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Biomedical subjects

E W Banister

Publications and source records attributed to E W Banister.

At least 19 recordsLinked to original sources
PubMed1992

Dose/response effects of exercise modeled from training: physical and biochemical measures.

This study has measured the pattern of elevated serum enzyme activity (ESEA) during extended daily training in a dose-response manner and compared ESEA to the pattern of accumulated fitness and fatigue predicted from a mathematical model previously described. Blood samples were taken regularly during the study from each subject and the activity of lactate dehydrogenase (LDH), creatine kinase (CK), and aspartate aminotransferase (AST) in the serum was measured. Although no single physiological/biochemical correlate of the hypothesized fatigue compartment of performance is firmly identified it is significant that the pattern of variation of model fatigue and ESEA throughout training were similar although slightly out of phase. With continued hard training, model fatigue began to plateau and concomitantly ESEA declined exponentially from its initial high value in early training. During relative rest throughout a tapering period following training both ESEA and fatigue reverted quickly towards baseline and follow the similar but earlier time course in blood of a degradative membrane enzyme phospholipase A2 observed in clinical studies.

Adult↗
PubMed1992

The clearance rate of exercise-elevated blood lactate following physical training.

In this paper, previous studies regarding the effect of physical training on the disappearance rate of blood La during recovery after strenuous exercise have been briefly summarized. The results of our own recent study of this problem have also been added. It may be concluded that there is some evidence for an improved lactate metabolic clearance rate resulting from physical training in human subjects, when the degradation rate is estimated from serial blood samples taken during a standard ramp ergometer test to exhaustion during each week of a training/detraining sequence. This beneficial effect of training, however, may also be influenced by the initial physical status of the subject and the nature of the training program.

Exercise↗
PubMed1991

Exercise breathing pattern during chronic altitude exposure.

Breathing pattern in response to maximal exercise was examined in four subjects during a 7-day acclimatisation to a simulated altitude of 4247 m (barometric pressure, PB = 59.5 kPa). Graded exercise tests to exhaustion were performed during normoxia (day 0), and on days 2 and 7 of hypoxia, respectively. Ventilation was significantly augmented in the hypoxic environment, as were both the mean inspiratory flow (VT/TI) and inspiratory duty cycle (TI/TTOT) components of it. VI/TI was increased due to a significant increase in tidal volume (VT) and a corresponding decrease in inspiratory time duration (TI). Throughout a range of exercise ventilation, TI/TTOT was increased due to an apparently greater decrease in expiratory time duration (TE) with respect to TI. In all cases, the relation between VT and TI displayed a typical range 2 behaviour, with evidence of a range 3 occurring at very high ventilatory rates. There was essentially no difference observed in the VT-TI relation during exercise between the normoxic and hypoxic conditions. No significant changes were observed in the breathing pattern in response to exercise within the exposure period (from day 2 to day 7), although there was a discernible tendency to a higher stage 3 plateau by day 7 of altitude exposure.

Acclimatization↗
PubMed1991

Optimizing athletic performance by influence curves.

Recent application of modeling techniques to physical training has opened the possibility for prediction from training. Solution of the inverse problem, determining a training program to produce a desired performance at a specific time, is also possible and may yield strategies for achieving better training and tapering (complete or relative rest for a period before competition) regimens for competitive athletes. A mathematical technique derived from model theory is described in this paper that allows the design of an optimal strategy of physical preparation for an individual to do well in a single future competitive event or cluster of events. Simulation results, using default parameters of a training model, suggest that presently accepted forms of taper for competition may remain too rigorous and short in duration to achieve the best result possible from the training undertaken.

Humans↗
PubMed1990

Exercise-induced hyperammonemia: peripheral and central effects.

The intent of this paper is to review the recent literature on exercise-induced hyperammonemia (EIH) and to compare the current interpretations of ammonia accumulation during exercise with the recognized clinical symptoms of progressive ammonia toxicity. In doing so, we will speculate on possible exercise-induced symptoms of CNS dysfunction which could result from elevated ammonia during intense short-duration or prolonged exercise. Ammonia is a ubiquitous metabolic product producing multiple effects on physiological and biochemical systems. Its concentration in several body compartments is elevated during exercise, predominantly by increased activity of the purine nucleotide cycle (PNC) in skeletal muscle. Depending on the intensity and duration of exercise, muscle ammonia may be elevated to the extent that it leaks (diffuses) from muscle to blood, and thereby can be carried to other organs. The direction of movement of ammonia or the ammonium ion is dependent on concentration and pH gradients between tissues. In this manner, ammonia can also cross the blood-brain barrier (BBB), although the rate of diffusion of ammonia from blood to brain during exercise is unknown. It seems reasonable to assume that exhaustive exercise may induce a state of acute ammonia toxicity which, although transient and reversible relative to disease states, may be severe enough in critical regions of the CNS to affect continuing coordinated activity. Regional differences in brain ammonia content, detoxification capacity, and specific sensitivity may account for the variability of precipitating factors and latency of response in CNS-mediated dysfunction arising from an exercise stimulus, e. g., motor incoordination, ataxia, stupor. There have been numerous suggestions that elevated ammonia is associated with, or perhaps is responsible for, exercise fatigue, although evidence for this relies extensively on temporal relationships. Fatigue may become manifest both as a peripheral organ or central nervous system phenomenon, or combination of both. Thus, we must examine the sequential or concomitant changes in ammonia concentration occurring in the periphery, the central nervous system (CNS), and the cerebrospinal fluid (CSF) induced by any effector, not only exercise, to interpret and rationalize the diverse physical, physiological, biochemical, and clinical symptoms produced by hyperammonemic states. Since more is known about elevated brain ammonia during other diverse conditions such as disease states, chemically induced convulsion, and hyperbaric hyperoxia, some of these relevant data are discussed.

Ammonia↗
PubMed1990

Modeling human performance in running.

This paper focuses on the characteristics of a model interpreting the effect of training on athletic performance. The model theory is presented both mathematically and graphically. In the model, a systematically quantified impulse of training produces dual responses: fitness and fatigue. In the absence of training, both decay exponentially with time. With repetitive training, these responses satisfy individual recurrence equations. Fitness and fatigue are combined in a simple linear difference equation to predict performance levels appropriate to the intensity of training being undertaken. Significant observed correlation of model-predicted performance with a measure of actual performance during both training and tapering provides validation of the model for athletes and nonathletes alike. This enables specific model parameters to be estimated and can be used to optimize future training regimens for any individual.

Adult↗
PubMed1988

Effect of cold air inhalation on core temperature in exercising subjects under heat stress.

Whether increasing respiratory heat loss (RHL) during exercise under heat stress can contain elevation of rectal temperature (Tre) was examined. Eight men cycled twice at 45-50% their maximum work rate until exhaustion at ambient temperature and relative humidity of 38 degrees C and 90-95%, respectively. They inspired either cold (3.6 degrees C) or ambient air in random sequence. When subjects breathed cold air during 23 min of exercise, a ninefold increase in RHL was observed vs. similar work during hot air inhalation (32.81 vs. 3.46 W). Respiratory frequency (f) and rate of rise in Tre decreased significantly (P less than or equal to 0.004 and P less than or equal to 0.002, respectively). The rise in skin temperature in each inhalant gas condition was accompanied by a parallel almost equal increase in core temperature above basal (delta Tre) for equivalent gains in skin temperature. The increase in tidal volume and decreased f in the cold condition allowed more effective physical conditioning of cold inspirate gas in the upper airways and aided RHL. Cold air inhalation also produced a significant (P less than or equal to 0.05) decrease in heart rate vs. hot air inhalation in the final stages of exercise. Insignificant changes in O2 consumption and total body fluid loss were found. These data show that cold air inhalation during exercise diminishes elevation of Tre and suggest that both the intensity and duration of work can thus be extended. The importance of the physical exchange of heat energy and any physiological mechanisms induced by the cold inspirate in producing the changes is undetermined.

Adult↗
PubMed1988

Possible mechanisms of the anaerobic threshold. A review.

The anaerobic threshold consists of a lactate threshold and a ventilatory threshold. In some conditions there may actually be 2 ventilatory thresholds. Much of the work detailing the lactate threshold is strongly based on blood lactate concentration. Since, in most cases, blood lactate concentration does not reflect production in active skeletal muscle, inferences about the metabolic state of contracting muscle will not be valid based only on blood lactate concentration measurements. Numerous possible mechanisms may be postulated as generating a lactate threshold. However, it is very difficult to design a study to influence only one variable. One may ask, does reducing F1O2 cause an earlier occurrence of a lactate threshold during progressive exercise by reducing oxygen availability at the mitochondria? By stimulating catecholamine production? By shifting more blood flow away from tissues which remove lactate from the blood? Or by some other mechanism? Processes considered essential to the generation of a lactate threshold include: (a) substrate utilisation in which the ability of contracting muscle cells to oxidise fats reaches maximal power at lactate threshold; and (b) catecholaminergic stimulation, for without the presence of catecholamines it appears a lactate threshold cannot be generated. Other mechanisms discussed which probably enhance the lactate threshold, but are not considered essential initiators are: (a) oxygen limitation; (b) motor unit recruitment order; (c) lactate removal; (d) muscle temperature receptors; (e) metabolic stimulation; and (f) a threshold of lactate efflux. Some mechanisms reviewed which may induce or contribute to a ventilatory threshold are the effects of: (a) the carotid bodies; (b) respiratory mechanics; (c) temperature; and (d) skeletal muscle receptors. It is not yet possible to determine the hierarchy of effects essential for generating a ventilatory threshold. This may indicate that the central nervous system integrates a broad range of input signals in order to generate a non-linear increase in ventilation. Evidence indicates that the occurrence of the lactate threshold and the ventilatory threshold may be dissociated; sometimes the occurrence of the lactate threshold significantly precedes the ventilatory threshold and at other times the ventilatory threshold significantly precedes the lactate threshold. It is concluded that the 2 thresholds are not subserved by the same mechanism.

Animals↗
PubMed1987

The pattern of breathing during hypoxic exercise.

Breathing pattern was studied in six subjects in normoxia (FIO2 = 0.21) and hypoxia (FIO2 = 0.12) at rest and during incremental work-rate exercise. Ventilation (V) as well as mean inspiratory flow (VT/TI) increased with exercise intensity and were augmented in the hypoxic environment, whereas the ratio between inspiratory (TI) and total (Ttot) breath durations increased with exercise intensity but was unaffected by hypoxia. The relationship of tidal volume (VT) and inspiratory time duration (TI) showed linear, coinciding ranges for the normoxic and hypoxic conditions up to VT/TI values of about 2.5 1.s-1. At higher VT/TI values TI continued to decrease, whereas VT tended to level off, an effect which was more evident in the hypoxic condition. The results suggest that the hypoxic augmentation of exercise hyperpnea is primarily brought about by an enhancement of central inspiratory drive, the timing component being largely unaffected by the hypoxic environment, and that at low to moderate levels of exercise hyperpnea inspiratory off-switch mechanisms are essentially unaffected by moderate hypoxia.

Adult↗
PubMed1986

Intrinsic rates and adrenergic responses of atria from rats on sprinting, endurance and walking exercise programmes.

The effects of three different physical training programmes on the control of sinoatrial rate in the young male rat were investigated. After training for 8 weeks, 5 d/week, the intrinsic rate and chronotropic response to cumulatively applied norepinephrine (NEp) were examined using isolated atrial preparations. Preparations from animals trained by walking for 60 min/d at 16.1 m/min possessed the same intrinsic atrial rate as sedentary controls, while preparations from an endurance-trained group running for 60 min at 32.2 m/min at 15% grade, and from a sprint-trained group running 50, 10-s efforts at 80.5 m/min, 15% grade with a 30-s rest interval, possessed lower intrinsic atrial rates. Atrial preparations from all groups demonstrated similar maximum rates after application of NEp. For all groups there was no statistically significant difference between the EC50 values for the chronotropic effect of NEp. Training induced a modification in intrinsic atrial rate without influencing NEp chronotropic responses.

Animals↗
PubMed1986

Diazinon treatment effects on heart and skeletal muscle enzyme activities.

The effect of low levels of diazinon treatment on four marker enzymes in rat heart and skeletal muscle have been investigated. Adult male Wistar rats were treated twice a week with a dose of 0.5 ml X kg-1 X day-1 diazinon for 28 weeks. Diazinon treated rats gained significantly less weight than Sham-treated controls. Typical differences in Succinate dehydrogenase (SDH), Lactate dehydrogenase (LDH), Phosphofructo kinase (PFK) and Hexokinase (HK) activities were observed between heart and skeletal muscles. Diazinon feeding had no effect on heart, soleus, gastrocnemius and plantaris SDH, LDH and PFK enzyme activities after 28 weeks. HK activity was significantly increased in sham-control soleus and plantaris muscles after 28 weeks. Diazinon feeding inhibited HK activity in plantaris muscle after 28 weeks treatment. These results demonstrate that chronic low levels of diazinon have little effect on the glycolytic and oxidative activity in heart and skeletal muscle.

Animals↗
PubMed1986

The Astrand-Ryhming nomogram revisited.

Relationships among O2 uptake (VO2), heart rate, and work rate during constant-load submaximal cycle ergometry and ramp-forced exercise to exhaustion have been studied in core groups of trained (n = 15) and untrained (n = 10), 20- to 29-yr-old males. A signal aim was to improve on the accuracy of the 1954 Astrand-Ryhming (A-R) nomogram predicting maximum aerobic power from heart rate elevation at submaximum work rates. A new nomogram has been developed based on a linear relationship, established in experimental groups, between VO2 and delta HR, the latter being defined as the elevation of exercise heart rate above that reached during zero-load pedaling at 90 rpm. The delta HR variable used in a nomogram linking it and submaximum VO2 (either derived by calculation from the concomitant steady-state work rate or measured directly from respiratory gas analysis) successfully differentiated maximum aerobic power of trained from untrained subjects in core groups whose different abilities could not otherwise be distinguished by the A-R nomogram itself. In a validation group of trained (n = 5), untrained (n = 5), and moderately trained (n = 4) 20- to 29-yr-old males, the correlation measured between VO2max values and those predicted from the new nomogram was significantly better (r = 0.98) (P less than 0.05) than predictions made from the A-R nomogram (r = 0.80).

Adult↗
PubMed1986

Effects of chronic intake of diazinon on blood and brain monoamines and amino acids.

Male rats were treated bi-weekly by gavage with the equivalent of 0.5 mg X kg-1 X day-1 technical diazinon for up to 28 weeks. The animals were sacrificed at specific time intervals (7, 14 and 28 weeks) and compared with age matched controls. Blood and brain tissues were analysed for cholinesterase activity and for concentrations of catecholamines and amino acids. Only Plasma cholinesterase was significantly reduced by the low level pesticide treatment. Erythrocyte acetyl cholinesterase and brain acetyl cholinesterase were unchanged while during the same period several putative brain neurotransmitters aspartate, glutamate (excitatory) and taurine as well as GABA (inhibitory) were significantly reduced in experimental vs control animals whereas no significant changes occurred between weeks in similarly fed animals. Blood serotonin was significantly elevated but no other blood or brain monoamine was significantly altered. Overt manifestations of brain toxicity observed were not apparent in experimental compared with control animals save for a significant decrease in growth observed in experimental animals. It was concluded that oral administration of low doses of diazinon exerts significant effects other than as an anticholinesterase on important brain neurotransmitters even at the low dose levels administered in this study.

Acetylcholinesterase↗
PubMed1985

Variations in iron status with fatigue modelled from training in female distance runners.

A low hemoglobin level or even frank anemia is common among female endurance runners; controversy presently exists on the effectiveness of iron supplementation. In the past inadequate descriptions of training and too infrequent measurement of iron indices over a sufficiently long period, have made it difficult to establish any relationship between iron status and training upon which to base a rational iron therapy. In this study 5 young women distance runners age 18-25 years have been studied for 300 days. A numerical index was used to quantify the extent of an individual's daily training effort and a conceptual model of the effect of training allowed definition of the extent of consequent fatigue, to be calculated. Red blood cell number and hemoglobin concentration were measured regularly throughout, and during the last 200 days serum iron, ferritin, total iron binding capacity and percent transferrin saturation were also measured. It has been shown in most subjects that serum iron and transferrin saturation varied in phase with training and the fatigue index, throughout the period while serum ferritin varied out of phase. It is suggested that supplementing iron intake may be of little use during heavy training and concomitant high fatigue because transferrin saturation is also very high at this time and ineffective in promoting absorption of dietary iron.

Adolescent↗
PubMed1985

Thermoregulation during prolonged actual and laboratory-simulated bicycling.

Thermoregulatory and cardiorespiratory responses to bicycling 55 km (mean speed 9.7 m X s-1) outdoors (15 degrees C DB) were compared to equivalent cycle ergometry (90 min at 65% VO2max) in the laboratory (20-23 degrees C DB, 50% RH) in 7 trained cyclists. Outdoor environmental conditions were simulated with fans and lamps, and were contrasted with standard no-wind, no-sun laboratory conditions. Sweating rate was similar during outdoor and laboratory simulated outdoor cycling (0.90 and 0.87 to 0.94 1 X h-1 respectively). During outdoor bicycling, mean heart rate (161 bt X min-1) was 7-13% higher (p less than .05) than under laboratory conditions, suggesting a greater strain for a similar external work rate. The increase in rectal temperature (0.8 degrees C) was 33-50% less (p less than 0.05) at the cooler outdoor ambient temperature than in the laboratory. Thermoregulatory stress was greater under the no-fan, no-lamp laboratory condition than during simulated outdoor conditions (36-38% greater (p less than 0.05) sweating rate, 15-18% greater (p less than 0.01) mean skin temperature, 6.4 to 7.8 fold greater (p less than 0.01) amount of clothing-retrained sweat). The cooling wind encountered in actual road bicycling apparently reduces thermoregulatory and circulatory demands compared with stationary cycle ergometry indoors. Failure to account for this enhanced cooling may result in overestimation of the physiological stress of actual road cycling.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1979

The perception of effort: an inductive approach.

A theoretical model has been proposed relating physical effort to perceived exertion. The model has been applied to a comparative investigation of the perception of various forces exerted by the adductor pollicis muscle and the quadriceps in five male subjects. The increase in perception of effort with increasing applied force in both muscle groups has been shown to increase exponentially. A force constant, defined in the paper, as the applied force at which perception of effort approximates two-thirds of maximum seems to discriminate effectively between the muscle groups concerned. The description of psychophysical data in this concise quantifiable manner may offer better insight into physiological processes contributing to the appreciation of effort.

Adult↗
PubMed1979

The time course of brain and blood catecholamines, catechol O-methyltransferase, and amino acids in rats convulsed by oxygen at high pressure.

The time course of changes in blood and brain catecholamines, catechol O-methyltransferase (COMT), ammonia, and amino acids leading to convulsion by high pressure oxygen breathing (OHP) in rats has been investigated. Brain catecholamines were suppressed by OHP. They changed in phase with brain COMT concentration and consequently were not due to the action of this degrading enzyme. Convulsive actions seem not to be influenced by brain catecholamine concentration. Blood adrenaline concentrations are, however, significantly elevated both prior to and during convulsions. In both brain and blood, ammonia concentration increases, glutamate decreases, and glutamine-aspargine increases. It is proposed that the efficacy of the glutamate-glutamine ammonia buffering system in blood and brain is important in the prevention of the onset of convulsions but that when brain gamma-aminobutyric acid is depressed to critical levels, convulsions result.

Amino Acids↗