Whole-body vibration (WBV) may positively influence performance acutely through the potentiation of the muscle’s series elastic components and neuromuscular mechanisms. The purpose of this investigation was to examine the acute effects of WBV on sprint performance in NCAA Division I collegiate male sprinters and jumpers. Twenty-one athletes (n=21) completed a control or WBV protocol (30 seconds, 50 Hz, low amplitude ~3mm) one minute before a 30 m flying sprint. Each athlete participated in three separate trials using randomized treatment sessions (1 treatment per session) over 12 weeks of preparation training prior to the indoor season. The control condition consisted of no vibration, while treatment 1 (T1) and treatment 1 repeated (T1-R) incorporated vibration. The vibration-sprint protocol was repeated after a five minute rest period following the first sprint (test-re-test ICC≥0.81). The sprint consisted of a 15 m run-in from a standing start and a 30 m flying sprint with a total distance of 45 m. A two-way factorial ANOVA with repeated measures (p ≤ 0.05) was used to compare treatments. Statistics showed no differences between the treatments at all distances (average sprint time of control vs. T1, control vs. T1-R, and T1 vs. T1-R). The results of this study indicate that WBV at 50 Hz and low amplitude has no potentiation effect on sprint times (15, 30, 45, or 30 m fly). Further research is needed to determine if different WBV protocols may elicit enhanced results in 30 m flying sprint performance. The present WBV protocol does not appear to have practical acute value for sprinting.

Countermovement vertical jump (CMVJ) performance may be acutely facilitated via potentiation (PAP) due to central and peripheral factors. PURPOSE: To investigate the effects of two methods of PAP in trained weightlifters (n=16); group 1: stronger (n=7) and group 2: weaker (n=9) upon unweighted countermovement jumps (CMVJs) over a 15 minute time period. METHODS: A series of maximal unweighted CMVJs were performed prior to, then at, 30, 60, 120, 180, 300, 480, 660, 780, and 900 seconds following two conditions: isometric mid-thigh clean pulls (C1) and dynamic mid-thigh clean pulls (C2). Dependent variables included, jump height (JH, cm), peak power (PP, W), peak velocity (PV, m·s-1), and peak force (PF, N). RESULTS: A series of repeated measures ANOVA: conditions (2); time points (10); groups (2) were performed on JH, PP, PV, and PF (p>.05). Significant main effects for JH existed by condition (C1>C2) (p=.001, ES=.571, 1-β=.979, mean diff=.053cm), group (G1>G2) (p=.018, ES=.339, 1-β=.702, mean diff=.053), and time (60s>900s, 120s>900s, 180s>900s) (p=.014, ES=.148, 1-β=.910).Within subjects main effects for JH were seen for the stronger group for JH by condition (C1>C2) (p=.055, ES=.757, 1-β=.947, mean diff=.053cm), and weaker group by condition (C1>C2) (p=.025, ES=.487, 1-β=.676, mean diff=.054cm). Significant main effects existed for PP by condition (C1>C2) (p=.000, ES=.631, 1-β=.995, mean diff=427.9W), group (G1>G2) (p=.008, ES=.405, 1-β=.819, mean diff=1660.1W), and time (60s>480s, 60s>660s, 60s>780s, 60s>900s>120s>900s, 180s>480s, 180s>660s, 180s>780s) (p=.000, ES=.355, 1-β=1.00, mean diff=240.1W ).Within subjects main effects for PP were seen for the stronger group for condition (C1>C2) (p=.055, ES=.761, 1-β=.951, mean diff=516.8W), and time (120s>900s) (p=.000, ES=.471,1-β=.999, mean diff=319.5W). In the weaker group; significant main effects by condition (C1>C2) (p=.025, ES=.485, 1-β=.672, mean diff=339.1W) and time (120s>900s, 180s>480s, 180s>900s, 300s>900s) (p=.003, ES=.281, 1-β=.963, mean diff=319.5W). Significant main effects were seen for jump PV by condition (C1>C2) (p=.001, ES=.536,1-β=.962, mean diff=.177 m·s-1), group (G1>G2) (p=.022, ES=.320, 1-β=.665, mean diff=.298m/s) and by time (60s>900s, 120s>900s, 180s>900s) (p=.016, ES=.145, 1-β=.904). Within subjects main effects for jump PV in the stronger group by condition (C1>C2) (p=.007, ES=.727, 1-β=.911, mean diff=.165m/s), and time (120s>900s) (p=.036, ES=.269, 1-β=.840, mean diff=.073 m·s-1). In the weaker group there were significant main effects for jump PV by condition (C1>C2) (p=.028, ES=.474, 1-β=.654, mean diff=.188 m·s-1). A significant main effect for jump PF by group (G1>G2) (p=.014, ES=.363, 1-β=.747, mean diff=647.0N) and time (60s>baseline) (p=.05, ES=.122, 1-β=.824, mean diff=71.0N) was seen. Within subjects, a significant main effect for jump PF in the weaker group by time (60s>780s) (p=.012, ES=.247, 1-β=.919). There were no significant interactions for any of the dependent variables (p >.05). CONCLUSION: Isometric mid-thigh clean pulls appear to have a greater potentiating effect than dynamic mid-thigh pulls on PP and PV during subsequent CMVJ0’s, and stronger weightlifters tend to have a more favorable response to both conditions. PRACTICAL APPLICATION: Whole-body isometric movements may be a more effective at eliciting a potentiation response than dynamic movements in strength and power athletes.

The purpose of this study was to compare ground contact time between an optical measurement system and a force platform. Participants in this study included six collegiate level athletes who performed drop jumps and sprint strike steps for a total of 15 repetitions each. Ground contact data was simultaneously collected from an optical measurement system and a force platform, at a sampling frequency of 1000 Hz. Data was then analyzed with Pearson’s correlation and paired sample t-tests. The measures from the optical measurement system were found to be significantly higher (p < 0.001) than measures from the force platform in both conditions. Although significantly different, the extremely large relationships (0.979, 0.993) found between the two devices suggest the optical sensor is able to detect similar changes in performance to that of a force platform. Practitioners may continue to utilize optical sensors to monitor performance as it may provide a superior user-friendly alternative to more traditional based monitoring procedures, but must comprehend the inherent limitations due to the design of the optical sensors.

Recent advancements in 3D data gathering have made it possible to measure the distance to an object at different time stamps through the use of time-of-flight cameras. Therefore, the purpose of this study was to investigate the validity and reliability of a time-of-flight camera on different mechanical sprint properties of the muscle. Fifteen male football players performed four 30m maximal sprint bouts which was simultaneously recorded with a time-of-flight camera and 1080 sprint device. By using an exponential function on the collected positional- and velocity-time data from both the devices, following variables were derived and analyzed: Maximal velocity (nmax), time constant (t), theoretical maximal force (F0), theoretical maximal velocity (V0), peak power output (Pmax), F-V mechanical profile (Sfv) and decrease in ratio of force (Drf). The results showed strong correlation in vmax along with a fairly small standard error of estimate (SEE) (r = 0,817, SEE = 0,27 m/s), while t displayed moderate correlation and relatively high SEE (r = 0,620, SEE = 0,12 s). Furthermore, moderate mean bias (&gt;5%) were revealed for most of the variables, except for vmax and V0. The within-sessions reliability using Intraclass correlation coefficient (ICC) and standard error of measurement (SEM) ranged from excellent to poor with Pmax displaying excellent reliability (ICC = 0,91, SEM = 72W), while vmax demonstrated moderate reliability (ICC = 0,61, SEM = 0,26 m/s) and t poor(ICC = 0,44, SEM = 0,11 s). In conclusion, these findings showed that in its current state, the time-of-flight camera is not a reliable or valid device in estimating different mechanical properties of the muscle during sprint running using Samozino et al’s computations. Further development is needed.

Past research on the acceleration phase in sprint running has concentrated on the kinematics of sprint blocks set-up and the initial steps after exiting the sprint blocks. In contrast, there has been limited research on the ground reaction forces (GRF) generated during the initial post-block foot contacts. These initial foot contacts in sprinting are important for optimising performance in the initial acceleration phase of sprinting. However, little is known about the GRF elite sprinters generate during the initial foot contacts and how these GRF characteristics relate to performance. It is the anterior-posterior (A-P) GRF that are of most importance as they indicate the sprinter’s motion from the start to the finish line. This thesis investigates the A-P GRF of the first two foot contacts of the sprint start after leaving the blocks. The participants included seventeen male and six female sprinters with a mean age of 22.6 (SD 4.4 years). Seventeen of the sprinters had competed at international/national level competitions and six at recreational/amateur level competitions. The athletes were classified as senior male elite (SME), senior female elite (SFE), junior male elite (JME) and senior male recreational (SMR). The sprinters were instructed to perform block starts at maximal effort to produce the fastest time over 5 metres on a 30 metre indoor laboratory track. Timing gates were used to record 5 metre times and two strain gauge force plates were placed in series to collect GRF data from the first two foot contacts after leaving the starting blocks. From the GRF data, braking time, maximum A-P braking force, A-P braking impulse, propulsive time, maximum A-P propulsive force, A-P propulsive impulse and A-P contact impulse were determined for each trial. The A-P propulsive phase constituted greater than 90% of the total contact time, had approximately twice the magnitude of the maximum force of the braking phase and accounted for more than 95% of the total contact impulse across the four groups of sprinters. The SME group produced a significantly larger A-P propulsive impulse on the first and second steps compared to the SFE (p less than 0.05 and p less than 0.05 respectively), JME (not significant and p less than 0.05 respectively) and SMR (p less than 0.05 and p less than 0.05 respectively) groups. The SME group’s maximum A-P propulsive force was significantly larger on the first and second steps than the SFE (p less than 0.05 and p less than 0.05 respectively), JME (p less than 0.05 and p less than 0.05 respectively) and SMR (p less than 0.05 and p less than 0.05 respectively) groups. The SME group’s propulsive time on the first and second steps was not significantly different compared to the SFE (both not significant) but was significantly shorter compared to the JME (p less than 0.05 and p less than 0.05 respectively) and SMR (p less than 0.05 and p less than 0.05 respectively) groups. The maximum A-P propulsive force correlated strongly with 5 metre time for the first step (rs = -0.670, p less than 0.01), second step (rs = -0.621, p less than 0.01) and the addition of the first and second steps (rs = -0.678, p less than 0.01) across all the sprinters. Whereas, the A-P propulsive impulse correlated strongly with 5 metre time for the first step (rs = -0.525, p less than 0.01), second step (rs = -0.592, p less than 0.01) and the addition of the first and second steps (rs = -0.584, p less than 0.01). Three A-P GRF patterns were observed during the first and second foot contacts of the sprinters examined in this study. A braking-propulsive (B-P) pattern was the most frequently observed followed by a propulsive-braking-propulsive (P-B-P) and a no braking (NB) pattern 82.7%, 15.4% and 1.9% respectively. The P-B-P and NB patterns, which have not been described previously, appeared most frequently in the least experienced sprinters. In the past, some sprinters and their coaches have tried to minimise the braking phase and maximise the propulsive phase of the first two foot contacts after exiting the blocks during sprinting. This study suggests that increasing the maximum propulsive force is the best way to increase performance over the first 5 metres of the acceleration phase. The research also suggests that there will be little benefit gained from trying to increase performance by focusing on the braking phase during these first two steps after exiting the blocks. As such, sprinters and coaches should focus their attention primarily on producing a large A-P propulsive force during the first two steps of a sprint.

<p>In today’s fast-paced world, there is a constant demand for better and more efficient ways of doing business. Motorola in Linköping are using the agile development framework, Scrum in their software development. A certain level of quality must also be assured of the delivered goods and services. Is it possible to use Scrum and still meet the quality requirements?</p><p>This Master Thesis is performed to investigate if it is possible to achieve a quality certificate from TL 9000, the telecom industry extension of ISO 9000, when using the agile development framework Scrum. The investigation consists of interviews and observations at Motorola, Linköping, along with literature studies about quality systems and agile development.</p><p>The conclusion is that it is possible to meet the TL 9000 requirements when using Scrum, under the condition that some additional processes are performed and that other parts of the organization also fulfills the remaining requirements. This is needed since there are requirements that are out of scope for the Scrum framework. Examples of the suggested additions are to follow the Scrum framework more strictly and to adopt a more specific definition of done.</p>

Thesis (Ph.D. (Human Movement Science))--North-West University, Potchefstroom Campus, 2007.

No description available.

We mainly study development velocity in agile teams in this dissertation. The concept of development velocity relates to the classical problem of time estimation in software development and software development planning. Building on previous literature as well as a case study, we explore and theorize the factors that cause ‘velocity flux’, i.e. fluctuations in development velocity through studying the relationship between development velocity and the rate of incoming customer feature requests. The aim of this study is to contribute to a better understanding of what causes velocity flux in agile development, and discusses the implications of the findings for research and practical implications for agile planning. As a result, we propose nine factors that cause velocity flux, and provide some strategies to overcome them in order to make a more effective sprint planning in agile teams.

The GPS tracking in sprint orienteering is often a poor supplement to the viewer experience during events taking place in urban areas because of multipath effects. Since the GPS tracking of runners is an important means to making the sport more spectator friendly, it is of interest to make it more accurate. In this thesis project, the information provided by the map of a competition is fused with the GPS tracker position measurements and punch time data in a particle filter to create estimates of the runner trajectories. The map is used to create constraints and to predict motion of runners, as well as to create a model of the GPS reliability depending on map position. A simple observation model is implemented, using the map to decide if a GPS measurement is reliable or not depending on the distance to the closest building. A rather complex motion model is developed to predict the runner motion within the constraints given by the map. The results show that given certain conditions the improvements are vast compared to the traditional GPS tracking. The estimates are bound to possible routes, and they are often very good given that alternative route choices are easily separable. It is however principally difficult to generally improve the tracking using this method. Better measurements or observation models are needed in order to receive a fully satisfying tracking.