[Truncated abstract] The inclusion of a warm-up in the form of prior exercise (PE) is generally advocated as a preparatory strategy of choice to improve sprint performance. Although there is evidence that both increasing muscle temperature and mobilising the cardiorespiratory system prior to exercise contribute largely to the benefit of PE on sprint performance, their relative importance is unknown. Another important question relates to situations where an athlete has to engage in a sprint shortly after one or several earlier sprints. Under these conditions, is engaging in mild exercise also the most effective preparatory strategy to adopt prior to sprinting when performed after a previous sprint(s)? It was the primary aim of this thesis to address these questions. Firstly, we hypothesised that there is a temporal shift in the mechanisms responsible for the effect of PE on power output during a maximal sprint effort, with temperature-dependent mechanisms playing a more important role at the onset of the sprint and mobilisation of the cardiorespiratory system playing a more important role later. To test this hypothesis, we compared the responses of a 30-s sprint to different PE protocols designed to control for either muscle temperature or pre-exercise VO2. ... A group of trained athletes was subjected to four consecutive bouts of 30-s sprint, each separated by 20 min of either active recovery at 40% VO2 peak or passive recovery. Our results show that PP, MP-20 and MP-10 did not fall between the first and last sprints, and were not affected by active recovery. In contrast, we found that MP10 and MP30 decrease significantly between the first and last sprint of the passive recovery trial, but not when active recovery is performed between consecutive sprints. Finally, this study also showed that the fall in mean power associated with repeated 30-s sprints in the passive recovery trial resulted primarily from a fall in early, but not late power output. These findings show that the early and late mean power output of repeated sprints respond differently to active and passive recovery, with the decrease in total mean power with repeated 30-s sprints resulting primarily from a fall in early as opposed to either late power output or peak power, thus highlighting the benefit of active recovery as a favourable preparatory strategy for the performance of repeated sprints of short (<10s) or longer duration (<30s), but not for repeated peak power.

Abstract Aim was to investigate the effects of heavy resisted and unresisted sprint training protocols and see its effects on sprint time, vertical and horizontal jumping and sprint mechanics. Youth male soccer players [n=27] participated in this study, they were all individually assessed for the horizontal force-velocity profile using two unresisted sprints and load-velocity profile using four progressively resisted sprints (25%, 50%, 75% and 100% body mass). For all sprints an isotonic braking device was used. They also performed vertical and horizontal jumps, counter-movement jump (CMJ) was used for the former and standing long jump (SLJ) for the latter. They were put in three groups (RST: resisted sprint training; UST: unresisted sprint training and TAU: control group – “training as usual”). Athletes performed a 4-week training intervention (5x20m resisted sprint group; 8x20m unresisted sprint group) and were tested 7 days after completing their final training session. Only RST improved all sprint times (T30, T20, T10, T5) substantially (-4.2% to -7.9% in split times) and provided trivial or small changes in sprint mechanics. The small changes were seen in sprint mechanical parameters of RFmax, Pmax and F0. UST only showed trivial effects in those parameters, while TAU showed a small decrease in both Pmax and Vmax. Regarding the jumps, RST and UST both showed a small increase in standing long jump and a trivial effect in counter-movement jump, while TAU decreased in both. Main conclusion is that resisted sprinting has proven to be a worthwhile method to improve acceleration and sprint performance and can be used by practitioners across a wide array of sports. It also improved jumping performance and sprint mechanical outputs, which point toward an improvement in better application of force in a horizontal direction.

Introduction: With batting in cricket, there is no known end point, making the allocation of resources and the development of a suitable pacing strategy more difficult. How batsmen allocate resources and pace themselves when repeatedly sprinting between the wickets is therefore not known. According to the ‘anticipatory feedback’ model, the level of expertise/experience has a substantial influence on the development of a suitable pacing strategy. Skilled or experienced batsmen may therefore have a greater ability to develop and implement a pacing strategy compared to that of novice or less-skilled batsmen. Purpose: To assess whether the absence of a known end point at the beginning of repeated sprint bouts between the wickets effects how batsmen pace themselves comparing skilled and less-skilled batsmen. Methods: Twenty-four male cricketers from a university league were selected. Twelve skilled batsmen (players in the top five batting order), and 12 less-skilled batsmen (players in the bottom five batting order) completed three experimental. All trials required batsmen to complete the same number of shuttle sprints (14 shuttles and therefore 28 runs), while only the information provided before each trial differed. Control Trial: This trial is also referred to as the ‘informed’ trial as the batsmen are aware of the exercise requirements (end point). Unknown Trial: The batsmen were not informed of the exercise end point and were required to run on command for an indefinite period (28 runs). Deceptive Trial: Batsmen’ were incorrectly informed with regards to the number of sprints (told they were only doing 14 runs when in fact they were doing 28 runs). Muscle activity, sprint times and RPE measures were obtained during all three trials and compared. Results: Significant (p<0.05) group effects were apparent for sprint times and, ‘central’ and ‘local’ RPE. Specifically, skilled batsmen obtained the faster mean sprint times, and less-skilled batsmen reported the higher mean ‘central’ and ‘local’ RPE values in all three experimental trials. There were no significant group effects for muscle activation. Skilled batsmen did however have lower muscle activation compared to less-skilled batsmen in all three trials. Furthermore, general trends revealed that sprint times and muscle activation decreased over time (from shuttle 1 to shuttle 14), and RPE (‘central’ and ‘local’) ratings increased, regardless of the experimental trials. Skilled batsmen performed the best in all three trials. This was determined by the attainment of faster sprint times, lower muscle activation and low RPE ratings in each of the three trials. The assessment of the relationship of the dependent variables measured in each trial, did however suggest that skilled batsmen performed best in the deceptive trial while less-skilled batsmen performed best in the control trial. Skilled batsmen thus showed superior performance when trial requirements were unclear. Less-skilled batsmen however, were seen to experience decrements in performance when information regarding the end point was unknown or misleading. Conclusion: It can thus be concluded that previous experience facilitates in the obtainment of improved sprint times between the wickets, especially when the exact end point is unknown.

Muscle strength has been identified as an important contributor to athletic performance. Little attention however, has been paid to the specific relationship between peak isokinetic muscle strength and sprint starting performance. The aim of this study was to determine the influence of an adapted front knee angle, as determined by isokinetic assessment (the angle of peak torque production), on starting performance. Sixteen track sprinters, of elite-national or competitive-regional standard, were asked to perform eight sprints over 50m using four separate starting techniques. Technique 1 featured the athlete’s usual starting preferences while Techniques 2, 3 and 4 featured a standardised set of starting preferences with experimental modifications of the front knee angle in the “set” position. Isokinetic muscle strength was measured at slow (60°/s) and fast (240°/s) test speeds in order to determine the angle of peak torque production for concentric knee extension of each subject’s lead leg. Using one-way analysis of variance (ANOVA) and Post Hoc analysis (LSD), no significant differences (p>0.05) were observed between the experimental techniques for: block time, force-time measures during block time, sprint times, sprint velocity and acceleratio n measures at intervals up to 50m. Significant differences (p<0.05) were however observed between reaction times for the experimental techniques. Slower reaction times are most likely due to increased upper body pretension, resulting from the increased hip elevation seen for these techniques. The results indicate that increased hip elevation may have delayed the initiation of the relevant motor response required to affect an optimal sprint start. Technique 1 resulted in the shortest reaction times, shortest block times, fastest sprint times and greatest sprint velocities for all four techniques. This result was possibly due to the athlete’s experience with, and repeated use of, this technique. The experimental techniques therefore provided no added advantage over the subject’s preferred starting technique and did not significantly optimise sprint starting performance. The results show that modification of the front knee angle had no significant influence on sprint starting performance and sprint running ve locity or acceleration patterns up to 50m. Using Pearson’s Correlation Coefficient to determine the strongest correlations between isokinetic knee strength and sprint starting performance, analysis revealed that the strongest relationships were found between sprint starting performance expressed as acceleration and isokinetic knee strength expressed as relative peak torque and absolute peak torque. For Technique 1 the strongest correlation was found between acceleration (30m - 40m) and relative peak torque as measured at a test speed of 240°/s (r = 0.62). For the remaining experimental techniques, the strongest correlation was found between acceleration (10m - 20m) and relative peak torque as measured at a test speed of 60°/s (r = 0.53) for Technique 2, between acceleration (40m - 50m) and peak torque measured at a test speed of 60°/s (r = 0.72) for Technique 3, and between acceleration (0m - 5m) and peak torque as measured at a test speed of 240°/s (r = 0.71) for Technique 4. These results suggest that isokinetic muscle strength does not correlate strongly with sprint starting performance and that additional factors, such as neuromuscular organisation and muscle fibre typing, possibly make a greater contribution to optimal sprint starting performance.

The problem of the study was to determine the better predictors of sprint performance for male and female sprinters from selected leg power and isokinetic strength tests. Ten male and five female sprinters volunteered to be measured for vertical jump performance, anaerobic power and capacity, peak isokinetic torque at the hip, knee, and ankle joint, and sprint performance. A forward stepwise multiple regression analysis was performed to allow selection from all strength and power variables regressed on the dependent variables of 30 meters, 60 meters, and flying 30 meter sprints. This procedure allowed one to examine the contribution of each predictor variable to the regression model. Only the independent variables that elicited a regression equation significant at the .05 level were used in final regression models. The regression models developed for the males were: 30 meters (crouch start) = 6.115 - .083(anaerobic power) - .055(vertical jump) - .044(plantarflex 120"/s) - .022(knee flex 60'/s); 60 meters (crouch start) = 11.111 - .145(vertical jump) - .086 (anaerobic power) - .172(hip flex 300'/s) - .098(knee flex 60'/s); and 30 meters (flying start) = 4.295- .055(anaerobic power) - .312(knee flex 180'/s) - .090(hip flex 300'/s). The regression models for the women were different than the males and were: 30 meters (crouch start) = 9.530 - .346(vertical jump); 60 meters (crouch start) = 18.083- .686(vertical jump); and 30 meters (flying start) = 8.733- .352(vertical jump) . By knowledge of the variance of the better strength and power measures, 83.2% to 98.0% of the variance of the respective sprint tests were explained. The regression models could allow for the identification of potential sprint performers and the development of optimal sprint training program.

No description available.

Understanding the effects of natural variation in environmental temperature on organisms and how those organisms evolve to live in different thermal environments is a central tenet of evolutionary physiology. Phenotypic differences among populations are the result of local adaptation, innate genetic differences between populations, and phenotypic plasticity, differential responses to the environment. Although not mutually exclusive, distinguishing between these paradigms can help illuminate species boundaries resulting from thermal limitations in physiology. For my dissertation, I examined geographic variation in measures of thermal physiology of the western fence lizard, Sceloporus occidentalis to understand the relative role of adaptation and acclimation in determining the thermal biology of populations of this species living in different thermal environments. To achieve this goal I measured three indices of physiological function; body temperature, thermal tolerance and heat shock protein (Hsp70) abundance, across geographic and seasonal variation in temperature. Furthermore, I examined variation in sprint speed performance before and after heat stress and its relationship to Hsp70 to determine if stress protein expression is a reliable indicator of whole organism physiological stress. I found that geographic location can have a major effect on thermal physiology and performance in S. occidentalis in that thermal tolerance, Hsp70, and sprint speed varied with site and season with warmer southern sites typically more heat adapted than cooler northern sites. I also found a trade off in thermal tolerance suggesting that specialization to temperature was occurring in these lizards. Finally, lizards with increased Hsp70 were typically slower after heat stress indicating that Hsp70 is a reliable indicator of organism stress. Despite these findings, there was no difference in body temperature among sites and seasonal patterns in thermal tolerance suggest that during certain times of the year plastic responses to temperature may mask adaptive differences. Here, I argue that temperature differences between sites has resulted in temperature adaptation at these sites, but that plastic responses to seasonal variation in temperature can become more important during certain times of the year. Although these relationships have been thoroughly studied in invertebrate organisms, further research should examine whether these patterns exist in other vertebrate ectotherm species.

An important issue for sports scientists, coaches and athletes is an understanding of the factors within a running stride that can enhance or limit maximal running speed. Previous research has identified many sprint-related parameters as potential kinetic limiters of maximal Center of Mass velocity (Chapman and Caldwell, 1983b; Weyand et al., 2001). Bilateral asymmetry is present for many of these parameters during running; however the degree to which such asymmetries change as running speed increases is unknown. It was hypothesized that asymmetries in key sprinting parameters would be larger at maximal speed than all other tested speeds. Kinematics and kinetics were collected from nine female competitive speed and power athletes (age = 21 ±3 years, mass = 60.58 ±7.48 kg, height = 1.64 ±0.07 m) who completed maximal and submaximal sprinting trials on a force-instrumented treadmill. A repeated-measures ANOVA was completed for each parameter to examine the asymmetry differences across speed. The only parameter for which asymmetry was statistically greater (p<0.05) during maximal speed than all other speeds was effective vertical stiffness, in which the level of asymmetry increased incrementally with speed (r2=0.97). Therefore the hypothesis that asymmetries would increase with speed for all key parameters is rejected. Bilateral asymmetries in effective vertical stiffness appeared to be related to asymmetries in both vertical and A/P propulsive impulse at maximal speed. Furthermore, asymmetries in effective vertical stiffness may force runners to resort to a less stable and less coordinated gait, limiting their ability to further increase stride frequency, and thus limiting maximal speed.

Bakgrund: Ruscher är en vanlig aktion som fotbollsspelare utför under fotbollsmatcher. Flera studier har undersökt ruschers roll i diverse situationer på fotbollen med olika resultat. Däremot finns det en kunskapslucka då inga studier på amatörfotbollsspelare har identifierats. Syfte: Syftet med studien var att undersöka mängden rusher som herrfotbollsspelare genomför mellan tre olika lägre divisioner under ordinarie seriematchspel samt undersöka om mängden ruscher påverkar antalet gjorda mål. Metod: För datainsamlingen användes accelerometrar av modell Actigraph GT3X+. Datamaterialet från accelerometrarna laddades ned till excel i sekundformat. I Excel skapades ett program som räknade ut antal cykler på minst 4 sekunder med över 200 counts i rad. Datan analyserades genom Kruskal-Wallis samt med parvisa Mann-Whitney tester för att upptäcka skillnad mellan grupperna. För att se korrelationen mellan antal mål och antal ruscher genomfördes Spearmans korrelationstest. Resultat: Signifikanta skillnader i antal ruscher hittades mellan divisioner. Ingen signifikant korrelation hittades mellan gjorda mål och antal ruscher. Slutsats: Slutsatsen är att det finns skillnader mellan divisionerna i utförda ruscher. Division 3 och 5 genomför i snitt lika många ruscher, men division 5 spelare har en större variation mellan spelarna i mängden utförda ruscher. Resultatet för studien visar också att antal ruscher inte korrelerar med antal mål vilket kan indikera att det inte är antal ruscher som avgör mål, utan andra faktorer såsom kvalitet och hastighet på ruscherna. / Background: Sprints is a regular action that football players perform during matches. Many studies have researched the variation of sprints in different football divisions with different results. There is no research found on sprint performance between amateur divisions in football which this study aims to research. Purpose: The purpose with this study was to compare the amount of sprints male football players carry out between three different lower Swedish football divisions during ordinary series matches. Adding to this, the study aims to also examine if the amount of sprints performed in matches is also affecting the amount of scored goals. Method: For the data collection, accelerometers of the model Actigraph GT3X was used. The data from the accelerometers were downloaded to excel in 1 second cycles. In excel a programme was created which counted the amount of cycles with at least 4 seconds with over 200 counts in a row. Data was analyzed through Kruskal-Wallis and Mann-Whitney tests to see if there was a significant difference between the groups. To see the correlation between the amount of goals and number of sprints the Spearman's correlation test was used. Results: Significant differences in the amount of sprints were found between divisions. No significant correlation could be found between scored goals and amount of sprints. Conclusion: The conclusion of the study is that there are differences between the divisions in performed sprints during matches. No significant differences were found between Division 3 and 5 players in the number of sprints performed, but division 5 players had a bigger variation in the amount of sprints performed. The result for the study also shows that the amount of sprints are not correlated with the amount of scored goals which can indicate that it is not the amount of sprints that is the deciding factor for goals but instead other factors like quality and speed off the sprints.

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.