João Gustavo Claudino

The countermovement jump to monitor neuromuscular status: A meta-analysis

OBJECTIVES The primary objective of this meta-analysis was to compare countermovement jump (CMJ) performance in studies that reported the highest value as opposed to average value for the purposes of monitoring neuromuscular status (i.e., fatigue and supercompensation). The secondary aim was to determine the sensitivity of the dependent variables. DESIGN Systematic review with meta-analysis. METHODS The meta-analysis was conducted on the highest or average of a number of CMJ variables. Multiple literature searches were undertaken in Pubmed, Scopus, and Web of Science to identify articles utilizing CMJ to monitor training status. Effect sizes (ES) with 95% confidence interval (95% CI) were calculated using the mean and standard deviation of the pre- and post-testing data. The coefficient of variation (CV) with 95% CI was also calculated to assess the level of instability of each variable. Heterogeneity was assessed using a random-effects model. RESULTS 151 articles were included providing a total of 531 ESs for the meta-analyses; 85.4% of articles used highest CMJ height, 13.2% used average and 1.3% used both when reporting changes in CMJ performance. Based on the meta-analysis, average CMJ height was more sensitive than highest CMJ height in detecting CMJ fatigue and supercompensation. Furthermore, other CMJ variables such as peak power, mean power, peak velocity, peak force, mean impulse, and power were sensitive in tracking the supercompensation effects of training. CONCLUSIONS The average CMJ height was more sensitive than highest CMJ height in monitoring neuromuscular status; however, further investigation is needed to determine the sensitivity of other CMJ performance variables.

Desenvolvimento de um método de familiarização individualizado para saltos verticais

OBJECTIVE: The aim of the present study was to propose an individualized familiarization method for vertical jumps and to verify its effect on intra-subject variability. METHODS: Fifty three men (mean ± S.D.; age 23.5 ± 3.3; height 1.76 ± 0.08 m; mass 72.8 ± 8.6 Kg; body fat 12.9 ± 5.2%) performed successive jumps to reach the proposed stability level. After 48 hours, this process was repeated and the stability between the days was verified; if necessary, more sessions were performed. The stability level was determined by a Z-Test with a confidence interval of 95%. After the familiarization process, two additional experimental sessions were performed in order to determine the reliability of the performance in the Squat Jump (SJ) and the Countermovement Jump (CMJ). The coefficient of variation and standard error of measurement were determined individually (CVi and SEMi). A paired T-Test was performed to verify differences in the CVi and SEMi before and after the familiarization process. RESULTS: The CVi presented a significant reduction after the familiarization process (p < 0.001), changing from 5.01 ± 2.40% to 2.95 ± 0.89% in the SJ. The CVi also changed in the CMJ (from 4.50 ± 2.19% to 2.58 ± 0.81%). The same also occurred with the SEMi in both the SJ and the CMJ, changing from 1.29 ± 0.53 cm to 0.83 ± 0.25 cm in the SJ and from 1.35 ± 0.51cm to 0.83 ± 0.26 cm in the CMJ. CONCLUSION: The proposed individualized familiarization method significantly decreased intra-subject variability, which allows for a higher statistical power in the laboratorial setting and a greater sensitivity for performance monitoring tools.

Autoregulating Jump Performance to Induce Functional Overreaching

Abstract Claudino, JG, Cronin, JB, Mezêncio, B, Pinho, JP, Pereira, C, Mochizuki, L, Amadio, AC, and Serrão, JC. Autoregulating jump performance to induce functional overreaching. J Strength Cond Res 30(8): 2242–2249, 2016—The purpose of this study was to determine whether autoregulating jump performance using the minimal individual difference (MID) associated with countermovement jump (CMJ) height could be used to regulate and monitor a training phase that elicited functional overreaching and tapering in team sport athletes. The participants were familiarized with the jump and then the CMJ height reliability was quantified to determine the MID. Countermovement jump height was assessed in the pretesting session (T0), at the end of 4 weeks of intensified training (T1), and after 2 weeks of tapering (T2). Eighteen national level U17 male futsal players were randomly allocated into the regulated group (RG; n = 9) and the control group (CG; n = 9). The RG performed 6 weeks of training with the training load regulated by mean height of CMJ with MID, whereas the CG performed the preplanned training. The differences between groups and across time points were compared by a 2-way analysis of variance. In the RG, the MID loading was increased in weeks 3 and 4 (8.2 and 14.5%, respectively; p < 0.001) compared with the preplanned loading of the CG during the overreaching phase. In the jump results, the RG significantly (p ⩽ 0.05) reduced CMJ height during T1 (effect size [ES] = −0.31; 95% confidence interval [CI]: −0.58 to −0.02); however, there were no significant changes in the CG jump height at T1 and T2. At T2, the RG significantly increased CMJ height above baseline (ES = 0.30; 95% CI: 0.09 to 0.51). Researchers and practitioners could use this autoregulating method to regulate and monitor training load to achieve functional overreaching in youth futsal players.

Individual analysis of creatine kinase concentration in Brazilian elite soccer players

OBJETIVO: determinar o perfil individual das concentracoes sanguineas de creatina quinase em jogadores de futebol de elite, bem como, analisar as concentracoes de CK em diferentes periodos durante o campeonato brasileiro.METODOS: a CK de repouso de 17 jogadores de futebol foi avaliada antes da competicao pre-temporada e apos as partidas 36 e 46 horas apos os jogos CKGamepara obter a CK sanguinea individual. O teste de Chi-quadrado foi utilizado para analisar a CK individual durante a temporada. A temporada competitiva foi dividida em tres periodos: inicial, intermediario e final. A ANOVA one-way com medidas repetidas seguida pelo teste post hoc Student-Newman-Keuls foi utilizada para comparar a CK individual de cada jogador de futebol em cada periodo competitivo. O nivel de significância adotado foi de p < 0,05.RESULTADOS: a maior frequencia da CK individual foi encontrada no segundo quartil 71 observacoes e a menor frequencia no primeiro 26 observacoes e no quarto quartil 40 observacoes em comparacao com o numero esperado de 45,8 x2= 22,21. As concentracoes de CK foram menores nos periodos intermediario media = 66,99% e final media = 60,21% do que no periodo inicial media = 89,33%.CONCLUSAO: os jogadores de futebol nao apresentaram dano muscular elevado e provavelmente uma adaptacao muscular ocorreu na competicao, devido a reducao observada das concentracoes de CK.OBJETIVO: determinar el perfil individual de las concentraciones sanguineas de creatina quinasa en futbolistas de elite, y evaluar las concentraciones de CK en diferentes periodos durante el campeonato brasileno.METODOS: la CK de reposo de 17 futbolistas se evaluo antes de la competicion pretemporada y despues de los partidos 36 y 46 horas despues de los juegos CKGamepara obtener la CK sanguinea individual. La prueba de Chi-cuadrado se utilizo para analizar la CK individual durante la temporada. La temporada competitiva se dividio en tres periodos: inicial, intermedio y final. El ANOVA one-way con medidas repetidas seguido por el test post hoc Student-Newman-Keuls se utilizo para comparar la CK individual de cada futbolista en cada periodo competitivo. El nivel de significacion se fijo en p < 0,05.RESULTADOS: la mayor frecuencia de la CK individual fue encontrada en el segundo cuartil 71 observaciones y la frecuencia mas baja en el primero 26 observaciones y el cuarto cuartil 40 observaciones en comparacion con el numero esperado de 45,8 x2 = 22,21. Las concentraciones de CK fueron menores en los periodos intermedio media = 66,99% y final media = 60,21% que en el periodo inicial media = 89,33%.CONCLUSION: las futbolistas no presentaron un dano muscular alto y probablemente una adaptacion muscular ocurrio en la competicion, debido a la reduccion observada de las concentraciones de CK.

CrossFit Overview: Systematic Review and Meta-analysis

BackgroundCrossFit is recognized as one of the fastest growing high-intensity functional training modes in the world. However, scientific data regarding the practice of CrossFit is sparse. Therefore, the objective of this study is to analyze the findings of scientific literature related to CrossFit via systematic review and meta-analysis.MethodsSystematic searches of the PubMed, Web of Science, Scopus, Bireme/MedLine, and SciELO online databases were conducted for articles reporting the effects of CrossFit training. The systematic review followed the PRISMA guidelines. The Oxford Levels of Evidence was used for all included articles, and only studies that investigated the effects of CrossFit as a training program were included in the meta-analysis. For the meta-analysis, effect sizes (ESs) with 95% confidence interval (CI) were calculated and heterogeneity was assessed using a random-effects model.ResultsThirty-one articles were included in the systematic review and four were included in the meta-analysis. However, only two studies had a high level of evidence at low risk of bias. Scientific literature related to CrossFit has reported on body composition, psycho-physiological parameters, musculoskeletal injury risk, life and health aspects, and psycho-social behavior. In the meta-analysis, significant results were not found for any variables.ConclusionsThe current scientific literature related to CrossFit has few studies with high level of evidence at low risk of bias. However, preliminary data has suggested that CrossFit practice is associated with higher levels of sense of community, satisfaction, and motivation.

Electromyographic activity during maximal isometric contraction combined with local sinusoidal vibration

Electromyographic activity during maximal isometric contraction combined with local sinusoidal vibration Study aim: To compare the electromyographic activity during maximal isometric contraction alone or combined with local sinusoidal vibration. Material and methods: A group of 6 men aged 23 - 29 years performed 3 maximal voluntary contractions of the dominant elbow flexors lasting 10 s each and separated by 5-min intermissions. One repetition was without vibration, one was associated with 15-Hz and the other one with 20-Hz vibrations of 5-mm amplitude, the sequence of repetitions being random. A new system to generate local vibration was applied, the parameters of the vibratory stimulus being measured using an accelerometer. Force and EMG activity were also measured. The subjects performed the task in sitting position in a Scott Bench-type device. Results: Mean acceleration RMS significantly (p<0.01) differed between vibration frequencies for the X, Y, Z-axes. No significant differences were found, however, for EMG RMS. Vibration frequencies coincided with the machine-predicted ones; acceleration frequencies around 5 Hz were present in all situations, even without vibration, most likely brought about by tremor. Conclusion: The local vibration applied was not enough to generate different responses in EMG activity. The features of vibratory stimulus confirmed the expected frequency range and revealed frequencies around 5 Hz, that could be attributed to muscle tremor.

INTENSIDADE MODERADA É O ESTÍMULO MAIS ADEQUADO PARA INDUZIR POTÊNCIA DE QUADRICEPS EM IDOSOS

Rev Bras Med Esporte – Vol. 24, No 3 – Mai/Jun, 2018 ABSTRACT Introduction: The best strategy for improving knee extensor power, a major functional capacity indicator in older adults, is power training. Nonetheless, the training intensity required to induce optimal gains is yet to be found. Objective: Our purpose was to compare knee extensor peak power responses between low, moderate, and high intensity load conditions (30%, 50% and 70% of 1RM). Methods: Thirteen sedentary elderly women performed six knee extensions in each load condition, calculating knee extensor mechanical work/power output and knee extension peak angular velocity. Results: No difference in peak power was found between the high (207.0 ± 68.1 W) and moderate (206.1 ± 71.6 W) load conditions (p = 0.994), and both had higher values (p ≤0.004) than the low intensity condition (135.6 ± 56.3 W). Conclusion: Moderate load at 50% of 1RM appears to be the preferred strategy for inducing knee extensor power output because in contrast with the high intensity condition, the moderate load yielded higher angular peak velocity, which is also a functional indicator. Level of Evidence ll; Therapeutic studies Investigating treatment results.

The validity and reliability of the “My Jump App” for measuring jump height of the elderly

Background The ability to jump has been related to muscle strength and power, speed and amplitude of the lower limbs movements, and specifically for the elderly, the vertical jump has been shown to be a good predictor of functional capacity and risk of falling. The use of a mobile application (App) which can measure the vertical jump (i.e., iPhone App My Jump) has recently emerged as a simple, cheap and very practical tool for evaluation of jump ability. However, the validity of this tool for the elderly population has not been tested yet. The elderly usually perform very low jumps and therefore the signal-to-noise ratio may compromise the validity and reliability of this method. Thus, the aim of the current study was to verify the validity and reliability of the iPhone App “My Jump” for the evaluation of countermovement jump (CMJ) height within an elderly population. Methods After familiarization, 41 participants performed three CMJs assessed via a contact mat and the My Jump App. The intraclass correlation coefficient (ICC) was used to verify the relative reliability, while the coefficient of variation (CV%) and the typical error of measurement (TEM) were used to verify the absolute reliability. Pearson’s correlation coefficient was used to verify the strength of the relationship between methods (i.e., concurrent validity), a Bland–Altman plot to show their agreement, and the Student’s t-test to identify systematic bias between them. For reliability analyses, all jumps were considered (i.e., 123). All jumps (i.e., 123), the average height of each attempt (i.e., 41), and the highest jump, were considered for validity analyses. Results The CMJ height of the highest jump was 10.78 ± 5.23 cm with contact mat, and 10.87 ± 5.32 with My Jump App, with an identified systematic bias of 0.096 cm (P = 0.007). There was a nearly perfect correlation between methods (r = 0.999; P = 0.000, in all cases) with a very good agreement observed (0.3255 to −0.5177 cm, 0.2797 to −0.5594 cm, and 0.3466 to −0.6264 cm, for highest jump height, average jump height, and all jump heights, respectively). The ICC of the My Jump App was 0.948, the TEM was 1.150 cm, and the CV was 10.10%. Conclusion Our results suggest that the My Jump App is a valid and reliable tool compared to the contact mat for evaluating vertical jump performance in the elderly. Therefore, it allows a simple and practical assessment of lower limbs’ power in this population. For the elderly, as well as for other populations with low jumping heights, the highest jump height and the average jump height could be used indistinctly.

Relationship Between Knee Valgus and Ground Reaction Force in Soccer Players Using Soccer Boots Landing on an Official Artificial Turf

RESEARCH ARTICLE Relationship Between Knee Valgus and Ground Reaction Force in Soccer Players Using Soccer Boots Landing on an Official Artificial Turf João Gustavo Claudino, Bruno Mezêncio, Rafael Soncin, Juliana Pennone, João Pedro Pinho, Eduardo Borges, Leonardo Castiglio, Pedro Sampaio Miyashiro, Eric Pomi, Wellington Masuko, Vinicius Soares, Paulo Dias, Luiz Henrique Goés, Alessandro Fromer Piazzi, Alberto Carlos Amadio and Júlio Cerca Serrão Laboratory of Biomechanics – School of Physical Education and Sports, University of São Paulo, São Paulo, Brazil. Centro de Formação de Atletas Sociedade Esportiva Palmeiras, São Paulo, Brazil.

Football scout analysis models (based in the 2013/2014 Champions League)

First places in major football competitions are no longer a few teams’ achievement. A better understanding of the game becomes crucial with this highly competitive background. Our purpose was to determine scout variables that best describe the technical and tactical characteristics of the 2013/2014 Champions League’s participating teams. All UEFA Champions League’s qualifying phases and play-offs matches (32 teams in 126 matches) were analyzed using scout public domain data. The analyzed variables were goals scored, goals difference, total attempts, attempts on target, disarms, corners, offside, passes completed, passes uncompleted, fouls committed and ball possession. A best subsets multiple regression analysis reveal that total attempts (r²=0.815), ball possession (r²=0.748), passes completed (r²=0.742) and scored goals (r²=0.699) are the most relevant variables to describe the match. The present study was able to show how scout information can be reduced to the coach easily application. Statistics, Soccer, UEFA, Competitions.