Thesis (Ed. D.)--University of the Pacific, 2005. / Includes bibliographical references (leaves 160-177).

Thesis (PH.D.) -- Syracuse University, 2006. / "Publication number AAT 3241849."

Introduction: Scientific investigations to determine physiological demands and performance characteristics in sports are integral and necessary to identify general fitness, to monitor training progress, and for the development, prescription and execution of successful training interventions. To date, there is minimal evidence based research considering the physiological demands and physical characteristics required for the equestrian sport of Eventing. Therefore, the overarching aim of this thesis was to investigate the physiological demands of Eventing and performance related fitness in female riders. Method: The primary aim was achieved upon completion of three empirical studies. Chapter Three: Anthropometric and physical fitness characteristics and training and competition practices of Novice, Intermediate and Advanced level female Event riders were assessed in a laboratory based physical fitness test battery. Chapter Four: The physiological demands and physical characteristics of Novice level female event riders throughout the three phases of Novice level one-day Eventing (ODE) were assessed in a competitive Eventing environment. Chapter Five: The physiological demands and muscle activity of riders on live horses in a variety of equine gaits and rider positions utilised during a novice ODE, including jumping efforts, was assessed in a novel designed live horse exercise test. Results: Chapter Three reported that aside from isometric endurance, riders anthropometric and physical fitness characteristics are not influenced by competitive level of Event riding. Asymmetrical development in isometric leg strength was reported with increased levels of performance; riders reported below average balance and hamstring flexibility responses indicating limited pelvic and ankle stability, and tightness in the hamstring and lower back. Chapter Four reports that physiological strain based upon heart rate during Eventing competition is considerable and close to maximal, however blood lactate data was not supportive of this supposition. Chapter Five reports that during horse riding, riders are exposed to intermittent and prolonged isometric muscle work. During horse-riding, riders have an elevated heart rate compared to the oxygen requirements for the activity, in addition to moderate blood lactate concentrations. Conclusion: This thesis indicates that the most physiologically demanding aspect of Event riding is the light seat canter and where jumping efforts are introduced. During these positions and gait combinations, heart rate is elevated compared to oxygen uptake. Additionally, moderate blood lactate (BLa) concentrations are reported suggesting though cardiac strain is high, physical demands are moderate. The use of heart rate as a marker of exercise intensity during horse riding activities is not appropriate as it is not reflective of actual physiologic demand and BLa may be a more indicative marker of exercise intensity for equestrian investigations. There are many factors that may affect heart rate as discussed throughout the thesis, such as cognitive anxiety, heat stress and isometric muscle work. The data from this thesis speculates that the elevated heart rate is in part affected by isometric muscle work; similar physiological profiles exist in sports such as Sailing and are attributed to the quasi isometric theory. Though this thesis is not able to comprehensively conclude that physiological responses are a direct result of quasi isometrics, the data set does infer this may be a potential contributor and as such is a recommended topic for future research. Regardless of the causal mechanism, riders should be conditioned to tolerate high heart rates to enable optimal physical preparation for competition; the physical characteristics and physiological demands placed upon Event riders reported throughout this thesis provides information for coaches and trainers to consider when designing such interventions.

Hyper-resistance at the joint is one of the most common symptoms in children with cerebral palsy (CP). There are both neural and non-neural factors contributing to the observed joint hyper-resistance. Non-neural alterations to the musculoskeletal system such as a reduced muscle length, increased tendon length and an increase in joint stiffness are commonly treated by physiotherapy interventions such as stretching exercises. However, the effectiveness of these interventions in terms of improvements in function is of a low magnitude and the response of spastic muscles to stretch is poorly understood. Therefore, the main aim of the programme of work presented in this thesis was to increase the effectiveness of stretching interventions at the ankle joint. To achieve this, it is important to understand the behaviour of the medial gastrocnemius muscle and Achilles tendon in response to a stretch applied at the joint. For this first sub-goal, three experimental studies were performed. First, the relationship between joint rotation and muscle and tendon contribution during a single stretch is described. We show that a smaller Achilles tendon moment arm leads to a decrease in muscle lengthening during joint rotation. Additionally, we show that the relative stiffness of the muscle to the tendon is increased in children with CP, which further limits lengthening of the muscle during joint rotation. Secondly, we document the acute effect of stretching on medial gastrocnemius fascicle lengthening properties. It was found that medial gastrocnemius muscle stiffness cannot explain the increased ankle joint range of motion acutely following passive stretching. These studies all indicate that the lengthening stimulus to the muscle is reduced in children with CP. Therefore, to increase the effectiveness of stretching exercises, an intervention was designed with the aim to increase this stretching stimulus seen by the muscle. By performing progressive resistance training, we showed an increase in the stiffness of the tendon, and thus a reduction in the relative stiffness of the muscle to the tendon. Therefore, the amount of stretch seen by the muscle was increased. We have shown that due to this combined intervention a remodelling of muscle is possible, as we showed muscle fascicle length to increase. Even though functional benefits were limited, the proof of principle was demonstrated and future work should explore this model of intervention further.

Running economy (RE) is defined as the rate of oxygen consumption at a given submaximal running velocity. Whilst the concept of running economy is well documented, little information is available about the to daily variation in RE, variation in RE within prolonged running bouts and the effects on RE of exercise-induced dehydration. Thus, the principal aim of this research was to investigate these aspects and attempt to contribute further knowledge and understanding of RE. The purpose of the first study (Chapter 4), was to investigate the daily variation in RE in twenty one habitually active Singaporean men (V0₂max = 51.6 ± 5.8 ml.kg⁻¹ min⁻¹). The RE was measured over three consecutive days during treadmill running at 3.33 m.s⁻¹, and at running speeds representing relative exercise intensities of 60% and 85% V0₂max (randomly assigned in a counterbalanced design). The running bouts were of 10 min duration at each speed, with 5 min rest between each running bout. The group mean (±SD) VO₂ during submaximal running at 3.33 m.s⁻¹ (82 ± 5.7% V0₂max) was 44.5 (±2.1), 43.8 (±2) and 44.2 (±2) ml.kg⁻¹ min⁻¹ for days one, two and three respectively. The mean coefficient of variation (CV) for RE at 3.33 m.s⁻¹ was 2.54 % (range = 0.24 - 5.41%). The group mean VO₂ during submaximal running at 60% and 85% VO₂max was similarly invariant over the three consecutive days. The results showed no differences in daily RE for the group (p > 0.05). The results suggest that for the individuals in this study RE does not change on a daily basis.

Variability in the discharge of human motor neurons was investigated in the context of aging and skill acquisition. In the aging experiment, young and older adults performed constant-force and complex sinusoidal isometric force-matching tasks while motor unit action potentials were recorded from the first dorsal interosseous (FDI) muscle. In three manuscript chapters, the characteristics of motor unit inter-spike interval (ISI) distributions were compared, patterns in the time series of ISIs were investigated with two experimental measures of complexity, and the extent of motor unit synchronization and common drive was compared between young and older adults. The sinusoidal force-matching conditions required substantial motor unit rate coding compared to the constant-force task. In both tasks, older adults utilized a greater proportion of motor units that were discharging at lower rates and with greater discharge variability. Positive skewness of ISI distributions from older adults indicated that motor unit discharge rates varied more freely towards lower rates and de-recruitment. That skewness was greater in older adults indicates that disruption of consistent discharge through de-recruitment and subsequent recruitment may be one reason why force fluctuations are greater and force-matching performance was poor in older adults. The complexity measures indicated that the fluctuations in motor unit discharge during constant-force contractions were random. Detrended fluctuation analysis, but not approximate entropy, was able to distinguish between the constant-force and sinusoidal force-matching tasks. It was demonstrated with simulated data that these techniques are sensitive to the manner in which motor unit data are pre-conditioned. Indeed, different methods of creating firing rate time series resulted in opposite conclusions regarding complexity. These complexity measures should be further evaluated with discharge data from patient populations in which patterns might be expected due to altered neural function. Motor unit synchronization and common drive were similar in young and older adults and greater synchronization was associated with greater discharge variability. (Abstract shortened by UMI.)

The purpose of this study was to examine the relationship between depression and three categories of physical activity: leisure, occupational, and household activity. Although several researchers have found that physical activity in the form of exercise alleviates symptoms of depression, few have examined the extent to which occupational or household activity alleviates depressive symptoms. This study proposed occupational, household, and total activity would predict lower depression scores in a relationship similar to that reported for exercise. Data for this study were derived from the database of a larger study of seasonal variation of blood cholesterol conducted at the University of Massachusetts Medical School in Worcester, Massachusetts. Five-hundred-twenty-eight participants (285 men, 243 women) between the ages of 20 and 70 years were included in the study. Data on leisure, occupational, and household activity had been collected over the course of one year using 24-hour phone recalls, as well as data on depression as measured by the Beck Depression Inventory (Beck & Steer, 1987). Leisure activity was predictive of lower depression scores in women, but not men. High intensity leisure activity was more predictive of depression scores than low intensity leisure activity. Occupational, household, and total activity were not found to be predictive of depression scores in either direction.

Popular biological and psychological theories strongly advocate that regular physical exercise brings about long-term and short-term psychological benefits. Similarly, Yoga tenets promise to generate significant improvements in psychological and physical health. However, considerate controversy exists, as rigorously designed experimental studies have consistently challenged the existence of a causal connection between physical activity and psychological changes. The current project was undertaken to test the hypothesis that physical activity moderates the students' experience of stress during an academic semester. The project suggested that psychological changes may take place as the students undergo changes in their physical self-concept. First, a quasi-experimental study assessed 97 students at a large state university, who either attended traditional physical education (PE) courses, enrolled in Yoga courses or abstained from physical activity. The students filled out self-report measures, at the beginning and the end of an academic semester. The results have showed that, at the beginning, all groups were similar in their psychological presentation but different in their attitude. The data obtained at the end of the semester suggested that, overall, the students' well-being did not change. However, contrast analyses showed that the Yoga students became more distressed than the exercise students, and that exercise students faired better than the control group. Also, the changes in psychological symptoms were significantly related to the changes in physical self-concept. Second, twenty structured interviews were conducted with the Yoga and exercise students. Qualitative analysis provided systematic description of the two groups, specifically of their motivation, stress, self-concept and the perceived effectiveness of their PE course. The results suggested that all students evaluated their PE courses as highly effective and beneficial. The statistical data has also supported a graphic model that connected the students' expectations, experience of stress and changes in self-concept. This model has shown that such connections are complex, and not direct one-to-one relationships. In conclusion, the project supported the hypothesis that physical activity brings about positive psychological benefits by promoting a change in physical self-concept. It showed strong similarities in the subjective experience of the Yoga and exercise students. The implications of such findings for clinical practice were discussed.

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