The purpose of this dissertation was to determine if a periodized strength and conditioning program resulted in long-term adaptations in NCAA Division I women’s volleyball athletes, and if these changes related to the team’s competitive performance. Specifically, this dissertation serves to: 1.) describe the changes in body composition and performance variables of 2 female volleyball athletes over a 4-year collegiate career, 2.) determine the degree and magnitude of change in performance variables after about 1, 2, and 3 years of periodized resistance training, and 3.) infer if volleyball performance characteristics are related to a team’s competitive success. The following are major findings of this dissertation. 1.) Positive changes in vertical jump height, strength, and explosiveness may be possible throughout 4 years of collegiate volleyball training even with increased body mass and percent body fat. Moreover, impaired ability to perform heavy lower-body resistance training exercises due to chronic injury negatively impacts long-term physical performance adaptations over 4 years. 2.) A combination of traditional resistance training exercises and weightlifting variations at various loads, in addition to volleyball practice, appear to be effective at increasing maximal strength by 44% and vertical jump height by 20%-30% in NCAA Division I women’s volleyball athletes after about two and half years of training. Furthermore, these characteristics can be improved in the absence of additional plyometric training outside of normal volleyball-specific practice. 3.) A rating percentage index RPI ranking ratio and unweighted match score ratio appear to be better predictors of overall team competitive season success than a weighted match score ratio. On the contrary, a weighted match score ratio may be better for determining an association between team match performance and volleyball-specific fitness. A considerable amount of research is needed to develop a volleyball-specific performance index that best quantifies team performance and whether or not a measurable association exists between improved fitness characteristics and increased overall team competitive success. The findings of this dissertation provide evidence that analyzing and monitoring volleyball-related performance variables over time can assist the sport performance group in making training based decisions as well as promote the successful development of an athlete.

No description available.

Healthcare costs for treating back pain have risen to 50 billion dollars a year in the past decade. In attempt reduce the risk of back pain; ergonomists use digital human modeling to assess the risks involved in functional tasks. However, current models are limited to analyzing the strength in static position. The overall goal of this study is to provide three-dimensional strength surfaces incorporating both static and dynamic strength for digital human models. Fifteen male and twenty-one female subjects were recruited. The study required two visits, were hip strength testing was performed in one visit and trunk strength testing was performed in the other visit. Hip strength was tested by completing flexion and extension isometric tests and isokinetic tests. Trunk flexion and extension strength was also measured by isometric and isokinetic tests. Isometric and Isokinetic tests were completed for trunk left and right rotation too. The data was analyzed using custom made MATLAB (Mathworks, Inc) programs and the three-dimensional strength surfaces were generated using SigmaPlot (SYSTAT Software, INC). The maximum peak torques were as followed: Hip flexion male 183Nm(57), hip flexion female 106 Nm (38), hip extension male 181 Nm (71), hip extension female 130 Nm (52), trunk flexion male 182 Nm (40.3), trunk flexion female 111.8 Nm (32), trunk extension male 328.5 Nm (52), trunk extension female 197.5 Nm (58), trunk right rotation male 71.6 Nm (20), trunk right rotation female 43 Nm (14), trunk left rotation male 71 Nm (24), and trunk left rotation female (43 Nm (17). Correlations were found between the hip and trunk joints, and the flexion and extension motion. Implementing this data into digital human models will provide realistic static and dynamic human strength parameters. Ultimately, this will help ergonomists predict and reduce high risk back injuries.

Carry-over of force production symmetry in athletes of differing strength levels. J Strength Cond Res 29(11): 3188–3196, 2015—This study sought to determine the level of association between bilateral force production symmetry assessment methods (standing weight distribution [WtD], unloaded and lightly loaded jumps, and isometric strength) and to determine whether the amount of symmetry carry-over between these tasks differs for strong and weak athletes. Subjects for this study included male (n = 31) and female (n = 32) athletes from National Collegiate Athletic Association Division I sports. Athletes performed WtD, unloaded and lightly loaded (20 kg) static and countermovement jumps, and isometric midthigh pull (IMTP) assessments on 2 adjacent force plates. Ground reaction force data were used to calculate symmetry variables and performance-related variables. Using Pearson zero order correlations, evaluations of the amount of symmetry carry-over were made. Weight distribution correlated strongly with jump peak force (PF) (r = 0.628–0.664). Strong relationships were also observed between loading conditions for jump variables (r = 0.568–0.957) as were the relationships between jump types for PF, peak power, and net impulse (r = 0.506–0.834). Based on the pooled sample, there was a lack of association between IMTP and WtD for jump symmetry variables. However, when examining strong and weak groups, rate of force development showed moderate to strong symmetry carry-over in the strongest athletes (r = 0.416–0.589). Stronger athletes appear to display similar explosive strength symmetry characteristics in dynamic and isometric assessments, unlike weaker athletes. Strength seems to influence the amount of force production symmetry carry-over between bilateral assessments. There may be optimal loads and variables for symmetry assessment, but these may differ based on population characteristics.

Objectives: The purpose of this study was to identify the relationship between isometric force production symmetry and jumping performance in weighted and un-weighted static and countermovement jumps (SJ and CMJ). Design: Bivariate correlation between isometric force production symmetry and vertical jump performance variables. Methods: Collegiate athletes were evaluated for this study (n=36). Subjects performed SJ, CMJ, and isometric mid-thigh pulls (IMTP). Jumps were analyzed for jump height (JH) and peak power (PP). IMTP was analyzed for peak force (PF) for left and right sides, and values were calculated to produce a peak force symmetry index (PF-SI) score. Correlational statistics were performed examining the relationship between PF-SI and jump variables. Results: Moderate statistically significant negative correlations were observed between PF-SI and all jump variables, indicating that as asymmetry increases jump performance decreases. SJ correlations weakened in weighted conditions (JH r=-0.52 @ 0 kg/r=-0.39 @ 20 kg, PP r=-0.43 @ 0 kg/r=-0.34 @ 20 kg), but CMJ produced similar correlations for both conditions (JH r=-0.47 @ 0 kg/r=-0.49 @ 20 kg, PP r=-0.28 @ 0 kg/r=-0.34 @ 20 kg). Unlike the SJ, which only contains the propulsive or concentric portion of the jump, the CMJ also contains the eccentric portion and performance contributions of the stretch-shortening cycle (SSC). The addition of the SSC may play a role in the maintaining the magnitude of asymmetry in the CMJ weighted condition. Conclusions: The results indicate that force production asymmetry may be detrimental to bilateral vertical jumping performance. The findings should be considered for further investigation on sport-specific tasks.

This study examined the validity of various scaling methods, isometric mid-thigh pull (IMTP) peak force using various scaling methods, and the relationships between IMTP peak force and countermovement jump height. Fifty-one collegiate baseball and soccer athletes performed two maximal IMTPs. Absolute peak force was compared between teams and when data were scaled using ratio (RS), traditional allometric (ALLOTrad), and fitted allometric (ALLOFit) scaling. ALLOTrad and ALLOFit validity was violated because different derived exponents existed for baseball (b = 0.20) and soccer (b = 1.20). Soccer athletes produced greater RS peak force compared to baseball (p = 0.012), while no difference existed with absolute, ALLOTrad or ALLOFit (all p > 0.05) peak force. Moderate relationships existed between body mass and absolute (r = 0.402, p = 0.003) and RS (r = -0.328, p = 0.019) peak force, while trivial relationships existed with ALLOTrad and ALLOFit (both r < -0.10, p > 0.05). Trivial relationships existed between countermovement jump height and absolute, RS, ALLOTrad, and ALLOFit (all r < 0.20, p > 0.05) peak force. The current dataset violated allometric scaling assumptions, making it inappropriate to use ALLOTrad and ALLOFit scaling. Practitioners must understand the assumptions, limitations, and purpose of scaling methods.

Neuromuscular control is believed to play an essential role during dynamic knee joint stabilisation. Evaluation of voluntary muscle action can be delineated as support strategies against external loading moments (Lloyd & Buchanan, 2001). The aim of this study was to determine if males and females exhibit differences in knee muscle action and cocontraction during voluntary isometric closed kinetic chain force generation in various directions in the horizontal plane representative of applied loads transverse to the long axis of the shank. Twenty-six healthy young adults (13 male, 13 female) stood with their dominant leg in a boot fixed to a force platform. A force target matching protocol required subjects to position a cursor (projected on a video screen) over a target and maintain the position for one second. To control the cursor, loads were applied against the force platform with their dominant leg to produce various combinations of anterior-posterior, medial-lateral loads while maintaining constant inferior-superior loads. A successful target match required a normalised force magnitude of equal effort for each subject and target location which triggered the recording of electromyography (EMG) for eight muscles crossing the knee joint. EMG was normalised to percent maximum voluntary isometric contraction. A mean magnitude of muscle activation, mean direction of muscle activation and a muscle specificity index was determined using EMG vectors. In addition, cocontraction indices were also computed for antagonist muscle pairs. Based on similar previous research, it was hypothesised that females would have greater quadriceps and hamstrings coactivation, greater muscle activation magnitudes, lower specificity for the quadriceps than males and no difference in hamstring characteristics. In our study, females significantly cocontracted their vastus lateralis and lateral gastrocnemius muscles to a greater degree than males (p=0.001). No significant differences were observed across sexes for the cocontraction of quadriceps and hamstrings or the lateral quadriceps and gastrocnemius muscles. Females displayed significantly lower specificity than males in their semitendinosus (p=0.025) and tensor fascia lata (p=0.012) activity patterns, greater magnitude of muscle activation in their lateral gastrocnemius (p=0.002) and tensor fascia lata (p<0.003) and no statistical difference in the other muscles. Furthermore, the activation patterns in our study grossly differed from previous open kinetic chain force target matching. These findings indicate that healthy young males and females have differences in their knee muscle control strategies and that knee muscle recruitment patterns differ during weight bearing and non-weight bearing tasks.

Neuromuscular control is believed to play an essential role during dynamic knee joint stabilisation. Evaluation of voluntary muscle action can be delineated as support strategies against external loading moments (Lloyd & Buchanan, 2001). The aim of this study was to determine if males and females exhibit differences in knee muscle action and cocontraction during voluntary isometric closed kinetic chain force generation in various directions in the horizontal plane representative of applied loads transverse to the long axis of the shank. Twenty-six healthy young adults (13 male, 13 female) stood with their dominant leg in a boot fixed to a force platform. A force target matching protocol required subjects to position a cursor (projected on a video screen) over a target and maintain the position for one second. To control the cursor, loads were applied against the force platform with their dominant leg to produce various combinations of anterior-posterior, medial-lateral loads while maintaining constant inferior-superior loads. A successful target match required a normalised force magnitude of equal effort for each subject and target location which triggered the recording of electromyography (EMG) for eight muscles crossing the knee joint. EMG was normalised to percent maximum voluntary isometric contraction. A mean magnitude of muscle activation, mean direction of muscle activation and a muscle specificity index was determined using EMG vectors. In addition, cocontraction indices were also computed for antagonist muscle pairs. Based on similar previous research, it was hypothesised that females would have greater quadriceps and hamstrings coactivation, greater muscle activation magnitudes, lower specificity for the quadriceps than males and no difference in hamstring characteristics. In our study, females significantly cocontracted their vastus lateralis and lateral gastrocnemius muscles to a greater degree than males (p=0.001). No significant differences were observed across sexes for the cocontraction of quadriceps and hamstrings or the lateral quadriceps and gastrocnemius muscles. Females displayed significantly lower specificity than males in their semitendinosus (p=0.025) and tensor fascia lata (p=0.012) activity patterns, greater magnitude of muscle activation in their lateral gastrocnemius (p=0.002) and tensor fascia lata (p<0.003) and no statistical difference in the other muscles. Furthermore, the activation patterns in our study grossly differed from previous open kinetic chain force target matching. These findings indicate that healthy young males and females have differences in their knee muscle control strategies and that knee muscle recruitment patterns differ during weight bearing and non-weight bearing tasks.

El objetivo general del trabajo fue realizar aportaciones al conocimiento dinamométrico y electromiográfico de la articulación del codo. Para ello se analizó la fuerza isométrica máxima y su variabilidad inter e intraobservador, así como el comportamiento electromiográfico de bíceps y tríceps en diferentes ejercicios dinámicos sobre una población de 23 sujetos sanos. Se determinó también la influencia del género y de la dominancia. Los resultados de las mediciones dinamométricas mostraron valores más altos de fuerza isométrica en los varones, observándose una alta correlación con la talla y el peso corporal. Un CCI>0.71 en todas las mediciones demostró la fiabilidad y reproductibilidad de este método a 90º de flexión. No se encontraron diferencias en cuanto a la lateralidad. La actividad EMGs aumentó con la carga e intensidad del ejercicio dinámico, principalmente en el bíceps. Se demostró la gran influencia del sexo y la dominancia sobre los resultados. / The aim of this study was to make contributions to the knowledge of isometric dynamometry and surface electromyography of the elbow joint. We analyzed the maximal isometric force and inter-intraobserver variability also the electromyographic behavior of biceps and triceps brachii in different dynamic exercises on a population of 23 healthy people. We determined the influence of gender and dominance too. Dynamometric measurements showed higher values of isometric strength in men, showing a high correlation with height and body weight. An ICC>0.71 for all measurements demonstrated the reliability and reproducibility of this method at 90º of elbow flexion. There were no differences between dominant and nondominant side. The sEMG activity increased with the load and intensity of dynamic exercise mainly in the biceps brachii. It showed the great influence of sex and dominance on the results.

An n-tuple of operators V=(V_1,…,V_n) acting on a Hilbert space H is said to be isometric if the corresponding row operator is an isometry. A free semigroup algebra is the weakly closed algebra generated by an isometric n-tuple V. The structure of a free semigroup algebra contains a great deal of information about V. Thus it is natural to study this algebra in order to study V. A free semigroup algebra is said to be analytic if it is isomorphic to the noncommutative analytic Toeplitz algebra, which is a higher-dimensional generalization of the classical algebra of bounded analytic functions on the complex unit disk. This notion of analyticity is of central importance in the general theory of free semigroup algebras. A vector x in H is said to be wandering for an isometric n-tuple V if the set of words in the entries of V map x to an orthonormal set. As in the classical case, the analytic structure of the noncommutative analytic Toeplitz algebra is determined by the existence of wandering vectors for the generators of the algebra. In the first part of this thesis, we prove the following dichotomy: either an isometric n-tuple V has a wandering vector, or the free semigroup algebra it generates is a von Neumann algebra. This implies the existence of wandering vectors for every analytic free semigroup algebra. As a consequence, it follows that every free semigroup algebra is reflexive, in the sense that it is completely determined by its invariant subspace lattice. In the second part of this thesis we prove a decomposition for an isometric tuple of operators which generalizes the classical Lebesgue-von Neumann-Wold decomposition of an isometry into the direct sum of a unilateral shift, an absolutely continuous unitary and a singular unitary. The key result is an operator-algebraic characterization of an absolutely continuous isometric tuple in terms of analyticity. We show that, as in the classical case, this decomposition determines the weakly closed algebra and the von Neumann algebra generated by the tuple.