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Biomedical subjects

J J Duncan

Publications and source records attributed to J J Duncan.

15 recordsLinked to original sources
PubMed1997

Effects of atenolol versus enalapril on cardiovascular fitness and serum lipids in physically active hypertensive men.

An ideal drug regimen for physically active hypertensive patients should not offset exercise-induced improvements in cardiovascular health or fitness. In this randomized, double-blind, placebo-controlled, crossover study of 39 physically active men with uncomplicated essential hypertension, we compared the effects of atenolol and enalapril on cardiovascular fitness and serum lipids. Drugs (atenolol, 50 or 100 mg once daily; enalapril, 10 or 20 mg once daily) were each administered for 4 weeks and each active drug period was preceded by 4 weeks of placebo therapy. Both drugs effectively (p < 0.001) lowered resting blood pressure when measured at the time of theoretical peak (i.e., 3 to 4 hours postdrug) and trough (i.e., 24 hours postdrug) drug blood levels. Atenolol reduced maximal oxygen uptake (by 7.3%, p < 0.001) 3 to 4, but not 24, hours after drug ingestion; no changes occurred with enalapril. Similarly, whereas serum lipids were essentially unchanged with enalapril, serum triglycerides (18.9% increase), high-density lipoprotein cholesterol (10.6% decrease), and ratio of low-density to high-density lipoprotein cholesterol (15.4% increase) were adversely impacted (p < or = 0.05) with atenolol. It is concluded that in contrast to enalapril, atenolol adversely impacts cardiovascular fitness and serum lipids and lipoproteins in physically active hypertensive men.

Antihypertensive Agents↗
PubMed1991

Women walking for health and fitness. How much is enough?

OBJECTIVE: We studied whether the quantity and quality of walking necessary to decrease the risk of cardiovascular disease among women differed substantially from that required to improve cardiorespiratory fitness. DESIGN: A randomized, controlled, dose-response clinical trial with a follow-up of 24 weeks. SETTING: A private, nonprofit biomedical research facility. PARTICIPANTS: One hundred two sedentary premenopausal women, 20 to 40 years of age, were randomized to one of four treatment groups; 59 completed the study (16 aerobic walkers [8.0-km/h group], 12 brisk walkers [6.4-km/h group], 18 strollers [4.8-km/h group], and 13 sedentary controls). Eighty-one percent were white, 17% black, and 2% Hispanic. INTERVENTION: Intervention groups walked 4.8 km per day, 5 days per week at 8.0 km/h, 6.4 km/h, or 4.8 km/h on a tartan-surfaced, 1.6-km track for 24 weeks. MAIN OUTCOME MEASURES: Fitness (determined by maximal oxygen uptake) and cardiovascular risk factors (determined by resting blood pressure and serum lipid and lipoprotein levels). RESULTS: As compared with controls, maximal oxygen uptake increased significantly (P less than .0001) and in a dose-response manner (aerobic walkers greater than brisk walkers greater than strollers). In contrast, high-density lipoprotein cholesterol concentrations were not dose related and increased significantly (P less than .05) and to the same extent among women who experienced considerable improvements in their physical fitness (8.0-km/h group, +0.08 mmol/L) and those who had only minimal improvements in fitness (4.8-km/h group, +0.08 mmol/L). High-density lipoprotein cholesterol also increased among the 6.4-km/h group, but did not attain statistical significance (+0.06 mmol/L; P = .06). Dietary patterns revealed no significant differences among groups. CONCLUSION: Thus, we conclude that vigorous exercise is not necessary for women to obtain meaningful improvements in their lipoprotein profile. Walking at intensities that do not have a major impact on cardiorespiratory fitness may nonetheless produce equally favorable changes in the cardiovascular risk profile.

Adult↗
PubMed1991

Effect of beta-blockers on exercise physiology: implications for exercise training.

We conducted a series of studies aimed at investigating the effect of beta-blockers on exercise physiology. On the basis of these and other existing studies, it is possible to draw the following conclusions and to make the following tentative recommendations for patients engaged in exercise training who receive beta-blocker therapy: i) CAD patients treated with beta-blockers are capable of deriving the expected enhancement of cardiorespiratory fitness during training, irrespective of the type of drug used; ii) beta1-selective blockers are preferable to nonselective agents for hypertensive patients engaged in exercise training; iii) because beta1-selective blockers impair exercise tolerance in some hypertensive patients, physicians should look out for this adverse reaction and, if present, consider alternative antihypertensive therapy; iv) intrinsic sympathomimetic activity confers no advantage during exercise training; v) exercise intensity prescription for patients receiving beta-blockers should be in accordance with traditional guidelines and based on results of individualized exercise testing performed on medication; vi) exercise training is desirable during beta-blocker therapy in that it appears to offset adverse alterations in lipoprotein metabolism; and vii) nonselective beta-blockers may increase predisposition to exertional hyperthermia, and patients must therefore be encouraged to adhere strictly to accepted guidelines for heat injury prevention.

Adrenergic beta-Antagonists↗
PubMed1990

Effect of intrinsic sympathomimetic activity on the ability of hypertensive patients to derive a cardiorespiratory training effect during chronic beta-blockade.

The effect of intrinsic sympathomimetic activity (ISA) on the ability of patients with high blood pressure (BP) to derive a cardiorespiratory training effect during long-term beta-blocker therapy was studied. Fifty sedentary hypertensive subjects were randomly assigned to propranolol (n = 23) or pindolol (n = 27) therapy for a 22 week double-blind parallel study. Over the first 2 weeks, during which subjects remained sedentary, drug doses were titrated to produce equipotent, clinically significant BP reductions. Subjects subsequently continued drug therapy and completed 20 weeks of exercise training. Although pindolol tended to preserve submaximal exercise heart rates to a greater degree than propranolol, the initial 2 weeks of drug therapy resulted in equivalent reductions in maximal oxygen uptake with propranolol (6% reduction) and pindolol (8% reduction). Likewise, 20 weeks of training induced similar, statistically significant (P = .0001) increases in maximal oxygen uptake during propranolol (10% increase) and pindolol (11% increase) treatment. We therefore conclude that ISA does not confer any advantage to patients with high BP who receive chronic beta-blocker therapy and wish to improve their cardiorespiratory fitness by participating in exercise training.

Adrenergic beta-Antagonists↗
PubMed1990

Exercise and mild essential hypertension. Recommendations for adults.

Chronic essential hypertension is a major public health problem afflicting an estimated 15 to 30% of persons from most Western industrialised countries. Persons with mild hypertension (diastolic blood pressure between 90 and 104mm Hg and/or systolic blood pressure between 140 and 159mm Hg) represent the overwhelming majority of hypertensive individuals in the general population. The achievement of long term blood pressure control in these individuals is of central strategic concern in the prevention of hypertension-related morbidity and mortality. Epidemiological studies suggest that regular participation in physical activity may be beneficial in preventing hypertension. The findings of epidemiological studies are supported by a recent meta-analysis of 25 longitudinal aerobic training studies, in which the average sample-size-weighted reductions in resting systolic and diastolic blood pressures were 10.8mm Hg and 8.2mm Hg, respectively. Moreover, preliminary analyses from our centre suggest that cardiorespiratory fitness and, by inference, aerobic exercise training may be of benefit in reducing mortality rates in hypertensive patients. When compiling an exercise prescription with the intention of reducing an elevated blood pressure and attenuating the risk for coronary artery disease, several factors must be considered in order to optimise the likelihood of a safe and effective response. Specifically, the 5 basic components of the exercise prescription for patients with mild hypertension are safety aspects, the type of exercise to be performed, and the frequency, intensity and duration of exercise training. For those patients who require pharmacotherapy, the interaction between the specific antihypertensive agent and exercise responses must also be considered. We recommend that aerobic exercise training be performed at an intensity corresponding to 60 to 85% of the maximal heart rate and that the duration and frequency be modulated to achieve a weekly energy expenditure of between 14 and 20 kcal/kg of bodyweight.

Adult↗
PubMed1989

Effect of opioid antagonism on the ability to tolerate maximal anaerobic exercise.

The effect of naloxone-induced endogenous opioid antagonism on the ability to tolerate maximal anaerobic exercise was studied in 11 young men. Volume-matched infusions of placebo or naloxone 4 mg were administered in a randomised double-blind crossover trial before a 30-second maximal cycle ergometer test (Wingate test). Mechanical power output was calculated for each 5 seconds of cycling and expressed as peak power (highest output during any 5-second period), average power (average output during the 30 seconds of cycling) and power decline (difference between peak power and the lowest 5-second power output divided by time). Naloxone did not significantly modify (P greater than 0.05) any index of anaerobic power. Similarly, the perception of leg pain during exercise was similar with placebo and naloxone. Therefore, insofar as naloxone may be used to examine the functional role of opioid-mediated mechanisms, these findings are not tenable with the hypothesis that endogenous opioids modulate the ability to tolerate maximal anaerobic exercise.

Adult↗
PubMed1987

Marathon performance in relation to maximal aerobic power and training indices in female distance runners.

The purpose of this study was to examine the relationships of marathon performance time (MPT) to maximal aerobic power (VO2 max), physical characteristics, and training indices recorded for 12 weeks prior to a race in 35 female distance runners. The marathon experience of the subjects ranged from two to fifteen races. Physical and aerobic power characteristics (mean +/- S.D.) were: age, 35.7 +/- 8.5 yr; height, 166.4 +/- 5.7 cm; weight, 55.1 +/- 5.7 kg; body fat, 15.7 +/- 5.0%; VO2 max, 56.5 +/- 6.2 ml . kg-1 . min-1. Marathon time for this race averaged 227.0 +/- 31.6 min. Records from individual training diaries indicated the runners averaged 71.0 +/- 10.0 workout days, 10.0 +/- 10.0 two X day-1 workouts, 81.0 +/- 8.0 total workouts, 12.3 +/- 1.8 mean km . workout-1, 5402.8 +/- 1302.6 total training min, 187.0 +/- 18.0 m . min-1 training pace, 112.2 +/- 32.1 max km . wk-1, 83.1 +/- 23.4 mean km . wk-1, 998.8 +/- 282.6 km . 12 wk-1 and 13.8 +/- 2.4 mean km . day-1. MPT was positively correlated to body mass index (r = 0.52), and body fat (r = 0.52) but negatively related to VO2 max (r = -0.65). MPT was also negatively related to previous marathons completed (r = -0.47), workout days (r = -0.47), two X day-1 workouts (r = -0.52), total workouts (r = -0.56), mean km . workout-1 (r = -0.58), total training min (r = -0.56), m . min-1, training pace (r = -0.66), max km . wk-1 (r = -0.70), mean km . wk-1 (r = -0.74), km . 12 wk-1 (r = -0.74), and mean km . day-1 (r = -0.77). MPT for our population of runners may be predicted (r = 0.82, R2 = 0.68) by the following equation: MPT, (min) = 449.88 - 7.61 (-/x km.day-1 run) - 0.63 (m.min-1, training pace); SEE = +/- 18.4 min.

Adipose Tissue↗
PubMed1985

The effects of aerobic exercise on plasma catecholamines and blood pressure in patients with mild essential hypertension.

The effects of a 16-week aerobic exercise program on blood pressure and plasma catecholamine levels were evaluated in 56 patients with baseline diastolic blood pressure of 90 to 140 mm Hg. The exercise group significantly improved their physical fitness, and reduced systolic and diastolic blood pressures, compared with controls. To evaluate the relationship between exercise, blood pressure, and plasma catecholamine values, the exercise group was further divided into hyperadrenergic and normoadrenergic subgroups. Reductions in systolic pressures were 6.3 mm Hg, 10.3 mm Hg, and 15.5 mm Hg for control, normoadrenergic, and hyperadrenergic groups, respectively. Diastolic changes were similar and also significant. Within the hyperadrenergic group, changes in blood pressures were associated with changes in values for plasma catecholamines following training. We conclude that an aerobic exercise program reduces blood pressure, which is at least partially mediated by changes in plasma catecholamine levels.

Adult↗
PubMed1984

Comparative physiological profiles among young and middle-aged female distance runners.

Physiological profiles of 42 middle-aged female marathoners (MAM) (means age = 38.2 yr) were compared with those of 9 young female marathoners (YM) (means age = 25.2 yr), 10 middle-aged female 10-km runners (MATK) (means age = 33.1 yr), and 37 middle-aged sedentary women (MAS) (means age = 38.8 yr). The groups were equivalent for height, maximum heart rate, and hematocrit, and, after adjusting for body size, hemoglobin concentration, lipids, and lipoproteins. Compared to the runners, MAS subjects had significantly higher resting heart rates and significantly lower treadmill performance times, maximum exercise minute ventilation, and VO2max. Compared to YM subjects, MATK runners had higher resting heart rates and lower treadmill performance times, and compared to both groups of marathoners, MATK runners had lower VO2max, but only when expressed relative to body weight. The YM and MAM subjects did not differ from each other except for resting heart rate values, which were higher in the MAM. These data suggest that runners have more favorable cardiorespiratory profiles than do sedentary women, but that lipid and lipoprotein values may be affected more by body size than by activity level.

Adult↗
PubMed1982

Absence of effect of potassium-magnesium aspartate on physiologic responses to prolonged work in aerobically trained men.

The effects of oral administration of potassium and magnesium aspartate (K + Mg Asp) on physiologic responses to 90 min of treadmill walking at approximately 62% VO2 max were evaluated in seven healthy males (VO2 max = 59.5 ml X kg-1 X min-1). A total of 7.2 g of K + Mg Asp were administered to each subject during a 24 h period prior to work and compared to control and placebo trials. For control, placebo, and K + Mg Asp trials, no significant differences were observed in resting or exercise values for ventilation (VE), oxygen uptake (VO2), carbon dioxide production (VCO2), respiratory exchange ratio (RO), heart rate (HR), or blood pressure (BP). In addition, there were no differences between the three trials for exercise-induced decreases in body weight and increases in rectal temperature, or for pre- and post-exercise alterations in serum lactic acid, creatine kinase, lactic dehydrogenase, and percentage change in plasma volume. The findings from this study indicate that oral ingestion of K+ Mg Asp prior to exercise had no effect on cardiorespiratory, hematologic, and metabolic responses to 90 min of work conducted at approximately 62% VO2 max.

Adult↗
PubMed1979

Carboxypeptidase B activity of cultured skin fibroblasts and relationship to cystic fibrosis.

Enzyme activity against hippuryl-L-arginine was studied in cultured skin fibroblasts from controls and cystic fibrosis patients. The enzyme had a lysosomal distribution and an acid optimum of pH 4.5 with little or no activity present above pH 7.0. Dithiothreitol was required for full activity and the kinetics of thiol activation were different for the control and cystic fibrosis enzyme. The properties and lysosomal distribution of the enzyme indicated that it was a carboxypeptidase B. Substrate affinity, thermolability, pH stability, the fall and rise in activity with subculture, the cyclical pattern of activity through serial passage and the level of activity were similar for the control and cystic fibrosis enzyme.

Arginine↗
PubMedDate not supplied

Comparison of diclofenac sodium and aspirin in the treatment of acute sports injuries.

A randomized, double-blind, parallel-group clinical trial compared diclofenac sodium (Voltaren, Ciba-Geigy Summit, NJ) with aspirin for the treatment of acute sprains and/or strains of the knee or ankle. One hundred thirty-nine patients were admitted to the study. Patients received either 150 mg (75 mg twice daily) of diclofenac (N = 69) or 3.6 g (1.2 g three times daily) of aspirin (N = 70) for 3 to 10 days. Forty-seven diclofenac patients and 49 aspirin patients, mean age for both groups 25 years, were evaluated to determine the efficacy of each treatment. Both groups experienced significant (P less than 0.001) improvements for all efficacy variables measured. Treating sprains and strains with diclofenac rather than with aspirin allowed an earlier return to activity. Of those patients who achieved playing fitness, those in the diclofenac group resumed athletic activities in a mean of 4.7 days, compared with a mean of 5.9 days for patients in the aspirin group. Although the overall multivariate F was nonsignificant (P = 0.19), the univariate F for days required to resume playing fitness was significantly (P = 0.025) shorter in the diclofenac group. While the nonsignificant multivariate result suggests that the significance may be due to chance, it is also possible that there was a trend toward earlier resumption of activities with diclofenac treatment compared to aspirin, but an insufficient sample size to demonstrate the trend statistically. Since others have reported such a trend without the greater controls of a multivariate analysis, this area warrants further research.

Acute Disease↗