Research has demonstrated a clear relationship between dynamic strength and vertical jump (VJ) performance; however, the relationship of isometric strength and VJ performance has been studied less extensively. The aim of this study was to determine the relationship between isometric strength and performance during the squat jump (SJ) and countermovement jump (CMJ). Twenty-two male collegiate athletes (mean ± SD; age 21.3 ± 2.9 years; height 175.63 ± 8.23 cm; body mass 78.06 ± 10.77 kg) performed isometric midthigh pulls (IMTPs) to assess isometric peak force (IPF), maximum rate of force development, and impulse (IMP) (I100, I200, and I300). Force-time data, collected during the VJs, were used to calculate peak velocity, peak force (PF), peak power (PP), and jump height. Absolute IMTP measures of IMP showed the strongest correlations with VJ PF (r 0.43-0.64; p ≤ 0.05) and VJ PP (r 0.38-0.60; p ≤ 0.05). No statistical difference was observed in CMJ height (0.33 ± 0.05 m vs. 0.36 ± 0.05 m; p 0.19; ES-0.29) and SJ height performance (0.29 ± 0.06 m vs. 0.33 ± 0.05 m; p 0.14; ES-0.34) when comparing stronger to weaker athletes. The results of this study illustrate that absolute IPF and IMP are related to VJ PF and PP but not VJ height. Because stronger athletes did not jump higher than weaker athletes, dynamic strength tests may be more practical methods of assessing the relationships between relative strength levels and dynamic performance in collegiate athletes.

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The aim of this study was to determine how the performance of the Egyptian high jumpers is depending on the kinematic parameters of a take-off phase. The sample of the study has been selected from competitors of the high jump event - three jumpers representing the Egyptian international athletic team. The researcher has studied the sample using a direct measurement by a synchronized 3D video system to measure the kinematic parameters. The researcher has found a relation between record level and vertical velocity components with improvement in technique and better fitness levels, thus the Egyptian jumpers can achieve further progress in their results. This raises optimism because Omer Samir (A2) is very young and his current record 2.02m gives hope for future World - Class. Key words High jump, kinematic parameters, take-off phase.

<p> The present study develops a foot model to improve segment power estimates in the vertical jump. Modifications to the traditional foot model included the addition of a forefoot segment to allow for power flow across the metatarsal-phalangeal joint, and a re-definition of the ankle joint position to decrease foot segment length variability. The foot model was evaluated by comparison of the total segment power (TSP) with the rate of change of energy (RCE) of the foot segment. Pearson's correlation coefficients and percent root mean square (% RMS) error were used to compare curves. </p> <p> Power flow analysis was performed on a counter-movement jump (CMJ) and a squat jump (SQJ) for each of 8 male and 8 female subjects. Both a 4-Link and a 5-Link, sagittal plane, link-segment model were used to calculate the joint and muscle powers. </p> <p> The combination of both modifications to the traditional foot model (i.e. 5-Link(ankle) model), resulted in dramatic improvements for the match between the TSP and RCE. When comparing the traditional model with the 5-Link(ankle) model for the CMJ, correlation coefficients improved from -0.46 to 0.92 for the male group and from -0.50 to 0.77 for the female group. The %RMS error decreased from 380.5% to 35.4% for the male group and from 466.9% to 71.6% for the female group. SQJ improvements were similar. </p> <p> Ankle joint position re-definition succeeded in compensating for foot segment length changes in most cases, and indicates that a single point can be located to act as a hinge joint between the foot and leg segments throughout the vertical jump motion. Improvements associated with the addition of a forefoot segment to the traditional linksegment model indicate that substantial power flow occurs through the metatarsal-phalangeal joint during vertical jump motions. </p> / Thesis / Master of Science (MSc)

In female college soccer players, there is no protocol for assessing fatigue. A total of 40 members of the Virginia Tech Women's Soccer team participated in the countermovement jump assessment to find a reliable way to gauge player fatigue and readiness in these athletes. These were tested by assessing the within and between-day similarity of a countermovement jump test as a measure of neuromuscular performance by comparing multiple jump heights during jumps performed within a single day and on separate days. Additionally, to determine the responsiveness of countermovement jump height as a marker of fatigue, we compared jump heights before and after activities thought to induce fatigue and competitive matches. All subjects wore a STATSports APEX unit that includes an 18Hz GPS, 952 Hz accelerometer, and 952 Hz gyroscope situated on the upper back over the second thoracic vertebra using a manufacturer-provided vest. After each training session or match, the data was downloaded using the manufacturer's software (APEXA). A custom MATLAB program was then used to calculate CMJ height from vertical acceleration. Results showed that CMJ heights were very reliable both within and between testing days. CMJ heights were found to accurately decrease following both high-load training sessions and a competitive soccer match. For both activities, the decrease in performance was dependent on the amount of load experienced. Lastly, CMJ height did not recover the day following high training load sessions. Across a training week, CMJ consistently decreased each day. This was followed by a recovery in performance following two off days. The results suggest that the use of a trunk-mounted, GPS-embedded accelerometer and a novel three-jump protocol is responsive to assess CMJ height. In addition, it is responsive to estimating fatigue following soccer activity. / Master of Science / In female college soccer players, there is no protocol for assessing fatigue. A total of 40 members of the Virginia Tech Women's Soccer team participated in the countermovement jump assessment to find a reliable way to gauge player fatigue and readiness in these athletes. We hypothesized that countermovement jump heights would not vary between jumps executed on the same day and on different days. We also hypothesized pre-training countermovement jump heights would vary across a 7-day training session with reductions dependent on the prior days' physical demands and would be reduced following a competitive soccer match, also dependent on each player's physical demands. These were tested by assessing the within and between-day reliability of a vertical jump test as a measure of performance by comparing multiple countermovement jump heights during jumps performed within a single day and comparing jumps on separate days. Additionally, to determine the feasibility of countermovement jump height as a marker of fatigue, we compared jump heights before and after activities thought to induce fatigue and competitive matches. All subjects wore a STATSports APEX unit that includes an 18Hz GPS, 952 Hz accelerometer, and 952 Hz gyroscope situated on the upper back over the second thoracic vertebra using a manufacturer-provided vest. After each training session or match, the data was downloaded using the manufacturer's software (APEX) and a custom MATLAB program was then used to calculate CMJ height from vertical acceleration. Results showed that CMJ heights were very reliable both within and between testing days. CMJ heights were found to decrease following both high-load training sessions and following a competitive soccer match. For both activities, the decrease in performance was dependent on the amount of load experienced. Lastly, CMJ height did not recover the day following a high training load sessions. Across a training week, CMJ consistently decreased each day. This was followed by a recovery in performance following two off days. The results suggest that the use of a trunk-mounted, GPS-embedded accelerometer and a novel three-jump protocol is reliable to assess CMJ height. In addition, it is feasible to estimating fatigue following soccer activity.

No description available.

Osteoporosis is one of the most common diseases experienced in the older adult population. This condition is not only costly to manage and treat, particularly so when osteoporotic fractures occur, but also negatively impacts functional health and health-related quality of life for many individuals. This indicates the need for more to be done to prevent osteoporosis from developing initially. While bone mineral density (BMD) testing recommendations are in place for women aged 65 and older and men aged 70 and older to diagnose osteoporosis, there currently are no BMD testing recommendations for preventive or screening purposes in the general, healthy, adult population. One potential screening tool for bone strength is a peak vertical jump test. Peak vertical jump height can be used as a proxy for lower body muscle power, which has been identified as an influential factor in determining bone mass and geometry, both of which are critical aspects of bone strength. This study ascertained the relationship between muscle power and bone strength, as well as the capacity of a peak vertical jump test to identify young adults with below-average areal BMD (aBMD). A total of 303 young adults (18 to 22 years, n=136 males, n=167 females) participated in these cross-sectional analyses. DXA was used to assess aBMD for total hip and femoral neck, and DXA images were used to calculate femoral neck section modulus (FN Z) values. Peripheral quantitative computed tomography (pQCT) was used to assess indices of bone strength at the tibia. Cortical bone area (CoA) and density-weighted polar section modulus strength-strain index (SSIp) were assessed at the 38% midshaft site, and bone strength index (BSI) was assessed at the 4% midshaft site. Lower body muscle power was predicted using peak vertical jump height and the Sayers et al. (1999) equation. Data were analyzed using Pearson bivariate and partial correlations to examine associations among bone strength outcomes and muscle power. Logistic regression was used to examine the probability of below-average bone strength based on muscle power. Receiver Operating Characteristic (ROC) curve analysis was used to show the tradeoff between sensitivity and specificity and to display the accuracy of a peak vertical jump test as an assessment tool for aBMD. Logistic regression indicated the odds ratio of below-average height-adjusted femoral neck aBMD decreased 5.4% for females and 3.6% for males per 50 Watts of power. ROC curve analysis showed the best sensitivity-specificity trade-off for identifying individuals with and without below-average aBMD was 5,038 Watts in males (sensitivity = 73.7%; specificity = 62.4%; AUC = 0.709, 95%CI = 0.572 - 0.847) and 3,261 Watts in females (sensitivity = 71.4%; specificity = 58.9%; AUC = 0.708, 95%CI = 0.586 - 0.829). These cut off values correspond to a vertical jump height of 54.39 cm and 36.16 cm for males and females, respectively. Taken together, the results of these analyses suggest acceptable sensitivity and specificity and moderate discriminate ability for using a measure of muscle power, assessed with a peak vertical jump test, to identify young adults with below-average aBMD.

This thesis examines the empirical performance of four Affine Jump Diffusion models in pricing and hedging S&P 500 Index options: the Black Scholes (BS) model, Heston???s Stochastic Volatility (SV) model, a Stochastic Volatility Price Jump (SVJ) model and a Stochastic Volatility Price-Volatility Jump (SVJJ) model. The SVJJ model structure allows for simultaneous jumps in price and volatility processes, with correlated jump size distributions. To the best of our knowledge this is the first empirical study to test the hedging performance of the SVJJ model. As part of our research we derive the SVJJ model minimum variance hedge ratio. We find the SVJ model displays the best price prediction. The SV model lacks the structural complexity to eliminate Black Scholes pricing biases, whereas our results indicate the SVJJ model suffers from overfitting. Despite significant evidence from in and out-of-sample pricing that the SV and SVJ models were better specified than the BS model, this did not result in an improvement in dynamic hedging performance. Overall the BS delta hedge and SV minimum variance hedge produced the lowest errors, although their performance across moneyness-maturity categories differed greatly. The SVJ model???s results were surprisingly poor given its superior performance in out-of-sample pricing. We attribute the inadequate performance of the jump models to the lower hedging ratios these models provided, which may be a result of the negative expected jump sizes.

This dissertation investigates the volatility of the relationships between exchange rates and interest rates. The first part of the paper explores the transmission relationship between these two markets using a time-series model. Previous studies have assumed that covariance was constant in both markets. However, if the volatilities of the exchange rate and interest rate markets are correlated over time, the interaction and spillover effects between the two markets may be affected by time-varying covariance. Hence, this paper utilizes the BEKK-GARCH model developed by Engle and Kroner (1995) to capture the dynamic relationship between the exchange rates and interest rates. This study uses the returns data for G7 members¡¦ exchange rates and interest rates to test whether these markets exhibited volatilities spillover from 1978 to 2009. The results show bi-directional volatility spillovers in the markets of the UK, the Euro countries, and Canada, where the volatilities of the two markets were interrelated. The second part of the paper explores the relationship between exchange rates and interest rates using a jump diffusion model. Previous studies assumed that the dynamic processes of exchange rates and interest rates follow a diffusion process with a continuous time path, but an increasing number of empirical studies have shown that a continuous diffusion stochastic model does not capture the dynamic process of these variables. Thus, this paper investigates the discontinuous variables of exchange rates and interest rates and assumes that these variables follow a jump diffusion process. The UIRP model is employed to explore the relationship between both variables and to divide the systematic risk into systematic continuous risk and systematic jump risk. The returns data for G7 members¡¦ exchange rates and interest rates from 2005 to 2010 were analyzed to test whether the expected exchange rate is affected by jump components when the interest rate market experiences a jump. The results show that the jump diffusion model has more explanatory power than the pure diffusion model does, and, when the interest rate market experiences a jump risk, the systematic jump risk has a significant relationship with the expected exchange rates in some G7 countries.

This thesis presents the modeling of credit risk by using structural approach. Three fundamental questions of credit risk literature are analyzed throughout the research: modeling single firm credit risk, modeling portfolio credit risk and credit risk pricing. First we analyze these questions under the assumptions that firm value follows a geometric Brownian motion and the interest rates are constant. We discuss the weaknesses of the geometric brownian motion assumption in explaining empirical properties of real data. Then we propose a new extended model in which asset value, volatility and interest rates follow affine jump diffusion processes. In our extended model volatility is stochastic, asset value and volatility has correlated jumps and interest rates are stochastic and have jumps. Finally, we analyze the modeling of single firm credit risk and credit risk pricing by using our extended model and show how our model can be used as a solution for the problems we encounter with simple models.