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Lactate produced during exercise is no longer thought of as a waste product and it is now understood it plays an important role in exercise metabolism. Exercise intensity during invasion sports elicits a mean heart rate of approximately 85% HRmax which equates to 80% V̇O2max and blood lactate concentration greater than 4mmol·l-1. It is likely that an athlete's ability to metabolise this lactate and maintain a lactate balance is a key determining factor in match performance. Supplemented lactate is utilised more rapidly and to a greater extent than glucose and helps maintain performance level for the repeated high intensity actions required throughout invasion sport match play. Study 1 examined the effect of supplementing calcium lactate during simulated rugby union match play to determine whether sprint speed and intermittent sprint performance could be improved. Ten recreationally active participants were recruited for part one of the study to determine the rate at which orally consumed lactate solution appears in the blood. For part two of the study, seven amateur rugby union players (age: 25 ± 5 years, weight: 84 ± 6kg, and height: 180 ± 4cm) underwent the BURST under three conditions to compare water, glucose, and lactate. Sprint performance was measured through 17 x 15m maximal sprints over the course of the BURST. An increase in blood lactate concentration ([La-]b) was evident within 10 minutes of ingestion and it was significantly (p ≤ 0.05) elevated from 20 to 60 minutes post ingestion. There was no change in blood glucose concentration throughout the testing period. There was no significant (p > 0.05) difference in sprint time between conditions at any performance test, with total sprint time per block, per half, and across the full BURST protocol also showing no difference. There was no significant difference in decrement of sprint performance between the first and second (p = 0.69), or third and fourth (p = 0.13) exercise blocks, or between the first and second halves (p = 0.59). There was a significant difference in peak heart rate between condition in both the first (C = 179 ± 4, L = 172 ± 6, G = 179 ± 9; p = 0.04) and second (C= 178 ± 3 L = 170 ± 7, G = 176 ± 6; p = 0.03) halves of simulated match play. There was no significant difference in respiratory rate between conditions in either the first (C = 44 ± 8, L = 38 ± 6, G = 47 ± 11; p =0.16) or second (C = 42 ± 17, L = 36 ± 6, G = 40 ± 19; p = 0.68) halves. Supplementation of 1% Wt/vol calcium lactate solution did not enhance sprint speed or significantly reduce the drop in sprint performance seen throughout a match. There was a trend for the decrement in performance to be less in the lactate condition and therefore, the use of calcium lactate may be recommended prior to rugby matches as an ergogenic aid to sustain sprint performance although any benefit is likely to be marginal. Study 2 investigated the effect of sprint interval training on soccer specific performance indices and lactate kinetics. In youth soccer, 23% of the distance covered happens at speeds above maximal lactate steady state (MLSS) which suggests lactate kinetics may be important to soccer performance. Thirteen elite soccer academy players (age 15 ± 0.5y) underwent baseline testing (Wingate anaerobic Test (WAnT) with blood lactate measurements, incremental V̇O2peak and time to exhaustion test, 0-10m and 10-20m sprint performance, repeated 20m sprint performance, and vertical jump performance) before being allocated to control or SIT group. The control group maintained training whilst the SIT group carried out twice-weekly all-out effort cycle sprints consisting of 6 x 10s sprint with 80s recovery. Training elicited significant improvements in V̇O2peak (pre: 54.89 ± 3.09ml· kg−1·min-1 post: 60.81 ± 5.73ml· kg−1·min-1; p = 0.001), TTE (pre: 655 ± 54s post: 688 ± 55s; p=0.001), 10 - 20m sprint time (pre: 1.29 ± 0.04s post: 1.25 ± .04s; p=0.02), and peak power during WAnT (pre: 12.4 ± 1.3 W.kg-1 post: 15.3 ± 0.7W.kg-1; p=0.003) which were not seen in the control group. The changes in performance were significantly correlated to changes in lactate kinetics (time to exhaustion: r=0.77, p = 0.04). Cycle-based SIT is an effective training paradigm for elite youth soccer players and the improvements in match specific fitness indices are associated with changes in lactate kinetics. These increased levels of lactate utilisation may facilitate a greater ergogenic benefit from supplemented lactate solution further enhancing its ability to mitigate the decline in sprint performance seen throughout invasion sport match play. Study 3 examined the effect of calcium lactate supplementation of laboratory-based performance tests specific to field hockey. It also sought to determine whether lactate kinetic altering sprint interval training would enhance any ergogenic effect of the supplementation. Invasion sports such as field hockey require players to perform multiple repetitions of maximal effort sprints, with the volume and intensity of these playing a critical role in determining level of match performance. The drop in sprint performance over the duration of match play is linked to reduced substrate availability leading to fatigue, and there a various ergogenic aids used to mitigate this. One such supplement is lactate which has been shown to possibly maintain high-intensity exercise performance with the effect being amplified as cardiorespiratory fitness increases. Eleven amateur female field hockey players underwent baseline testing for CP, V̇O2peak, TTE, PP and RSA both with and without supplemented calcium lactate solution. This was followed by a control period where normal training and match play were maintained. Testing was then repeated before and after carrying out twice-weekly all-out effort cycle sprints consisting of 6 × 10 s sprint with 80 s recovery. There were no differences in performance between either condition at the baseline testing or following the control period (p > 0.05).There was no change in any performance indicator following three-week control period (p > 0.05). Training elicited significant improvements in CP (Pre 2: 210 ± 2W; Post: 222 ± 25W, p = 0.01), V̇O2peak (Pre 2: 40.27 ± 6.04 ml· kg−1·min-1; Post: 44.52 ± 4.11 ml· kg−1·min-1, p = 0.02), and TTE (Pre 2: 613 ± 99s; Post: 677 ± 118s, p = 0.01). There were no changes in either power at LT (Pre 2: 118 ± 21W; Post: 118 ± 18W, p = 1.00), or [La-]b at LT (Pre 2: 3.15 ± 0.64 mmol·l-1; Post: 2.91 ± 0.47 mmol·l-1, p = 0.17). With the exception of TTE (p = 0.003) which saw a significant detrimental effect of lactate supplementation, there were no differences between condition during post-training testing (p > 0.05). It is evident performing cycling-based SIT training twice-weekly in addition to the regular field hockey training sessions can help players develop aerobic and anaerobic capacity in a short period of time. It would appear supplementation of a 2% calcium lactate solution offers no ergogenic benefit for short-duration performance tests and may in fact have a detrimental effect on endurance capacity. Together, these studies show that supplementation of calcium lactate solution is not an effective method to enhance physical performance during aerobic and anaerobic performance tests. It may provide a small mitigation to the decline in sprint performance seen over the course of invasion sport match play. Therefore, the use of calcium lactate could be recommended prior to invasion sport to help sustain sprint performance which is a critical component of match success. Although any benefit seen would be small, at an elite level these small changes may enhance overall team performance giving an advantage over oppositions.

Previous work has shown the potential to improve sprinting performance through adaptations to the bending stiffness of sprint shoes. In addition, it has been suggested that the bending stiffness need customising to the individual to achieve maximal performance. However, ambiguous sprint performance results in recent literature with increasing bending stiffness of sprint shoes, in addition to a lack of detailed biomechanical data collected, has lead to considerable uncertainty of the potential to customize the bending stiffness of sprint shoes to individuals for maximal performance. Thus, the aim of this work is to develop functional sprint footwear in a range of different bending stiffnesses in order to explore the effects of increased sprint shoe bending stiffness on sprinting performance and lower limb dynamics. Mechanical test procedures were implemented to both validate the mechanical testing methodologies and benchmark the mechanical properties. A novel mechanical test apparatus and methodology were specifically designed to evaluate the traction properties of sprint shoes. A minimum level of traction generated among commercially available shoes was identified as the minimum level of sufficient traction. The methodology developed by Toon (2008) was used to measure bending stiffness. No trends were detected towards the introduction of stiffer commercially available sprint shoes. A novel construction method using laser sintered (LS) nylon-12 was introduced, producing bespoke sprint shoes sole units in a range if bending stiffnesses with sufficient traction for sprinting. A novel process for assembling the LS sole units with standard uppers was presented, producing durable shoes with a high quality finish. Methodological concerns were addressed in an examination of the effect of commonly used sampling rates (SR), filtering frequencies (fc), and definition of the MPJ on resulting metatarsophalangeal joint (MPJ) kinematics and kinetics in sprinting. MPJ angular range of motion and angular velocity were significantly reduced with changes in SR, fc and MPJ definition, while significant differences in MPJ kinetics with changes of MPJ definition. The influence of shoe stiffness on sprinting performance and step characteristics was assessed using three sprint shoe conditions, up to 7 times stiffer than average commercially available. Results showed a significant increase in sprint time and a significant decrease in ground contact time in the stiffest shoe condition, with all of the participants producing their best sprints in the least stiff shoe condition, indicating the shoe conditions were too stiff. The differences in the trends observed between the group mean and the individual results indicate that both a single subject and group mean analysis be carried out in future research. The influence of shoe stiffness on sprinting performance and the kinematics and kinetics of the MPJ and ankle was assessed separately in the acceleration and maximal speed phases using three sprint shoe conditions, up to 3.5 times stiffer than the average commercially available. Results showed no change in sprinting performance. Increasing the bending stiffness resulted in significant decreases in the amplitude of MPJ and ankle kinematics, in addition to temporal changes in the occurrence of peak values. The effects of increasing the bending stiffness of sprint shoes on the kinematics and kinetics of the lower limb were more pronounced in the acceleration phase compared to the maximal speed phase.

RasGAP is a GTPase activating protein (GAP) that deactivates Ras by promoting Ras-GTP hydrolysis to Ras-GDP. In Drosophila melanogaster, RasGAP is required for the long-term survival of neurons in the adult brain because mutants in the RasGAP gene (vap) show an age-related neurodegenerative phenotype, with dying neurons showing morphological features of autophagy. RasGAP was shown to have a GAP-independent role within fly neurons that is dependent on its SH2 domains. The aim of this study was to identify proteins that interact with the SH2 domains of RasGAP and to understand the roles of these proteins in neuronal survival. By using tagged RasGAP affinity purification and mass spectrometry of RasGAP protein complexes from S2 cells, Sprint, a Ras effector and putative activator of the endocytic GTPase Rab5, was identified as a novel SH2-dependent RasGAP interacting protein. The interaction between Sprint and RasGAP is phosphotyrosine-dependent, since it requires tyrosine phosphorylation of Sprint. In addition, Sprint and RasGAP interaction requires the SH2 domains of RasGAP but not Sprint or the conserved site of RasGAP tyrosine phosphorylation (pTyr363), indicating an association between these two molecules. RasGAP and Sprint co-localised with Rab5-positive early endosomes and this co-localisation depended on the SH2 domains of both RasGAP and Sprint. This study demonstrates a key role for this interaction in neurodegeneration: mutation of Sprint (or Rab5) suppressed the autophagic neuronal cell death caused by the loss of RasGAP. These results indicate that the long-term survival of adult neurons in Drosophila depends on a critical balance between Ras activation and endocytosis, and that this balance is maintained by the interplay between RasGAP and Sprint.

Although soccer is one of the more researched intermittent team sports, there is a surprisingly modest amount of information available on the effects of fatigue on skill performance. The main reasons for this are due to the problems of overcoming the barriers of controlling the many variables in the field and a lack of reliable and valid skill tests. The Loughborough Intermittent Shuttle running Test (LIST) is a recently developed exercise protocol which closely simulates the demands of multiple-sprint sports such as soccer in a controlled environment. Furthermore, the Loughborough Soccer Passing Test (LSPT) and Loughborough Soccer Shooting Test (LSST) were developed (and modified further as part of this thesis, Chapters 5 and 6) and found to be reliable and valid indicators of soccer skill. Therefore, one of the main aims of this thesis was to investigate the influence of 90 min of the LIST on soccer skill performance. Early researchers (e. g. Karlsson, 1969 and Saltin, 1973) reported the -benefits of maintaining a high muscle glycogen content on soccer performance and more recent investigators looked at the effect of providing carbohydrate (CHO) during exercise on work rate and soccer skill. However, many of these experiments were completed in the field setting and used poor tests of skill. Therefore, the primary aim of these series of experiments was to determine the influence of ingesting a carbohydrate-electrolyte (CHO-E) solution during the LIST on soccer skill performance. There was an 8% deterioration in LSPT performance following 90 min of intermittent high-intensity running, even with fluid ingestion (p<0.05). Furthermore, the ingestion of a CHO-E solution during exercise showed tendencies for better maintenance of skill performance towards the end of exercise. Moreover, CHO-E supplementation better maintained sprint performance and a higher relative exercise intensity during exercise (p<0.05). This is crucial in soccer perfon-nance, as players who are unable to sprint to get to the ball will be unable to perform the necessary skill. From the results of Chapters 5 and 6 it was found that the modified passing (LSPT) and goal-shooting (LSST) tests were valid and reliable tests of soccer skill. Moreover, they were found to be more repeatable when higher calibre players performed the tests. As in previous studies there was a speed-accuracy trade-off' in LSST performance i. e. subjects increased the time taken to complete each shot sequence and reduced the shot speed to maintain shooting accuracy post-LIST. There was a trend for CHO-E ingestion to maintain a better shot speed and time taken for each sequence. The ingestion of CHOE also reduced the perception of effort (p<0.05) and led to more positive feelings of affective valence during the last 30 min of the LIST. Therefore, based on these findings, it was concluded that the ingestion of CHO-E solutions over water alone should be encouraged to soccer players because of the tendency to better maintain soccer skill and the associated physiological, biochemical and psychological benefits during such exercise.

Statement of Problem: The development of fatigue is influenced by simply rinsing the mouth with a carbohydrate solution and is related to telo-anticipation. However, the extent to elicit a strong enough ergogenic response to mitigate fatigue in intense exercise lasting less than 60 minutes is quite limited. Therefore, further investigations are needed to determine an ideal strategy for rinsing carbohydrates to improve short duration and intense exercise performance is needed.Method: Sixteen sprint-trained participants (8=male and 8=female) performed a series of repeated sprint tests under two different conditions in a counterbalanced order; one where they were administered a carbohydrate solution that was rinsed for five seconds and another condition in which the beverage was rinsed incrementally (five, 10, and 15 seconds). Each testing session consisted of three repeated sprint exercise sets (RSE) on a non-motorized treadmill with seven minutes of recovery between sets. Peak speed, average speed, rating of perceived exertion (RPE), perceived recovery status (PRS), perceived activation (FA) were all measured. Approximately 15 minutes following the final sprint, participants provided a session rating of perceived exertion (S-RPE) to rate the global difficulty of the session.Results: Results from the analyses revealed no significant differences between conditions on peak (p = 0.179) or average (p = 0.414) sprint performance. Nor was there any difference between male and female sprint performance. Furthermore, there were no perceptual (PRS, RPE, FA) or metabolic (lactate) differences of fatigue. However, during latter portions of the repeated sprint protocol, average and peak speed of participants showed a trend towards a difference between both conditions in repeated sprint set 2 (RSE2) and repeated sprint set 3 (RSE3). The decrements in sprint performance (p = 0.795) and recovery scores (p = 0.847) were not significantly different between CMR conditions.Conclusions: The administration of carbohydrate mouth rinsing (CMR) with increasing duration did not significantly yield improved average or peak sprint performance as compared to rinsing with a consistent duration. More investigations are needed to help further understand the perceptual responses that relate the central and peripheral integration of fatigue with carbohydrate supplementation with repeated sprints.

Using the tools of structural and network analysis developed by Ronald R. Burt and others, this study investigated the communication patterns among corporate officers of American Telephone and Telegraph Corporation (A.T. & T.) and United Telecommunications Corporation (Sprint). Data on contacts, efficiency, network density, and constraint indicate that opportunities for power and constraint have remained relatively stable at United Telecommunications between 1980 and 1990. A. A.T. & T., on the other hand, was more affected by the drastic changes in the telecommunication industry. The span of A.T. & T. has grown smaller and the potential for constraining relations among A. T. & T. and financial institutions has increased during the period 1980 and 1990.