Net Impulse and Net Impulse Characteristics in Vertical Jumping

The purpose of this dissertation was to explore the potential use of net impulse and its characteristics in vertical jumping to monitor athletes\u27 performance status and responses/adaptations to interventions. Five variables were proposed as net impulse characteristics: net impulse height and width, rate of force development, shape factor, and net impulse proportion. The following were then examined: 1) test-retest reliability of a new approach to identify net impulse in a force-time curve and of net impulse characteristics and criterion validity of the new approach; 2) effective measures of net impulse characteristics; 3) relationships between training-induced changes in its characteristics and force production ability. The following are major findings of the dissertation. Rate of force development particularly for the countermovement jump require a large magnitude of change to overcome the variable\u27s inherent variability. Shape factor and net impulse proportion for the static jump should be used with caution and requires further investigations. Alternative net impulse can be used interchangeably to criterion net impulse. Of the proposed net impulse characteristics, net impulse height and width and shape factor were found to contribute to countermovement jump height, whereas all the net impulse characteristics were found to contribute to static jump height. Of the characteristics found to contribute, relative net impulse height (net impulse height divided by system mass) appears to be an important characteristic to achieve a high jump height for the countermovement and static jumps and net impulse proportion for the static jump. A mechanism behind increased countermovement jump height may be an increased countermovement displacement as a result of increased force production ability. A mechanism behind increased static jump height is the increased proportion of the entire positive impulse occupied by net impulse (i.e. increased net impulse proportion). The findings of this dissertation show the possibility of the use of the net impulse characteristics to monitor athletes\u27 performance status and responses/adaptations to interventions. However, because this dissertation was the first to explore the potential use of the net impulse characteristics for athletes\u27 performance monitoring, the existing knowledge is still preliminary and further research is required before practical recommendations are made

Pressure Study of BiS2-Based Superconductors Bi4O4S3 and La(O,F)BiS2

We report the electrical resistivity measurements under pressure for the recently discovered BiS2-based layered superconductors Bi4O4S3 and La(O,F)BiS2. In Bi4O4S3, the transition temperature Tc decreases monotonically without a distinct change in the metallic behavior in the normal state. In La(O,F)BiS2, on the other hand, Tc initially increases with increasing pressure and then decreases above ? 1 GPa. The semiconducting behavior in the normal state is suppressed markedly and monotonically, whereas the evolution of Tc is nonlinear. The strong suppression of the semiconducting behavior without doping in La(O,F)BiS2 suggests that the Fermi surface is located in the vicinity of some instability. In the present study, we elucidate that the superconductivity in the BiS2 layer favors the Fermi surface at the boundary between the semiconducting and metallic behaviors.Comment: 4 pages, 6 figures, Accepted for publication in J. Phys. Soc. Jp

Role of the Ce valence in the coexistence of superconductivity and ferromagnetism of CeO1−x_{1-x}Fx_{x}BiS2_{2} revealed by Ce L3L_3-edge x-ray absorption spectroscopy

We have performed Ce $L_3$-edge x-ray absorption spectroscopy (XAS) measurements on CeO$_{1-x}$F$_x$BiS$_2$, in which the superconductivity of the BiS$_2$ layer and the ferromagnetism of the CeO$_{1-x}$F$_x$ layer are induced by the F-doping, in order to investigate the impact of the F-doping on the local electronic and lattice structures. The Ce $L_3$-edge XAS spectrum of CeOBiS$_2$ exhibits coexistence of $4f^1$ (Ce$^{3+}$) and $4f^0$ (Ce$^{4+}$) state transitions revealing Ce mixed valency in this system. The spectral weight of the $4f^0$ state decreases with the F-doping and completely disappears for $x>0.4$ where the system shows the superconductivity and the ferromagnetism. The results suggest that suppression of Ce-S-Bi coupling channel by the F-doping appears to drive the system from the valence fluctuation regime to the Kondo-like regime, leading to the coexistence of the superconducting BiS$_2$ layer and the ferromagnetic CeO$_{1-x}$F$_x$ layer.Comment: 5 pages, 5 figure

Application of Principal Components Analysis in Kinetics Study for Isometric Squat

Abstract available in the 10th Annual Coaches and Sport Science College

Effects of Weightlifting Training on Isometric Mid-Thigh Pull Rate of Force Development

PURPOSE: To examine the influence of three distinct training phases on isometric mid-thigh pull (IMTP) measures in well-trained weightlifters. METHODS: Pre- and post-block IMTP data from 11 collegiate weightlifters was used for analysis. The mean of the best two attempts from each athlete for measures of PF and RFD from 0-50ms, 0-100ms, 0-150ms, 0-200ms, and 0-250ms were used for comparison. In total, results from five timepoints for each of the 11 athletes were examined in order to compare the effects of the three training phases. RESULTS: A repeated measures ANOVA revealed no statistically significant (p ≥ 0.05) effects of training on any of the variables measured. When comparing post block values from each phase to pre-training cycle values, the largest increase in RFD200 (d = 0.22) and RFD250 (d=0.22) occurred post strength-power (SP) phase, while the peak in RFD50 (d = 0.32), RFD100 (d = 0.31), and RFD150 (d = 0.22) occurred after the peak/taper (PT) phase. CONCLUSIONS: Based on the results of the study, it is possible that changes in IMTP RFD may reflect the expected adaptations of block periodization. Rather than examining RFD changes at only one time-band, it may be valuable to monitor RFD across multiple time bands as changes in early and late RFD may not occur proportionally during a peak/taper phase

Using the Minimax Accelerometer to Quantify the Demands of Preseason Training in NCAA Volleyball: A Descriptive Case-Study Study

Abstract available in the 9th Annual Coaches and Sport Science College

Positive Impulse Phase versus Propulsive Impulse Phase: Correlations between Asymmetry and Countermovement Jump Performance

The relationship between asymmetry and performance is still undetermined in the literature. Methods of assessing asymmetry have been inconsistent and focused on the analysis of jumping asymmetry. Dual ground reaction forces are prevalent in athlete monitoring, though underutilized in asymmetry research. The purpose of this study was to assess the relationship of countermovement jump (CMJ) impulse asymmetry to performance in collegiate soccer athletes. Male and female athletes were selected from an ongoing athlete research repository database of NCAA D-I soccer athletes. All athletes contributed two maximal effort unweighted (CMJ0) and weighted countermovement jumps (CMJ20) using the mean for calculations. Propulsive phase asymmetry scores (PrPAS) and positive impulse asymmetry scores (PIAS) were calculated to determine the magnitude of asymmetry for each prospective phase. Statistically significant correlations were found between CMJ0 jump height and unweighted PIAS (r = −0.43) in females. Males had statistically significant correlations between CMJ20 jump height and weighted PIAS (r = −0.49). Neither unweighted PrPAS nor weighted PrPAS produced statistically significant correlations (r \u3c 0.26) to their prospective jump heights. When assessing CMJ asymmetry, it is recommended to conduct both weighted and unweighted CMJ testing, utilizing PIAS as the metric to be assessed

The Physical Demands of NCAA Division I Women\u27s College Soccer

Extensive research into women\u27s collegiate soccer is scarce, leaving gaps in the literature with little information available detailing the physical demands at different standards of play. Our purpose was to elucidate the physical demands of the Division I collegiate level and identify differences between playing positions. Twenty-three field players were observed during four competitive seasons using 10-Hz GPS units (Catapult Sports, Melbourne, Australia). Descriptive statistics and 95% confidence intervals were used to determine group and position-specific physical demands. Linear mixed modelling (LMM) was used to compare attacker, midfielder, and defender position groups. Total distance, high-speed distance, and sprint distance were 9486 ± 300 m, 1014 ± 118 m, and 428 ± 70 m, respectively. Furthermore, attackers were observed to cover the greatest distance at all speeds compared to midfielders and defenders. Our findings suggest that the physical demands of Division I women\u27s soccer differ by position and appear lower compared to higher standards of play. Therefore, coaches and sports scientists responsible for the physical training of Division I collegiate players should consider the specific physical demands of the collegiate level and playing position when prescribing training, as well as in the development of their annual training programs