that exercise induced blood volume (BV) changes may have on the concentrations of leucocyte and lymphocyte subpopulations following exercise is controversial. Eight nationally ranked swimmers undertook 15 x 100 m swimming intervals (ITS) at 70% and 95% of maximal exercise intensity separated by 2 min recovery periods. Venous blood samples were collected prior to exercise (PRE), immediately post exercise (POST) and at 30, 60, 120 and 150-min post exercise. Control samples were taken on a rest day (R). Only the 95% ITS induced a significant (p < 0.01) reduction in PV (-7.3 +/- 1.1%) and BV (-4.0 +/- 0.6%) POST as calculated according to changes in haemoglobin and haematocrit. Total leucocyte and subset numbers (neutrophils, lymphocytes, monocytes), with the exception of eosinophils, increased significantly (p < 0.01) POST following the 95% ITS, and total leucocyte and neutrophils remained elevated (30% and 114% respectively) (p < 0.01) while lymphocytes progressively decreased by 36% (p < 0.01) at 150-min after exercise. The 70% ITS elicited a decrease (30%) (p < 0.01) only in lymphocyte cell numbers at 60 and 120-min post exercise. The 95% ITS induced significant increases (p < 0.01) in most lymphocyte cell subsets [CD19+ (27%); CD16+ (525%); CD16+ CD25+ (58%); CD4+ (48%); CD8+ (65%)] POST, with a significant reduction (32%) (p < 0.01) in the CD4+:CD8+ lymphocyte ratio. Numbers of CD19+; CD16+; CD5+; CD4+ and CD8+ lymphocytes, while not significantly changed POST following the 70% ITS, were significantly depressed (p < 0.01) during the recovery period. No significant changes were seen in leucocyte or lymphocyte subset numbers during R. All measured leucocyte and lymphocyte subset cell numbers at each ITS were corrected for changes in BV, and there were no significant differences between measured or BV corrected values for any of the cell populations at either of the ITS. Results suggest that while high intensity swimming exercise stress caused significant changes in the numbers and proportions of leucocytes, lymphocytes and their sub-classes, BV changes did not contribute significantly to the changes which occurred. The cell changes therefore, were truly representative of cell movements into and out of the peripheral blood circulation.

Adolescent↗

PubMed1997

Training adaptation and biological changes among well-trained male triathletes.

The distinction between training and overtraining responses is an important prerequisite for any potential marker for monitoring overtraining in athletes. In this study, eight well-trained male triathletes undertook physical performance assessments, at 6 weekly intervals, throughout a 9-month intensive training season. At each assessment, a resting blood sample was obtained for determination of a number of biological parameters previously associated with overtraining. All athletes produced significant (P < 0.05) improvements in running speed at anaerobic threshold (ATRS) from 15.6 +/- 0.2 k.h-1 at the start of the season to 16.6 +/- 0.6 k.h-1 at the time of major competitions. This improvement in performance was taken as evidence of well balanced training programs. Significant changes (P < 0.05) in plasma glutamine and plasma uric acid concentrations were observed during the training season, and both correlated moderately with ATRS (r = 0.365 and r = -0.328, respectively). None of the other parameters measured showed any significant changes during the training season. The elevations in plasma glutamine concentration observed in response to long-term balanced training may be distinguishable from previous reports of decreased glutamine concentrations in overtrained athletes, making it a potentially valuable tool in the monitoring of overtraining in athletes.

Adult↗

PubMed1997

Influence of exercise-induced plasma volume changes on the interpretation of biochemical data following high-intensity exercise.

OBJECTIVE: To assess the effects that exercise-induced plasma volume changes (PVCs) have on the interpretation of biochemical and hormonal parameters in the blood of athletes after high-intensity exercise. It was hypothesized that two unrelated high-intensity exercise protocols, performed by two separate subject groups each using different exercise modes, would result in similar percentage changes in plasma volume (% delta PV). It was further hypothesized that the % delta PV, measured in both protocols, would comparably influence the interpretation of biochemical variables measured following exercise. DESIGN: An experimental before-after trial on volunteers was performed. Two different exercise modes employing two different high-intensity acute exercise protocols were investigated. Eight male swimmers performed an interval training session (ITS) consisting of 15 x 100-m freestyle efforts at 95% of their maximal exercise intensity, and eight male runners performed a multistage discontinuous treadmill test (MSD) to volitional exhaustion. SETTING: The Human Performance Laboratory at the Department of Human Movement at the University of Western Australia. MAIN OUTCOME MEASURES: Blood samples obtained before, immediately after, and 30, 60, and 120 min during recovery were analyzed for plasma volume changes, urea, uric acid, creatinine, albumin, calcium, iron, transferrin, testosterone, cortisol, and sex hormone-binding globulin (SHBG). MAIN RESULTS: The ITS and MSD protocols produced similar and significant alterations (p < 0.01) in plasma volume. Both protocols also elicited significant fluctuations (p < 0.01) in the concentration of most of the parameters measured (excluding iron). When albumin, transferrin, testosterone, and SHBG values were adjusted for the significant % delta PV, their concentrations did not change over the experimental period, suggesting that the changes in measured concentration of these parameters may be, in part, due to changes in plasma volume. However, urea, uric acid, creatinine, calcium, and cortisol, when corrected for % delta PVC, still demonstrated significant changes (p < 0.01). CONCLUSIONS: It is recommended, when sampling biochemical and hormonal parameters in blood following an acute bout of exercise, that corrections for PVCs should be conducted. Apparent changes in blood solutes may reflect PVCs. PVCs should be taken into consideration when interpreting results regardless of exercise protocol and exercise mode performed.

Blood Chemical Analysis↗

PubMed1997

The independent and combined effects of aerobic exercise and dietary fish intake on serum lipids and glycemic control in NIDDM. A randomized controlled study.

OBJECTIVE: The triglyceride-lowering effects of omega-3 fats and HDL cholesterol-raising effects of exercise may be appropriate management for dyslipidemia in NIDDM. However, fish oil may impair glycemic control in NIDDM. The present study examined the effects of moderate aerobic exercise and the incorporation of fish into a low-fat (30% total energy) diet on serum lipids and glycemic control in dyslipidemic NIDDM patients. RESEARCH DESIGN AND METHODS: In a controlled, 8-week intervention, 55 sedentary NIDDM subjects with serum triglycerides > 1.8 mmol/l and/or HDL cholesterol < 1.0 mmol/l were randomly assigned to a low-fat diet (30% daily energy intake) with or without one fish meal daily (3.6 g omega-3/day) and further randomized to a moderate (55-65% VO2max) or light (heart rate < 100 bpm) exercise program. An oral glucose tolerance test (75 g), fasting serum glucose, insulin, lipids, and GHb were measured before and after intervention. Self-monitoring of blood glucose was performed throughout. RESULTS: In the 49 subjects who completed the study, moderate exercise improved aerobic fitness (VO2max) by 12% (from 1.87 to 2.07 l/min, P = 0.0001). Fish consumption reduced triglycerides (0.80 mmol/l, P = 0.03) and HDL3 cholesterol (0.05 mmol/l, P = 0.02) and increased HDL2 cholesterol (0.06 mmol/l, P = 0.01). After adjustment for age, sex, and changes in body weight, fish diets were associated with increases in GHb (0.50%, P = 0.05) and self-monitored glucose (0.57 mmol/l, P = 0.0002), which were prevented by moderate exercise. CONCLUSIONS: A reduced fat diet incorporating one daily fish meal reduces serum triglycerides and increases HDL2 cholesterol in dyslipidemic NIDDM patients. Associated deterioration in glycemic control can be prevented by a concomitant program of moderate exercise.

Adult↗

PubMed1997

Impact of portable APD on patient perception of health-related quality of life.

We assessed the impact of the introduction of a portable automated peritoneal dialysis (APD) system (Homechoice, Baxter Healthcare) on health-related quality of life (HRQOL). We evaluated HRQOL in 26 patients using the RAND 36-item Health Survey 1.0, which measures physical functioning, role limitations (physical and emotional), social functioning, emotional well-being, pain, energy, and general health perceptions. Questionnaires were administered prior to changing to the new system and 3 months later. Kt/V and albumin levels were measured at both time points. Eight patients had been on continuous ambulatory peritoneal dialysis (CAPD), and 18 had been using other APD systems (PacXtra, Baxter and AMP80, Fresenius). Kt/V increased significantly (p = 0.026); albumin was unchanged (p = 0.09). There was an improvement in the pain score (p = 0.079), although this did not reach statistical significance in the overall sample. Subgroup analysis showed that most of the improvement was from the group that had used the AMP80. No other statistically significant differences were found overall in the domains of HRQOL. Questioning of a random sample of patients indicated that perceived advantages of the new system were ease of setup and portability within the home. Neither of these translated into improvement in role-functioning domains of HRQOL. The improvement in pain score may reflect the capacity of newer cyclers to switch from drain to fill after a set proportion of dialysate has drained, leaving the patient empty for less of the time. Portable APD systems did not bring about predicted improvements in HRQOL. The HRQOL instrument may be insensitive, but technologically convenient advances may have limited impact on HRQOL due to its multifactorial nature.

Attitude to Health↗

PubMed1996

A specific activity questionnaire to measure the functional capacity of cardiac patients.

Exercise testing is often performed in persons with cardiac disease to measure their functional capacity. Physical activity questionnaires assessing functional capacity have been used a low-cost and convenient alternative to exercise testing, but have not been well validated against measured oxygen consumption in a cardiac population. This study assesses the ability of a simple, 13-item activity questionnaire, known as the Specific Activity Questionnaire (SAQ), to measure functional capacity prospectively in a large sample of cardiac patients. Ninety-seven consecutive cardiac outpatients (85 men and 12 women aged 59 +/- 10 years [mean +/- SD]) completed the SAQ before an elective symptom-limited treadmill test. Subjects returned within 10 days to repeat the treadmill test, following the same protocol, with the additional measurement of peak oxygen consumption, VO2 (ml x kg(-1)min(-1)), using open circuit spirometry. The SAQ score was significantly related to measured peak VO2(r=0.57, p<0.001). Stepwise multiple linear regression analysis found that the addition of patient age, height, and body weight to SAQ score improved the measurement of peak VO2, accounting for 51% of the sample variance (R=0.71, p<0.001). Peak VO2 was obtained from the following regression formula: [formula: see text]. Thus SAQ, a simple 13-item self-administered activity questionnaire, is able to provide a moderately good measure of functional capacity in cardiac patients and may be useful tool in studies of the cardiac population when formal exercise testing is impractical or uneconomical.

Activities of Daily Living↗

PubMed1996

Self-delivery of hemodialysis care: a therapy in itself.

Patient autonomy, sense of control, and well-being are thought to be enhanced by self-care hemodialysis as a therapy for end-stage renal disease. Dialysis in a satellite setting reduces travel time and can diminish therapy intrusiveness. Health-related quality of life (HRQOL), in terms of functional status and well-being, was measured in a group of patients trained for self-care, and then measured again after these patients were transferred to a satellite unit. Comparison was made with an age- and comorbidity-matched cohort of full-care patients. Patients trained for self-care tended to score higher than the full-care patients in the psychosocial domains of HRQOL, such as role function, social function, and emotional well-being, before and after transfer to the satellite unit. Physiological measurements did not differ significantly between groups at any time during the study, indicating that differences in HRQOL were not attributable to differences in metabolic stability. We conclude that patients trained for self-care hemodialysis experience better subjective quality of life than their full-care counterparts. This study highlights both the usefulness of measuring HRQOL as an outcome of hemodialysis therapy and the potential benefits of therapies such as self-care and satellite dialysis.

Activities of Daily Living↗

PubMed1996

Exercise and weight control in sedentary overweight men: effects on clinic and ambulatory blood pressure.

OBJECTIVE: To examine whether restriction of caloric intake and exercise of vigorous intensity can independently and additively influence clinic and ambulatory blood pressures in sedentary overweight men. DESIGN: Sixty subjects aged 20-50 years were randomly allocated either to continue their normal caloric intake or to restrict it by 4186-6279 kl/day, with 15% provided by protein, 30% by fat and 55% by carbohydrate, for 16 weeks. Within each of these groups subjects were further randomly allocated either to a control light intensity programme of exercise or to a vigorous intensity programme of exercise for 30 min three times a week. The light exercise group performed stationary cycling against no resistance, flexibility exercises and slow walking. The vigorous intensity group cycled on an ergometer at 60-70% of maximum their workload. RESULTS: Fifty-one subjects completed the study. Their maximal oxygen uptake was increased by approximately 24% with vigorous exercise but did not change with light exercise. Caloric intake restriction led to a significant loss of body mass of 9.5 kg (95% confidence interval 7.6-11.3), whereas vigorous exercise had no effect. Restriction of caloric intake reduced supine clinic systolic and diastolic blood pressures significantly by 5.6 (2.3-8.9) and 2.4 mmHg (0.4-4.2), respectively. Relative to the control light exercise group, exercise of vigorous intensity exercise had no significant effect on clinic blood pressure. In contrast, time series analysis revealed that both caloric intake restriction and vigorous exercise were associated with lower daytime ambulatory systolic blood pressure, the reduction in systolic blood pressure being sustained throughout the 24 h period when vigorous exercise and caloric intake restriction were combined. CONCLUSION: Compared with the effects of caloric intake restriction, the effects of a vigorous exercise programme on blood pressure are inconsistent, there being no influence on clinic blood pressure but a reduction in daytime ambulatory blood pressure. However, when combined with caloric intake restriction, regular vigorous exercise exhibits a synergistic effect in reducing ambulatory blood pressure throughout a 24 h period.

Adult↗

PubMed1996

Is salmeterol ergogenic?

OBJECTIVE: To assess the effects of 50 micrograms of inhaled salmeterol on pulmonary function, selected physical capacities, and fine motor control in 16 nonasthmatic male cyclists and triathletes, mean age of 23.2 (SD = 3.5) years. DESIGN: Randomized double-blind placebo-controlled crossover trial. SETTING: Human Physical Performance Laboratory, the University of Western Australia. SUBJECTS: Sixteen healthy male high-performance nonasthmatic athletes with a mean age of 23.2 years participated in the study. INTERVENTION: Subjects attended three experimental testing sessions at which salmeterol (50 micrograms), a placebo, or "no treatment" was administered in random order in a double-blind fashion, on separate occasions, prior to exercise. MAIN OUTCOME MEASURES: During each testing, session lung function was measured before and 10 min after the treatment. Tests of reaction time and hand steadiness and then two anaerobic cycle tests followed. The first, a 10-s all-out sprint was followed, after a 3-min rest, by a 30-s all-out sprint performed on a front access bicycle ergometer. After 10 min recovery, leg flexion-extension peak torque was measured on a Biodex isokinetic dynamometer at speeds of 120 and 180 degrees s-1. MAIN RESULTS: Lung function variables, reaction time, movement time, alactic anaerobic power, lactacid anaerobic power, and leg-flexion and leg-extension muscular strength were similar among the three treatment groups. CONCLUSIONS: The preexercise administration of 50 micrograms of inhaled salmeterol has no performance-enhancing effects in nonasthmatic athletes. We believe that athletes with asthma should be permitted to use salmeterol before competition.

Administration, Inhalation↗

PubMed1996

The emerging role of glutamine as an indicator of exercise stress and overtraining.

Glutamine is an amino acid essential for many important homeostatic functions and for the optimal functioning of a number of tissues in the body, particularly the immune system and the gut. However, during various catabolic states, such as infection, surgery, trauma and acidosis, glutamine homeostasis is placed under stress, and glutamine reserves, particularly in the skeletal muscle, are depleted. With regard to glutamine metabolism, exercise stress may be viewed in a similar light to other catabolic stresses. Plasma glutamine responses to both prolonged and high intensity exercise are characterised by increased levels during exercise followed by significant decreases during the post-exercise recovery period, with several hours of recovery required for restoration of pre-exercise levels, depending on the intensity and duration of exercise. If recovery between exercise bouts is inadequate, the acute effects of exercise on plasma glutamine level may be cumulative, since overload training has been shown to result in low plasma glutamine levels requiring prolonged recovery. Athletes suffering from the overtraining syndrome (OTS) appear to maintain low plasma glutamine levels for months or years. All these observations have important implications for organ functions in these athletes, particularly with regard to the gut and the cells of the immune system, which may be adversely affected. In conclusion, if methodological issues are carefully considered, plasma glutamine level may be useful as an indicator of an overtrained state.

Animals↗

PubMed1996

Assessment of health status in peritoneal dialysis patients: a potential outcome measure.

OBJECTIVES: To determine the feasibility and practicality of measuring general health status (GHS) in an outpatient peritoneal dialysis population. To determine whether GSH correlated intuitively with biochemical, socio-demographic and co-morbidity measurements. DESIGN: The Medical Outcomes Study 20-item short form was administered on a voluntary basis in the outpatient setting. Demographic and current biochemical data were extracted from the medical record. The effects of the socio-demographic, biochemical and physiologic variables on the six subscales of GHS generated by the questionnaire were estimated using multivariate linear regression analysis resulting in the development of six separate models. SETTING: Peritoneal dialysis program of a University Hospital. PATIENTS: Sixty stable patients on home peritoneal dialysis completed the GHS questionnaire during regularly scheduled outpatient visits. Ages ranged from 13 to 81 years. The study group included 14 diabetics (23%). RESULTS: Administering the questionnaire caused no logistical difficulties in the outpatient setting. Regression models for predicting GHS were both significant and intuitively correct. The presence of co-morbidities such as diabetes mellitus (p = 0.002; Social Subscale) and peripheral vascular disease (p = 0.016: General Health Subscale) had the most significant negative impact on GHS. An increased length of time on dialysis was associated with a higher GHS (p = 0.002; Physical Subscale). CONCLUSION: General Health Status questionnaires can be readily administered to peritoneal dialysis patients in the outpatient setting. They have face validity as a measurement of wellness and functioning. The longitudinal use of such instruments in conjunction with clinical and laboratory findings may identify both medical and non-medical factors impacting on our peritoneal dialysis population.

Adolescent↗

PubMed1995

Depression of plasma glutamine concentration after exercise stress and its possible influence on the immune system.

OBJECTIVE: To determine whether plasma glutamine levels can be used as an indicator of exercise-induced stress, and to consider the possible effects of low plasma glutamine concentrations on the immune system. METHODS: We used two exercise regimens: in Trial 1 seven male subjects were randomly stressed on a treadmill at 0, 30%, 60%, 90% and 120% of their maximal oxygen uptake (VO2max); in Trial 2 five highly trained male subjects underwent intensive interval training sessions twice daily for ten days, followed by a six-day recovery period. RESULTS: Plasma glutamine concentrations decreased significantly from an average of 1244 +/- 121 mumol/L to 702 +/- 101 mumol/L after acute exercise at 90% VO2max (P < 0.05) and to 560 +/- 79 mumol/L at 120% VO2max (P < 0.001). Four of the five subjects showed reduced plasma glutamine concentrations by Day 6 of the overload training trial, with all subjects displaying significantly lower glutamine levels by Day 11. However, glutamine levels showed a variable rate of recovery over the six-day recovery period, with two subjects' levels remaining low by Day 16. CONCLUSIONS: Reduced plasma glutamine concentrations may provide a good indication of severe exercise stress.

Exercise↗