Abstract: The purpose of this study was to evaluate the effects of continuous and interval training on changes in lactate and ventilatory thresholds during incremental exercise. Seventeen males were assigned...

Abstract: Plasma potassium rises during muscular exercise and falls rapidly when exercise is stopped. Since the sympathoadrenal system is stimulated with exertion and both alpha- and beta-adrenergic agonists affect internal potassium homeostasis, we studied the influence of catecholamines on potassium shifts during and after exercise. Six healthy subjects were given maximal exercise stress tests under three conditions: with no medication (control), during beta-blockade with propranolol, and during alpha-blockade with phentolamine. Compared with a peak rise in plasma potassium of 1.23 +/- 0.27 mmol per liter (mean +/- S.E.M.) during the control study, propranolol caused a rise of 1.89 +/- 0.35 (P less than 0.01) and a sustained elevation during recovery. Phentolamine diminished the rise of potassium (0.70 +/- 0.21 mmol per liter; P less than 0.01) and lowered the potassium level throughout recovery. These effects of catecholamines were independent of the venous pH, the plasma bicarbonate and serum glucose levels, and urinary potassium excretion, and they did not appear to be due to insulin. High norepinephrine and epinephrine levels confirmed the release of catecholamines capable of stimulating alpha- and beta-receptors. Exercise work did not differ among the groups. beta-Adrenergic receptors appear to moderate the acute hyperkalemia of exercise, whereas alpha-adrenergic receptors act to enhance hyperkalemia and may protect against hypokalemia when exertion ceases.

Abstract: Exercise has numerous effects on the pregnant woman, the developing fetus, and the placenta. In turn, pregnancy affects the ability to perform physical activity. During pregnancy, increased metabolism at rest results almost exclusively from the gestational increase in mass. Because of this increase, a higher cardiorespiratory effort is required to perform a given amount of external work. One would expect the result to be some training effect, unless a more sedentary lifestyle is adopted. The possibility that maximal O2 consumption may increase during pregnancy has not been studied extensively, yet it is a most important variable that puts other changes in perspective. The sedentary lifestyle commonly adopted in late pregnancy in most western societies may reflect a cultural rather than a physiological phenomenon. In contrast to the physiological alterations in the mother and despite the reductions in uterine blood flow during maternal exercise, physiological changes in the fetus are small. Relatively minor changes occur in the blood concentrations of O2 and substrates during prolonged exhaustive exercise. In addition, despite a temperature increase of 1 to 2 degrees C, there is little evidence for significant alteration in fetal metabolism, cardiovascular hemodynamics, or blood catecholamine concentrations. These observations suggest that acute exercise normally does not represent a major stress for the fetus. Of course, most of the information concerning the fetus is derived from studies in experimental animals, particularly in sheep. In humans the upright position and increased uterine contractibility may affect the fetal responses differently. Virtually nothing is known about the physiological effects of exercise training on the fetus. The most likely effect may be a relatively small reduction in birth weight in some species, but this needs further investigation. Further studies are also needed for a more complete understanding of the mechanisms involved in the remarkably effective mechanisms that account for the relative homeostasis of the fetus during maternal exercise.

Abstract: We evaluated the effect of strenuous aerobic exercise on joint symptoms and compared the functional capacity and muscle strength among patients with rheumatoid arthritis (RA) and osteoarthritis (OA), and very sedentary matched controls. Strenuous ergometer exercise did not exacerbate joint symptoms in these patients. Isotonic leg extension and flexion as well as grip strength were diminished in the RA and OA subjects compared to controls (p less than 0.05). All subjects displayed low maximum oxygen consumption indicating reduced functional capacity. Acute bouts of strenuous exercise performed on bicycle ergometer do not appear harmful to the nonacute arthritis patient.

Abstract: The effects of coenzyme Q10(CoQ10) on exercise performance were studied in 12 patients, average age 56 years, with stable angina pectoris. The study involved a double-blind, placebo-controlled, randomized, crossover protocol, using multistage treadmill exercise tests. CoQ10(150 mg/day in 3 daily doses) was administered orally for 4 weeks, tended to reduce anginal frequency from 5.3 +/- 4.9 to 2.5 +/- 3.3 attacks for 2 weeks and nitroglycerin consumption from 2.6 +/- 2.8 to 1.3 +/- 1.7 tablets for 2 weeks compared with patients receiving the placebo, but the reduction was not statistically significant. Exercise time increased from 345 +/- 102 seconds with placebo to 406 +/- 114 seconds during CoQ10 treatment (p less than 0.05). The time until 1 mm of ST-segment depression occurred increased from 196 +/- 76 seconds with placebo to 284 +/- 104 seconds during CoQ10 treatment (p less than 0.01). During the exercise test, ST-segment depression, heart rate and pressure-rate product at the same and at the maximal workload showed no significant difference between patients after placebo and CoQ10 administration. The average CoQ10 plasma concentration increased from 0.95 +/- 0.48 microgram/ml to 2.20 +/- 0.98 microgram/ml after CoQ10 treatment. This increase was significantly related to the increase in exercise duration (r = 0.68, p less than 0.001). Only 1 patient had a loss of appetite, but continued therapy. This study suggests that CoQ10 is a safe and promising treatment for angina pectoris.

Abstract: : The effects of physical exercise and sleep deprivation on mood and cognitive performance were studied in 12 healthy young male volunteers deprived of sleep on two occasions. During the first 60-hr period without sleep, half of the subjects walked on a treadmill at 25-30% of their maximum aerobic capacity (Exercise condition) for 1 out of every 3 hrs while the remaining 6 subjects remained physically inactive (No Exercise condition) during that same hour. Eight weeks later the same 12 subjects underwent an identical sleep-deprivation protocol except that those who were previously inactive exercised, while those who previously exercised remained inactive. Throughout the sleep deprivation periods, subjects in both conditions completed subjective assessments of fatigue, sleepiness and mood every 3 hrs, performed an auditory vigilance task every 6 hours, and completed a cognitive test battery every 12 hrs. The results revealed clear decrements in mood and performance as a function of sleep loss. However, with the exception of somewhat more long reaction times in the Exercise condition, exercise neither increased nor decreased the impairment induced by sleep deprivation. Keywords: Sleep deprivation, Sleep loss, Exercise, Mood, Performance, Fatigue, Stress.

Abstract: Strenuous exercise induces profound changes in renal hemodynamics and the protein content of urine. Postexercise proteinuria seems to be directly related to the intensity of exercise, rather than to its duration. The pattern of proteins identified in urine collected after exercise is different from normal physiological proteinuria. Immunochemical techniques demonstrate that postexercise proteinuria is of mixed glomerular-tubular type when heavy exercise is involved. The origin of proteinuria after light exercise seems to be preponderantly of glomerular type. Clearance of individual plasma proteins suggests an increased glomerular permeability and a partial tubular-reabsorption inhibition of macromolecules.

Abstract: Alterations in the intensity and pattern of spontaneous running activity as rats increase in age from 7 wk to 1 yr was studied in male rats placed in exercise wheel cages. Daily running records wer...

Abstract: Exercise is frequently recommended as part of a comprehensive program of prevention, treatment or rehabilitation of chronic degenerative disease. General guidelines on prescribing exercise are based more on the characteristics of exercise required to improve physical performance than on preventing disease. Most exercise regimens are evaluated according to their effect on aerobic power or endurance. Health benefits of exercise may occur in conjunction with an improvement in physical performance capacity, but some benefits appear to be achieved by exercise that normally does not lead to improved physical fitness. Health benefits may occur as a result of repeated acute responses to exercise (but without producing a training effect) and by frequent performance of low intensity exercise (inadequate for increasing fitness). Psychological benefits may also be derived by the process of exercising. The persons who benefit most from an increase in exercise are the very inactive because the detrimental health-related consequences of extreme inactivity are rapidly reversed. There is less evidence that an increase in exercise by the already active person results in significant health benefits.

Abstract: Six healthy active women in the third trimester of pregnancy participated in a graded exercise protocol to levels of exertion perceived to be equivalent to that of their usual exercise regimen. Fetal heart rate response (FHR) was documented by ultrasound transducer and confirmed (n = 1) by ultrasonic visualization. Resting maternal O2 consumption was 277 +/- 50 (SD) ml/min and rose to 1,132 +/- 202 ml/min at a mean final exercise intensity of 79 +/- 9 W after 12.8 +/- 1.7 min on a cycle ergometer. There was no significant change in maternal serum insulin, growth hormone, glucose, or pH values. Maternal leukocyte count, hemoglobin, and venous lactate levels rose significantly during the exercise (P less than 0.05). FHR prior to exercise was 142 +/- 4 beats/min and decreased to 84 +/- 34 beats/min during exercise. The decrease in FHR was documented within 1 min of initiating exercise in all cases. During exercise, fetal movements were not accompanied by FHR accelerations. Within 1 min following the cessation of exercise, FHR rose to 143 +/- 8 beats/min and fetal movements were accompanied by FHR accelerations. Since the recovery of FHR occurred immediately after cessation of maternal exercise, this level of maternal exercise does not appear to be harmful to the fetus.

Abstract: Alternative methods of exercise testing are needed for patients with vascular, orthopedic or neurologic conditions who cannot perform leg exercise. To determine the sensitivity of arm exercise in detecting coronary artery disease (CAD), 30 patients with angina pectoris performed both arm ergometry and treadmill testing before coronary angiography. All patients had at least 70% diameter reduction in 1 or more major coronary arteries. Ischemic ST depression (≥1 mm) or angina occurred more frequently (86%, 26 patients) with leg exercise than with arm exercise (40%, 12 patients). There was no significant difference in peak rate-pressure product achieved with either test, although the peak oxygen consumption was greater during leg exercise than during arm exercise (18 vs 13 ml/kg/min, respectively, p

Abstract: Male rats maintained under constant environmental conditions were randomly assigned to nonrunner (NR) and voluntary exercise (R) groups. At 9 mo, voluntary exercise significantly increased muscle cytochrome c concentration and citrate synthase activity. Also, at the same age, R animals had significantly greater glycosaminoglycan concentration than NR, but no changes in dry weight and collagen concentration were significant. By age 28 mo, the R groups had reduced daily running by 70%, and elevation of tendon glycosaminoglycans relative to NR animals was no longer statistically significant. A similar trend was noted for muscle mitochondrial markers. Aging significantly decreased tendon glycosaminoglycans and increased collagen concentration. Although aging reduced the total amount of voluntary exercise, the concentration of tendon glycosaminoglycans in 28-mo-old runners was equivalent to levels in 9-mo-old sedentary rats, suggesting that voluntary exercise slowed the decline in galactosamine-containing glycosaminoglycans with aging.

Abstract: In muscle phosphorylase deficiency (McArdle's disease) there is an abnormally rapid fatigue during strenuous exercise. Increasing substrate availability to working muscle can improve exercise tolerance but the effect on muscle energy metabolism has not been studied. Using phosphorus-31 nuclear magnetic resonance (31P-NMR) we examined forearm muscle ATP, phosphocreatine (PCr), inorganic phosphate (Pi) and pH in a McArdle patient (MP) and two healthy subjects (HS) at rest and during intermittent maximal effort handgrip contractions under control conditions (CC) and during intravenous glucose infusion (GI). Under CC, MP gripped to impending forearm muscle contracture in 130 s with a marked decline in muscle PCr and a dramatic elevation in Pi. During GI, MP exercised easily for greater than 420 s at higher tensions and with attenuated PCr depletion and Pi accumulation. In HS, muscle PCr and Pi changed more modestly and were not affected by GI. In MP and HS, ATP changed little or not at all with exercise. The results suggest that alterations in the levels of muscle PCr and Pi but not ATP are involved in the muscle fatigue in McArdle's disease and the improved exercise performance during glucose infusion.

Abstract: Muscular performance was tested during 64 hours of sleep deprivation with and without intermittent excercise (treadmill walking at 28% of maximum oxygen intake). The subjects (12 males aged 22·7 ± 2·2 years) carried out a cross-over trial with an 8 week interval separating the two periods of sleep deprivation. The sleep deprivation did not change the time for a 40 m dash, isometric handgrip force or balance (stabilometer test). Vertical jump height decreased, the change being significant for simple sleep deprivation, but not for the combination of deprivation and intermittent exercise. Sleep deprivation decreased isokinetic extension force at 60° s−1, while intermittent walking decreased isokinetic extension force at both 60 and 180° −1; however, there was no significant difference between exercise plus sleep deprivation and sleep deprivation alone at either angular velocity. We conclude that the moderate intensity of physical activity likely in industrial work has little influence upon human performance ...

Abstract: Seventeen children developed reproducible early and late asthmatic responses (dual reactions) after cycle ergometer exercise. There was a significant correlation between the magnitude of their early and late reactions, emphasizing the direct relationship of these events. No ;significant differences were observed in the clinical severity of asthma, diurnal variations in FEV 1 and extent of the early reaction after exercise between children with dual responses and 19 children with single reactions. These findings suggest that the occurrence of late reactions after exercise is not determined by differences in severity of disease or baseline airway reactivity in the asthmatic subjects. This view is supported by the finding that there was no significant difference in the dose of acetylcholine necessary to elicit a 20% decrease in FEV, between eight children with dual response and seven children with single early response after exercise . The rate of spontaneous recovery from early reactions was slower in children with dual responses, suggesting that this variable may predict development of late-phase reactions in exercise-induced asthma.

Abstract: To evaluate the effect of endurance training on ventilatory function in older individuals, 1) 14 master athletes (MA) [age 63 +/- 2 yr (mean +/- SD); maximum O2 uptake (VO2max) 52.1 +/- 7.9 ml . kg-1 . min-1] were compared with 14 healthy male sedentary controls (CON) (age 63 +/- 3 yr; VO2max of 27.6 +/- 3.4 ml . kg-1 . min-1), and 2) 11 sedentary healthy men and women, age 63 +/- 2 yr, were reevaluated after 12 mo of endurance training that increased their VO2max 25%. MA had a significantly lower ventilatory response to submaximal exercise at the same O2 uptake (VE/VO2) and greater maximal voluntary ventilation (MVV), maximal exercise ventilation (VEmax), and ratio of VEmax to MVV than CON. Except for MVV, all of these parameters improved significantly in the previously sedentary subjects in response to training. Hypercapnic ventilatory response (HCVR) at rest and the ventilatory equivalent for CO2 (VE/VCO2) during submaximal exercise were similar for MA and CON and unaffected by training. We conclude that the increase in VE/VO2 during submaximal exercise observed with aging can be reversed by endurance training, and that after training, previously sedentary older individuals breathe at the same percentage of MVV during maximal exercise as highly trained athletes of similar age.

Abstract: The present study was conducted to investigate the metabolic regulation of leucine oxidation during exercise. Ten rats per group were run at 27 m/min (0% grade) on a treadmill for 30 and 120 min or until exhausted, and the total and basal activity of branched-chain keto acid dehydrogenase was examined in the muscle, liver, and heart. The total activity of the dehydrogenase in the heart, liver, or skeletal muscle was unchanged by exercise. However, exercise increased the basal activity levels of the dehydrogenase about 10-fold in muscle and 5-fold in heart. The basal dehydrogenase activity in the liver was unchanged by exercise. Activation of the dehydrogenase in both muscle and heart was statistically elevated after 30 min exercise and continued to increase during the remainder of the exercise bout. The basal activity of the dehydrogenase returned to resting levels by 10 min postexercise. The activation of the dehydrogenase in muscle and heart during exercise likely is due to dephosphorylation because activity of the enzyme in mitochondria isolated from exercised muscles reverts to control values when the mitochondria are incubated in the presence of ATP. Thus the increased leucine oxidation observed during exercise is due to activation of the branched-chain keto acid dehydrogenase by dephosphorylation. This is the first example of a large increase in branched-chain keto acid dehydrogenase activity caused by a physiological process. This demonstrates that the muscle's latent capacity of oxidize branched-chain amino acids is much larger than previously thought and that this capacity is used in exercising muscle.