In sports, one might wish to test new ideas regarding player movement, tactics, or strategy without subjecting the athletes to possibly wasteful or even harmful habit formations. If a method of simulation of the athlete can be devised, experiments might reasonably be conducted to evaluate the ideas independently of actual training or trial in the field. Simulation of a complex system generally begins with a long period of analysis. During this time there may be mathematical and programming explorations and constructions to sharpen and examine different approaches. Meetings are usually held by the participants to try to define the task and explore alternatives. Ideas are amplified, possibly discarded as not feasible, or incorporated into the system package. Gradually there evolves a tighter and more acceptable formulation using logical and mathematical expressions (Preface, p. vii)

This study investigated the effects of incremented loads greater than maximal acceptable loads on selected locomotor kinematic and psychophysical variables for four different hand-held load-carriage methods. Ten male and ten female subjects, between the ages of 18 and 30, participated in four experimental sessions. Data collection involved obtaining selected anthropometric, strength, maximal load and preferred load, gait kinematic, and psychophysical values. The anthropometric, strength and load capacity variables enabled absolute and morphology normalised sex-based comparisons to be made. The kinematic and psychophysical parameters were used to quantify any changes from two sets of baseline values,"unloaded" and "maximal acceptable load" values, when loads were increased and carrying methods changed. Statistical analysis revealed that males were taller, heavier and stronger than females (p<0.05). Males chose significantly greater maximal acceptable loads and absolute maximal loads than females when expressed in their absolute or relative terms. Preferred walking speeds were not significantly different for unloaded or loaded conditions, although males walked significantly faster in absolute terms (but not in relative terms) than females. Different load carrying methods and incremented loads brought. about significant changes to several of the kinematic parameters investigated. Finally, ratings of perceived exertion, as well as the number of exertion sites, were seen to increase significantly as load increased. These values were not, however, significantly affected by differences in load carriage method.

No description available.

No description available.

The present study sought to determine the influence of environmental conditions and protective clothing on physiological, perceptual and performance responses during batting activity. The investigation examined mean skin temperature, average heart rate, estimated sweat rate, rating of perceived exertion, thermal sensation rating, average sprint time and pre-post choice reaction time. Twenty-five cricketers (18-22 yr, 73.1 ± 9.6 kg, 1768 ± 75 mm, 12.6 ± 3.1% body fat, 1.89 ± 0.16 m2) performed a work-bout consisting of a seven-Over batting period, during which time they faced deliveries from a bowling machine and performed two shuttle runs every third ball to total four sprints per Over. Trials were carried out under High-stress (23.8 ± 2.2 °C) and Low-stress (13.3 ± 1.9 °C) environmental conditions (WBGT). Within each environmental condition subjects performed the test wearing full protective batting gear and no protective gear. Thus, four specific conditions were examined; high full-gear (HFG), high no-gear (HNG), low full-gear (LFG) and low no-gear (LNG). Two-way ANOVAs were calculated to determine whether there were differences between environmental conditions and whether differences existed between the clothing conditions. One-way ANOVAs were utilised to compute differences between the four specific conditions combining clothing and environment. High environmental stress and wearing protective clothing caused batsmen to experience significant physiological strain. The environment was the greatest stressor, with the protective gear exacerbating these effects. However, when padding covered skin areas directly, this was the primary skin temperature stressor, particularly later in the activity. For skin temperature and heart rate, the strain was the most pronounced at the end of the trials. Perceptual responses indicated that the protective gear had no influence on effort sense, thermal sensation or thermal comfort. However, environmental conditions had an effect, and High-stress conditions resulted in significantly higher perceptions of effort, elevated sensations of heat and greater thermal discomfort. Effort was perceived to be greatest towards the end of the trial. There were mixed findings for performance factors. In general sprint performance was not hindered by environmental stress, but protective clothing caused a reduction in several sprint times. Choice reaction times were for the most part unaffected by either environment or clothing and few differences were observed between pre and post times. It is contended that intense short duration batting activity, likely encountered during one-day participation, imposes a stress on batsmen. The stress is greater when conditions are warmer and protective padding is worn, although it is not sufficient to impede choice reaction time. However, protective gear did have a deleterious effect on sprint performance.

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The nonrecurring-items delayed nonmatching-to-sample (DNMS) task is an integral part of contemporary monkey models of brain-damage-produced amnesia. This thesis began the development of a comparable rat model of brain-damage-produced amnesia. First, a DNMS task for rats was designed by adapting key features of the monkey task. Then, the rat DNMS task was studied in three experiments; each assessed the comparability of the rat DNMS task to the monkey DNMS task. Experiment 1 determined the rate at which the rat DNMS task is learned and the asymptotic level at which it is performed, Experiment 2 assessed the memory abilities that it taps, and Experiment 3 investigated the brain structures that are involved i n its performance. In Experiment 1, rats were trained on the DNMS task and their performance was assessed at retention delays of 4, 15, 60, 120, and 600 s. All of the rats learned the DNMS task, and their performance was comparable to that commonly reported for monkeys in terms of both the rate at which they acquired the nonmatching rule at a brief retention delay and their asymptotic accuracy at delays of up to 120 s. These results establish that rats can perform a DNMS task that closely resembles the monkey DNMS task and that they can approximate the level of performance that is achieved by monkeys. Experiment 2 examined the effects of distraction during the retention delay on the DNMS performance of rats. Rats were tested at retention delays of 60 s. On half of the trials, the rats performed a distraction task during the retention delay; on the other half, they did not. Consistent with findings from monkeys and humans, distraction during the retention delay disrupted the DNMS performance of rats. This suggests that similar memory abilities are involved in the DNMS performance of rats, monkeys, and humans. Experiment 3 investigated the effects of separate and combined bilateral lesions of the hippocampus and the amygdala on DNMS performance in pretrained rats. Rats were tested both before and after surgery at retention delays of 4, 15, 60, 120, and 600 s. Each experimental rat received bilateral lesions of the hippocampus, amygdala, or both. There were no significant differences among the three experimental groups, and the rats in each of the three experimental groups were significantly impaired, in comparison to no-surgery control rats, only at the 600-s delay. In contrast, rats that had sustained inadvertent entorhinal and perirhinal cortex damage during surgery displayed profound D N M S deficits. These results parallel the results of recent studies of the neural basis of DNMS in monkeys. They suggest that, in contrast to one previously popular view, neither the hippocampus nor the amygdala play a critical role in the DNMS of pretrained animals and that the entorhinal and perirhinal cortex are critically involved. On the basis of these findings, it appears that the rat DNMS task may prove to be a useful component of rat models of brain-damage-produced amnesia. This conclusion is supported by the preliminary results of several experiments that are currently employing the task. / Arts, Faculty of / Psychology, Department of / Graduate

Plasma catecholamines have been measured in chronically adrenalectomised (ADX) ducks, in chronically adrenal denervated ducks (DNX), in their respective sham-operated controls (SH-adx, SH-dnx) as well as in intact ducks after 3 minutes forced submergence. The results showed that 100% of the plasma Epinephrine (EP) and 40 to 80% of plasma Norepinephrine (NE) released during the dive came from the adrenal glands. 20 to 60% of plasma NE came from endings of the autonomic vascular sympathetic nerves which are strongly stimulated during diving. Adrenal catecholamines were released by nerve activation only; non neural mechanisms did not play any role in their release. Maximum dive times (MDT) in chronically adrenalectomised ducks (ADX: 5 min. 19 ± 20 sec.) and in chronically adrenal denervated ducks (DNX: 7 min. 10 ± 13 sec.) were significantly lower than in sham-operated controls (respectively SH-adx: 9 min. 58 ± 45 sec., SH-dnx: 12 min. 10 ± 28 sec). Venous infusion of catecholamines in ADX and DNX during the dive increased MDT: MDT of DNX ducks perfused with catecholamines (9 min. 46 ± 20 sec.) were significantly higher than in DNX perfused with saline (7 min. 21 ± 17 sec.), but did not reach the MDT observed in the SH-dnx: other adrenal products must be involved. Diving heart rates of ADX and DNX (at 4 min. dive respectively: 62 ± 16 and 31 ± 2 beats/min.) were significantly higher than in their sham-operated controls (23 ± 3 and 17 ± 2 beats/min.) . Blood pressure during the dive was signifi- cantly lower in ADX and DNX (at 4 min. dive respectively: 93 ± 8 and 98 ± 4 mmHg) compared with their sham-operated controls (131 ± 12 and 118 ± 6 mmHg). Infusion of catecholamines in DNX raised blood pressure towards SH-dnx values, but there was no change in heart rate. PaO₂, CaO₂, pHa and lactate levels in DNX (respectively: 42 ± 2 mmHg, 4.5 ± 0.8 ml 02 /100ml blood, 7.233 ± 0.016, 3.1 + 0.3 mM) were significantly lower than in SH-dnx after 5 minutes submergence (53 ± 1 mmHg, 6.8 ± 0.4 ml 02 /100 ml blood, 7.301 ± 0.007, 4.8 + 0.4 mM). There was also a significant increase of plasma N⁺ (+ 5.4 ± 1.7 mEq/L) in SH-dnx after 5 minutes submergence, but this was not the case in DNX where it was K⁺ (+ 1.1 ± 0.4 mEq/L) which increased. This suggested that adrenal catecholamines increase tolerance to underwater submersion by enhancing peripheral vasoconstriction, thus preserving the O₂ stores for the heart and brain. Moreover, they may affect the acid-base equilibrium during diving by increasing the activity of the Na⁺K⁺ pump and may also have a direct effect on the rate of glycogenolysis. Preventing the actions of catecholamines on the heart by injecting beta-blocker during forced submersion did not decrease MDT; however the cardiovascular response was markedly affected. During beta-blockade, diving heart rate rose steadily from 24 ± 6 beats/minute after 2 minutes to 52 ± 8 beats/minute after 6 minutes diving. In contrast, heart rates remained close to the levels reached at 2 minutes (17 ± 3 and 19 ± 4 beats/minute) throughout the control dives. Perfusion pressure and blood flow have been recorded simultaneously in both hind limbs of ducks. One leg was perfused with different blood mixtures devoid of catecholamines (Test leg) and compared with the other, perfused with the ducks'own blood (autoperfused leg). This showed that hyper-capnia has a depressant effect on the neural component of the peripheral vasoconstriction. Perfusion of test legs with hypoxic-hypercapnic blood to which catecholamines were added, showed that circulating catecholamines are needed to increase peripheral vasoconstriction during diving. In summary, during forced submergence circulating catecholamines, released mainly by the adrenal glands, compensate for the depressant action of hypercapnia on the neural component of peripheral vasoconstriction. Maintenance of this peripheral vasoconstriction during forced diving ensures that O₂ stores are not wasted on peripheral tissues, and this explains how MDT is prolonged. / Science, Faculty of / Zoology, Department of / Graduate

The purpose of this study was to examine differences in 2,3-diphospho-glycerate concentrations among groups of smokers and nonsmokers, to determine relationships between 2,3-DPG concentrations and other blood parameters affecting oxygen transport, and to examine the effects of acute exercise on 2,3-DPG concentrations. Antecubital venous blood from each subject, before and after exercise, was analyzed for 2,3-DPG, hematocrit, hemoglobin and blood pH. Mean corpuscular hemoglobin concentration (MCHC) was calculated by dividing hemoglobin by hematocrit. Forty university-aged males constituted the sample population. Each subject was assigned to one of five groups, eight subjects per group, based on his status in relation to the variables of physical activity and cigarette smoking. The task consisted of one hour of exercise on a bicycle ergometer at a work rate producing a heartrate of approximately 150 beats per minute (70 per cent of maximal aerobic capacity). Blood samples were taken immediately prior to and immediately following the bout of exercise. A 12 hour fast preceded the work phase of the experiment. The hypotheses were: highly fit subjects have significantly higher 2,3-DPG concentrations and sedentary subjects have significantly lower 2,3-DPG concentrations than moderately fit subjects; smokers have significantly higher 2,3-DPG levels than nonsmokers; exercise produces significant increases in 2,3-DPG; negative relationships exist between 2,3-DPG levels and hemoglobin levels as well as between pre exercise 2,3-DPG levels and change of 2,3-DPG as a result of exercise. A priori orthogonal comparisons of pre exercise red cell 2,3-DPG levels indicated that differences between groups were not significant, i.e. highly fit groups did not demonstrate 2,3-DPG levels significantly higher, nor did sedentary groups demonstrate 2,3-DPG levels significantly lower than moderately fit groups. A definite trend towards higher 2,3-DPG levels was observed as training intensity increased, indicating that the hypothesis of physical training producing an increase in 2,3-DPG levels should not be totally rejected. Demonstration of differences in the carrying capacity of the blood, as reflected by differences in MCHC, hemoglobin and hematocrit, between groups appeared to be related to the trend observed in 2,3-DPG levels. Differences between smokers and nonsmokers in relation to 2,3-DPG concentrations were not significant,indicating that the hypoxia produced through cigarette smoking is not an important stimulator of 2,3-DPG production. Multivariate analysis of results indicated that 2,3-DPG levels were not significantly increased as a result of one hour of exercise at 70 per cent of maximal aerobic capacity. This is indicative of a slow-acting response mechanism affecting 2,3-DPG production, which requires more than one hour, or a more severe stress, to produce a physiological beneficial effect on oxygen transport by the blood. A significant negative correlation was observed between pre exercise levels of 2,3-DPG and hemoglobin levels. This was also reflected in the significant negative correlation between 2,3-DPG and hematocrit and 2,3-DPG and MCHC. A negative correlation was also observed between the change in 2,3-DPG and the change of MCHC that occurred as a result of exercise. The results are interpreted as showing a compensatory effect of 2,3-DPG in producing increased unloading of oxygen when the carrying capacity of the blood is reduced through a reduction in hemoglobin levels. An intimate relationship between 2,3-DPG and MCHC, tending to produce homeostasis in the position of the oxygen dissociation curve of hemoglobin, has been postulated. Changes in 2,3-DPG as a result of exercise were not related to the pre exercise concentration of 2,3-DPG indicating that change of 2,3-DPG is not significantly affected by the amount of 2,3-DPG present before physical activity is initiated. / Education, Faculty of / Curriculum and Pedagogy (EDCP), Department of / Graduate

The experiment was designed to demonstrate the effects of exercise and confinement on the calcium metabolism of rats. A subsidiary purpose was to determine if any such effects are mediated by a humoral agent. Twenty-four male Sprague Dawley rats were divided into three groups. One group was exercised in motorized activity cages for one hour per day five days per week; one group was confined in small individual metabolism cages for 26 days and in body holders for 12 days; one group was housed in individual metabolism cages and served as controls. Half of the rats of each of the above three groups received 2 ml whole blood from rats similarly treated (exercised, confined or control), on each of the last five days of the experiment. Thus the exercised rats received blood from confined rats, the confined rats received blood from exercised rats and the control rats received blood from control rats. A calcium balance study was carried out for the last 26 days of the 38 day experiment and a calcium-45 balance study was carried out for the last six hours of the experiment. Thus the following specific parameters of calcium metabolism were measured: calcium balance, per cent calcium utilization, food intake, faecal calcium, urinary calcium, total carcass calcium, femur calcium, calcium-45 absorption and femur calcium-45. The entire experiment was performed twice and the data analyzed using a randomized complete block design analysis of variance. The exercise or confinement did not significantly alter the calcium metabolism of the male Sprague Dawley rat under the conditions of this study. Two possible conclusions were discussed. Either this experiment casts some doubt on the current concepts regarding immobilization and osteoporosis, or that the humane conditions adopted in this study did not successfully immobilize the rats. The present experiment also suggests that regular vigorous exercise may not affect the calcium metabolism of the rat to a greater extent than normal activity or mild exercise. No conclusions could be drawn about the role of the blood in regulating or controlling the effects of exercise or confinement on calcium metabolism. / Medicine, Faculty of / Cellular and Physiological Sciences, Department of / Graduate