The purposes of this dissertation were to examine the phase characteristics of the countermovement jump force-time curve between athletes based on jumping ability, examine the influence of maximal muscular strength on the countermovement jump force-time curve phase characteristics of athletes, and to examine the behavior of the countermovement jump force-time curve phase characteristics over the course of a training process in athletes of varying strength levels. The following are the major findings of these dissertations. The analysis of athletes by jumping ability suggested that proficient jumpers are associated with greater relative phase magnitude and phase impulse throughout the phases contained in the positive impulse of the countermovement jump force-time curve. Additionally, phase duration was not found to differ between athletes based on jumping ability or between male and female athletes. The analysis of athletes based on maximal muscular strength suggested that only unweighted phase duration differs between strong and less-strong athletes. Interestingly, in both investigations based on jumping ability and maximal strength indicated the relative shape of the stretching phase representing the rise in positive force was related to an athlete’s jumping ability (jump height). The results of the longitudinal analysis of countermovement jump force-time phase characteristics identified that these variables can be frequently assessed throughout a training process to provide information of regarding an athlete performance state. Furthermore, based on the contrasting behaviors of many of the countermovement jump force-time curve phase characteristics over time, an athlete’s level of muscular strength may influence how these characteristics are expressed in the context of a training process.

Eight male collegiate weightlifters (age: 21.2 ± 0.9 years; height: 177.6 ± 2.3 cm; and body mass: 85.1 ± 3.3 kg) participated in this study to compare isometric to dynamic force-time dependent variables. Subjects performed the isometric and dynamic mid-thigh clean pulls at 30–120% of their one repetition maximum (1RM) power clean (118.4 ± 5.5 kg) on a 61 X 121.9–cm AMTI forceplate. Variables such as peak force (PF) and peak rate of force development (PRFD) were calculated and were compared between isometric and dynamic conditions. The relationships between force-time dependent variables and vertical jump performances also were examined. The data indicate that the isometric PF had no significant correlations with the dynamic PF against light loads. On the one hand, there was a general trend toward stronger relationships between the isometric and dynamic PF as the external load increased for dynamic muscle actions. On the other hand, the isometric and dynamic PRFD had no significant correlations regardless of the external load used for dynamic testing. In addition, the isometric PF and dynamic PRFD were shown to be strongly correlated with vertical jump performances, whereas the isometric PRFD and dynamic PF had no significant correlations with vertical jump performances. In conclusion, it appears that the isometric and dynamic measures of force-time curve characteristics represent relatively specific qualities, especially when dynamic testing involves small external loads. Additionally, the results suggest that athletes who possess greater isometric maximum strength and dynamic explosive strength tend to be able to jump higher. Eight male collegiate weightlifters (age: 21.2 ± 0.9 years; height: 177.6 ± 2.3 cm; and body mass: 85.1 ± 3.3 kg) participated in this study to compare isometric to dynamic force-time dependent variables. Subjects performed the isometric and dynamic mid-thigh clean pulls at 30–120% of their one repetition maximum (1RM) power clean (118.4 ± 5.5 kg) on a 61 X 121.9–cm AMTI forceplate. Variables such as peak force (PF) and peak rate of force development (PRFD) were calculated and were compared between isometric and dynamic conditions. The relationships between force-time dependent variables and vertical jump performances also were examined. The data indicate that the isometric PF had no significant correlations with the dynamic PF against light loads. On the one hand, there was a general trend toward stronger relationships between the isometric and dynamic PF as the external load increased for dynamic muscle actions. On the other hand, the isometric and dynamic PRFD had no significant correlations regardless of the external load used for dynamic testing. In addition, the isometric PF and dynamic PRFD were shown to be strongly correlated with vertical jump performances, whereas the isometric PRFD and dynamic PF had no significant correlations with vertical jump performances. In conclusion, it appears that the isometric and dynamic measures of force-time curve characteristics represent relatively specific qualities, especially when dynamic testing involves small external loads. Additionally, the results suggest that athletes who possess greater isometric maximum strength and dynamic explosive strength tend to be able to jump higher.

Examining a countermovement jump (CMJ) force-time curve related to net impulse might be useful in monitoring athletes' performance. This study aimed to investigate the reliability of alternative net impulse calculation and net impulse characteristics (height, width, rate of force development, shape factor, and proportion) and validate against the traditional calculation in the CMJ. Twelve participants performed the CMJ in two sessions (48 hours apart) for test–retest reliability. Twenty participants were involved for the validity assessment. Results indicated intra-class correlation coefficient (ICC) of ≥ 0.89 and coefficient of variation (CV) of ≤ 5.1% for all of the variables except for rate of force development (ICC = 0.78 and CV = 22.3%). The relationship between the criterion and alternative calculations was r = 1.00. While the difference between them was statistically significant (245.96 ± 63.83 vs. 247.14 ± 64.08 N s, p < 0.0001), the effect size was trivial and deemed practically minimal (d = 0.02). In conclusion, variability of rate of force development will pose a greater challenge in detecting performance changes. Also, the alternative calculation can be used practically in place of the traditional calculation to identify net impulse characteristics and monitor and study athletes' performance in greater depth.

No description available.

Examining a countermovement jump (CMJ) force-time curve related to net impulse might be useful in monitoring athletes' performance. This study aimed to investigate the reliability of alternative net impulse calculation and net impulse characteristics (height, width, rate of force development, shape factor, and proportion) and validate against the traditional calculation in the CMJ. Twelve participants performed the CMJ in two sessions (48 hours apart) for test–retest reliability. Twenty participants were involved for the validity assessment. Results indicated intra-class correlation coefficient (ICC) of ≥ 0.89 and coefficient of variation (CV) of ≤ 5.1% for all of the variables except for rate of force development (ICC = 0.78 and CV = 22.3%). The relationship between the criterion and alternative calculations was r = 1.00. While the difference between them was statistically significant (245.96 ± 63.83 vs. 247.14 ± 64.08 N s, p < 0.0001), the effect size was trivial and deemed practically minimal (d = 0.02). In conclusion, variability of rate of force development will pose a greater challenge in detecting performance changes. Also, the alternative calculation can be used practically in place of the traditional calculation to identify net impulse characteristics and monitor and study athletes' performance in greater depth.

Made available in DSpace on 2014-06-11T19:22:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-09-15Bitstream added on 2014-06-13T18:08:48Z : No. of bitstreams: 1 goncalves_r_me_rcla.pdf: 1648455 bytes, checksum: a169bc59e57fd832a6bbe9380247a8a5 (MD5) / O objetivo do presente estudo foi analisar o efeito agudo do alongamento estático sobre diferentes parâmetros da curva força-tempo (Cf-t) isométrica e atividade eletromiográfica (EMG) de idosas em exercícios monoarticular e multiarticular. A amostra foi composta por 27 mulheres (65,4 ± 4,3 anos; 69,3 ± 9,0 Kg; 1,57 ± 1,0 m; 28,0 ± 4,0 Kg/m2). A contração voluntária máxima (CVM), taxa de desenvolvimento de força (TDF) (30, 50, 100, 150 e 200 ms relativos ao início da contração muscular) e TDF pico (TDFP) (inclinação mais íngreme da curva nos primeiros 200 ms) foram testadas em dois exercícios (Leg Press ou cadeira extensora) em 2 condições separadas: alongamento (A) (3 séries de 30 segundos para o quadríceps femoral) e controle (C). Em cada dia, apenas uma condição e um tipo de exercício foram testados e a ordem de emprego para cada condição e exercício foram determinadas aleatoriamente. A atividade eletromiográfica dos músculos vasto medial (VM), vasto lateral (VL) e bíceps femoral (BF) também foi avaliada. Quatro avaliações póscondições (imediatamente após; 10; 20 e 30 minutos) foram realizadas para acompanhar o comportamento da força e da atividade muscular. Com exceção da TDF para os 100 ms durante exercício multiarticular, a ANOVA 2x2, seguida do teste post-hoc de Tukey não demonstrou interações condição vs. tempo significativas (p > 0,05) para a CVM, TDFP e TDF nos diferentes períodos de tempo avaliados para exercício monoarticular e multiarticular. Também não foi observada interação condição vs. tempo significativa para a iEMG dos músculos VM, VL e BF durante CVM e TDF nos diferentes períodos de tempo. Não foram observadas interações exercício vs. tempo (p > 0,05) para TDFP e TDF nos diferentes períodos de tempo durante comparação entre exercício monoarticular e multiarticular. Em conclusão séries agudas de alongamento... / The aim of this study was to analyze the acute effects of static stretching on different parameters of the isometric force-time curve (Cf-t) and electromyography activity (EMG) of elderly women during single and multiple joint exercises. Twenty-seven women (65,4 ± 4,3 years old; 69,3 ± 9,0 Kg; 1,57 ± 1,0 m; 28,0 ± 4,0 Kg/m2) were studied. The maximal voluntary contraction (MVC), rate of force development (RFD) (50, 100, 150, and 200 ms relative to onset of muscular contraction), and peak RFD (PRFD) (the steepest slope of the curve during the first 200 ms) were tested during two exercises (Leg Press and knee extension) under 2 separate conditions: stretching (S) (3 sets of 30 seconds) and control (C). Only one condition and exercise was tested on each day and the order of application of each condition and exercise was determined randomly. Electromyographic (EMG) activity of the vastus medialis (VM), vastus lateralis (VL), and biceps femoris (BF) muscles also was assessed. Four post-condition assessments (post-treatment, 10, 20, and 30 minutes) were performed to monitor muscle strength and muscular activity. With the exception of TDF for 100 ms during multiple joint exercise, the ANOVA 2x2, followed by Tukey post-hoc test showed no significant interactions between condition vs. time (p> 0.05) for MVC, PRFD and RFD in different periods of time for single and multiple joint exercises. There was also no significant interaction between condition vs. time to the iEMG for VM, VL and BF during MVC and RFD in different periods of time. There were no significant interactions between exercise vs. time (p> 0.05) for PRFD and RFD and in different time periods for comparison between single and multiple joint exercises. In conclusion, acute bouts of static stretching of the quadríceps do not affect the ability of rapid and maximum muscle force production and the EMG activity for VM, VL and BF of older women at single and multiple joint exercises

Orientador: Sebastião Gobbi / Banca: Paulo de Tarso Veras Farinatti / Banca: Claudio Alexandre Gobatto / Resumo: O objetivo do presente estudo foi analisar o efeito agudo do alongamento estático sobre diferentes parâmetros da curva força-tempo (Cf-t) isométrica e atividade eletromiográfica (EMG) de idosas em exercícios monoarticular e multiarticular. A amostra foi composta por 27 mulheres (65,4 ± 4,3 anos; 69,3 ± 9,0 Kg; 1,57 ± 1,0 m; 28,0 ± 4,0 Kg/m2). A contração voluntária máxima (CVM), taxa de desenvolvimento de força (TDF) (30, 50, 100, 150 e 200 ms relativos ao início da contração muscular) e TDF pico (TDFP) (inclinação mais íngreme da curva nos primeiros 200 ms) foram testadas em dois exercícios (Leg Press ou cadeira extensora) em 2 condições separadas: alongamento (A) (3 séries de 30 segundos para o quadríceps femoral) e controle (C). Em cada dia, apenas uma condição e um tipo de exercício foram testados e a ordem de emprego para cada condição e exercício foram determinadas aleatoriamente. A atividade eletromiográfica dos músculos vasto medial (VM), vasto lateral (VL) e bíceps femoral (BF) também foi avaliada. Quatro avaliações póscondições (imediatamente após; 10; 20 e 30 minutos) foram realizadas para acompanhar o comportamento da força e da atividade muscular. Com exceção da TDF para os 100 ms durante exercício multiarticular, a ANOVA 2x2, seguida do teste post-hoc de Tukey não demonstrou interações condição vs. tempo significativas (p > 0,05) para a CVM, TDFP e TDF nos diferentes períodos de tempo avaliados para exercício monoarticular e multiarticular. Também não foi observada interação condição vs. tempo significativa para a iEMG dos músculos VM, VL e BF durante CVM e TDF nos diferentes períodos de tempo. Não foram observadas interações exercício vs. tempo (p > 0,05) para TDFP e TDF nos diferentes períodos de tempo durante comparação entre exercício monoarticular e multiarticular. Em conclusão séries agudas de alongamento... (Resumo completo, clicâr acesso eletrônico abaixo) / Abstract: The aim of this study was to analyze the acute effects of static stretching on different parameters of the isometric force-time curve (Cf-t) and electromyography activity (EMG) of elderly women during single and multiple joint exercises. Twenty-seven women (65,4 ± 4,3 years old; 69,3 ± 9,0 Kg; 1,57 ± 1,0 m; 28,0 ± 4,0 Kg/m2) were studied. The maximal voluntary contraction (MVC), rate of force development (RFD) (50, 100, 150, and 200 ms relative to onset of muscular contraction), and peak RFD (PRFD) (the steepest slope of the curve during the first 200 ms) were tested during two exercises (Leg Press and knee extension) under 2 separate conditions: stretching (S) (3 sets of 30 seconds) and control (C). Only one condition and exercise was tested on each day and the order of application of each condition and exercise was determined randomly. Electromyographic (EMG) activity of the vastus medialis (VM), vastus lateralis (VL), and biceps femoris (BF) muscles also was assessed. Four post-condition assessments (post-treatment, 10, 20, and 30 minutes) were performed to monitor muscle strength and muscular activity. With the exception of TDF for 100 ms during multiple joint exercise, the ANOVA 2x2, followed by Tukey post-hoc test showed no significant interactions between condition vs. time (p> 0.05) for MVC, PRFD and RFD in different periods of time for single and multiple joint exercises. There was also no significant interaction between condition vs. time to the iEMG for VM, VL and BF during MVC and RFD in different periods of time. There were no significant interactions between exercise vs. time (p> 0.05) for PRFD and RFD and in different time periods for comparison between single and multiple joint exercises. In conclusion, acute bouts of static stretching of the quadríceps do not affect the ability of rapid and maximum muscle force production and the EMG activity for VM, VL and BF of older women at single and multiple joint exercises / Mestre

Abstract available in theJournal of Strength and Conditioning Research

Introdução - A análise da força de preensão manual durante a força realizada ao longo do tempo fornece dados referentes ao funcionamento biomecânico dos grupos musculares, com destaque à influência da musculatura flexora profunda e superficial dos dedos, bem como traz informações pertinentes ao desempenho funcional para atividades cotidianas. Objetivos - Analisar as curvas força-tempo da preensão palmar sob os aspectos de seus parâmetros discretos e de sua característica temporal. Identificar a influência da musculatura flexora profunda de dedos na preensão palmar. Método - Os voluntários realizaram o teste de esforço isométrico máximo utilizando o dinamômetro Jamar® e o transdutor de força computadorizado com duas empunhaduras, uma que permitia a ação do músculo flexor superficial de dedos e outra que a bloqueava. Foram analisadas as curvas força-tempo geradas de 9 indivíduos tanto em seus parâmetros discretos como em suas características temporais. Resultados - A força máxima média obtida com o Jamar® na Posição 1, sem distinção entre os sexos, (30,76 Kgf) aproximou-se dos valores da média nacional para mulheres (30,4 Kgf). Tanto no teste com o Jamar® como com o transdutor de força, os valores discretos foram maiores na Posição 1 (Fmáx Jamar®: 30,76/25,14 kgf; Fmáx transdutor: 22,16/17,37 kgf; Tmáx: 1,41/1,54 seg; Finf: 7,06/5,80 kgf). A fase de manutenção da força, equivalente a força de resistência, teve menor decréscimo nos testes realizados na Posição 2 (-1,02/-0,61). Além disso, os valores obtidos entre os dinamômetros mostram que o Jamar® superestima os valores de força máxima. Conclusões - Os dados apontam que há diferença na capacidade de manutenção da força, para a qual a ação do músculo flexor profundo dos dedos mostrou-se mais eficaz do que quando em conjunto com o flexor superficial dos dedos, tendo assim, grande importância funcional para a execução das atividades de vida diária. Evidencia-se que a análise da força por meio de suas características temporais fornece maior elucidação do desempenho muscular durante a força de preensão do que testes dinamométricos pontuais. / Introduction - The analysis of the manual grip force along time presents the biomechanical movement of muscle groups data, with emphasis on the deep and superficial flexor musculature of the fingers, as well as provides relevant information for the functional performance of daily activities. Objectives - To analyze the force-time curves of the palmar grip under the aspects of its discrete parameters and its temporal characteristic. Either, to identify the the influence of the flexor muscles of fingers in the palmar grip. Method - The volunteers performed the maximum isometric effort test using the Jamar® dynamometer and the computerized force transducer with two grips, one that allowed the action of the flexor superficial finger muscle, and another that blocks it. The force-time curves generated from 9 individuals were analyzed in both their discrete parameters and their temporal characteristics. Results - The medium of maximum strength obtained with Jamar® at Position 1, without distinction between gender, (30.76 Kgf) approached the national average for women (30.4 Kgf). In both the Jamar® and the force transducer tests, the discrete values were higher in Position 1 (Fmax Jamar®: 30.76 / 25.14 kgf; Fmax transducer: 22.16 / 17.37 kgf; Tmax: 1.41 / 1.54 sec; Finf: 7.06 / 5.80 kgf). The strength maintenance phase, equivalent to the resistive force, had a smaller decrease in the tests performed in Position 2 (-1.02 / -0.61). In addition, the values obtained between the dynamometers show that the Jamar® overestimates the maximum force values. Conclusions - The data points that there is a difference between the action of the flexor profound muscle group of the fingers and the flexor superficial one in the capacity of maintaining the force, showing that the profound group is more effective than combined with the superficial flexor, thus, the first one has great functional importance for performing activities of daily life. It evidences that the analysis of force on its temporary characteristics is more elucidative of the muscular performance during the grip force than the punctual dynamometric tests.

The purpose of this investigation was to study the effects of an 11-week training period performed by female weightlifters. Two weeks before this investigation, baseline measures for total testosterone, cortisol, and testosterone:cortisol ratio were collected. The 11-week training program consisted of the core exercises (i.e., clean, clean and jerk, and snatch) and other supplemental exercises (i.e., clean pull, snatch pull, squat, and front squat). Hormonal, isometric, and dynamic middle thigh pull force-time curve characteristics were assessed biweekly throughout the duration of the investigation, whereas volume load and training intensity were assessed weekly throughout the investigation. The testosterone:cortisol ratio of the baseline (1.19 ± 0.64) was significantly different from the ratio of weeks 1 (0.67 ± 0.36) and 9 (0.94 ± 0.66). When the week-to-week values were compared, week 1 (0.67 ± 0.36) was significantly different (P < 0.05; ηsup>2= 0.84) from week 3 (1.06 ± 0.54). A very strong correlation (r = −0.83; r 2 = 0.69) was found between the percentage change of the testosterone:cortisol ratio and volume load from weeks 1 to 11. Moderate to very strong correlations were noted between the percentage change in volume load and isometric peak force, peak force during the 30% isometric peak force trial, and peak force during the 100-kg trial during the 11 weeks of training. The primary finding of this study was that alterations in training volume load can result in concomitant changes in the anabolic-to-catabolic balance, as indicated by the testosterone:cortisol ratio, and the ability to generate maximal forces.