Exercise induced fatigue can have a negative impact on motor skill performance. While part of the decline is attributable to physiological factors that directly influence the coordination of movement, psychological factors may also contribute. Typically, motor learning environments encourage the accumulation of task-relevant declarative knowledge, which can be depended on to consciously support performance. The literature suggests that skills learnt in this way are vulnerable to demanding performance environments, including those in which the performer is fatigued. Recent empirical work has demonstrated that ‘implicit’ motor learning environments, devised to limit declarative knowledge buildup and/or dependence on working memory, promote resilient skill performance even after exhaustive fatigue protocols. Such findings imply that dependence on declarative knowledge to support motor skill execution may be a limiting factor under physiologically fatigue. However, it remains unclear the effect fatigue has on attentional resources, such as working memory. Using established experimental paradigms and EEG methodology, a research project was designed to investigate. Two explanations were considered: (1) fatigue distracts attention away from the control of movement or (2) fatigue directs attention to the skill, which interferes with automated control of the movement. In this study novice participants were allowed to freely accumulate declarative knowledge before completing a targeted muscle-fatigue protocol. A probe response paradigm assessed participants’ ability to recall the position of movement at the time a tone sounded, under the assumption that better recall reflects skill-focused attention. Neural activity was monitored by wireless EEG technology. Neural co-activation (or coherence) between brain regions associated with motor planning (Fz or F3) and with verbal-analytical processing (T3) has been suggested to reflect conscious control of motor skills. Therefore, a fatigue induced increase in T3-F3 coherence can be interpreted as increased conscious involvement in movement control, whereas, a decrease suggests a shift of attention away from movement control. The data collected suggests that to some extent fatigue raises visual-spatial and verbal-analytical contributions to motor control, but highlights methodological issues and limitations of the work. / published_or_final_version / Human Performance / Master / Master of Philosophy

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In man, tolerance to an orthostatic stress varies widely. Compensatory cardiovascular responses to orthostatic stressors such as head-up tilt, +Gz acceleration, and lower body negative pressure (LBNP) have been identified. However, physiologic reactions associated with the capacity to withstand a presyncopal- limited orthostatic exposure requires additional clarification. The relationship between maximal oxygen uptake (‘VO₂ max) and presyncopal-limited LBNP tolerance was examined in adult male subjects categorized into high (HAC) and low (LAC) aerobic capacity groups. In addition to similar (N.S.) cardiovascular responses, the (mean) and cumulative LBNP stress indices (CS)) observed in the HAC (722 torr•min) and LAC (784 torr•min) groups were also similar (N.S.). These data fail to support a relationship between LBNP tolerance and ‘VO₂ max. Cardiovascular responses associated with LBNP tolerance were measured during the control period (pre-LBNP) and final minute (peak LBNP) of decompression. The CSI criterion distinguished high (HT, n = 10) and low (LT, n = 8) LBNP tolerant groups was 640 torr•min. A greater (p < 0.05) end-diastolic volume and cardiac output was observed in the HT subjects during pre-LBNP may have provided a larger reserve to utilize throughout exposure to LBNP. At peak LBNP, both groups demonstrated similar (N.S.) cardiac outputs despite a higher (p < 0.05) HT heart rate. These data suggest that a major mechanism in prolonging LBNP tolerance may have been a greater LBNP-induced tachycardia. Blood samples were drawn to determine group differences in vasoactive neuroendocrine response. During peak LBNP, concentrations of norepinephrine increased (p < 0.05) in both groups. The HT group displayed greater (p < 0.05) LBNP-induced increases in vasopressin and plasma renin activity. These data suggest that HT subjects may have supplemented the catecholamine pressor response by involving the vasopressin and renin-angiotensin systems. The affect of cholenergic and beta-adrenergic blockades on cardiovascular responses to LBNP were examined in six HT and five LT subjects. CSI in both groups were unchanged (N.S.) by administration of atropine as compared to a placebo LBNP exposure. Propranolol however, reduced (p < 0.05) LBNP tolerance in both groups. This CSI reduction was greater (p < 0.05) in the HT subjects. The reduction in LBNP tolerance appeared closely associated with the negative chronotropic effect.

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No description available.

In a cross-sectional study we examined Iipoprotein composition and CETP mass in 15 sedentary and 12 exercising, healthy male volunteers, aged between 17-35 years. The exercising group were defined as individuals participating in at least five weekly 45 minute exercise sessions of an aerobic nature (60-85% estimated maximal oxygen uptake). The sedentary subjects were only irregularly engaged in bouts of physical activity, not more than 45 minutes per week. Seasonal data were collected: one data collection in the fall and one in the spring. A 20 day food and exercise journal was maintained during each season's data collection period. Blood lipids were measured on two and anthropometric and aerobic capacity testing were performed on 1 occasion during each season. Statistical analyses consisted of a two way ANOVA (exercise and season) to control for seasonal effects on blood lipids and Iipoprotein levels. Pearson product moment correlations were calculated between those variables that showed significant seasonal or level of activity changes. Exercising males consumed significantly greater amounts of energy (p<O.OOI), carbohydrates (p<O.OOOI), protein (p<O.OOOI), and dietary fibre (p<O.OOOI) than sedentary males; sedentary males however, consumed significantly greater amounts of alcohol than exercising males. Exercising males had significantly higher aerobic capacities and degrees of mesomorphy than sedentary subjects and exhibited significantly lower apo AI values. No differences were noted between the 2 groups in BMI, % body fat, other plasma lipids or CETP mass. In summary, regular physical activity in young, healthy male subjects was associated with increased energy and carbohydrate intake and improved aerobic capacity as compared to sedentary subjects. Moderate differences in physical activity were not however associated with alterations in plasma Iipoprotein composition or CETP concentration.

Nitric Oxide (NO) has been detected in the expiratory air of normal animals and human subjects. Recent experiments revealed that expiratory NO production rises during exercise and correlates well with O$ sb2$ consumption and heart rate. Whether or not physical conditioning influences expiratory NO output production remains unclear. In this study, NO concentration in expired gas was measured in 18 healthy male volunteers subdivided into 3 groups (sedentary, intermediate, athletes) based on their state of physical conditioning. Measurements were taken at rest and during two steady-state exercise bouts on a bicycle ergometer designed to elicit VO$ sb2$ of 1 and 2 1/min with the athletes performing an additional bout at VO$ sb2$ of 4 1/min. In the sedentary and intermediate groups, expired NO concentrations declined significantly with increasing VO$ sb2.$ In contrast, expired NO levels declined only slightly with increasing VO$ sb2$ in athletes. At a VO$ sb2$ of 2 1/min, expired NO concentrations were significantly higher in athletes compared with the other groups. When correlated with V$ rm sb{E},$ expired NO concentrations declined linearly with the increase in $ rm V sb{E}$ in sedentary and intermediate groups but not in the athletes. Only the athletes had a significant linear increase in NO output (expired NO x V$ rm sb{E})$ with increasing VO$ sb2$ (p $<$ 0.001). These results support the notion that physical conditioning increases expiratory NO output during exercise. We speculate that the rise in expiratory NO output in athletes might be due to increased vascular and/or epithelial production of NO. Enhanced vascular NO production may be the result of increased shear stress and/or upregulation of endothelial NO synthase gene expression.

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No description available.

In a cross-sectional study we examined lipoprotein composition and CETP mass in 15 sedentary and 12 exercising, healthy male volunteers, aged between 17-35 years. The exercising group were defined as individuals participating in at least five weekly 45 minute exercise sessions of an aerobic nature (60-85% estimated maximal oxygen uptake). The sedentary subjects were only irregularly engaged in bouts of physical activity, not more than 45 minutes per week. Seasonal data were collected: one data collection in the fall and one in the spring. A 20 day food and exercise journal was maintained during each season's data collection period. Blood lipids were measured on two and anthropometric and aerobic capacity testing were performed on 1 occasion during each season. Statistical analyses consisted of a two way ANOVA (exercise and season) to control for seasonal effects on blood lipids and lipoprotein levels. Pearson product moment correlations were calculated between those variables that showed significant seasonal or level of activity changes. Exercising males consumed significantly greater amounts of energy (p $<$ 0.001), carbohydrates (p $<$ 0.0001), protein (p $<$ 0.0001), and dietary fibre (p $<$ 0.0001) than sedentary males; sedentary males however, consumed significantly greater amounts of alcohol than exercising males. Exercising males had significantly higher aerobic capacities and degrees of mesomorphy than sedentary subjects and exhibited significantly lower apo AI values. No differences were noted between the 2 groups in BMI, % body fat, other plasma lipids or CETP mass. In summary, regular physical activity in young, healthy male subjects was associated with increased energy and carbohydrate intake and improved aerobic capacity as compared to sedentary subjects. Moderate differences in physical activity were not however associated with alterations in plasma lipoprotein composition or CETP concentration.