Acute and delayed effects of strength training in ball velocity and accuracy in young competition tennis players

This study aimed to investigate the acute and delayed effects of medicine ball throws and resistance training in ball velocity and accuracy of serve, forehand and backhand in young competition tennis players. A crossover-randomized design was used with 10 competition tennis players (6 girls and 4 boys between 14 and 18 years old). The subjects performed 6 stroke test sessions, 3 for each strength protocol. The velocity and accuracy of strokes were measured before (basal situation), 3 minutes, 24 and 48 hours after the protocol. Medicine ball throws protocol was performed by accomplishing 3 sets of 6 repetitions using a 2 kg ball, throwing it at maximal speed. Resistance training protocol was performed by accomplishing 3 sets of 6 repetitions at 75% one-repetition maximum, lifting the load at maximal speed of bench press, dead lift, one hand row and half squat. There were no significant (p > 0.05) differences in all strokes, regarding ball velocity and accuracy after each method and each recovery time, compared to the basal situation. These results suggest that medicine ball throws and resistance training methods have no acute and delayed detrimental effects on stroke velocity and accuracy in young competition tennis players.

Softball bat inertial considerations and their effects on female softball swing mechanics and estimated bat performance

This paper discusses the role of the inertial properties in the design and selection of the softball bat, and their interrelated effects on female softball swing mechanics and bat performance. The study was performed using 14 collegiate subjects whose swings were analyzed via a computer model, which included methods for estimating post-impact ball velocity. The model was driven kinematically by subject swing recordings using two different trial bats with markedly different inertial properties. Using this method, the following information was determined: subjects altered their linear kinetic inputs while applying consistent angular kinetic inputs to maintain nearly consistent trajectories; subjects compensated for increased bat inertia by modification of the bat instantaneous center-of-rotation trajectory ( ICR); and swing trajectory influenced the bat’s inertial feel, actual, and ideal impact locations, and batted-ball velocity. Subsequently, the mass properties of 27 collegiate level bats were input into the model for each subject trial. Using this information, the relative changes in kinetic inputs were quantified and the performance of the bats was estimated. Results showed that bat inertial properties varied considerably, and independent manipulation of individual properties was evident. In addition, subject kinetic inputs and bat performance measures were most affected by changes in mass center (CG) location, mass, and CG inertia. A modified definition of IGRIP based upon the ICR was presented, and practical implications for designers and practitioners were offered based upon these findings.

Risk Factors of Shoulder and Elbow Injuries in Baseball: A Scoping Review of 3 Types of Evidence

Background: Shoulder and elbow overuse injuries are the most common problems in baseball players. No scoping review has compared the findings from different types of evidence. Purpose: To map the broad evidence from 3 types of evidence (epidemiological, biomechanical, and narrative) on potential risk factors for shoulder and elbow injuries in baseball and identify gaps in the existing literature to guide future research. Study Design: Scoping review. Methods: Eight electronic databases were searched from inception to May 14, 2020. Any peer-reviewed papers that investigated or discussed potential risk factors for shoulder and elbow injuries in baseball were included. Results: A total of 302 studies (107 epidemiological studies, 85 biomechanical studies, and 110 narrative reviews) were included. Risk factors were categorized into 9 domains: sports profiles, physical characteristics/functions, pitching mechanics, performance, behavioral, psychosocial, biological and developmental, injury/sports profiles, and environmental factors. Studies were consistent in supporting limited shoulder range of motion (ROM) and player positions (pitchers or catchers) as risk factors for shoulder injuries. For elbow injuries, the majority of the included studies suggested that being pitchers or catchers and working with higher ball velocity can be risk factors. Conclusion: Findings were consistent in some risk factors, such as limited shoulder ROM and positions. However, findings were inconsistent or limited for most factors, and substantial research gaps were identified. Research assessing those factors with inconsistent or limited evidence in the current literature were recognized to be priorities for future studies.

Individualised Ball Speed Prediction in Baseball Pitching Based on IMU Data

Ball velocity is considered an important performance measure in baseball pitching. Proper pitching mechanics play an important role in both maximising ball velocity and injury-free participation of baseball pitchers. However, an individual pitcher’s characteristics display individuality and may contribute to velocity imparted to the ball. The aim of this study is to predict ball velocity in baseball pitching, such that prediction is tailored to the individual pitcher, and to investigate the added value of the individuality to predictive performance. Twenty-five youth baseball pitchers, members of a national youth baseball team and six baseball academies in The Netherlands, performed ten baseball pitches with maximal effort. The angular velocity of pelvis and trunk were measured with IMU sensors placed on pelvis and sternum, while the ball velocity was measured with a radar gun. We develop three Bayesian regression models with different predictors which were subsequently evaluated based on predictive performance. We found that pitcher’s height adds value to ball velocity prediction based on body segment rotation. The developed method provides a feasible and affordable method for ball velocity prediction in baseball pitching.

Relación de las características antropométricas con la velocidad del balón en el fútbol (Relationship of Anthropometric Variables with speed ball in soccer)

En el fútbol la posibilidad de generar tiros estáticos con alta velocidad, puede determinar el resultado de un juego al disminuir la posibilidad de reacción del guardameta. La investigación se planteó analizar las características antropométricas con la velocidad del balón en el fútbol. Se evaluaron 17 futbolistas masculinos de la selección del estado Barinas categoría sub-20. (173,2 cm ±6,9 y 65 kg ±7,8). Las variables antropométricas se recolectaron según protocolo de ISAK, para la valoración de la proporcionalidad y la composición corporal se utilizó el método escalable, comparándose mediante un prototipo ontogénico deportivo; se aplicó una prueba de la velocidad pico del balón en el tiro estático sin intención de precisión utilizando un radar doopler para el registro de las velocidades. Los resultados muestran que existe una correlación significativa (<,05) directa para el índice Z de la altura ileoespinal, e inversa para el índice Z del panículo del muslo con respecto a la velocidad máxima del balón en el tiro estático, ambas correlaciones presentan un coeficiente de determinación de 24% y 25,8% respectivamente. No se hallaron correlaciones (>,05) para los índices Z de la altura tibial lateral, la longitud trocánter tibial lateral, ni para el área magra del muslo con la velocidad máxima del balón. De esta manera la menor acumulación de tejido adiposo y mayor altura del miembro inferior se consideran variables relacionadas a la generación de mayores velocidades con el balón. Abstract. In Soccer the possibility of generating static shots with high speed can determine the outcome of a game to reduce the chance of reaction of the goal keeper. This research study analyzes the relationship of body proportionality and body composition with maximum ball speed shooting of soccer. 17 male players under the age of 20 (U-20) of Barinas State (173.2 cm ± 6.9 and 65 ± 7.8 kg) were evaluated. The anthropometric variables were collected according to ISAK protocol. For the assessment of proportionality and body composition scalable method was used being compared through an ontogenetic sport prototype. A test of peak ball velocity was applied in the static shot without focusing on precision using a doopler radar to record speeds. The results show that there is a significant direct correlation (<.05) for Z ileoespinal height index, and inverse for Z index panículo thigh with respect to the maximum speed of the ball in the static shot. Both correlations present a coefficient of determination of 24% and 25.8% respectively. No correlations (> -.05) were found for the Z indices of lateral tibial height, lateral tibial length trochanter or for the lean thigh area with the maximum speed of the ball. Therefore, the lower accumulation of adipose tissue and greater height of the lower limb are considered variables related to the generation of higher velocities with the ball.

The Effects of Exercise Difficulty and Time-of-Day on the Perception of the Task and Soccer Performance in Child Soccer Players

In soccer, accurate kicking skills are important determinants of successful performance. A successful kick must meet several criteria, including speed, accuracy, and timing. In fact, players who are able to kick the ball more accurately under various difficulties, such as time pressure, space constraints, the opponent’s pressure, and the distance between the kicking point and the goal, have a clear advantage during soccer games. The aim of the present study was to investigate the effect of exercise difficulty and time-of-day on perceived task difficulty and kicking performance. Accordingly, 32 boys (age: 11 ± 0.7 years; height: 1.45 ± 0.07 m; body-mass: 38.9 ± 7.8 kg) performed shooting accuracy tests under two difficulty levels (distance (long-distance (LD) vs. short-distance (SD)) and time pressure (Without-time-pressure (WTP) vs. With-time-pressure (TP)) at 08:00 h and 17:00 h. Absolute-error, variable-error, and constant-error were evaluated during the kicking tasks, in addition to ball velocity and shooting quality. Moreover, rating-of-perceived-exertion score (RPE), feeling-scale (FS), and perceived difficulty were completed immediately at the end of each test. The results showed that shooting quality was not affected by the time-of-day, but it was better in WTP vs. TP (p < 0.05), and in SD vs. LD (p < 0.05), respectively. Higher values for FS and lower values for RPE were observed in the morning compared to the afternoon (p < 0.05) and in WTP vs. TP (p < 0.05). In conclusion, specific soccer skills of boys were not time-of-day dependent, but they may be associated with time pressure and task difficulty.

Comparison of Kinematic Sequences During Curveball and Fastball Baseball Pitches

Performance of a sequential proximal-to-distal transfer of segmental angular velocity (or Kinematic Sequence) is reported to reduce stress on musculoskeletal structures and thus the probability of injury while also maximizing ball velocity. However, there is limited investigation regarding the Kinematic Sequence of the five body segments (Pelvis, Trunk, Arm, Forearm, and Hand) among baseball pitchers. Some biomechanical and epidemiology studies have reported an association of the curveball with increased risk for elbow injury among youth pitchers. Kinematic Sequences with altered distal upper extremity (forearm and hand) sequences have been associated with greater elbow valgus and shoulder external rotation torques compared to other Kinematic Sequences. Identifying Kinematic Sequence patterns during curveball pitches may lead to improved understanding of injury susceptibility. This study investigated the Kinematic Sequence patterns (and their variability) during curveball pitching and compared them to the sequences identified during fastball pitches. Using 3D motion analyses, 14 baseball pitchers (four high school, eight college, and two professional) performed 5–6 curveball pitches and 12 pitchers also threw fastball pitches in a simulated bullpen session. Eleven different curveball Kinematic Sequences were identified and 8 fastball Kinematic Sequences. There was no significant variability in the number of Kinematic Sequences performed between the two pitch types, (Z = −0.431, p = 0.67). The median number of KSs performed by each group was 2.5. The most frequently used Kinematic Sequences for both pitch types were due to alteration in the sequence of the distal segments. The total percentage of Kinematic Sequences with altered distal segment sequencing for the curveball pitches was 49% and 43% for fastball pitches. Identifying the frequency of Kinematic Sequences with altered timing of hand and forearm peak velocities across pitch types may lead to a better understanding of the stresses that individual pitchers incur.

The Effects of Plyometric Conditioning Exercises on Volleyball Performance with Self-Selected Rest Intervals

Post-activation performance enhancement remains a topic of debate in sport science. The purpose of this study was to examine the effects of lower-body plyometric conditioning activity (CA) with a self-selected intra-complex rest interval on upper and lower-body volleyball specific performance. Eleven resistance-trained female volleyball players participated in the study (age: 20 ± 2 years; body mass: 67.8 ± 4.4 kg; height: 178 ± 6 cm; half back squat one-repetition maximum: 78.6 ± 10.2 kg; experience in resistance training: 5.5 ± 2.1 years and in volleyball training: 10 ± 2.3 years). Each participant performed a plyometric CA followed by two different sport-specific tests: an attack jump and a standing spike attack. The changes in jump height (JH), relative mean power output (MP) and ball velocity (BV) were analyzed before and after the CA with self-selected rest intervals. The applied plyometric CA with self-selected intra-complex rest intervals led to an insignificant decline in JH (p = 0.594; effect size [ES]: −0.27) and MP (p = 0.328; ES: −0.46) obtained during the attack jump as well as a significant decline in BV (p = 0.029; ES: −0.72) during the standing spike attack. This study showed that a plyometric CA with self-selected intra-complex rest intervals failed to elicit localized and non-localized PAPE effect in a group of sub-elite volleyball players.