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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
PubMed1999

Training theory and taper: validation in triathlon athletes.

This paper defines a training theory with which to predict the effectiveness of various formats of taper in optimizing physical performance from a standardized period of training and taper. Four different taper profiles: step reduction vs exponential (exp) decay and fast vs slow exp decay tapers, were simulated in a systems model to predict performance p(t) resulting from a standard square-wave quantity of training for 28 days. The relative effectiveness of each of the profiles in producing optimal physical improvement above pre-taper criterion physical test standards (running and cycle ergometry) was determined. Simulation showed that an exp taper was better than a step-reduction taper, and a fast exp decay taper was superior to a slow exp decay taper. The results of the simulation were tested experimentally in field trials to assess the correspondence between simulation and real-training criterion physical tests in triathlon athletes. The results showed that the exp taper (tau = 5 days) group made a significantly greater improvement above a pre-taper standard (P < or = 0.05) than the step-reduction taper group in cycle ergometry, and was better, but not significantly so, in a 5-km run. A fast exp taper group B (tau = 4 days) performed significantly better (P < or = 0.05) in maximal, cycle ergometry above a pre-taper training standard than a slow exp taper group A (tau = 8 days) and was improved more, but not significantly so, than group A in a 5-km criterion run. The mean improvement on both physical tests by exp decay taper groups all increased significantly (P < or = 0.05) above their pre-taper training standard. Maximum oxygen uptake increased significantly in a group of eight remaining athletes during 2 weeks of final taper after three athletes left early for final preparations at the race site.

Adult↗
PubMed1999

Effectiveness of rest pauses and cooling in alleviation of heat stress during simulated fire-fighting activity.

This study examined whether cooling a fire-fighter with a high velocity fan, during 10 min rest pauses between, and following, 10 min work periods, decreases heat stress during repetitive fire-fighting activity. Twelve professional fire-fighters (mean age 31.8 +/- 6.7 years) completed two, 40 min work/recovery trials in an environmental chamber at 40 degrees C and 70% relative humidity (RH). One trial was termed an enhanced recovery (ER) trial and the other was termed a normal recovery (NR) trial. In both conditions subjects wore full protective clothing and breathing apparatus during the work. In the ER trial a subject removed his protective coat and sat in front of a fan during each recovery period. In the NR trial a subject merely unbuckled his coat and was not cooled by a fan during either recovery period. The group mean metabolic cost (VO2), and the exercise and recovery heart rates were significantly lower (p < or = 0.05) during the ER trial than in the NR condition. Group mean rectal temperature increased by 1.5 degrees C in the NR trial but by only 0.8 degree C during the ER trial. The latter group's more effective cooling indicates the potential of fan cooling to reduce physiological strain and decrease the risk of heat exhaustion during repetitive fire-fighting activity. The results suggest that a fire-fighter's short 10 min exposure to heavy work in a hot environment of 40 degrees C and 70% RH produces minimal heat stress in a healthy fire-fighter. However, a period of fire-fighting exposure greater than 10 min without adequate rest and cooling may lead to a significant accumulation of heat stress and fatigue during further fire-fighting activity, irrespective of physical prowess.

Adult↗
PubMed1999

Effect of endurance training on blood lactate clearance after maximal exercise.

The aim of this study was to measure serial changes in the rate of blood lactate clearance (gamma2) in response to sequential periods of training and detraining in four male triathletes aged 22-44 years. There were two major phases of training and taper, each lasting 4-5 weeks (training 1 = 5 weeks, taper 1 = 2 weeks, training 2 = 4 weeks and taper 2 = 2 weeks), in preparation for a triathlon competition. The training stimulus absorbed by each subject was carefully quantified from the duration and intensity of the training exercise. A serial weekly measure of each trainee's physical response to training was evaluated as the peak power, termed a 'criterion performance', developed by a subject during a 30 W x min(-1) ramp cycle ergometer test to exhaustion each week. During 30 min of recovery after this test, 13 samples of venous blood were drawn sequentially from a subject to measure the blood lactate recovery curve. The rate constant of blood lactate clearance was estimated by a non-linear least-squares regression technique. In addition, the concurrent time to peak lactate concentration and the peak lactate concentration were also estimated to help define changing lactate kinetics. The criterion performance generally declined throughout each period of incremental training and improved during each taper period, rising iteratively in this way to be clearly above baseline by the end of the second taper. The blood lactate clearance rate increased transiently in early training before declining from the middle of the first training period to the middle of the first taper; thereafter, gamma2 increased above baseline in each trainee throughout the remaining first taper and the major portion of the second training period, decreasing only in the final criterion performance test. The time to peak lactate declined from baseline throughout all phases of training and taper. Peak blood lactate increased in all subjects to the end of the first taper before declining by the end of the second training period, rising again to baseline levels during the second taper. The change in gamma2 was examined relative to the work rate achieved in cycle ergometry above an initial baseline score (deltaCP) and against concurrent peak blood lactate. There was a clear upward shift in gamma2 above baseline throughout the first and second training and taper in two subjects; this was less clear in the remaining two subjects, each of whom had a lower deltaCP. We conclude that this indicates improved lactate clearance, manifest by the change in gamma2 induced by endurance training.

Adult↗
PubMed1995

Modelling the effect of taper on performance, maximal oxygen uptake, and the anaerobic threshold in endurance triathletes.

The purpose of this study was to determine the nature of taper required to optimize performance in Ironman triathletes. Eleven triathletes (26 +/- 4 yrs, 77.0 +/- 6.5 kg) took part in 3 months of training interspersed with two taper periods, one of 10 days (Taper 1) and another six weeks later for 13 days (Taper 2). Reducing training volume by 50% in an exponential fashion (tau < or = 5 days) in one group of triathletes during Taper 1 resulted in a 46 second (4%) improvement in their 5 km criterion run time and a 23 W (5%) increase in maximal ramp power output above the same measurement at the beginning of taper. A 30% step reduction in training volume in the second group did not result in any significant improvement in physical performance on the same measures. Training volume was reduced exponentially from the end of training in both a high volume group (tau > or = 8 days) and a low volume group (tau < or = 4 days) during Taper 2. Criterion run time improved significantly by 74 seconds (6%) and 28 seconds (2%) in the high and low volume groups respectively, while maximal ramp power increased significantly by 34 W (8%) only in the low volume taper group. Maximal oxygen uptake increased progressively from 62.9 +/- 5.8 ml.kg-1.min-1 two weeks prior to taper, to a significantly higher level 68.9 +/- 4.2 ml.kg-1.min-1 during the final week of Taper 2 (p < or = 0.5). The anaerobic threshold determined by a non-invasive method was also observed to increase from 70.9% to 74.9% of a subject's maximal oxygen uptake during Taper 2. These results demonstrate that proper placement of training volume during taper is a key factor in optimizing performance for a specific competition and a high volume of training in the immediate days preceding an event may be detrimental to physical performance.

Adult↗
PubMed1995

The influence of inspired oxygen on the oxygen uptake response to ramp exercise.

The relation between VO2 and work rate (WR) was examined in seven male subjects who performed ramp (1 W.3s-1) two-legged cycle ergometry to exhaustion while inspiring either hypoxic (12% O2), normoxic (21% O2), or hyperoxic (40% O2) air. The anaerobic threshold was estimated from respiratory gas exchange threshold (RGET). Prior to the RGET, the delta VO2/delta WR was greater under normoxic [mean (SD); 10.19(1.04) ml O2.min-1.W-1] and hyperoxic [10.44 (0.72)] conditions compared with hypoxia [9.34 (0.89)]. Above the RGET, the delta VO2/delta WR for hypoxia [8.91 (0.63)], normoxia [10.40 (0.77)], and hyperoxia [11.08 (0.48)] were all significantly different from each other. These data indicated that for two-legged, cycle, ramp ergometry in normoxia below the RGET, both the delta VO2/delta WR and response time was constant. Above the RGET, the normoxic VO2 response was the net result of a declining delta VO2/delta WR and a longer response time to the unsteady state character of a ramp exercise protocol.

Adult↗
PubMed1994

Statistical evidence consistent with two lactate turnpoints during ramp exercise.

A number of studies have identified the existence of two ventilation thresholds during ramp or incremental exercise to exhaustion on the cycle ergometer. This study was undertaken to investigate whether two threshold turnpoints could be identified in blood lactate concentration data collected at such times. Five trained athletes provided serial blood samples on several occasions each during a 3-month period of training. Blood lactate concentration was analysed by fitting models with no, one or two turnpoints. Ordinary residuals from the first two models were often found to exhibit an oscillatory behaviour consistent with the existence of two turnpoints in lactate concentration. A comparative analysis of goodness of fit of these models revealed that the model with two turnpoints was significantly better than either of the simpler models. This suggests that two transitions exist, which divide the time domain for blood lactate concentration in ramp exercise into three regions. These two transitions may correspond to the two ventilation thresholds.

Adult↗
PubMed1994

Musculoskeletal problems in VDT work: a review.

This paper discusses the possible causes of musculoskeletal pain in VDT workers and outlines strategies to minimize it. The paper reviews workstation, chair, and keyboard design, and makes recommendations to improve user comfort. Also discussed is worker selection, training, posture, conditioning, and rest breaks. Short term musculoskeletal discomfort is experienced by many VDT operators in the telecommunications industry and chronic disability may result in the long term. It is important that the ergonomist and office manager work together to improve the working conditions in this important occupational area.

Back Pain↗
PubMed1993

Cardiovascular and muscular strain during a tree planting season among British Columbia silviculture workers.

Cardiovascular and muscle strain were determined in 16 British Columbia reforestation workers during a period of tree planting (75 days). Serial data collected from each worker included pre- and post-work blood chemistry on the first day of the work shift; working heart rate (HR), a PWC170 fitness test, and a daily diary of an individual's work-rest schedule. Repeated blood samples from each planter were analysed for the elevated serum enzyme activities (ESEA) of creatine kinase (CK), lactate dehydrogenase (LDH), and aspartate transaminase (AST), and for the blood haematology parameters (BH) of haematocrit (Hct), red blood cell count (RBC), and haemoglobin (Hgb). HR and BH were used as an index of cardiovascular strain and ESEA was used as an index for musculoskeletal strain. A group mean working heart rate of 116.5 +/- 9 b.min-1 (range 100.0-139.1) was sustained throughout the period of an 8.0 hour day representing 39.2% of the delta Heart Rate ratio (ratio of elevated working Hr above resting to maximum HR). Grouped data were analysed by sample day for a subset of planters (n = 10) participating in six sample dates during the first 32 days of planting. Pre- and post-work ESEA were significantly higher throughout the entire planting period when compared with a pre-season resting control group (n = 9, p < or = 0.01). The post-work rise in CK and AST from pre-work values decreased during successive weeks of work as some adaptation to the work rate occurred. LDH continued to rise and was significantly elevated on day 32 compared with day 1. No significance was found in the BH variables between sample dates, yet a decreasing trend was observed. However, pooled data from all subjects for all sample dates showed a highly significant difference (p < or = 0.01) between pre- and post-work samples for both ESEA and BH. ESEA increased and BH decreased. These data present evidence that the work rate and rest time of a tree planter are not well ordered within the daily and seasonal working routine, and may compromise worker well-being in the silviculture industry.

Adult↗
PubMed1993

Physiological effects of work stress and pesticide exposure in tree planting by British Columbia silviculture workers.

Tree planters in British Columbia have reported symptoms that are congruent with musculoskeletal stress and organophosphate or carbamate pesticide intoxication. The purpose of this research was to determine the existence of any physiological or biochemical correlate supporting the existence of these potential hazards in tree planting. Worker's health complaints were assessed from regularly distributed questionnaires. Blood samples were obtained from 14 male and three female Canadian subjects before and after tree planting work on 10 occasions throughout a tree planting season. The strenuous physical challenge of tree planting was confirmed by a significant elevation of serum enzyme activity (ESEA) at the beginning of the season, which did not return to a normal level during the remainder of the season. Significant (p < or = 0.05) inhibition of erythrocyte acetylcholinesterase activity (AChE) postwork was observed in 15.9% of individuals, and a significant group mean prework-postwork difference of AChE or plasma pseudocholinesterase (PChE) was observed on two days of testing, indicating a potential toxicological hazard from pesticide absorption. No correlation was found between the degree of ESEA or cholinesterase inhibition and the number of health complaints.

Acetylcholinesterase↗
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↗