Effects of Resistance Training of Upper Limb and Trunk Muscles on Soccer Instep Kick Kinematics

The upper body and trunk muscles are crucial to perform soccer kicks. Resistance training targeting these muscles may modify the pattern adopted during kicking. This study aimed to investigate the effect of resistance training of the arm and anterior trunk muscles on instep kicking kinematics. Twenty-six male participants were randomly allocated into a training group or control group. The training group underwent resistance training of arm and trunk muscles and practiced the instep kick for 8 weeks. The control group only practiced kicking during the same period. The trunk, hip, and knee kinematics were assessed during the instep kick before and after the intervention. Kinematics were analyzed according to their data distribution with statistical parametric or nonparametric mapping. The effect of the training on the 1-repetition maximum test was analyzed using a repeated-measures multivariate analysis of variance. The training group showed greater hip extension after the training during the backswing phase (Hedge g effect size of 0.316-0.321) and increased 1-repetition maximum for all exercises. There were no other differences. The present study documented the nonlocal effect of strengthening training in which arm and trunk muscle training resulted in changes in hip kinematics during the backswing phase of the instep kick.

Physical Activity Levels and Psychological Well-Being during COVID-19 Lockdown among University Students and Employees

During the lockdown for the coronavirus disease 2019 (COVID-19), entire populations were instructed to live in home confinement. We investigated the effects of the COVID-19 lockdown on the physical activity (PA) and mental health of students and employees in a Colombian University. A cross-sectional study was conducted through an online survey during the first isolation. A total of 431 respondents (192 males) aged 18-60 years old (28.1 ± 11.1 years) participated. The international Physical Activity Questionnaire (IPAQ) and the short version of the Psychological General Well-Being Index (PGWBI-S) were used. The lockdown had a negative effect on PA levels, with students exhibiting the greatest decrease (~34%; p ˂ 0.001) compared to employees (~24%; p ˂ 0.01). The analysis showed a greater change in PA behavior before and during the lockdown in highly active student participants (5750 vs. 5141 MET min/week; p < 0.05). Additionally, the psychological assessment revealed a lower score in students compared to employees in the male (70.1 vs. 82.6) and female groups (60.2 vs. 79.6). Moreover, the results revealed an influence of sex, with only the female students exhibiting a state of distress. Self-reported PA and psychological well-being were compromised during the COVID-19 lockdown in the academic community, with students and females being more affected.

Asymmetric velocity profiles in Paralympic powerlifters performing at different exercise intensities are detected by functional data analysis

Asymmetries compromise performance in powerlifting and Paralympic powerlifting, but its quantification can be complex. Previous studies consider average or peak values to quantify asymmetries, however this approach does not consider the pattern of movement like velocity profiles. Here we demonstrate that conducting a functional analysis of variance (FANOVA) permits to quantify asymmetries in bench press performance by Paralympic powerlifting at different submaximal intensities. Kinematic data were collected from 10 Paralympic powerlifting athletes performing in bench press at submaximal intensities (50% and 90% of the one-repetition maximum). Linear velocity was quantified considering mean values and the entire waveform. Mean values were compared by analysis of variance (ANOVA) and the waveforms were compared by FANOVA. FANOVA identified asymmetry profiles that ANOVA did not recognize at the highest intensity, which is the closest to a competition. This way, FANOVA can bring advantages to the analysis of competitive performance. FANOVA data analysis identifies asymmetries at higher intensity of effort considering the whole pattern of movement. Therefore, we consider that the FANOVA's approach may benefit the biomechanical assessment of the Paralympic powerlifting.

Functional data analysis reveals asymmetrical crank torque during cycling performed at different exercise intensities

Pedaling asymmetry is claimed as a factor of influence on injury and performance. However, the evidence is still controversial. Most previous studies determined peak torque asymmetries, which in our understanding does not consider the pattern of movement like torque profiles. Here we demonstrate that asymmetries in pedaling torque at different exercise intensities can be better described when the torque profiles are considered using functional analysis of variance than when only the peak values are analyzed. We compared peak torques and torque curves recorded while cyclists pedaled at submaximal intensities of 60%, 80%, and 95% of the maximal power output and compared data between the preferred and non-preferred legs. ANOVA showed symmetry or rather no difference in the amount of peak torque between legs, regardless of pedaling intensity. FANOVA, on the other hand, revealed significant asymmetries between legs, regardless of cycling intensity, apparently for different sections of the cycle, however, not for peak torque, either. We conclude that pedaling asymmetry cannot be quantified solely by peak torques and considering the analysis of the entire movement cycle can more accurately reflect the biomechanical movement pattern. Therefore, FANOVA data analysis could be an alternative to identify asymmetries. A novel approach as described here might be useful when combining kinetics assessment with other approaches like EMG and kinematics and help to better understand the role of pedaling asymmetries for performance and injury risks.

Manipulating the Pitch Size Constrains the Players’ Positioning during Unbalanced Soccer Small-Sided Games Played by Different Age Groups

We aim to investigate the impact of variable soccer pitch sizes on the position of players during unbalanced small-sided games (SSGs) and compare the responses of players from two different age groups. Forty-eight young players (n = 24 under-13 and n = 24 under-14) took part in the study and played 3 vs. 3 + 1 SSGs on two different pitch sizes (smaller: 36 x 27 m / 139m2 per player; and larger: 40 x 29 m / 166 m2 per player). Players’ positions on the pitch (length, width, length-to-width ratio, stretching index, and spatial exploration index) were assessed by the positional data provided by global position system devices and were compared within age groups and between game formats using a two-way analysis of variance. Results showed higher values of spatial exploration index in the larger SSGs than in the smaller format (p&lt;.001). Moreover, a higher length (p&lt;0.001) and length-to-width ratio (p&lt;.001) was observed in the younger group. Finally, the larger format presented higher values of SEI and stretching index, independent of the age group (p&lt;.001). In the smaller format, U-14 players presented a higher stretching index, while in the larger format U-13 players presented higher values in the same variable. We conclude that enlarging the pitch size constrains players’ behaviour during SSGs, and older players are more able to deal with this more complex task context than younger ones.

Basketball small-sided games

This study compared athletes’ rate of perceived exertion (RPE) and the number of their technical-tactical actions in small-sided basketball games (SSG) played within the same relative area with adjusted bout durations in (a) varied game formats; and (b) in two successive bouts of different formats. Ten young female basketball players (14.3±1.3 years) played two bouts of five small-sided game (SSG) formats (1x1, 2x2, 3x3, 4x4, and 5x5). The number of technical-tactical actions per player per minute decreased from the smaller to the larger SSG format, and players’ RPE tended to be higher in larger compared to smaller formats. We concluded that the smaller basketball SSG formats increased players’ participation. In addition, adjustments of the relative playing area and bout duration seemed to decrease players’ effort. The use of two SSG bouts did impact the number of technical-tactical actions and RPE.

Correlation between running asymmetry, mechanical efficiency, and performance during a 10 km run

Running asymmetry is considered a matter of concern for performance and injury, but the association between asymmetry and performance remain unclear. There are different strategies to address asymmetries and its relationship with performance. Here we investigated the correlation between global symmetry index and mechanical efficiency during 10 km running. Thirteen amateur trained athletes (8 men and 5 women) performed a 10 km running at a fixed pace while a 3D accelerometer attached to the pelvic region recorded position data throughout the course of the run and gas exchanges were monitored breath by breath. Global symmetry index was determined for 3 directions, and mechanical efficiency was calculated as the ratio of external work output to energy expenditure determined from gas analysis. Global Symmetry Index and mechanical efficiency decreased (-55.5% and -44.8%, respectively) during the course of the 10 km run (p < 0.01). A positive correlation was observed between global symmetry index and efficiency (r = 0.66, p = 0.01). Asymmetry in the vertical direction had a relatively higher impact on the global symmetry index. The global symmetry index accounted for 43.1% of the variance in mechanical efficiency (p = 0.015). Symmetry, evaluated by the global symmetry index, directly correlates with mechanical efficiency during a 10 km run.

TDCS of the Primary Motor Cortex: Learning the Absolute Dimension of a Complex Motor Task

The primary motor cortex (M1) is one of the main cortical areas involved in motor learning. However, little is known about its differential role in the learning of the relative and absolute dimensions of motor skills. We investigated the role of M1 in the learning of the dimensions of a complex motor skill. Forty-eight participants practiced golf putting and were stimulated for 20 minutes with real or sham bihemispheric tDCS before acquisition. tDCS improved global performance from pre- to post-test. Only those with worse initial performance who were stimulated by tDCS showed a significant improvement in the skill's absolute dimension. No effects of tDCS were found for the relative dimension. Our results suggest that M1 has a distinct participation in the learning of the absolute dimension of complex motor skills, and tDCS effects are influenced by the learner's level of initial performance.

The Effects of Altering the Concentric/Eccentric Phase Times on EMG Response, Lactate Accumulation and Work Completed When Training to Failure

This study compared the electromyographic response, the blood lactate concentration (BLC), and the maximum number of repetitions (MNR) between protocols of different concentric/eccentric duration taken to muscle failure. This comparison may help to understand how different concentric/eccentric duration may influence performance and the central and metabolic responses in trained men. Seventeen strength-trained men performed two protocols in a counterbalanced design. Three sets of the Smith bench press exercise were performed to failure at 60% of the one-repetition maximum (1RM) using each protocol (4-s concentric/2-s eccentric [4 s: 2 s]; and 2-s concentric/4-s eccentric [2 s: 4 s]). The normalized root mean square (EMGRMS) and the mean frequency (EMGMF) of the electromyographic signals for the pectoralis major and the triceps brachii were compared in the first, middle, and last repetitions. The BLC was assessed at rest, during and after the test sessions. To compare the EMG and BLC, a 3-way ANOVA with repeated measures with a post hoc Tukey's test was used. To compare the MNR performed across the sets, an ANOVA-type rank test with the Dunn's post hoc test was used. The ANOVA indicated a greater EMGRMS for Protocol 4 s: 2 s in the pectoralis major and a lower EMGMF for Protocol 4 s: 2 s in the triceps brachii at the middle and last repetitions. Both protocols increased the EMGRMS and decreased the EMGMF across repetitions. Despite the results show different levels of activation and neuromuscular fatigue between protocols, the BLC and the MNR were similar.

The effect of 10 weeks of strength training on the electromyographic response of quadriceps portions

Abstract This study investigate the effect of 10-week strenght training on the amplitude of the electromyographic (EMG) signal of vastus medialis, vastus lateralis and rectus Femoris. Twenty three untrained volunteers performed 3-5 sets (3 sets - weeks 1 and 2; 4 series - weeks 3 and 4; 5 series weeks 5 to 10) with 6 repetitions, intensity of 50% of 1 repetition maximum (1RM), 3 min rest between sets and 6 s repetition duration at the knee extensor exercise. One group (5:1) performed concentric action of 5 s and eccentric of 1 s and the other (3:3) performed concentric of 3 s and eccentric of 3 s. The VM, VL and RF EMG (RMS) activities were recorded in each repetition of the three series at the first training session and the first three series at the last session. The protocol 5:1 led to EMG reduction in all portions, with a greater number of repetitions presenting differences at the VL and RF. VM and RF presented similar results at Group 3:3. It was verified that all the differences occurred in the second half of the series. It was also verified differences in EMG ratios just in group 3:3 and only in VM/VL and VM/RF. These results suggest that the coordination was not affected when equivalent repetitions of series were compared. It was also suggested that these results were influenced by the reduced degrees of freedom of the exercise and the training load progression adopted.

Effects of match period and playing position on the individual and collective dynamics in professional soccer: a case study

Abstract This study aimed to compare the width, the length, the length per width ratio, and the stretch index between the first and the second halves in official soccer matches, and to compare the spatial exploration index between players from different positions. Seventeen professional soccer players from a Brazilian club participated in the study and were monitored during six official matches by a GPS device. Collective positional data were compared between the two halves using a paired t-test, while the spatial exploration index was compared between the playing positions and within the halves by a mixed two-way ANOVA. The results revealed no differences between the two halves for the collective variables. The highest values of spatial exploration index were reported for central midfielders and wing forwards. We conclude that the tactical behavior of professional soccer players is position-dependent, and midfielders are the most exploratory players on the pitch.

Influence of Match Status on Players' Prominence and Teams' Network Properties During 2018 FIFA World Cup

The analyses of players and teams’ behaviors during the FIFA World Cup may provide a better understanding on how football tactics and strategies have developed in the past few years in elite football. The Social Network Analysis (SNA) has been carried out in the investigations about passing distribution, improving the understanding on how players interact and cooperate during a match. In football official matches, studies have used the SNA as a means of coding players’ cooperation and opposition patterns. However, situational variables such as match status were previously investigated and associated with changes on teams’ dynamics within and/or between matches, but were not considered in studies based on Social Network Analysis. This study aimed to analyze the influence of match status on teams’ cooperation patterns and players’ prominence according to playing positions during 2018 FIFA World Cup. Fourteen matches of the knockout stage were analyzed. Macro and micro network measures were obtained from adjacency matrixes collected for each team, in each match status (winning, drawing, and losing). A one-way ANOVA was used to compare teams’ networks (macro-analysis variables) within each match status, while a two-way ANOVA (match status × playing position) was used to compare the micro-analysis variables. Results showed no differences between match status for macro analysis. Winning situations induced higher prominence in central midfielders (0.107; p = 0.001), wide midfielders (0.093; p = 0.001), and center forward (0.085; p = 0.001), while in losing situations lower prominence levels were observed for goalkeepers (0.044; p = 0.001) and center forward (0.074; p = 0.001). Data revealed that teams do not change macrostructures according to match status. On the other hand, the microstructures showed important adaptations regarding game styles, with changes in players’ behaviors according to playing positions. In general, the levels of centrality and prestige in players of different positions indicated a more direct play style in winning situations and a more build-up style in losing situations. These results allow a better understanding about the influence of match status on players’ and teams’ performance during high-level football competitions and may help coaches to improve athletes’ performance in these situations.

IMPACT OF COMPETITIVE LEVEL AND AGE ON THE STRENGTH AND ASYMMETRY OF YOUNG SOCCER PLAYERS

ABSTRACT Introduction: Muscular strength is an essential capacity for soccer players; however, the profile of this capacity has not yet been clearly established in young players. Objective: To compare muscular strength performance in the countermovement jump (CMJ) task and the presence of lower limb asymmetry among soccer athletes of the under 15 (U15), under 17 (U17) and under 20 (U20) categories, and between two teams of different competitive levels. Methods: One hundred and fifty one young soccer players of three different categories (U15, U17 and U20) from two teams in the Brazilian first and second divisions performed six vertical jumps in a system of two force plates. Ground reaction force (GRF) was used to calculate jump height and to obtain the variables Peak force (FMAX), Impulse (I) and Peak power (PMAX) with regard to body mass and the respective asymmetry values. Results: No differences were found in the performance and asymmetry variable between the categories (Jump height: p=0.23; FMAX: p=0.15; I: p=0.11; PMAX: p=0.32; FMAX asymmetry: p=0.21; I asymmetry: p=0.58; PMAX asymmetry: p=0.58). The first division club had higher muscle strength and asymmetry values than the second division club (Jump height: p<0.01; I: p<0.01; PMAX: p<0.01; FMAX asymmetry: p<0.01; I asymmetry: p<0.01; PMAX asymmetry: p<0.01), except for FMAX (p=0.63). No variable had an interaction effect (club x category). Conclusion: As categories progress, jump height, relative I, PMAX and FMAX values and their respective asymmetries are stable. The asymmetry and strength performance of the first division club were higher than that of the second division club, except for FMAX, indicating that the competitive level may influence strength performance and the development of asymmetry. Level of Evidence II; Diagnostic study – Investigating a diagnostic test.

TEST-retest reliability of kinetic variables measured on campus board in sport climbers

Sport climbers frequently use campus board (CB) to improve their upper limb strength under similar conditions of high-difficulty sport climbing routes. The objective of this study was to assess the test-retest reliability of peak force and impulse measured using a CB instrumented with two load cells on starting holds. The same evaluator examined 22 climbers on two days with 48 h between the assessments. The participants performed five concentric lunges (CL) and five lunges with stretch-shortening cycle with 1 min intervals between repetitions and 10 min between exercises. All variables were associated with significant intraclass correlation coefficient (ICC) values (p = 0.001), and none variable showed systematic errors (p > 0.05). Peak force ICC was higher than 0.88, and the standard error of measurement (SEM%) was less than 5%. Impulse ICC for the CL was greater than 0.90, and the SEM% was less than 14%. We conclude that the kinetic variables measured using the CB were reliable. The ability of the hands to maintain contact with the holds (peak force) and the abilities of the arms and shoulders vertically move the centre of mass (impulse) should be taken into account by coaches on CB training prescription as well for further research.

DEMANDAS FÍSICAS SÃO INFLUENCIADAS PELO ESTATUTO POSICIONAL EM PEQUENOS JOGOS DE FUTEBOL?

RESUMO Introdução: Pequenos jogos são utilizados no treinamento de jogadores de futebol porque replicam as demandas técnicas, táticas, físicas e fisiológicas num contexto semelhante ao do jogo. Contudo, não se sabe se esse modo de treinamento é suficiente para demandar as especificidades observadas no jogo com relação ao estatuto posicional. Objetivo: Comparar a demanda física de defensores, meio-campistas e atacantes durante a realização de pequenos jogos de futebol. Métodos: Dezoito jovens jogadores de futebol (16,4 anos) participaram do estudo, divididos em seis equipes compostas por um defensor, um meio-campista e um atacante. Realizaram-se seis sessões de coleta de dados constituídas por duas séries de quatro minutos com quatro minutos de pausa passiva. Utilizou-se equipamento de GPS de 15 Hz para coleta das informações. Os dados foram analisados por meio da ANOVA One-way e teste de Kruskal-Wallis, com nível de significância em 5%. Resultados: Observou-se diferença significativa na demanda física de jogadores de diferentes estatutos posicionais. Meio-campistas percorreram maior percentual da distância em velocidades superiores, enquanto defensores apresentaram distância total reduzida, aumento da distância na velocidade inferior e redução na realização de ações de aceleração. Conclusão: Demandas físicas variam durante a realização de pequenos jogos em função do estatuto posicional.

Confiabilidade das medidas de demanda física, fisiológica e tática em pequenos jogos com superioridade e igualdade numérica no futebol

DOI: http://dx.doi.org/10.5007/1980-0037.2016v18n5p602 The aim of this study was to investigate the physical, physiological (HR) and tactical demands of small-sided soccer games (SSG) with numerical equality (3x3) and numerical superiority (4x3). Eighteen male players of a soccer team played against each other both types of SSG, both played as two 4-minute bouts interspersed with 4-minute rest. Physical (distances, velocities and accelerations) and HR demands were recorded by a GPS system (15hz) and a heart rate monitor during SSG. The individual tactical behaviors proposed by the System of Tactical Assessment in Soccer were registered by an observer who analyzed the SSG videos. Reliability was verified calculating the intraclass correlation coefficient (ICC) and the absolute and percentage standard error of measurement (SEM and %SEM, respectively), both considering athletes’ individual scores in each SSG bout. As a result, higher number of variables related to physical and physiological demands presented significant ICC values, being classified as moderate to excellent in relation to variables related to tactical demands. Considering these variables that presented significant ICC values in both SSG, the SEM% values found for physical and physiological variables ranged from 3.0 to 42.0%, while those found for the tactical variables ranged from 31.6 to 75.0%. It could be concluded that several variables related to physical and physiological demands present moderate to excellent reliability. Differently, the majority of variables related to tactical demands were not reliable in both types of SSG. 

Task difficulty and inertial properties of hand-held tools: An assessment of their concurrent effects on precision aiming

Aiming hand-held tools at targets in space entails adjustments in the dynamical organization of aiming patterns according to the required precision. We asked whether and how these adjustments are modified by the tool's mass distribution. Twelve participants performed reciprocal aiming movements with a 50-cm long wooden probe. Kinematic patterns of probe movements were used as a window into the behavioral dynamic underlying performance of a reciprocal aiming task. We crossed three levels of task difficulty (IDs 2.8, 4.5 and 6.1) with two types of probe varying in their mass distribution (proximal vs distal loading). Movement duration was affected by task difficulty and probe loading (shorter for larger targets and proximal probe loading). Progressive deviations from a sinusoidal movement pattern were observed as task difficulty increased. Such deviations were more pronounced with proximal probe loading. Results point to a higher degree of non-linearity in aiming dynamics when the probe was loaded proximally, which might reflect employment of additional perceptual-motor processes to control the position of its less stable tip at the vicinity of the targets. More generally, the effects of probe loading on aiming pattern and dynamics suggest that perceptual-motor processes responding to task level constraints are sensitive to, and not independent from, biomechanical, end-effector constraints.

Brain Temperature in Spontaneously Hypertensive Rats during Physical Exercise in Temperate and Warm Environments

This study aimed to evaluate brain temperature (Tbrain) changes in spontaneously hypertensive rats (SHRs) subjected to two different physical exercise protocols in temperate or warm environments. We also investigated whether hypertension affects the kinetics of exercise-induced increases in Tbrain relative to the kinetics of abdominal temperature (Tabd) increases. Male 16-week-old normotensive Wistar rats (NWRs) and SHRs were implanted with an abdominal temperature sensor and a guide cannula in the frontal cortex to enable the insertion of a thermistor to measure Tbrain. Next, the animals were subjected to incremental-speed (initial speed of 10 m/min; speed was increased by 1 m/min every 3 min) or constant-speed (60% of the maximum speed) treadmill running until they were fatigued in a temperate (25°C) or warm (32°C) environment. Tbrain, Tabd and tail skin temperature were measured every min throughout the exercise trials. During incremental and constant exercise at 25°C and 32°C, the SHR group exhibited greater increases in Tbrain and Tabd relative to the NWR group. Irrespective of the environment, the heat loss threshold was attained at higher temperatures (either Tbrain or Tabd) in the SHRs. Moreover, the brain-abdominal temperature differential was lower at 32°C in the SHRs than in the NWRs during treadmill running. Overall, we conclude that SHRs exhibit enhanced brain hyperthermia during exercise and that hypertension influences the kinetics of the Tbrain relative to the Tabd increases, particularly during exercise in a warm environment.

Comportamento tático coletivo em Pequenos Jogos no Futebol: influência de jogadores adicionais

DOI: http://dx.doi.org/10.5007/1980-0037.2016v18n1p62 The aim of this study was to compare the collective tactical behavior between numerically balanced and unbalanced small-sided soccer games. Eighteen male soccer players (mean age 16.4 years) participated in the study. Polar coordinate analysis was performed using positional data obtained with a 15-Hz GPS device. Collective variables including length, width, centroid distance (average point between teammates), and length per width ratio (LPWratio) were collected. Data were analyzed using Friedman’s test. The results showed greater length and width values in 4vs.3 games, while a higher LPWratiowas observed in 3vs.3+2 games compared to the other configurations. In games with an additional player (4vs.3), ball circulation and the increase in effective game space were alternatives to overcome the more concentrated defensive systems near the goal. On the other hand, 3vs.3+2 games allowed more actions in the length axis and a fast reach of the opponent’s goal.

Validação das propriedades psicométricas do RESTQ-Coach na versão brasileira

O objetivo do estudo foi determinar a validade da aplicação do The recovery,stress questionnaire for coaches (RESTQ-Coach) que, na versão brasileira, adotará o nome de Questionário de Estresse e Recuperação para Treinadores Esportivos (RESTQ-Coach-versão brasileira) como ferramenta de avaliação de treinadores esportivos no Brasil. Ainda, o segundo objetivo foi verificar a sua adequação ao modelo teórico proposto por Kallus e Kellmann (1993) através de análises fatoriais confirmatória (AFC) e exploratória (AFE). A amostra deste estudo foi composta por 424 treinadores com idade média de 37,06 (±9,20) anos, de onze modalidades esportivas, sendo cinco coletivas e seis individuais. Os resultados da AFC demonstraram que o modelo original do questionário proposto por Kallus e Kellmann (1993) é inadequado para esta amostragem. Através da AFE identificou-se que a melhor solução para a validação fatorial do instrumento é composta por seis fatores. Esta solução revelou valores de consistência interna geral de α = .85. Os valores dos indicadores de ajustamento do modelo brasileiro de seis fatores da AFE foram: χ² = 9.660,239 e gl = 2695, p=0,001; CFI= 0,96; TLI= 0,95; RMSEA 0,07, os quais expressam a sua qualidade. Conclui-se que a proposta de modelo Kallus e Kellmann (1993) não pode ser confirmada através da AFC nesta amostragem brasileira. E que a melhor solução fatorial para o RESTQ-Coach versão brasileira é composta por seis constructos.