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It is known that endurance-trained athletes possess higher levels of high density lipoprotein cholesterol (HDL-C) than sedentary controls, and it has been shown in previous studies that acute exercise may elevate these levels even further. The purpose of this study was to investigate the acute exercise response of the plasma HDL's and to determine if the magnitude of the acute response would be affected by the intensity of the exercise. Twelve men (19-41 yrs) ran an equivalent distance (9-12 km) on a treadmill on two separate occasions. On one occasion the exercise was performed at a speed corresponding to 60% of the subject's VO₂ max, and on the other occasion at a speed corresponding to 90% of VO₂ max. Changes in total cholesterol (TC), triglycerides (TG), HDL-C, HDL Apoprotein A (HDL-A), HDL Saturation (HDL-C/HDL-A), lactate (LA) and free fatty acids ( FFA) were measured, and all values were corrected for changes in plasma volume. There were significant increases (p<.01) in HDL-C, HDL-A, and HDL saturation with exercise at both intensities, but greater increases in HDL-C (25% vs 14%) and HDL-A (18% vs 8%) were observed with the higher intensity exercise. Plasma FFA and TG were no different between conditions, although LA concentration rose significantly during the high intensity exercise. The results indicate that increases in HDL components can occur with a relatively moderate exercise session, and that these increases are directly related to the intensity of the exercise. / Thesis / Master of Science (MSc)

Traditional approaches to exercise testing in children may not provide the most appropriate measures of a child's physiological responses to exercise, partly because they do not reflect children's normal intermittent activity patterns. The measurement of the rate and magnitude of change of oxygen uptake to dynamic exercise, oxygen uptake kinetics (V02 KINETICS provides an alternative approach to exercise testing. A submaximal, intermittent, pseudo-random binary sequence (PRBS) exercise test to measure V02 KINETICS may provide a useful method of measuring the metabolic responses of children to exercise. Traditional methods used in the analysis of V02 KINETICS require the fitting of explicit models in order to characterise the data. These models have not however been validated for use in children. As the responses to the PRBS protocol are analysed in the frequency domain, explicit models and their physiological correlates are not required to characterise the data. Another potential problem in the measurement of V02 KINETICS in children are the small work rate changes that can be employed to stimulate the exercise response whilst constraining the test to the aerobic range. In respiratory gas measurement, breath-by-breath variability (noise) can be large in comparison to the magnitude of the metabolic response and this signal noise can obscure some characteristics of the response. The aim of the study was to develop appropriate measurement techniques to reduce the effects of breath-by-breath variability and to apply the techniques to the measurement of V02 KINETICS in children. The main experimental study compared the V02 KINETICS of children with those of adults. Ten children (3 females) in the age range 8 to 13 and twenty adults (10 females) in the age range 20 to 28 years completed a PRBS test to measure V02 KINETICS and an incremental ramp protocol on a cycle ergometer (Bosch 550 ERG) to establish V02 MAX, T VENT and delta efficiency. Breath-by-breath respiratory gas analysis was undertaken using a respiratory mass spectrometer (MGA1100). Estimates of alveolar gas exchange were made using the algorithm of Beaver et al. (1981) and a post hoc value of an effective lung volume was calculated to minimise the breath-by-breath variability. A cross-correlation technique (CC) was used to filter out the effects of anomalous (nonphysiologic) V02 responses recorded during the PRBS protocol. Subsequent Fourier analysis of the auto-correlation and CC functions provided a description of V02 KINETICS in the frequency domain in terms of amplitude ratio and phase delay over the frequency range of 2.2-8.9mHz. At each of the frequencies assessed amplitude ratio was higher in children (P<0.001) than in either of the adult groups. Phase delay was also significantly shorter in children compared to adults males (P<0.01) and adult females (P<0.001) but this effect was not identifiable at any specific frequency. Maximal oxygen uptake was not significantly different in adult males (42.5 ml"kg "min) and children (44.7 ml-kg'-min') but was lower in adult females (36.9 ml"kg "min) than adult males (P<0.01) and children (P<0.001). Ventilatory threshold (% V02 MAX) was not different between groups. Delta efficiency was significantly lower in children than adult males (P<0.05) and adult females (P<0.01). These results support the contention that there are maturational differences between adults and children in the metabolic processes involved in the utilisation of oxygen during physical activity. It has been argued, theoretically, that in adults the control of V02 KINETICS is driven by ATP demand in the skeletal muscle. As the mitochondria] capacity and the concentration of oxidative enzymes is higher in children than in adults it is likely that the controlling factor(s) for V02 KINETICS in children also relates to some aspect of peripheral metabolism. It is suggested that the PRBS protocol, with appropriate noise reduction techniques, is considered a suitable method for investigating the metabolic responses of children to dynamic exercise.

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Exercise can have very beneficial effects on health and body satisfaction, but sometimes a negative body image gets in the way of exercising. Modern society holds certain beauty ideals in high regard, and these standards are often unattainable and unrealistic. These outside pressures to look a certain way can have a very negative effect on an individual’s body image, or the way that a person perceives his or her own appearance. There have been many studies done that have attempted to define the relationship between body image with exercise behaviors (Burger and Diony 2002, Hall and Pearson 2013). Some studies have shown that a negative body image is related with higher prevalence of exercise, while others have shown that a negative body image is a major barrier to participation in exercise at all (Berry, McHugh, and Pankratow 2013, Burger and Diony 2002, Gammage and Lamarche 2012, Hall and Pearson 2013). While the data from these studies has shown different relationships, there is an abundance of research on the topic. There is a lack of information, however, on the relationship between body image and exercise type. This study focused on this relationship in an attempt to determine if body image, positive or negative, had any effect on what type of exercise activities an individual chose to participate in. A total of 70 undergraduate college students were surveyed using a 9 question health and exercise questionnaire and a 6 question body image survey, written and published by Thomas Cash and previously utilized in other body image survey studies (Cash, et al. 2002). The data collected was analyzed using chi-square tests and a significant correlation between body image and exercise type, as well as body image and gender. Participants with a negative body image reported a preference for aerobic exercise while those with a positive body image preferred anaerobic exercise. The analysis also found that females were more likely to have a negative body image than males, which supports previous research trends (Burger and Diony 2002). This study only surveyed 70 individuals, and so the results can not necessarily be generalized to the entire population. Further research could include a larger sample size so as to find a more generalizable relationship between body image and exercise type.

The effective prescription of resistance exercise for strength and power development has been a source of debate amongst practitioners and sport scientist alike. One of the key issues in this area relates to the training load that would best facilitate strength and power adaptation. Heavy loads (>60-70% 1RM) have been traditionally used for maximal strength development by facilitating changes in neural function (strength) and muscle size (hypertrophy). However, many studies have now found lighter load (>45%1RM) training equally effective in improving both strength and hypertrophy. Similarly, many studies have found heavy load training effective in enhancing various measures of power though lighter loads (e.g. 45% 1RM) are thought to maximise the mechanical power output of muscle. Realising that adaptation depends upon some interaction between the mechanical, hormonal and metabolic stimuli, examining these responses would enhance our understanding of the underlying determinants of strength and power, and thereby improve strength and conditioning practice. Therefore, the purpose of this study was to examine the mechanical, hormonal and metabolic responses to equal volume light and heavy loading schemes. Eleven males (mean 26.6 ± 6.7 years; mean 79.0 ± 8.1 kg) with a minimum of 12 months weight training experience each performed two exercises (Smith squat and supine squat) at a light (45% 1RM) and heavy (88% 1RM) intensity. The light scheme consisted of eight sets of six repetitions, with six sets of four repetitions performed in the heavy scheme. Rest periods of three and four minutes respectively were used. Saliva sampling was used to determine the hormonal (cortisol and testosterone) and metabolic (lactate) responses. Samples were collected at rest (pre-), immediately after the first exercise (mid-), at the conclusion of the second exercise (P0) and every 15 minutes thereafter for one hour (P15, P30, P45, P60). Mean values for all variables were analysed with a paired sample T-test. Chances that the true effects were substantial (% and qualitative) were also calculated. No significant (P>0.05) difference in total forces was found between schemes; however, the light scheme produced significantly greater total time under tension (36%), total work (37%) and total power output (115%). Total impulse (38%) was the only variable found to be greater in the heavy scheme. A decrease in testosterone (TST) was observed in the heavy scheme (-4 to -29%) with no significant changes found across the light scheme (1 to 12%). Cortisol decreased in the light (-6 to -30%) and heavy (-14 to -44%) schemes until P45. An increase in the TST/cortisol ratio was observed in both the light (17 to 49%) and heavy (2 to 44%) schemes. Both loading schemes resulted in similar increases in lactate (0.3 to 1.0nmol/l). Equating two schemes by volume resulted in differential responses, many of which favoured the lighter scheme in terms of mechanical, hormonal and metabolic outputs. These findings suggest that load or intensity employed may be not as important as initially proposed and that other factors (e.g. volume, technique) may explain the similar strength and hypertrophy adaptation reported in studies comparing light and heavy schemes.

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