Swimmers' Effective Actions during the Backstroke Start Technique.

The analysis of the external forces of swimming starts has revealed how swimmers propel themselves out of the block, but data should be properly interpreted to fully understand force-generation mechanisms. This study aimed to assess horizontal and vertical forces in the backstroke start based on swimmers' structural and propulsive actions. Firstly, a simulated structural force was estimated by two transient backstroke-start inter-segmental realistic body positions: a maximally tucked position and an extended one (just before the hands-off and the take-off, respectively). Secondly, 10 competitive backstroke swimmers performed four 15 m maximal backstroke starts with the external forces estimated. Thirdly, the simulated structural force was subtracted from raw horizontal and vertical force data, measured between hands-off and take-off instants, resulting in the propulsive forces. The application of the algorithm has evidenced that backstrokers' horizontal and vertical simulated-structural-force components contributed to ~40% of total force during start propulsion (~0.2-0.12 s before the take-off), followed by the propulsive horizontal force increment and a progressive vertical component reduction (~0.05 s) with ~20° take-off angle. Based on these findings, researchers and coaches can better guide swimmers as to the proper mechanical strategies to achieve effectiveness in the backstroke start, and to improve direct transfer of resistance training programs.

Reliability of impulse oscillometry parameters in healthy children and in children with cystic fibrosis.

INTRODUCTION & AIMS: Impulse oscillometry system (IOS) is an instrument developed to evaluate the mechanical lung properties. It has been reported that to analyse the exam in a proper way it is necessary to carry out more than one measure. However, studies addressing the standardisation are still scarce. The objective was to determine within trial reliability of three measures in IOS parameters in healthy children and children with cystic fibrosis (CF). METHOD: Weight, height, body mass index, forced spirometric and the oscillometric parameters (resistance, respiratory impedance, respiratory reactance and resonance frequency) data were collected, in a way that all participants performed three IOS measures. To evaluate, the reproducibility was used the intraclass correlation coefficient [two-way mixed model, absolute agreement definition, ICC]. The response stability was appraised using the standard error of measurements (SEM) in three repetitions of the IOS in the healthy children group (HCG) and in the cystic fibrosis group (CFG). RESULTS: About 95 subjects participated, in each group with a mean age of 10.89 ± 2.21 years old in the HCG and 9.73 ± 2.43 years old in the CFG, having been 41 and 43 boys and 54 and 52 girls, in the respectively group. In both groups, all IOS parameters evaluated in the three measures presented an ICC of 0.9, which is a high reproducibility. CONCLUSION: The IOS parameters are reproducible for healthy children and CF children in three measures. However, according to the population studied, the performance of only one measure is sufficient to assess respiratory mechanics, whereas the SEM were low, except for Fres, in both groups.

Effect of Immersion on Ground Reaction Force and Contact Time During Drop Jump Exercise.

Dell'Antonio, E, Ruschel, C, de Brito Fontana, H, Haupenthal, A, Pereira, SM, and Roesler, H. Effect of immersion on ground reaction force and contact time during drop jump exercise. J Strength Cond Res 30(12): 3443-3449, 2016-This study analyzed the effect of water immersion on vertical ground reaction force (GRF) peaks and contact times during the braking, propulsion, and landing phases of drop jumps (DJs). Twenty-five healthy male athletes of volleyball and track and field (age 18.0 ± 2.4 years) participated in this study. Peak vertical GRF during braking, propulsion, and landing phases; time duration of braking and propulsion phases; and total contact time were measured during maximum DJs performed on land and in water at 4 levels of immersion (tibia, knee, thigh, and hip). A force plate was used to collect GRF data, and the braking and propulsion phases of contact were determined by using an electrical goniometer placed on subject's knee. The effect of immersion level on variables was analyzed through the use of a repeated measures analysis of variance (p ≤ 0.05). The results showed that increasing immersion leads to a decrease in peak force during the braking phase, landing phase, and in the propulsion phase of the DJ, with the decrease in peak forces between immersions being greater as the immersion level gets deeper. Concerning the contact times, increasing immersion levels caused an increase in total contact time and in the duration of the braking phase. No differences were found for the duration of the propulsion phase between the conditions. Our results have shown that temporal features of the DJ were not preserved in water, and this must be taken into account when choosing the aquatic environment as an alternative for plyometric training. If the rationale of performing plyometric training in water is the reduction of GRFs, then hip immersion seems to offer an interesting combination of significantly lower GRF but without further modification of important temporal features when compared with the other water conditions analyzed.

Kinematic, kinetic and EMG analysis of four front crawl flip turn techniques.

This study aimed to analyse the kinematic, kinetic and electromyographic characteristics of four front crawl flip turn technique variants. The variants distinguished from each other by differences in body position (i.e., dorsal, lateral, ventral) during rolling, wall support, pushing and gliding phases. Seventeen highly trained swimmers (17.9 ± 3.2 years old) participated in interventional sessions and performed three trials of each variant, being monitored with a 3-D video system, a force platform and an electromyography (EMG) system. Studied variables: rolling time and distance, wall support time, push-off time, peak force and horizontal impulse at wall support and push-off, centre of mass horizontal velocity at the end of the push-off, gliding time, centre of mass depth, distance, average and final velocity during gliding, total turn time and electrical activity of Gastrocnemius Medialis, Tibialis Anterior, Biceps Femoris and Vastus Lateralis muscles. Depending on the variant, total turn time ranged from 2.37 ± 0.32 to 2.43 ± 0.33 s, push-off force from 1.86 ± 0.33 to 1.92 ± 0.26 BW and centre of mass velocity during gliding from 1.78 ± 0.21 to 1.94 ± 0.22 m · s(-1). The variants were not distinguishable in terms of kinematical, kinetic and EMG parameters during the rolling, wall support, pushing and gliding phases.

Validity and reliability of an instrumented leg-extension machine for measuring isometric muscle strength of the knee extensors.

CONTEXT: Isometric muscle strength of knee extensors has been assessed for estimating performance, evaluating progress during physical training, and investigating the relationship between isometric and dynamic/functional performance. OBJECTIVE: To assess the validity and reliability of an adapted leg-extension machine for measuring isometric knee extensor force. DESIGN: Validity (concurrent approach) and reliability (test and test-retest approach) study. SETTING: University laboratory. PARTICIPANTS: 70 healthy men and women aged between 20 and 30 y (39 in the validity study and 31 in the reliability study). MAIN OUTCOME MEASURE: Intraclass correlation coefficient (ICC) values calculated for the maximum voluntary isometric torque of knee extensors at 30°, 60°, and 90°, measured with the prototype and with an isokinetic dynamometer (ICC2,1, validity study) and measured with the prototype in test and retest sessions, scheduled from 48 h to 72 h apart (ICC1,1, reliability study). RESULTS: In the validity analysis, the prototype showed good agreement for measurements at 30° (ICC2,1 = .75, SEM = 18.2 Nm) and excellent agreement for measurements at 60° (ICC2,1 = .93, SEM = 9.6 Nm) and at 90° (ICC2,1 = .94, SEM = 8.9 Nm). Regarding the reliability analysis, between-days' ICC1,1 were good to excellent, ranging from .88 to .93. Standard error of measurement and minimal detectable difference based on test-retest ranged from 11.7 Nm to 18.1 Nm and 32.5 Nm to 50.1 Nm, respectively, for the 3 analyzed knee angles. CONCLUSIONS: The analysis of validity and repeatability of the prototype for measuring isometric muscle strength has shown to be good or excellent, depending on the knee joint angle analyzed. The new instrument, which presents a relative low cost and easiness of transportation when compared with an isokinetic dynamometer, is valid and provides consistent data concerning isometric strength of knee extensors and, for this reason, can be used for practical, clinical, and research purposes.

The Effect of Aquatic Plyometric Training on Jump Performance Including a Four-week Follow-up in Youth Female Volleyball Players.

This study aimed to analyze the effect of aquatic plyometric training (APT) on jump performance in volleyball players. Twelve female athletes (16.6 ± 0.9 years) were assessed through the following jump tests: spike height (SH), squat jump (SJ), countermovement jump (CMJ) and CMJ with an arm swing (CMJA). Jump height in each test and the eccentric utilization ratio (EUR) were the outcome measures. APT consisted of sets of drop jumps for 6 weeks (2 sessions/week) at a water depth of 0.75 m. Tests were performed at the beginning of a five-week pre-season period, before and after APT, and four weeks later for the follow-up. Repeated measures ANOVAs were used to analyze data and Hedges' g to estimate effect size (ES). Performance of all jumps did not change from baseline to Pre-APT. Performance improved in SH (p < 0.001, ES: 1.09), the SJ (p = 0.045, ES: 0.76) and the CMJA (p < 0.001, ES: 0.78) after APT when compared to Pre-APT. No changes were observed after the follow-up period. In conclusion, including six weeks of APT in the training routine of youth volleyball players improved performance of a sport-specific task (SH), the SJ and CMJA, with gains preserved after a four-week follow-up.

Activation of the gluteus maximus, gluteus medius and tensor fascia lata muscles during hip internal and external rotation exercises at three hip flexion postures.

BACKGROUND: Hip internal and external rotation exercises are usually performed in clinical practice. However, given the synergies required to stabilize the hip in the frontal plane, it is not clear how the activation of target muscles will differ between the two exercise directions. OBJECTIVE: I) Compare the activation of the upper and lower fibers of gluteus maximus (GMax), gluteus medius (GMed) and tensor fascia lata muscles between the hip internal and external rotation exercises; ii) Compare the maximal isometric force between hip internal and external rotation exercises and; iii) Assess the effect of varying hip flexion angles on muscle activation and maximal isometric force. STUDY DESIGN: A cross sectional study. METHODS: Electromyography and force production of twenty-one participants were measured during maximum isometric hip internal and external rotation in three postures: 0°, 45° and 90° of hip flexion. RESULTS: MANOVA results showed a larger activation of the GMed, tensor fascia lata and upper GMax (p < .001) for hip internal rotation compared to external rotation regardless of hip flexion angle. For the lower GMax, the same was observed when the hip was kept at 90° of flexion. Maximal isometric force during hip external rotation was greater than during hip internal rotation at 0° posture, and lower at 90° posture (p < .001). CONCLUSION: The gluteus and the tensor fascia lata muscles were substantially recruited during the hip internal rotation exercise, and barely recruited during the hip external rotation exercise. Hip flexion influences the myoeletric activity and isometric force production during the internal rotation exercise.

Analysis of the lateral push-off in the freestyle flip turn.

The aim of this study was to examine the contact phase during the lateral push-off in the turn of front crawl swimming to determine which biomechanical variables (maximum normalized peak force, contact time, impulse, angle of knee flexion, and total turn time within 15 m) contribute to the performance of this turn technique. Thirty-four swimmers of state, national, and international competitive standard participated in the study. For data collection, the following equipment was used: an underwater force platform, a 30-Hz VHS video camera, and a MiniDv digital camera within an underwater box. Data are expressed as descriptive statistics. Inferential analyses were performed using Pearson's correlation and multiple linear regressions. All variables studied had a significant relationship with turn performance. We conclude that a turn executed with a knee flexion angle of between 100° and 120° provides optimum peak forces to generate impulses that allow the swimmer to lose less time in the turn without the need for an excessive force application and with less energy lost.

Isokinetic hip muscle strength: a systematic review of normative data.

The aim of this study was to conduct a systematic review to determine the quality of evidence of studies assessing isokinetic hip muscle strength in adult non-injured individuals. We also aimed to summarise and pool data of normative values for hip muscle strength. The influence of methodological and participant-related factors on hip strength performance was explored as well. Guidelines proposed in the PRISMA were used to undertake a search strategy involving the keyword 'hip' associated with a set of keywords reflecting muscle strength. Five databases were searched: ProQuest, PubMed, Science Direct, Scopus and Web of Science. From the 2,939 records initially retained, 28 articles were included in this systematic review. Eight articles were classified as high quality. This systematic review exposed the methodological fragility of most studies assessing hip strength in non-injured adult population. Only data from studies with a small number of participants are available to be used as reference. A few individual studies suggest no differences in torque parameters between dominant and non-dominant lower limbs; differences in torque parameters between age groups; and between male and female participants. Overall, reference values for hip muscle performance in isokinetic tests are mostly unclear.

Prediction of ground reaction forces while walking in water.

Despite being a key concept in rehabilitation, controlling weight-bearing load while walking, following lower limb injury is very hard to achieve. Walking in water provides an opportunity to prescribe load for people who have pain, weakness or weight bearing restrictions related to stages of healing. The aim of this experimental study was to evaluate and validate regression models for predicting ground reaction forces while walking in water. One hundred and thirty seven individuals (24±5 years, 1.71±0.08 m and 68.7±12.5 kg) were randomly assigned to a regression group (n = 113) and a validation group (n = 24). Trials were performed at a randomly assigned water depth (0.75 to 1.35 m), and at a self-selected speed. Independent variables were: immersion ratio, velocity, body mass, and waist, thigh and leg circumferences. Stepwise regression was used for the prediction of ground reaction forces and validation included agreement and consistency statistical analyses. Data from a force plate were compared with predicted data from the created model in the validation group. Body mass, immersion ratio, and velocity independently predicted 95% of the vertical and resultant ground reaction force variability, while, together, velocity and thigh circumference explained 81% of antero-posterior ground reaction force variability. When tested against the data measured in validation samples, the models output resulted in statistically similar values, intraclass correlation coefficients ranging from 0.88 to 0.90 and standard errors of measurement, 11.8 to 42.3 N. The models introduced in this study showed good predictive performance in our evaluation procedures and may be considered valid in the prediction of vertical, antero-posterior and resultant ground reaction forces while walking in water. All predictive variables can be easily determined in clinical practice. Future studies should focus on the validation of these models in specific populations.

Effect of land- and aquatic-based plyometrics on spike and block reaches in young volleyball players: a pilot study

Abstract Aim: The purpose of this pilot study was to analyze the feasibility of the intervention and measures of a six-week land- and aquatic-based plyometric training on spike and block reaches in young volleyball athletes. Methods: Twelve female players were divided into a land group (LG) (n = 6, 12.4 ± 0.3 years, 1.61 ± 0.04 m, 57.0 ± 9.3 kg) and a water group (WG) (n = 6, 12.5 ± 0.5 years, 1.57 ± 0.06 m, 48.9 ± 8.5 kg). The spike and block (without step, with slide step, and with crossover step) reach and countermovement jump height were evaluated before and after a 6-week plyometric training protocol. Duration (total and of each session), adhesion and adherence, and safeness of the intervention; completion of assessments, within-trial reliability, and variability of the outcome measures and preliminary results were the variables of interest. To analyze the effect of the training on jump performance, the Wilcoxon test was used (p < 0.05), and effect sizes (r) were calculated. Results: All participants concluded the intervention and the assessments as planned. No dropouts or adverse events were registered during the study. The within-trial reliability for all assessment tests was considered excellent (ICC ≥ 0.9). Preliminary results indicate that LG improved the reach of the spike and block with the slide step; and that WG improved the spike, block with the slide step to the left, and block without movement reaches (p < 0.05; large effect size). Conclusion: An intervention of six weeks of plyometric training on land and in water is feasible, and preliminary results indicate that both training protocols may benefit the performance of spike and block in young volleyball athletes.

Vertical ground reaction force in stationary running in water and on land: A study with a wide range of cadences.

PURPOSE: The aim of this study was to analyze the effect of cadence, immersion level as well as body density on the vertical component (Fymax) of ground reaction force (GRF) during stationary running (SR). METHODS: In a controlled, laboratory study, thirty-two subjects ran at a wide range of cadences (85-210 steps/min) in water, immersed to the hip and to the chest, and on dry land. Fymax. was verified by a waterproof force measurement system and predicted based on a statistical model including cadence, immersion ratio and body density. RESULTS: The effect of cadence was shown to depend on the environment: while Fymax increases linearly with increasing cadence on land; in water, Fymax reaches a plateau at both hip and chest immersions. All factors analyzed, cadence, immersion level and body density affected Fymax significantly, with immersion (aquatic × land environment) showing the greatest effect. In water, different cadences may lead to bigger changes in Fymax than the changes obtained by moving subjects from hip to chest immersion. A regression model able to predict 69% of Fymax variability in water was proposed and validated. CONCLUSION: Cadence, Immersion and body density affect Fymax in a significant and non-independent way. Besides a model of potential use in the prescription of stationary running in water, our analysis provides insights into the different responses of GRF to changes in exercise parameters between land and aquatic environment.

Factors associated with injuries in Hawaiian canoe paddlers / Fatores associados a lesões em remadores de canoa havaiana

Abstract Introduction The Hawaiian canoe has numerous bene-fits for those who use it. Furthermore, it is considered a moderate/high-intensity cyclic sport that can cause injuries. Studies on factors associated with injuries in Hawaiian canoe paddlers are considered limited and scarce. Objective To identify the profile of canoe paddlers and determine the main factors associated with injuries. Methods A cross-sectional study was conducted with 100 Hawaiian canoe paddlers (54% females, 45.6 ± 10.0 years old; 46% males, 44.8 ± 11.7 years old) using an online survey, with questions on sociodemographic and anthropometric information and practice and injuries. Results Participants reported having at least four years of experience with the modality, training approximately four times a week for a total of six hours. Almost half (45%) of the sample reported having been injured at least once while canoeing. The back/spine was the body region with the highest injury prevalence, with 38.6%. Intense training was considered the only associated factor for injuries (odds ratio: 3.98; 95% confidence interval: 1.71 - 9.26). Conclusion This pioneering study in Brazil allowed us to profile Hawaiian canoe paddlers and identify the main factors associated with injuries. Paddlers who train intensely are more likely to develop injuries during practice. Therefore, this variable must be considered when planning sessions.

Resumo Introdução A canoagem havaiana apresenta inúmeros benefícios para os praticantes. Apesar disso, é uma prática considerada com gestos cíclicos, realizada com intensidade moderada/intensa e que pode ocasionar lesões. As evidências sobre os fatores associados às lesões em remadores de canoa havaiana são consideradas limitadas e escassas. Objetivo Identificar o perfil dos remadores brasileiros de canoa havaiana e verificar os fatores associados às lesões. Métodos Trata-se de um estudo transversal conduzido em 100 remadores de canoa havaiana (54% sexo feminino, 46,2 ± 8,5 anos; 46% do sexo masculino, 44,8 ± 11,7 anos) por meio de uma pesquisa online. O instrumento utilizado continha perguntas sobre as variáveis sociodemográ-ficas, antropométricas, prática da modalidade e lesões. Resultados Os participantes reportaram ter experiência de pelo menos quatro anos com a modalidade, treinando aproximadamente quatro vezes por semana e totalizando seis horas de treino semanal. Quarenta e cinco por cento da amostra relatou ter sido lesionada pelo menos uma vez durante a prática da modalidade. As costas/coluna foi a região corporal com maior prevalência de lesão, com 38,6%. Treinos intensos foram considerados os únicos fatores associados para lesões (razão de chance: 3,98; intervalo de confiança: 1,71 - 9,26). Conclusão Este estudo pioneiro no Brasil permitiu traçar o perfil dos remadores de canoa havaiana, bem como identificar os principais fatores associados a lesões. Remadores que treinam intensamente estão mais propensos a desenvolver lesões durante a prática, portanto, esta variável deve ser levada em consideração no planejamento das sessões.

Dynamometric analysis of the maximum force applied in aquatic human gait at 1.3m of immersion.

BACKGROUND: This work had the objective to analyze the values of the vertical and anteroposterior components of the ground reaction force (GRF) during the aquatic gait and the influence of the speed and the upper limb position on the GRF components values. METHODS: Sixty subjects, with average height between 1.6 and 1.85m and average age of 23 years, were divided in three groups according to the immersion level. The citizens walked over a walking platform, which had two force plates attached. The platform was located at a depth of 1.3m. The subjects walked over the platform in four different situations, with speed and upper limb position variations. For data analysis, descriptive and inferential statistics were used. FINDINGS: For the vertical component, the force values varied between 20% and 40% of the subjects' body weight according to the different data collection situations. For the anteroposterior component, the force values reached between 8% and 20% of the subjects' body weight corporal, also according with the data collection situation. INTERPRETATION (DISCUSSION): It was noted that for a given immersion level, the forces can vary according to the request that is imposed to the aquatic gait. It was concluded that either the speed as well as the position of the upper limb influence the values of the GRF components. An increase in the gait speed causes increase of the anteroposterior component (Fx), while an increase in the corporal mass out of the water causes increase mainly of the vertical component (Fy). Knowing the value of these alterations is important for the professional who prescribes activities in aquatic environment.

Aerials and their influence on World Surfing League surfer performance (WSL flights) / Os aéreos e sua influência no desempenho dos surfistas da Liga Mundial de Surf (Aéreos WSL)

Abstract This research aimed to verify whether the number of airplanes run by surfers in the 2016 Word Surf League (WSL) men's season and their grades were related to their final classification in the events and season. Were viewed 3475 waves from 49 surfers and selected for analysis 275 waves. Spearman's correlation test, one-way ANOVA, and t-test, with p?0.05, were used for statistical analysis. The air proved to be an effective maneuver in isolated clashes, helped to reach the finals and decide events, but did not prove to be the main determinant of the season's final standings. The average of the marks attributed to the reverse 360 ??aerial was significantly higher than the notes attributed to the reverse aerial, however, the variables the position of the surfer in front or back to wave and whether or not to grab the board edge did not present significant differences.

Resumo Esta pesquisa teve como objetivo verificar se a quantidade de aéreos executados pelos surfistas na temporada masculina da Word Surf League (WSL) de 2016 e suas respectivas notas tiveram relação com a classificação final deles nos eventos e na temporada. Foram visualizadas 3475 ondas de 49 surfistas e selecionadas para analise 275 ondas. Utilizou-se o teste de correlação de Spearman, ANOVA um fator e o teste t, com p?0.05, para análise estatística. O aéreo se mostrou uma manobra eficaz em confrontos isolados, ajudou a chegar às finais e a decidir eventos, mas não se mostrou ser o principal determinante para a classificação final da temporada. A média das notas atribuídas ao aéreo reverse 360 foi significativamente maior que as notas atribuídas ao aéreo reverse, no entanto, as variáveis posições do surfista de frente ou de costas para onda e agarrar ou não borda da prancha, não apresentaram diferenças significativas.

Trunk muscular endurance, lumbar spine mobility and hip flexibility in sailors with and without low back pain / Análise da resistência muscular do tronco, mobilidade da coluna lombar e flexibilidade do quadril em velejadores com e sem dor lombar

Abstract Introduction: Low back pain is one of the most common injuries in sailors. Findings in the literature indicate that poor trunk endurance, flexibility and muscle strength are common in individuals with low back pain (LBP). Objective: Analyze trunk muscle endurance, lumbar spine mobility and hip flexibility in windsurfers with and without low back pain. Method: Sailors of both sexes with at least three years' experience in the sport answered the Nordic Musculoskeletal Questionnaire and were submitted to Schober's test, the passive straight leg raise (PSLR), the modified Thomas test, and isometric endurance assessment of the flexor, extensor and lateral flexor muscles of the torso. The sailors were divided into two groups (with and without LBP) and compared using the Student's t-test or Mann Whitney U test. Results: Participants were 22 national-level sailors, 11 with low back pain (LBP) and 11 without (NLBP). The LBP group obtained longer holding times for the trunk extensors (p=0.028) and a greater difference in endurance between the right and left sides for lateral trunk muscles (p=0.030). Both groups obtained results below normative values in most of the tests performed. Conclusion: Sailors with low back pain exhibited greater trunk extensor endurance and a larger imbalance between lateral trunk muscles when compared to those with no LBP. Spinal mobility and hip flexibility were similar between groups.

Resumo Introdução: A dor lombar é uma das lesões que mais afeta os velejadores. Achados na literatura mostram que a deficiência de força do tronco, flexibilidade e resistência muscular é comum em indivíduos com dor lombar. Objetivo: Analisar a resistência muscular do tronco, a mobilidade da coluna lombar e a flexibilidade do quadril em velejadores com e sem dor lombar. Método: Velejadores de ambos os sexos e com no mínimo três anos de prática responderam ao questionário nórdico de lesões osteomusculares e realizaram os testes de Schöber, de Elevação Passiva da Perna Estendida, de Thomas Modificado e de resistência isométrica dos músculos flexores, extensores e laterais do tronco. Os velejadores foram divididos em dois grupos (com e sem dor lombar), comparados por meio do teste t de Student para amostras independentes ou U de Mann Whitney. Resultados: 22 velejadores de nível nacional, 11 com dor lombar (CDL) e 11 sem dor lombar (SDL), participaram do estudo. O grupo CDL apresentou maior tempo de permanência no teste de resistência dos extensores do tronco (p=0,028) e maior diferença entre os lados direito e esquerdo no teste de resistência dos músculos laterais do tronco (p=0,030). Na maioria dos testes realizados, os dois grupos apresentaram resultados abaixo dos valores normativos. Conclusão: Velejadores com dor lombar apresentaram maior resistência dos extensores do tronco, porém maior desequilíbrio entre as cadeias laterais do tronco, em comparação a velejadores sem dor lombar. A mobilidade da coluna e a flexibilidade do quadril foram semelhantes entre os grupos.

Effective Swimmer's Action during the Grab Start Technique.

The external forces applied in swimming starts have been often studied, but using direct analysis and simple interpretation data processes. This study aimed to develop a tool for vertical and horizontal force assessment based on the swimmers' propulsive and structural forces (passive forces due to dead weight) applied during the block phase. Four methodological pathways were followed: the experimented fall of a rigid body, the swimmers' inertia effect, the development of a mathematical model to describe the outcome of the rigid body fall and its generalization to include the effects of the inertia, and the experimental swimmers' starting protocol analysed with the inclusion of the developed mathematical tool. The first three methodological steps resulted in the description and computation of the passive force components. At the fourth step, six well-trained swimmers performed three 15 m maximal grab start trials and three-dimensional (3D) kinetic data were obtained using a six degrees of freedom force plate. The passive force contribution to the start performance obtained from the model was subtracted from the experimental force due to the swimmers resulting in the swimmers' active forces. As expected, the swimmers' vertical and horizontal active forces accounted for the maximum variability contribution of the experimental forces. It was found that the active force profile for the vertical and horizontal components resembled one another. These findings should be considered in clarifying the active swimmers' force variability and the respective geometrical profile as indicators to redefine steering strategies.

Hip morphology and its relationship with hip strength, mobility and lower limb biomechanics: a systematic review in adults / Relação da morfologia do quadril com força, mobilidade e biomecânica dos membros inferiores: uma revisão sistemática em adultos

Abstract This systematic review (PROSPERO registration n.43640) aimed to summarise and determine the quality of evidence relating hip bone morphology to (i) hip strength, (ii) mobility and (iii) lower limb biomechanics during functional activities. A standardized search on MEDLINE/PubMed, Web of Science, ScienceDirect and Scopus resulted in 17 papers that met inclusion criteria: i) original investigations with a minimal sample of n=10, ii) studies on humans and iii) presence of at least one quantitative hip morphological parameter and one hip functional (i.e. strength and mobility) and/or one lower limb biomechanical parameter. Risk of bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies tool with adaptations. Sixteen out of the 17 included studies showed high risk of bias. We observed that primary evidence pointed to the influence of hip morphology on hip mobility in the transverse plane. Specifically, positive correlations between femoral anteversion angle and range of internal hip rotation in physical examination were observed. Regarding biomechanical parameters, no clear evidence of association between hip morphology, and kinematic and kinetic parameters were found. Our results point to a field that is currently under explored and future studies with low risk of bias addressing these relationships are required.

Resumo Essa revisão sistemática (PROSPERO registro no 43640) tem por objetivo sintetizar e determinar a qualidade da evidência que relaciona morfologia do quadril à (i) força do quadril, (ii) mobilidade e (iii) biomecânica dos membros inferiores durante atividades funcionais. Uma busca padronizada no MEDLINE/PubMed, Web of Science, ScienceDirect e Scopus resultou em 17 artigos em acordo com os critérios de inclusão: i) estudos originais com amostra mínima de n=10; ii) estudos em humanos e iii) presença de no mínimo um parâmetro quantitativo da morfologia do quadril e um parâmetro funcional do quadril (ex.: mobilidade e força) e/ou um parâmetro biomecânico do membro inferior. A avaliação do risco de viés foi realizada através da ferramenta Quality Assessment of Diagnostic Accuracy Studies (QUADAS) com adaptações. Dezesseis dos 17 estudos incluídos apresentaram alto risco de viés. Observamos que a evidência primária aponta para influência da morfologia do quadril em sua mobilidade no plano transverso. Foram observadas, especificamente, correlações positivas entre o ângulo de anteversão femoral e a mobilidade de rotação interna do quadril durante o exame físico. Em relação aos parâmetros biomecânicos, não foram encontradas evidências claras sobre associação entre morfologia do quadril e parâmetros cinemáticos e cinéticos. Nossos resultados apontam para um campo atualmente subexplorado e investigações futuras com baixo risco de viés que avaliem essas relações são necessárias.

In vivo vastus lateralis force-velocity relationship at the fascicle and muscle tendon unit level.

The force velocity relationship of in vivo human muscle fibers has often been derived from the torque-angular speed relationship during maximal voluntary isokinetic contractions. However, the assumption of a close association between joint performance and muscle mechanics is questionable. We aimed to determine the relationship between knee extension angular speeds, vastus lateralis fascicle and muscle tendon unit (MTU) shortening speeds, and maximal knee extensor force for the entire range of knee joint movement, for the isokinetic range, and for the ranges before, after and at peak torque occurrence, with different commonly used pre-loading conditions. Higher peak forces were observed when knee extensions were preceded by a pre-load, despite the similarity in fascicle shortening speeds. For the entire and the isokinetic range, MTU always shortened faster than fascicles, and this difference increased as joint speed increased. Interestingly, fascicle shortening velocities were greater before compared to after peak torque occurrence while the opposite happened at the MTU level. Assuming a close relationship between joint and fascicle dynamics results in an overestimation of muscle contractile component shortening velocity or force production at peak torque. The force velocity relationships obtained in vivo depend crucially on the test conditions, and the movement range used for analysis.

Ground reaction forces in shallow water running are affected by immersion level, running speed and gender.

OBJECTIVES: To analyze the effect of depth of immersion, running speed and gender on ground reaction forces during water running. DESIGN: Controlled laboratory study. METHODS: Twenty adults (ten male and ten female) participated by running at two levels of immersion (hip and chest) and two speed conditions (slow and fast). Data were collected using an underwater force platform. The following variables were analyzed: vertical force peak (Fy), loading rate (LR) and anterior force peak (Fx anterior). Three-factor mixed ANOVA was used to analyze data. RESULTS: Significant effects of immersion level, speed and gender on Fy were observed, without interaction between factors. Fy was greater when females ran fast at the hip level. There was a significant increase in LR with a reduction in the level of immersion regardless of the speed and gender. No effect of speed or gender on LR was observed. Regarding Fx anterior, significant interaction between speed and immersion level was found: in the slow condition, participants presented greater values at chest immersion, whereas, during the fast running condition, greater values were observed at hip level. The effect of gender was only significant during fast water running, with Fx anterior being greater in the men group. Increasing speed raised Fx anterior significantly irrespective of the level of immersion and gender. CONCLUSIONS: The magnitude of ground reaction forces during shallow water running are affected by immersion level, running speed and gender and, for this reason, these factors should be taken into account during exercise prescription.