Search PubMed⌕ Search

Biomedical subjects

J R Sutton

Publications and source records attributed to J R Sutton.

162 records · Page 9Linked to original sources
PubMed1977

Effect of acute hypoxia on the hormonal response to exercise.

The hormonal responses to submaximal exercise under normoxic and hypoxic conditions were studied in eight fit males, aged 22--28 yr, with mean maximal oxygen uptake of 4.4 +/- 0.7 l/min. Studies were performed in a hypobaric chamber, decompressed to a simulated altitude of 4,550 m (PIO2 = 83 Torr). The subjects exercised for 20 min at 750 kpm/min on a cycle ergometer. Venous blood samples were obtained at rest, during exercise and for 60 min after exercise. Plasma glucose, free fatty acids, lactate, cortisol, and serum growth hormone concentrations all increased more during hypoxic exercise than under normoxic conditions. Serum insulin concentration showed a small decrease under normoxic conditions, but decreased by 50% during hypoxic exercise, and was followed by marked rebound when exercise stopped. These changes suggest that energy substrate-hormone interrelationships are altered by hypoxic exercise, resulting in increased fat mobilization and increased gluconeogenesis.

Adult↗
PubMed1977

Renin, aldosterone, electrolyte, and cortisol responses to hypoxic decompression.

Responses of plasma renin activity, plasma aldosterone, plasma cortisol, and plasma electrolyte concentration and urinary electrolyte and aldosterone excretion were studied in four men during hypoxic decompression to a stimulated altitude of 4,760 m in a pressure chamber. Three of the four subjects developed significant acute mountain sickness. Plasma sodium and potassium concentrations were unchanged. No significant change in plasma renin activity was observed, but values tended to fall. Plasma aldosterone concentration was depressed while plasma cortisol was elevated and diurnal variation lost. Urinary sodium excretion was unchanged, but urinary potassium and aldosterone excretion were decreased. The decrease in plasma and urinary aldosterone and urinary potassium in the absence of change in plasma renin activity or plasma potassium is of uncertain origin. It is unlikely to be due to a decrease in adrenocorticotropin secretion since plasma cortisol rose during the same time. None of the changes could be causally implicated in the development of acute mountain sickness although the increase in plasma cortisol was greatest in the most ill.

Adult↗
PubMed1977

Biochemical adaptation of human skeletal muscle to heavy resistance training and immobilization.

Nine healthy subjects were studied under control conditions and following 5 mo of heavy resistance training and 5 wk of immobilization in elbow casts. Needle biopsies were taken from triceps brachii and analyzed for adenosine triphosphate (ATP), adenosine diphosphate (ADP), creatine (C), creatine phosphate (CP, and glycogen concentrations. Training resulted in an 11% increase in arm circumference and a 28% increase in maximal elbow extension strength. Immobilization resulted in decreases in arm circumference and elbow extension strength of 5% and 35%, respectively. Training also resulted in significant increases in resting concentrations of muscle creatine (by 39%), CP (by 22%), ATP (by 18%), and glycogen (by 66%). Conversely, immobilization significantly reduced CP concentration by 25% and glycogen concentration by 40%. It was concluded that heavy-resistance training results in increases in muscle energy reserves which may be reversed by a period of immobilization-induced disuse.

Adenosine Diphosphate↗
PubMed1977

Effect of pH on cardiorespiratory and metabolic responses to exercise.

Five male subjects performed exercise at 33, 66, and 95% of their maximum power output on three occasions in random order. Each study was preceded by a 3-h period in which capsules were taken by mouth, containing either CaCO3 (control, NH4Cl (acidosis), or NaHCO3 (alkalosis) in a dose of 0.3 g/kg body wt; preexercise blood pH was 7.38 +/- 0.015, 7.21 +/- 0.033, and 7.43 +/- 0.029, respectively. Exercise was continuous and maintained for 20 min at the two lower power outputs and for as long as possible at the highest. Compared with control (270 +/- 13 s), endurance time at the highest power output was reduced in acidosis (160 +/- 22 s) and increased in alkalosis (438 +/- 120 s). No differences were observed for central cardiovascular changes in exercise (cardiac output, frequency, or stroke volume). The respiratory changes expected from changes in blood pH were observed, with a higher alveolar ventilation in acidosis. At all power outputs arterialized venous lactate was lowest in acidosis and highest in alkalosis. Plasma glycerol and free fatty acids were lowest in acidosis. Changes in blood [HCO3-] and pH were shown to have major effects on metabolism in exercise which presumably were responsible for impaired endurance.

Acidosis↗
PubMed1977

Nitrogen washout studies in acute mountain sickness.

We assessed the severity of Acute Mountain Sickness (A.M.S.), indices of pulmonary gas exchange and nitrogen washout curves in healthy volunteers acutely exposed to high altitude. Symptoms of A.M.S. ranged from malaise to vomiting with intractable headache. The slope of phase III of the nitrogen washout curve increased most in those subjects with the most severe A.M.S. and who were most hypoxemic. The sickest subject also had the greatest increase in (A-a)DO2 and the largest increase in the slope of phase III. These abnormalities in gas exchange and nitrogen washout curves in the subjects with the most marked A.M.S. suggest that the manifestations of cerebral and pulmonary dysfunction at altitude develop simultaneously, although not necessarily by identical mechanisms.

Adolescent↗
PubMed1976

Growth hormone secretion in acid-base alterations at rest and during exercise.

1. Seven healthy males were studied during cycle ergometer exercise at 33%, 66% and 90% of VO2 max. on three occasions when NH4C1, NaHCO3 or CaCO3 (as a control substance) were administered in gelatin capsules double blind and in randomized order. Plasma growth hormone (HGH), lactic acid and hydrogen ion concentration ([H+]) were measured at frequent intervals. 2. Ammonium chloride produced highest blood [H+] and NaHCO3 the lowest. These differences were maintained during exercise and in recovery. Plasma lactic acid concentrations were similar at rest. At 66%, 90% VO2 max. and recovery lactic acid was highest with NaHCO3 and lowest with NH4C1. 3. Exercise stimulated HGH secretion in all studies and the elevation was proportional to the intensity of the exercise. NH4C1 caused a variable elevation of HGH at rest and 33% VO2 max. At 66% VO2 max., plasma HGH was significantly elevated to similar concentrations in all studies and, at 90% VO2 max., HGH was highest with NaHCO3. 4. An infusion of sodium L(+)-lactate producing plasma lactate concentrations of 3-5 mmol/l did not influence HGH secretion. 5. Exercise is a physiological stimulus to HGH secretion and the mechanism is independent of blood [H+] and lactate concentrations.

Acid-Base Equilibrium↗
PubMed1976

Pulmonary gas exchange in acute mountain sickness.

The severity of acute mountain sickness (AMS) was investigated in healthy volunteers, airlifted to high altitude (5,360 m). Blood gases were measured at 2,990 m and 5,360 m. Symptoms of AMS were found in all subjects, but ranged from malaise to vomiting with intractable headache. The clinical severity of AMS was directly related to the arterial PCO2 and inversely to pH, but unrelated to the PO2 on arrival at high altitude. However, PO2 fell and was lowest 48 h after arrival at high altitude in those subjects with the most severe AMS. These were the only subjects to show an increase in the alveolar-arterial PO2 difference and in the venous admixture ratio during the first 48 h. These abnormalities in gas exchange, which developed in the subjects with the most marked cerebral symptoms, suggest that the manifestations of cerebral and pulmonary dysfunction at altitude develop simultaneously, a finding that suggests coexisting cerebral and pulmonary edema.

Acute Disease↗
PubMed1973

Androgen responses during physical exercise.

The serum androgen response to physical exercise was studied in highly trained athletes and in normal male medical students. Serum androgens rose in response to maximal exercise and the rise was independent of serum luteinizing hormone. No response was obtained with submaximal exercise.

Adolescent↗
PubMedDate not supplied

Operation Everest II: cardiac filling pressures during cycle exercise at sea level.

To examine the relationship between cardiac filling pressures during exercise in man and oxygen transport, we examined sea level data from Operation Everest II. The results showed that, (1) both right atrial and wedge pressures rose with heavy exercise in normal man, (2) the magnitude of the rise in these filling pressures related both to stroke volume and maximum exercise capacity, (3) wedge pressure was tightly coupled to right atrial pressure, with each mm Hg increase in right atrial pressure resulting in a 1.4 mm Hg increase in wedge pressure, and (4) very high wedge pressures occurred (in some subjects greater than 30 mm Hg), which contributed to an elevation of pulmonary arterial pressure. Thus direct measurements indicate right heart filling pressure increases with exertion in normal man, probably providing the necessary right heart output to fill the left heart. We speculated that the high cardiac filling pressures might be needed to maintain oxygen transport during heavy exercise, and that such pressures could contribute both to elevated pulmonary arterial pressure and to increased filtration of water into the lung.

Adult↗
PubMedDate not supplied

Endorphins and exercise.

The endogenous opioids seem likely to be assigned a significant role in the integrated hormonal and metabolic response to exercise. This article reviews the present evidence on exercise and the endogenous opioids, and examines their involvement in a number of widely disparate physiological processes. In considering the role of individual opioid peptides, it is important to remember that many of the tools and techniques now used are still relatively crude. Most studies have demonstrated that serum concentrations of endogenous opioids, in particular beta-endorphin and beta-lipotrophin, increase in response to both acute exercise and training programmes. Elevated serum beta-endorphin concentrations induced by exercise have been linked to several psychological and physiological changes, including mood state changes and 'exercise-induced euphoria', altered pain perception, menstrual disturbances in female athletes, and the stress responses of numerous hormones (growth hormone, ACTH, prolactin, catecholamines and cortisol). Many reports have described a role for the endorphin response as seen during exercise and have used the opioid receptor antagonist, naloxone, to investigate and verify the degree of involvement of the opioids. However, whether the observed increases in peripheral endorphin concentrations are sufficient to cause immediate mood changes, create menstrual cycle dysfunction or alter pain perception is still not resolved. A relatively new implication for the endorphins and associated changes with exercise is in ventilatory regulation. A number of studies have suggested that endogenous opioids depress ventilation and may, therefore, play a role in ventilatory regulation by carbon dioxide, hypoxia and exercise. It may also be possible that during exercise, the perception of fatigue is modulated by an increase of endogenous opioids.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

The aetiology of sport injuries. A review of methodologies.

Although participation in many sporting activities has increased dramatically in recent years, the study of injuries sustained during training or participation is still in its infancy. The most commonly used strategy is to describe the characteristics of a suitable case-series. This approach is relatively easy to implement, can be used to estimate the total morbidity load in a population, and can identify the relative frequency of various types of injury. However, the case series method cannot validly identify risk factors for injury or athletes at high risk; similarly, it cannot be used to estimate the absolute level of risk associated with sports participation. Finally, the population from which the injuries arose is often difficult to identify, and the series may not be representative of all injuries occurring in that population, and this may produce quite misleading results. In contrast, a variety of epidemiological designs may be employed to address questions of aetiology and to identify high risk groups of athletes. With careful attention to the underlying population denominators, one may estimate the relative or absolute risk of injury for athletes with given risk characteristics, defined by type and intensity of their participation in sports or by their individual physiology. This is achieved by inclusion of suitable control subjects in the epidemiological sample; these controls may be uninjured athletes or random samples of the general population. The comparison of injured and uninjured groups permits valid inferences to be drawn concerning risk factors, avoiding the many potential biases which affect inferences drawn from injured athletes only.

Adult↗
PubMedDate not supplied

Not so fun run.

Explore the source record for details and available documents.

Australia↗