Controlling cholesterol levels through exercise.
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Cholesterol↗
Biomedical subjects
N F Gordon
Publications and source records attributed to N F Gordon.
Comparison of diltiazem and atenolol in young, physically active men with essential hypertension.
The antihypertensive efficacy and effect on maximal exercise performance of diltiazem was evaluated and compared with atenolol in patients specifically selected on the basis of their being young and physically active. Diltiazem (sustained-release preparation, 90 mg twice daily) was administered to 14 patients (aged 33 +/- 2 years) and atenolol (50 mg once daily) to 13 patients (aged 30 +/- 2 years) with essential hypertension in a 16-week randomized, double-blind, parallel study. The 2 drugs had comparable antihypertensive effects at rest, with mean decreases of 18 and 17 mm Hg (p less than 0.001) for supine and standing diastolic blood pressure (BP), respectively, during diltiazem treatment, and mean decreases of 21 and 18 mm Hg (p less than 0.001) during atenolol treatment. During maximal graded exercise testing, systolic BP, diastolic BP, heart rate and heart rate-BP product were significantly reduced by both drugs. However, the reductions in systolic BP, heart rate and heart rate-BP product during exercise were considerably greater (p less than 0.001) with atenolol than with diltiazem. Maximal exercise performance was essentially unchanged with diltiazem and slightly (3%, p less than 0.05) reduced with atenolol. Thus, diltiazem is effective and well-tolerated single therapy for young patients with mild to moderate essential hypertension who lead a physically active life style and compares favorably with atenolol.
Adult↗
Isoproterenol sensitivity in heat tolerant and relatively heat intolerant men.
Recent research has demonstrated that pharmacologic blockade of beta-adrenoceptors predisposes to hyperthermia during prolonged exercise. To investigate the hypothesis that beta-adrenoceptor sensitivity to catecholamines may be an important determinant of exertional heat tolerance, we performed a cross-sectional study comparing the heart rate responses to graded doses of isoproterenol in 6 heat tolerant and 6 relatively heat intolerant men. We observed no significant difference (p greater than 0.1) between the heat tolerant (0.9 +/- 0.68 microgram) and heat intolerant (1.19 +/- 0.61 microgram) subjects in the dose of isoproterenol that produced a 25 beat.min-1 increment in heart rate. Although the possibility of a relationship between beta-adrenoceptor sensitivity and the ability to tolerate exercise in heat cannot be entirely excluded on the basis of these data, our study clearly demonstrates the lack of a correlation between cardiac pacemaker sensitivity to isoproterenol and exertional heat tolerance.
Adolescent↗
Effect of beta-adrenoceptor blockade and calcium antagonism, alone and in combination, on thermoregulation during prolonged exercise.
The effect of clinically used doses of propranolol, atenolol, nifedipine, propranolol plus nifedipine, and atenolol plus nifedipine on thermoregulatory responses of 11 healthy men was studied during 2-h block-stepping in heat. Drug intervention did not alter ventilation during exercise. In contrast, propranolol and atenolol produced equivalent reductions in exercise tachycardia, implying a similar level of beta 1-adrenoceptor blockade. The heart rate response to exercise was unaffected by nifedipine and during dual beta-adrenoceptor blockade and calcium antagonism was equivalent to that with beta-adrenoceptor blockade alone. While rectal temperature rises were not modified by drug ingestion, propranolol and, to a lesser degree, atenolol and combination therapy, but not nifedipine alone, attenuated skin temperature rises. Moreover, although atenolol, nifedipine, and their combination did not alter sweating, propranolol and its combination with nifedipine enhanced sweating during the 1st and 2nd h of exercise. This study concludes that nifedipine does not modify thermoregulation during exercise and allows for greater confidence of its use during cardiac rehabilitation. Furthermore, the present data confirm that propranolol does enhance sweating during exercise and demonstrate that this effect is not mediated simply by an earlier onset of rapid sweating nor abolished by concomitant calcium antagonism.
Adrenergic beta-Antagonists↗
Comparison of continuous and intermittent multistage maximal exercise testing during beta-adrenoceptor blockade in physically active men.
Cardiorespiratory responses of 11 healthy males were studied, with placebo and propranolol, during a continuous and an intermittent multistage maximal treadmill test. With placebo, equivalent maximal heart rates were attained for the disparate test modes, and the intermittent protocol yielded a slightly higher (2%, P less than 0.01) maximal O2 consumption. In contrast, during beta-adrenoceptor blockade, higher maximal heart rates (5.1%, P less than 0.01) and O2 consumptions (4.4%, P less than 0.02) were reached with intermittent compared with continuous testing. Values were, however, markedly lower (P less than 0.001) for both protocols than with placebo. These results demonstrate that the precise degree of attenuation of maximal heart rate and O2 consumption observed in physically active persons receiving propranolol is partly dependent upon the actual test protocol utilized. Furthermore, the present data suggest an advantage for intermittent testing when accurate evaluation of the maximal cardiorespiratory capacity is desired in such individuals.
Adrenergic beta-Antagonists↗
The role of endogenous opioids in thermoregulation during sub-maximal exercise.
The involvement of the endogenous opioid system in the thermoregulatory response to sub-maximal exercise was investigated using naloxone as a pharmacologic probe. Volume-matched infusions containing either a placebo, 2 mg naloxone, or 10 mg naloxone were administered (in a randomized, double-blind, cross-over fashion) to nine physically active male volunteers (age 23.4 +/- 1.1 yr). Subjects performed 30 min of cycling at a fixed work rate (average 133 W or 54% of maximal oxygen uptake) chosen to elicit approximately 70% of the pre-determined maximal heart rate. Heart rate, blood pressure, ventilatory responses, and perceived exertion were unaffected by naloxone during exercise. Likewise, the rise in rectal temperature that occurred during exercise was essentially equivalent for placebo (0.69 +/- 0.04 degrees C increase from 0 to 30 min, P less than 0.001), 2 mg naloxone (0.60 +/- 0.04 degrees C increase from 0 to 30 min, P less than 0.001), and 10 mg naloxone (0.60 +/- 0.04 degrees C increase from 0 to 30 min, P less than 0.001). In agreement with the rectal temperature observations, naloxone did not modify sweating during exercise. Thus, insofar as naloxone may be used as an inferential tool to examine the physiologic significance of the endogenous opioid system, these data suggest that endogenous opioids are unlikely to play a significant role in the maintenance of thermal homeostasis during 30 min of sub-maximal exercise.
Adult↗
Effect of dual beta-blockade and calcium antagonism on endurance performance.
The effect of oral clinically used doses of propranolol, atenolol, nifedipine, propranolol + nifedipine, and atenolol + nifedipine on endurance performance and ventilatory responses to graded treadmill testing was studied in 12 healthy physically active men. Maximal exercise duration was reduced by propranolol (8.5%, P less than 0.001) and its combination with nifedipine (11.1%, P less than 0.001), and to a lesser degree by atenolol (3.2%, 0.05 less than P less than 0.1), nifedipine (2.1%, P less than 0.05), and atenolol + nifedipine (3.9%, P less than 0.01). Exercise duration and heart rate (HR) and ventilatory responses to maximal exercise were equivalent with a beta-blocker and its combination with nifedipine. At submaximal exercise, beta-blockade reduced the HR and oxygen uptake, nifedipine accentuated the HR but did not alter ventilation, and all drugs modified the relative oxygen uptake corresponding to 85% of the maximal HR. Physiologic responses to submaximal exercise during combination therapy were similar to those during beta-blockade alone. This study concludes that, in physically active men, nifedipine induces a small impairment of maximal performance, but does not accentuate the reduction in effort tolerance resulting from beta-blockade. Furthermore, HR and ventilatory responses to exercise during combined beta-blockade and calcium antagonism can be predicted from those during beta-blockade alone.
Adrenergic beta-Antagonists↗
Effect of beta-blockade on exercise core temperature in coronary artery disease patients.
The effect of pharmacologic blockade of beta-adrenoceptors on the relationship between rectal (Tre) and pulmonary artery (Tpa) temperatures was studied in six coronary artery disease patients during 30 min of exercise. Exercise was performed at a set work rate (120 W) on a cycle ergometer before and 2 h after the ingestion of 80 mg propranolol. The heart rate on completion of exercise was reduced (P less than 0.001) from 140 +/- 5 to 108 +/- 3 beats.min-1 by propranolol demonstrating a considerable degree of beta-adrenoceptor blockade. At rest, neither Tre nor Tpa were modified by propranolol. Likewise, propranolol failed to modify the Tre response to exercise. However, propranolol induced an alteration of the normal relationship between Tre and Tpa during exercise. In particular, although Tre was essentially unchanged, propranolol accentuated both the initial fall (by 0.28 degrees C, P less than 0.001) and the subsequent rise (by 0.46 degrees C, P less than 0.01) in Tpa during exercise. The present data therefore demonstrate a considerable limitation to the use of Tre when assessing thermal homeostasis during acute beta-adrenoceptor blockade. Furthermore, although research with more chronic therapy is warranted, our study suggests an accentuated risk of hyperthermia and, by implication, its adverse physiologic consequences during prolonged exercise performed by coronary artery disease patients treated with propranolol.
Adult↗
The South African Defence Force physical training programme. Part I. Effect of 1 year's military training on endurance fitness.
The effect of the South African Defence Force's (SADF) military training on the endurance fitness of recruits was investigated. Pre-military training maximal O2 consumption (53,14 ml/kg/min) did not change significantly during the study. In contrast, lactate turnpoint (ml O2/kg/min) and treadmill performance time were moderately enhanced (7,5% and 8% respectively; P less than 0,05) by the initial 10-week basic training programme. Further analysis of the results showed this endurance-training effect to be limited to recruits of average and, in particular, below-average fitness. The salutary effect of basic training on fitness levels was, however, transient, the values on completion of 1 year's military training being unaltered from those before conscription. This preliminary assessment of the SADF physical training programme suggests a need for the introduction of changes during and, in particular, after basic training.
Adipose Tissue↗
The South African Defence Force physical training programme. Part II. Effect of 1 year's military training on muscular strength, power, power-endurance, speed and flexibility.
The effect of the South African Defence Force (SADF) military training on recruits' muscular strength, power, power-endurance, speed and flexibility was investigated. In the entire study group, a significant enhancement by basic training was observed for the isokinetic muscular strength of the right elbow extensors alone (17% increase; P less than 0,05). Stratification of training responses on the basis of initial fitness levels revealed significant improvements with basic training for all measures of muscular strength, power, power-endurance and speed, but not flexibility, in the below-average fitness recruit. For all variables the training effect was transient and values documented on completion of 1 year's military training differed insignificantly from those recorded before conscription. In contrast, with the exception of elbow extensor muscular strength, fitness levels of the average and above-average recruits were not increased by basic training. While further research to assess physical requirements of various military work and emergency situations is needed to evaluate the desirability of this observed selective enhancement of recruit fitness levels during basic training, it is evident that greater emphasis should be placed on flexibility training, and physical conditioning after basic training.
Adolescent↗
The South African Defence Force physical training programme. Part III. Exertion-related injuries sustained at an SADF basic training centre.
The incidence and nature of exertion-related injuries were studied at a South African Defence Force basic training centre. A total of 404 separate injuries were sustained by 359 of 947 recruits during the 10-week basic training cycle. Of these injuries, 18,3% were sustained with (group 1) and 81,7% without (group 2) an obvious sudden precipitating event. Exertion-related injuries were responsible for a loss of 2711 recruit-days of basic training. While the knee sustained the largest number of group 2 injuries, lower leg trauma resulted in the greatest loss of basic training time. Forty-two separate radio-graphically confirmed stress fractures were incurred by 39 recruits, an incidence of 4,12%, which is considerably higher than that in the US Army. These data leave little doubt that the present training programme is costly in terms of training-time lost and may prevent large numbers of recruits from deriving the optimum conditioning benefits.
Adolescent↗
Effect of acute calcium slow-channel antagonism on the cardiorespiratory response to graded exercise testing.
The effect of acute calcium slow-channel antagonism on the cardiorespiratory responses of 12 healthy males was studied during multistage maximal exercise testing. Oral diltiazem (60 mg), nifedipine (10 mg), verapamil (80 mg), and placebo were administered in a randomized double-blind crossover fashion 1.5 h before an intermittent multistage cycle ergometer exercise test. At peak effort, heart rate, pulmonary ventilation, CO2 production, and respiratory exchange ratio were not significantly modified by drug ingestion. In contrast, maximal O2 consumption (2.6% reduction, P less than 0.02) and performance time (6.4% reduction, P less than 0.02) were reduced by nifedipine. During submaximal exercise, the chronotropic response was accentuated by nifedipine but not by diltiazem or verapamil. Furthermore, nifedipine altered the relationship of percentage of maximal O2 consumption to percentage of maximal heart rate, and both the relative and absolute O2 consumption corresponding to 70% and 85% of the maximal heart rate were significantly reduced after nifedipine ingestion. The results indicated that in persons without symptomatic coronary artery disease exercise performed at a given percentage of the maximal heart rate will yield a lower than expected relative and absolute intensity in the presence of acute nifedipine-induced calcium slow-channel antagonism.
Adult↗
Effect of selective and nonselective beta-adrenoceptor blockade on thermoregulation during prolonged exercise in heat.
The effect of selective and nonselective beta-adrenoceptor blockade on the thermoregulatory responses of 11 physically active, healthy, young adult men was studied during 2-hour block-stepping in heat. The trial consisted of 3 periods of 6 days each during which propranolol (160 mg/day), atenolol (100 mg) or matching placebo was administered in a randomized, double-blind crossover fashion. Propranolol and atenolol induced similar, significant (p less than 0.001) increases in subjective ratings of perceived exertion. The mechanism of this increased fatigue was not evident from the documented alterations in serum electrolyte, blood glucose and blood lactate levels or ventilatory parameters. Propranolol did, however, induce a postexercise delayed serum-potassium reversion. Although rectal and mean skin temperature responses were essentially unaltered by beta-adrenoceptor blockade during block-stepping, an increased total sweat loss was observed with propranolol (p less than 0.01 versus placebo) and to a lesser degree with atenolol (p = not significant versus placebo). This indicates that persons receiving beta-adrenoceptor blockers have an increased need to adhere to a strict fluid-replacement regimen during exercise. This potentially adverse response was minimal with atenolol in contrast to propranolol, and this in turn suggests the use of beta1-selective adrenoceptor blockers during prolonged exercise when adequate fluid replacement is not possible.
Adult↗
Thermoregulatory responses to weight training.
Thermoregulatory responses of eight healthy males (age 25.5 +/- 4.5 yrs) were studied during weight training comprising 3 sets of 15 repetitions of 9 exercises performed at a work cadence of 15 repetitions.min-1 with 1-min recovery intervals. The load for each exercise was increased from 50% of the 15-repetition maximum for the first set to 75% and 100% for the second and third sets, respectively. The thermoregulatory response was characterized by only moderate sweat rates (0.69 +/- 0.18 l.h-1) and rectal temperature rises (1.3 degree +/- 0.4 degree C, P less than 0.001), suggesting that dehydration and hyperthermia are unlikely to complicate weight training of the format used in this study. Despite a considerable lactic acidosis, small elevations in serum levels of aspartate aminotransferase and lactate dehydrogenase occurred, the core temperature rise being inadequate for significant cellular damage to ensue. Serum electrolyte levels measured immediately and 24 h post-exercise indicated that electrolyte supplementation is unlikely to be of benefit. Weight training induced a marked reduction of plasma volume (11.8% +/- 3.7%, P less than 0.001) in the presence of a minor water deficit (0.8% +/- 0.23%) and an O2 consumption of 32% +/- 8% of the predetermined treadmill exercise maximal O2 consumption. This finding suggests that exercise intensity as assessed by percentage maximal voluntary contraction rather than percentage maximal O2 consumption might determine the degree of hemoconcentration encountered during exercise.
Adult↗
Effect of beta1 selective adrenoceptor blockade on physiological response to exercise.
The effect of the beta1 selective adrenoceptor blocker, atenolol, on the physiological response to exercise was studied in 12 healthy young men. Oral atenolol (100 mg) and placebo were administered in a randomised double blind crossover fashion an hour and a half before an intermittent multistage cycle ergometer exercise test. At maximal effort oxygen consumption, pulmonary ventilation, carbon dioxide output, and respiratory exchange ratio were not modified by atenolol. In contrast, maximal heart rate and performance time were significantly reduced after atenolol. Nevertheless, because the relation of percentage of maximal oxygen consumption to percentage of maximal heart rate was not changed by atenolol both the absolute and relative oxygen consumption corresponding to 70% and 85% of the maximal heart rate remained unaltered. These data suggest that recommendations of exercise intensity may be determined on the basis of a calculated percentage of the predetermined maximal heart rate in persons without symptomatic coronary heart disease receiving beta1 selective adrenoceptor blockers.
Adult↗
Effect of beta-adrenoceptor blockade on thermoregulation during prolonged exercise.
The effect of clinically used equipotent doses of nonselective (beta 1/beta 2; propranolol) and selective (beta 1; atenolol) beta-adrenoceptor blockers on thermoregulation was studied during prolonged exercise in the heat. Oral propranolol (160 mg/day), atenolol (100 mg/day) or matching placebo were taken for 6 days each by 11 healthy young adult caucasian males. Subjects participated in 2 h of block-stepping at a work rate of 54 W in an environmental chamber with a temperature of 33.2 +/- 0.3 degree C dry bulb and 31.7 /+- 0.3 degree C wet bulb, 2 h after ingestion of the final dose of each drug. Both active agents produced similar marked (P less than 0.001) increases in subjective perception of effort, the mechanism of which was not immediately evident from changes in serum electrolytes, blood glucose, blood lactate, or ventilatory parameters. Propranolol did, however, cause a greater rise in serum K+ than placebo (P less than 0.02) and atenolol (P = NS) after exercise. Although rectal and mean skin temperatures were insignificantly altered by beta-adrenoceptor blockade, an increased total sweat production was noted with propranolol (P less than 0.01 vs. placebo) and to a lesser degree atenolol (P = NS vs. placebo) therapy. Analysis of the time course of sweat production showed the propranolol-mediated enhancement of sweating to ensue largely during the initial hour of block-stepping and to be transient in nature. The scientific and clinical implications of this observation will be dependent upon the precise underlying mechanism, a factor not identified by the present study.
Adrenergic beta-Antagonists↗
Inpatient cardiac rehabilitation.
Documentation of the deleterious effects associated with prolonged bed-rest provided the physiological basis for recommending more aggressive and earlier mobilization of the acute myocardial infarction patient. The 1 Military Hospital inpatient cardiac rehabilitation programme is discussed, together with the importance of the predischarge graded exercise test.
Exercise Test↗
Assessment of a geriatric exercise programme using ambulatory electrocardiography.
The purpose of this study was to assess the efficacy as well as the immediate possible cardiovascular risk of a geriatric exercise programme, administered without prior medical screening or evaluation of the exercise capacity of the participants, in improving cardiorespiratory fitness. Ambulatory electrocardiography performed during exercise on 6 randomly selected male participants in a physiotherapist-controlled geriatric exercise programme revealed heart rates of 72-97/min, values unlikely to produce significant improvements in cardiorespiratory fitness. This low-intensity exercise session did not induce any ischaemic ST-segment displacements, or arrhythmias displaying the generally accepted criteria for premonitory arrhythmias known to precede the development of ventricular fibrillation. However, subsequent stress testing, performed at the lower threshold intensity of exercise needed to elicit a significant physiological training effect, resulted in an adverse cardiac response in 3 subjects, of whom 2 were asymptomatic. We conclude that the geriatric exercise programme under investigation would be unlikely to result in improved cardiorespiratory fitness in the majority of participants, but if such a programme is to be implemented in a safe manner in a geriatric population, prior medical screening including exercise testing is mandatory.
Aged↗