Can the structure of motor variability predict learning rate?

Recent studies show that motor variability is actively regulated as an exploration tool to promote learning in reward-based tasks. However, its role in learning processes during error-based tasks, when a reduction of the motor variability is required to achieve good performance, is still unclear. In this study, we hypothesized that error-based learning not only depends on exploration but also on the individuals’ ability to measure and predict the motor error. Previous studies identified a less auto-correlated motor variability as a higher ability to perform motion adjustments. Two experiments investigated the relationship between motor learning and variability, analyzing the long-range autocorrelation of the center of pressure fluctuations through the score of a Detrended Fluctuation Analysis in balance tasks. In Experiment 1, we assessed the relationship between variability and learning rate using a standing balance task. Based on the results of this experiment, and to maximize learning, we performed a second experiment with a more difficult sitting balance task and increased practice. The learning rate of the 2 groups with similar balance performances but different scores was compared. Individuals with a lower score showed a higher learning rate. Because the scores reveal how the motor output changes over time, instead of the magnitude of those changes, the higher learning rate is mainly linked to the higher error sensitivity rather than the exploration strategies. The results of this study highlight the relevance of the structure of output motor variability as a predictor of learning rate in error-based tasks

Descriptive profile of hip range of motion in elite tennis players

Objective: To describe the range of motion (ROM) profile (flexion, extension, abduction, internal and external rotation) of the hip in elite tennis players; and (b) to analyse if there are sex-related differences in the hip ROM. Design: Cohort study. Setting: Controlled laboratory environment. Participants: 81 male and 28 female tennis players completed this study. Main outcome measures: Descriptive measures of passive hip flexion, extension and abduction, and internal and external active and passive hip rotation ROM were taken. Magnitude-based inferences on differences between sex (males vs. females) and hip (dominant vs. non-dominant) were made by standardising differences. Results: No clinically meaningful bilateral and sex-related differences in any of the hip ROM measures. In addition, it was found that both males and females had restricted mobility measures on hip flexion (25 ] and passive [35 ]) Conclusions: Asymmetric hip joint ROM measures found during clinical examination and screening may indicate abnormalities and the need of rehabilitation (e.g., flexibility training). In addition, clinicians should include specific exercises (e.g., stretching) in their conditioning, prevention and rehabilitation programmes aiming to avoid restricted mobility of hip flexion (males ¼ 74 ; females ¼ 78 ), extension (males ¼ 1.5; females ¼ 0.4), abduction (males ¼ 35 ; females ¼ 34 ) and internal rotation (males ¼ 30 ; females ¼ 35) that might be generated as a consequence of playing tennis

Prescripció de programes d’entrenament abdominal. Revisió i posada al dia

L’èxit dels programes d’entrenament abdominal depèn de factors múltiples, principalment, del nombre i tipus d’exercicis utilitzats, del tipus i velocitat de contracció muscular i de la intensitat, volum i freqüència de l’entrenament. L’objectiu del nostre treball és revisar aquests factors i aportar informació per a la prescripció de programes d’entrenament abdominal. Segons els treballs existents a la literatura, cada sessió ha d’combinar tipus d’exercicis diversos: exercicis de flexió del tronc per al desenvolupament del recte de l’abdomen, exercicis de rotació i de flexió lateral per al desenvolupament dels músculs oblics i exercicis d’estabilització per millorar la funció abdominal estabilitzadora. Es recomana la utilització d’intensitats elevades (pesos, màquines de musculació, etc.) per tal de desenvolupar la força abdominal i grans volums d’entrenament (15-30 repeticions per sèrie o més) per a l’increment de la resistència. En general, es realitzen tres sessions d’entrenament setmanals en dies alterns, encara que dues sessions podrien ser suficients per al condicionament de la musculatura abdominal en individus no entrenats

Comparison of shoulder rotation range of motion in professional tennis players with and without history of shoulder pain

A glenohumeral internal rotation deficit of the dominant shoulder relative to the non-dominant shoulder (GIRD) is considered a risk factor for shoulder injury in overhead athletes. The aim of this study was to investigate whether professional tennis players with a history of self-reported shoulder pain show differences in rotation range of motion (ROM) of the dominant and non-dominant shoulder compared to asymptomatic controls. Forty-seven professional tennis players belonging to the Association of Tennis Professionals World Tour took part in the study: 19 with shoulder pain history and 28 without. Passive shoulder ROM was measured using a process of photography and software calculation of angles. The dominant shoulder had reduced internal rotation (IR) ROM and total rotation ROM, and increased external rotation (ER) ROM compared to the non-dominant side. These differences did not correlate significantly with years of tennis practice, years of professional play, nor the players' age. However, glenohumeral rotation ROMs correlated negatively with the duration of tennis practice and players' age. Although tennis players with shoulder pain history showed less IR ROM in both shoulders compared with the no-pain group, no significant differences between groups were found for ER ROM, side-to-side ROM asymmetries, years of tennis practice or years of professional play. In professional tennis players, limited IR ROM rather than a GIRD, seems to be associated with shoulder pain history, duration of tennis practice and the players' age, when compared to a similar cohort with no history of shoulder pain

EFFECT OF PERFORMANCE SPEED ON THE KINEMATICS AND KINETICS OF TWO TRUNK AND HIP STRENGTHENING EXERCISES

The aim of this work was to study the effect of speed on the sit-up (SU) and leg raising-lowering (LRL) exercise technique. Seventeen subjects volunteered to participate, performing at 3 cadences. Video 3D analysis was conducted and ground reaction forces were record. The anterior-posterior displacement of the centre of pressure (COP) and mean range of motion (ROM) for 6 angles were calculated. Results indicate that when SU speed increases, hip and knee ROM increase, while there is a decrease in the upper trunk flexion. In the LRL there is a decrease in the pelvic tilt and hip angle, and an increase in the knee angle. It seems that in higher speed exercises, subjects modified their technique to keep up with the cadence. Coaches and trainers should control the subjects’ technique during the execution of these high speed exercises

Prescripción de programas de entrenamiento abdominal. Revisión y puesta al día

El éxito de los programas de entrenamiento abdominal depende de múltiples factores, principalmente, del número y tipo de ejercicios utilizados, del tipo y velocidad de contracción muscular y de la intensidad, volumen y frecuencia del entrenamiento. El objetivo de nuestro trabajo es revisar estos factores y aportar información para la prescripción de programas de entrenamiento abdominal. Según los trabajos existentes en la literatura, cada sesión debe combinar varios tipos de ejercicios: ejercicios de flexión del tronco para el desarrollo del rectus abdominis, ejercicios de rotación y de flexión lateral para el desarrollo de los músculos oblicuos y ejercicios de estabilización para mejorar la función abdominal estabilizadora. Se recomienda la utilización de intensidades elevadas (pesas, máquinas de musculación, etc.) con el objeto de desarrollar la fuerza abdominal y grandes volúmenes de entrenamiento (15-30 repeticiones por serie o más) para el incremento de la resistencia. Generalmente, se realizan tres sesiones de entrenamiento semanales en días alternos, aunque dos sesiones podrían ser suficientes para el acondicionamiento de la musculatura abdominal en individuos no entrenados

Activació dels músculs del tronc durant situacions que requereixen l’estabilització del raquis. Estudi de cas únic

L’objectiu d’aquest estudi va ser analitzar la intensitat de la contracció i la coordinació de 14 músculs del tronc i del muscle d’un subjecte durant la recepció i el llançament d’una pilota medicinal (acció pliomètrica), una acció d’embranzida en posició dempeus (pressió de pit horitzontal amb politja) i l’ús del Bodyblade® (barra flexible l'oscil·lació de la qual sotmet el cos a vibracions i desequilibris continus). Igualment, amb l'objecte de facilitar la discussió en relació amb l'estabilització activa del raquis, es va registrar la resposta dels músculs esmentats durant l'aplicació controlada sobre el tronc de càrregues i descàrregues desequilibrants. Els nostres resultats indiquen que l'activació dels músculs del tronc és important, tant per a estabilitzar el raquis davant pertorbacions i desequilibris sobtats, com per a l'execució d'accions on els membres superiors manegen objectes. En aquest sentit, la coactivació dels músculs del tronc va ser necessària per estabilitzar el raquis davant les oscil·lacions del Bodyblade® i davant les forces de reacció produïdes en empènyer una càrrega pesada en posició erecta. De la mateixa manera, la recepció i el llançament immediat de la pilota medicinal és una activitat relativament complexa que requereix l'acció coordinada dels músculs del tronc i de les extremitats

Reliability assessment and correlation analysis of 3 protocols to measure trunk muscle strength and endurance

Different methods have been developed to quantify trunk muscle strength and endurance. However, some important protocol characteristics are still unclear, hindering the selection of the most suitable tests in each specific situation. The aim of this study was to examine the reliability and the relationship between 3 representative tests of the most common type of protocols used to assess trunk muscle strength and endurance. Twenty-seven healthy men performed each test twice spaced 1 month apart. Trunk strength and endurance were evaluated with an isokinetic dynamometer and 2 field tests including Biering-Sørensen test and Flexion–rotation trunk test. All tests showed a good relative consistency (intraclass correlation coefficient [ICC]> 0.75), except for the isokinetic endurance variables which had low–moderate reliability (0.37 0.65). Absolute reliability seemed slightly better in the isokinetic protocol than in the field tests, which showed about 12% of test–retest score increase. No significant correlations were found between test scores. After a familiarisation period for the field tests, the 3 protocols can be used to obtain reliable measures of trunk muscle strength and endurance. Based on the correlation analysis, these measures are not related, which highlights the importance of selecting the most suitable trunk test for each situation

Isokinetic trunk flexion–extension protocol to assess trunk muscle strength and endurance: Reliability, learning effect, and sex differences

PurposeThe purpose of this study was to examine the reliability and the learning effect of an isokinetic trunk flexion–extension protocol designed to simultaneously assess trunk muscle strength and endurance. In addition, the effect of the participants' sex on the reliability data was examined.MethodsFifty-seven healthy and physically active young men (n = 28) and women (n = 29) performed the isokinetic protocol 5 times, separated by a week between each of the first 4 sessions and by a month between the last 2 sessions. The protocol consisted of performing 4 trials of 15 maximum flexion–extension concentric exertions at 120°/s (range of trunk motion = 50°). The absolute and relative peak torque and total work were calculated to assess trunk flexion and extension strength. In addition, endurance ratio, modified endurance ratio, fatigue final ratio, recovery ratio, and modified recovery ratio variables were used for the assessment of trunk muscle endurance in both directions.ResultsRegarding the absolute reliability, no relevant changes were found between paired-comparison sessions for most strength and endurance variables, except for total work and relative total work variables in the flexion movement in both sexes. In addition, the typical error of the isokinetic variables was lower than 10% in both males and females, and minimum detectable changes ranged from 7%–20%, with a tendency to be higher in females and in endurance variables. The strength variables showed high intraclass correlation coefficients (ICC; >0.74); however, for the endurance variables only the endurance ratio and the modified endurance ratio obtained moderate to high ICC values (0.57 < ICC < 0.82). In addition, the analysis of the variance reported no significant differences between consecutive pairs of sessions for most variables in both sexes.ConclusionOverall, these findings provide clinicians, trainers, and researchers with a 10-min single-session protocol to perform a reliable muscle strength and endurance evaluation of trunk flexor and extensor muscles, all within the same protocol

Progressions of core stabilization exercises based on postural control challenge assessment

Purpose The intensity progression of core stabilization exercises (CSEs) is usually based on personal criteria rather than on objective parameters. To develop exercise progressions for four of the most common CSEs based on the postural control challenge imposed on the participants, and to analyze the effect of participants’ sex and postural control level on these progressions. Methods Seventy-six males and females performed five variations of front bridge, back bridge, side bridge and bird-dog exercises on two force platforms. The mean velocity of the center of pressure displacement was calculated to assess exercise intensity through the measurement of the participants’ body sway (PBS). Results In general, long bridges produced higher PBS than short bridges, bridging with single leg support produced higher PBS than bridging with double leg support and bridging on a hemisphere ball produced higher PBS than bridging on the floor. The most difficult bridging variations were those performed on a hemisphere ball with single leg support. Regarding the bird-dog, two-point positions produced higher PBS than three-point positions and the positions performed on a hemisphere ball produced higher PBS than those performed on the floor. Conclusion The CSE progressions obtained by males and females were very similar. However, the participants with high trunk control showed less significant differences between exercise variations than the participants with low trunk control, which shows the need to individualize the progressions according to the participants’ training level. Overall, this study provides useful information to guide the prescription of CSE progressions in young physically active individuals