This thesis comprises one review paper and five experimental studies, all of which are presented in the form of journal article submissions. These six research papers attempt to further our understanding of the physiological and metabolic requirements of repeated-sprint activity, specific to field-based team sports. Although coaches and sport scientists have suggested that repeated-sprint ability is an important fitness component of team sports, this area of investigation has only become more common in the past 10 years.

[ Truncated abstract] The purpose of this series of studies was to further our understanding of the relationship between muscle buffer capacity and training. Study one was performed to determine if there were differences in muscle buffer capacity (βmin-vitro) between females of differing training status (i.e., team-sport, endurance-trained and untrained subjects). Studies two and three were then performed to determine if short-term training could improve muscle buffer capacity and what type of training best improves this muscle characteristic (i.e., high-intensity, moderate-intensity or resistance training). Studies four and five were performed to determine if the accumulation of H+ during exercise was a mechanism by which training improved muscle buffer capacity. Below is a summary of these five studies. Study 1. The team-sport group had a significantly higher βmin-vitro than either the endurance-trained or the untrained groups (181 ± 27 v 148 ± 11 v 122 ± 32 'mol H+?g dm-1?pH-1 respectively; P<0.05). The team-sport group also completed significantly more relative total work (299 ± 27 v 263 ± 31 v 223 ± 21 J?kg-1, respectively; P<0.05) and absolute total work (18.2 ± 1.6 v 14.6 ± 2.4 v 13.0 ± 1.9 kJ, respectively; P<0.05) than the endurance-trained or untrained groups during a repeated sprint ability (RSA) test. There was a significant correlation between βmin-vitro and RSA (r=0.67; P<0.05). These findings show that young females competing in team sports have a larger βmin-vitro than either endurance-trained or untrained females. This may be the result of the intermittent, high-intensity activity during training and the match play of team-sport athletes... Conclusions. Our results show that training intensity is an important determinant of muscle buffer capacity. High-intensity interval training (120-150% LT) improved muscle buffer capacity (9 27%), however, neither moderate-intensity or resistance training improved muscle buffer capacity. In contrast higher training intensity (150-180% LT) may negatively affect muscle buffer capacity. Differences in the accumulation of H+ during high-intensity interval training does not appear to be the underlying mechanism for changes to muscle buffer capacity, however changes to this muscle characteristic were associated with pre-training muscle buffer capacity.

In response to challenging situations physiological and psychological adaptations result in elevated levels of arousal and when these levels are 'optimal' performance is enhanced. There are however, limitations to the amount of physiological and mental stimulation one can tolerate, with cumulative fatigue effects being the outcome when stressful conditions are imposed on the individual over an extended period of time. As a result of the extreme physical and cognitive demands placed on military forces while in combat, with soldiers being thrust into battle and required to make critical life-or-death determining decisions followed by appropriate motor responses, the physical and psychological capabilities of the troops are pushed to maximal limits, often resulting in undesirable decrements in physical and mental performance, with consequential human and materiel losses. Thirty-two soldiers participated in a battery of combat-related field and laboratory tests, first under 'normal' conditions with no prior physical activity and then immediately after the participation of an intensive bout of exercise. Physiological and perceptual responses plus standard of performance were measured at various stages of testing. Results of the Rating of Perceived Exertion (RPE), Body Discomfort Scale and heart rate responses revealed significantly higher levels of psychophysical strai,n in response to the strenuous physical activity. Despite these findings, the electromyographic (EMG) activity and efficiency of the combat-related skills were not negatively affected. Rather, nominal improvements in post-activity performance were noted, specifically response time, and this was attributed to elevated arousal and activation as a result of the exercise that was of sufficient duration to enhance arousal without imposing long term cumulative fatigue effects.

The purpose of this study was to (1) assess the reliability and validity of anger/hostility measures, (2) examine the relationship between anger/hostility and other negative emotions, and (3) examine the relationship between anger/hostility and health history. Sixty-five subjects were given the Buss Durkee Hostility Inventory (BDHI), the State-Trait Anger Expression Inventory (STAXI), the Profile of Mood States pomsS), the Clinical Analysis Questionnaire (CAQ), the State-Trait Anxiety Inventory (STAI), the Health and Wellness Attitude Inventory (HWAI), and a health questionnaire designed to provide information about past disease and alcohol/drug use. Overall, the BDHI and POMS displayed good test-retest reliability. All six of the global indices of anger/hostility intercorrelated at a significant level, thus demonstrating good concurrent validity. The six global measures of anger/hostility also correlated at a significant level with other negative emotions.

The purpose of this project is to review current literature on the mechanics and physiology of the vertical jump and to provide an understanding of the jump itself. The second purpose is to develop a step by step program to increase vertical jump from grade school through high school.

The purpose of this study was to investigate the effect of hand-weights and exaggerated arm swing on heart rate, blood pressure, and ratings of perceived exertion during submaximal walking. Twenty middle-aged (40- 59 years) female volunteers were given four submaximal treadmill tests at 3.0 mph and 0 grade. The four treatment conditions were as follows: 1) walking with unexaggerated arm swing (AS); 2) walking with unexaggerated arm swing with hand-held weights (ASHW); 3) walking with exaggerated arm swing (EAS), and 4) walking with exaggerated arm swing with hand-held weights (EASHW). The testing sequence was randomized and a minimum of 48 hr was given between tests.

No description available.

No description available.

We can hold conversations with people in environments where typically there are additional simultaneous talkers in background acoustic space or noise like vehicles on the street or music playing at a café on the sidewalk. This seemingly trivial everyday task is difficult for people with hearing deficits and is extremely hard to model in machines. This dissertation focuses on exploring the neural mechanisms of how the human brain encodes such complex acoustic environments and how cognitive processes like attention shapes processing of the attended speech. My initial experiments explore the representation of acoustic features that help us localize single sound sources in the environment- features like direction and spectrotemporal content of the sounds, and the interaction of these representations with each other. I play natural American English sentences coming from five azimuthal directions in space. Using intracranial electrocorticography (ECoG) recordings from the human auditory cortex of the listener, I show that the direction of sound and the spectrotemporal content are encoded in two distinct aspects of neural response, the direction modulates the mean of the response and the spectrotemporal features contributes to the modulation of neural response around its mean. Furthermore, I show that these features are orthogonal to each other and do not interact. This representation enables successful decoding of both spatial and phonetic information. These findings contribute to defining the functional organization of responses in the human auditory cortex, with implications for more accurate neurophysiological models of spatial speech processing. I take a step further to investigate the role of attention in encoding the direction and phonetic features of speech. I play a mixture of male and female spatialized talkers eg. male at left side to the listener and female at right side (talker’s locations switch randomly after each sentence). I ask the listener to follow a given talker e.g. follow male talker as they switch their location after each uttered sentence. While the listener performs this experiment, I collect intracranial EEG data from their auditory cortex. I investigate the bottom-up stimulus dependent and attention independent encoding of such a cocktail party speech and the top-down attention driven role in the encoding of location and speech features. I find a bottom-up stimulus driven contralateral preference in encoding of the mixed speech i.e. Left brain hemisphere automatically and predominantly encodes speech coming from right direction and vice-versa. On top of this bottom-up representation, I find that attended talker’s direction modulates the baseline of the neural response and attended talker’s voice modulates the spectrotemporal tuning of the neural response. Moreover, the modulation to attended talker’s location is present throughout the auditory cortex but the modulation to attended talker’s voice is present only at higher order auditory cortex areas. My findings provide crucially needed evidence to determine how bottom-up and top-down signals interact in the auditory cortex in crowded and complex acoustic scenes to enable robust speech perception. Furthermore, they shed light on the hierarchical encoding of attended speech that have implications on bettering the auditory attention decoding models. Finally, I talk about a clinical case study where we show that electrical stimulation to specific sites in planum temporale (PT) of an epilepsy patient implanted with intracranial electrode leads to enhancement in speech in noise perception. When noisy speech is played with such an electrical stimulation, the patient perceives that the noise disappears, and that the speech is similar to clean speech that they hear without any noise. We performed series of analysis to determine functional organization of the three main sub regions of the human auditory cortex- planum temporale (PT), Heschl’s gyrus (HG) and superior temporal gyrus (STG). Using Cortico-Cortical Evoked Potentials (CCEPs), we modeled the PT sites to be located between the sites in HG and STG. Furthermore, we find that the discriminability of speech from nonspeech sounds increased in population neural responses from HG to the PT to the STG sites. These findings causally implicate the PT in background noise suppression and may point to a novel potential neuroprosthetic solution to assist in the challenging task of speech perception in noise. Together, this dissertation shows new evidence for the neural encoding of spatial speech; interaction of stimulus driven, and attention driven neural processes in spatial multi-talker speech perception and enhancement of speech in noise perception by electrical brain stimulation.

No description available.