<p>he purpose of this investigation was to examine possible differences in the acute systemic arterial blood pressure and esophageal pressure and left ventricular function responses to various intensities of static-dynamic and isometric single-leg press and cycle ergometry exercise. Intra-arterial blood pressure, intra-esophageal pressure and left ventricular function were measured in eight subjects (mean age: 23 years) during 6 and 12 repetitions of static-dynamic single-leg press at 70% (SLP70) and 90% (SLP90) of the subjects's 1 repetition maximum (l RM) respectively, 30 seconds of isometric single-leg press exercise at 70% (ILP70) and 90% (ILP90) of maximum capacity and during 60 seconds of steady state cycle ergometry at 70 % of maximum power output (MPO) (CE70). ILP70 produced significantly greater (p < 0.05) circulatory responses (arterial blood pressure, esophageal pressure, heart rate and rate-pressure product) than SLP70. CE70 produced greater (p < 0.05) peak mean (PM) systolic blood pressure (PMSBP), heart rate (PMHR) and rate-pressure product (PMRPP) than either ILP70 and SLP70 but had similar PM diastolic blood pressure (PMDBP), mean arterial blood pressure (PMAP) and esophageal pressure (PMEP) to SLP70. SLP90 and ILP90 for the same absolute time period produced similar cardiovascular responses as did ILP90 and ILP70. Greater (p < 0.05) rates of increase and PM responses were found to occur during SLP90 than during SLP70. Differences in response to SLP70 and ILP70 may be due to the greater: duration of active muscle contraction, esophageal pressure (due to the Valsalva maneuver), occlusion of the vascular beds in the exercising muscles and degree of effort associated with ILP70. CE70 produced greater (p < 0.05) PMSBP, PMHR and PMRPP responses due to a greater cardiac output known to occur with this form of exercise. The increased HR and stroke volume (SV) and decreased total peripheral resistance (TPR) would be expected to result in the greater PMSBP and unchanged PMDBP which were observed. The similar circulatory responses during SLP90 and ILP90 appear to be linked to comparable increases in intra- esophageal pressure from enlisting of the Valsalva maneuver and similar amounts of effort required to perform these exercises.</p> / Master of Science (MS)

<p>The purpose of this dissertation was to develop an understanding of physical activity behaviour and to promote physical activity participation among individuals with spinal cord injury (SCI) within the context of the theory of planned behaviour (Ajzen, 1985). Using a "bottom-up," programmatic research approach, this three-study thesis involved (1) validating a new measure of physical activity that is appropriate for use among individuals with SCI, (2) identifying theoretically meaningful, psychosocial predictors of physical activity participation in the SCI population, and (3) implementing and testing a theory-based intervention focused on helping people with SCI follow through with their physical activity intentions. Specifically, Study 1 examined the construct validity of the Physical Activity Recall Assessment for Individuals with SCI (PARA-SCI). An assessment of convergent validity (n = 73) and construct validation by extreme groups (n = 158) provided evidence of the construct validity of the leisure time physical activity (LTPA) PARA-SCI category but not the lifestyle or cumulative activity PARA-SCI categories. It was concluded that the PARA-SCI is suitable for assessing LTPA among individuals with SCI and should be used to advance research examining physical activity determinants. Using the LTPA PARA-SCI category as a primary outcome, the purpose of Study 2 was to examine determinants of physical activity among people with SCI (n = 110) within the context of the theory of planned behaviour (Ajzen, 1985). This prospective study revealed that attitudes, subjective norms and perceived behavioural control (PBC) predicted physical activity intentions while intentions, but not PBC, explained a small amount of the variance in LTPA. The poor prediction of behaviour suggested a need to investigate whether strategies that facilitate the translation of intentions into behaviour can serve to strengthen the intention-behaviour relationship. Study 3 utilized a randomized, controlled design to examine the efficacy of an 8-week implementation intention intervention as a means of helping individuals with SCI (n = 53) follow through with their intentions for physically active living. The results indicated that participants who formulated implementation intentions (i.e., the implementation intention condition) spent more time engaged in physical activity and were more likely to enact their intentions than individuals who did not create implementation intentions (i.e., the control condition). Further, participants in the implementation intentions condition had stronger intentions and greater confidence to schedule their physical activity than participants in the control condition, suggesting that implementation intentions may influence cognitions related to physical activity. (Abstract shortened by UMI.)</p> / Doctor of Philosophy (PhD)

No description available.

<p>Three experiments are reported that examined the lnfluence of prior judgements on implicit and expliclt tests of memory in gymnastic judging. The rationale was that if gymnastlc Judging ls affected by the memory for prior eplsodes, then the accuracy of judgements should change as a result of the prior episode. The results of Experiment 1 revealed that perceptual judgements dlffered as a functlon of an item's relationship between the study phase and the perceptual test phase. Moves that had the same performance ln both phases resulted ln the hlghest level of accuracy (M = 79%). New moves were less accurate (M = 75%). The lowest level of accuracy was achieved for items where the performance was altered between study and the perceptual test (M = 72%) . Similarly, recognition judgements differed as a functlon of an item's relationship between the study phase and recognition test phase. Novlce and expert Judges revealed similar memory lnfluences for perceptual and recognition Judgements (Experiment 1). Memory influences were reduced, but still evident when subjects were given prior knowledge of these effects and procedural changes were adopted (Experiment 2). Spacing of repetitions dld not enhance prior processlng effects of perceptual Judgements, but superior retention was noted for spaced repetitions in the recognition test phase (Experiment 3). These findings are discussed in terms of memory influences on subjective experience and the practical implications of Judges' exposure to an athlete's performance prlor to competition.</p> / Master of Science (MS)

<p>Self-presentation (SP) is the process individuals use to control the perceptions others have of them (Leary, 1995: Leary & Kowalski, 1990). Research suggests that self-presentation plays a role in older adults' exercise participation and beliefs about the appropriateness of exercise and exercise clothing for older people (Martin et al. 2000). The purpose of this thesis was to evaluate how SP variables relate to exercise-related attitudes, motives, and the exercise environment among older women.</p> <p>Study 1 evaluated the reliability and validity of measures of physical self-perceptions and exercise motives (N=40; M age=68.22). The Social Physique anxiety Scale (Hart et al. 1989) and the Reasons for exercise Inventory (Silberstein. et. al.. 1988) were found to be reliable and valid when used in a sample of older women. In addition, while fitness motives were of primary importance to older women, self-presentational concerns (i.e., social physique anxiety [SPA]) were related to self-presentational motives for exercise suggesting that for some women, SP is an issue in exercise contexts.</p> <p>In Study 2, the moderating effects of SPA and physical activity) PA on attitude towards different exercise environments were examined. Overall, women's (N = 81: M age = 70.85 years) attitudes toward conservative and revealing exercise attire environments were not significantly different. However, PA level, but not SPA, moderated their preferences such that for the revealing attire condition, as PA decreased, attitudes toward the exercise setting also decreased. As well, women's confidence in their ability to present themselves as exercsers (i.e., self-presentational efficacy, SPE) was not differentially affected across the two video conditions. However, SPA. but not PA level, moderated the effect of the videos on SPE such that for the revealing condition, as SPA increased. SPE decreased. Taken together, this research has expanded our knowledge concerning the role that self-presentation plays in exercise settings among older women. Furthermore, consideration of the exercise environment, self-presentational concerns, and physical activity level is recommended when developing exercise programs that older women will feel comfortable initiating and maintaining throughout their years.</p> / Master of Science (MS)

<p>It is known that human skeletal muscle has several fiber types, each with a different metabolic and physiological profile. It is not known whether there are different ultrastructural characteristics within each fiber type which may account for the different contractile properties. The purpose of this study was to examine the relationship between fiber type and ultrastructural characteristics.</p> <p>Needle biopsies were obtained from the right vastus lateralis of five healthy males. According to the method described by Alway et al (1980), the tissue was prepared for electron microscopy and fiber types were identified based on their myoglobin content. Three non-overlapping electron micrographs were taken from the interior of each fiber under a Philips 300 electron microscope, and 50 type I and 50 type II fibers were examined from each subject. The constituents which were studied included: myofibrillar protein, mitochondria, cytoplasm, lipid and sarcoplasmic reticulum (SR). Volume densities were calculated for each constituent by means of a l68-point counting technique from electron micrographs projected onto a screen.</p> <p>The results indicated that type I fibers were significantly greater with respect to mitochondrial volume density and lipid volume. However type II fibers had significantly greater myofibrillar volume densities and sarcoplasmic reticulum volume density (by approximately twofold). Fiber areas were also greater in type II than type I fibers while myosin packing density did not differ between fiber types.</p> <p>It was concluded that SR and myofibrillar protein ultrastructural differences between fiber types may be important factors in determining twitch contraction properties and tension production for type I and II fibers. Finally, differences in mitochondrial volume density may be important in determining fatiguability of fiber types.</p> / Master of Science (MSc)

<p>The effects of a 12-week physical conditioning program on cardiorespiratory responses and the subjective assessment of work intensity (RPE) during exercise in healthy, middle-aged females and females with coronary heart disease (CHD) were studied. A physical conditioning program was developed for healthy, middle-aged females and females with CHD using an exercise prescription based on current practice in middle-aged males with and without CHD. The progress included cycle ergometer exercise prescribed at 65-75% of maximal VO₂ for 30-45 minutes 3 times per week.</p> <p>Six cardiac females (aged 40 to 57 years) and 9 healthy females (aged 44 to 52 years) started the program. The cardiac females had a significantly lower maximal work capacity, VO₂ and VCO₂ (p<0.05) than the healthy females. Measures of other variables were similar in the two groups. Following physical conditioning the healthy females demonstrated a significant increase in maximal PO(27.6%), VO₂ (15.9%), VE (23.9%) and VCO₂ (17.8%); a significant decrease in HR (10.5%), SBP (7.1%), RPP (17.5%), VCO₂ (12.0%) and RPE (33.1%) at a standard submaximal PO; and a significant decrease in steady state VO₂ (6.7%), Qc (13.4%) and HR (9.4%) (p<0.05). No changes were observed in other variables. Since only 3 cardiac females completed the 12-week program, they were treated as case studies. These 3 cardiac females showed considerable variation in their cardiorespiratory responses to physical conditioning but each exhibited a reduction in RPE at submaximal power outputs following physical conditioning. It was concluded that the physical conditioning program; (a) improved cardiorespiratory functioning, and reduced perceived exertion, during exercise in the healthy, middle-aged females; and (b) was effective as a mode of psychophysical rehabilitation, but not necessarily as a mode of physiological rehabilitation, for the females with CHD.</p> / Master of Science (MSc)

<p>The present study was undertaken to investigate the mechanism underlying the observation that the maximal voluntary strength of the two legs acting together or bilaterally in isometric leg extension was less than the summed unilateral (sum of the left and right legs tested separately) strength. Observations were made on this phenomenon under both isometric and concentric contraction conditions by testing young adult males performing unilateral and bilateral leg press contractions on a modified isokinetic dynamometer.</p> <p>Electromyographical evidence indicated that there was a lesser activation of motor units in bilateral contractions, as compared to unilateral, under isometric conditions and at a low and high concentric velocity. To determine whether a particular type of motor unit was being activated to a lesser extent in bilateral contractions, two physiological parameters of unilateral and bilateral contractions were compared: the strength-velocity relation and fatigability. This investigative method was based on the known physiological differences between the motor unit types; namely fast-twitch (FT), type two motor units have a faster twitch contraction time, greater force output at high velocities of shortening and lesser resistance to fatigue than the slow-twitch (ST), type on units.</p> <p>Results showed a greater relative decline in the strength of bilteral contractions as the velocity of contraction was increased through a range from 0°/s to 424°/s (0 to 7.40 radians/s). The bilateral to summed unilateral strength ratio (B/U ratio) decreased from 0.91 under isometric conditions to 0.51 at the highest test velocity. Lesser fatigability was found in the bilateral condition in a 100 consecutive concentric contraction fatigue test. These results provided complementary evidence for the conclusion that FT motor units were active to a lesser degree in bilateral contractions.</p> / Doctor of Philosophy (PhD)

<p>This study was designed to compare the effects of two weight training systems, the Interval Circuit and High Intensity systems on muscular strength, cardio-respiratory endurance, girth measures and self-concept of high school boys.</p> / Master of Science (MSc)

Vehicle occupants are typically exposed to unpleasant whole-body vibration (WBV) for extended period of time. It is well known that the transmission of unwanted vibration to the human body can lead to fatigue and discomfort. Moreover, the unwanted vibration normally distributed in the low-frequency range has been found as the main risk factor for lower back pain and lumbago, which seriously affect the health and working performance of occupants. Thus vibration cancellation on seats has attracted considerable interest in recent years. So far, for most vehicle seats, vibration isolation is achieved passively by using seat cushions and conventional energy absorbers, which have very limited performance in the low-frequency range. The work presented in this thesis forms a successful development and experimental study of an active seat and control algorithm for occupants’ WBV reduction under low frequency excitations. Firstly, a modelling study of the seat human subjects (SHS) and an extensive experimental measurement of the vibration transmissibility of a test dummy and vehicle seat are carried out. The biodynamic responses of SHS exposed to uncoupled vertical and fore-and-aft WBV is modelled. A comparison with the existing models is made and the results show that an improved fit with the aggregated experimental data is achieved. Secondly, an active seat is developed based upon the observations and understanding of the SHS and seat system. The characteristics of the active seat dynamics are identified through experimental tests found suitable for the development of an active seat to attenuate the vibration experienced by vehicle occupants. The vibration cancellation performance of the active seat is initially examined by feedforward plus proportional-integral (PI) control tests. Through these tests, the effectiveness of the actuators control authority is verified, but the limitations are also revealed. Because the active seat system is subject to non-linear and time-varying behaviour, a self-tuning fully adaptive algorithm is a prime requirement. The Filtered-x Least-Mean-Square (FXLMS) algorithm with the Fast-block LMS (FBLMS) system identification technique is found suitable for this application and is investigated through experimental tests. Substantial vibration reductions are achieved for a variety of input vibration profiles. An excellent capability of the active seat and control system for efficiently reducing the vibration level of seated occupants under low-frequency WBV is demonstrated.