Ball Kicking Research Articles

The Level of Accuracy of the Expert System Training Data Uses the Naive Bayes Algorithm to Measure the Distance of A Ball Kick

The importance of data accuracy in the implementation of long-distance kicking tests as basic data for coaches requires adequate facilities and requires large costs, so technology is needed for facility and budget efficiency. The purpose of this research is to determine the accuracy of expert system training data using the Naive Bayes algorithm to measure the distance of a ball kick. The research design used is a quantitative method with an experimental model. The type of experimental design is pre-experimental design. Participants amounted to 100 male soccer players with saturated sample technique. The instruments were question forms to obtain information on gender and age, while to measure leg muscle strength and leg muscle strength using a tape roll meter and leg dynamometer. Data validity uses calibrated tools. The data analysis technique uses probability (naive bayes) using data testing and evaluation. The results of the study obtained the accuracy level of the expert system training data using the naïve bayes algorithm with the best accuracy of 100%. There is a training data learning model used using the 99 scheme and test 1 and 98 and test 2. The conclusion is that the accuracy level of expert system training data using the naive bayes algorithm is declared to be accountable for use in classifying new data. The contribution for further research is testing using new data to determine the level of accuracy further to improve accuracy in learning training data.

The Effects of a 6-Week Plyometric and Sprint Interval Training Intervention on Soccer Player's Physical Performance.

Despite the well-documented benefits of sprint interval training (SIT) and plyometric training (PT) in improving the physical fitness of soccer players, it remains unclear which of these training methods is superior for enhancing players' aerobic and anaerobic performance. Therefore, this study aimed to compare the effects of SIT and PT on physical performance measures of male soccer players. Thirty male soccer players were randomly assigned to PT (n = 10), SIT (n = 10), and an active control group (CON, n = 10). Before and after the training period, participants underwent a battery of tests consisting of vertical jump, Wingate, linear sprint with and without ball dribbling, change of direction, ball kick, and the Yo-Yo intermittent recovery level 1 (Yo-Yo IR1) tests. Both groups exhibited similar improvements in maximal kicking distance (PT, effect size [ES] = 0.68; SIT, ES = 0.92) and measures of aerobic fitness including maximum oxygen uptake (PT, ES = 1.24; SIT, ES = 1.26) and first (PT, ES = 0.85; SIT, ES = 1.08) and second (PT, ES = 0.86; SIT, ES = 0.98) ventilatory thresholds. However, PT intervention resulted in greater changes in vertical jump (ES = 1.72 vs. 0.82, p = 0.001), anaerobic power (peak power, ES = 1.62 vs. 0.97, p = 0.009; mean power, ES = 1.15 vs. 1.20, p = 0.05), linear speed (20-m, ES = -1.58 vs. -0.98, p = 0.038; 20-m with ball, ES = -0.93 vs. 0.71, p = 0.038), and change of direction ability (ES = -2.56 vs. -2.71, p = 0.046) than SIT. In conclusion, both PT and SIT demonstrated effectiveness in enhancing aerobic performance among male soccer players. However, PT yielded superior improvements in anaerobic power, vertical jump, linear speed, and change of direction performance compared to SIT. These findings suggest that PT may offer additional benefits beyond aerobic conditioning.

Moderate-dose caffeine enhances anaerobic performance without altering hydration status.

The effects of direct nutritional supplements on athletic performance are still being investigated and arouse curiosity. Only one study in the literature was found that investigated the kicking speed performance of futsal players following low-dose caffeine supplementation (3 mg/kg); thus, the question of whether caffeine supplementation improves kicking speed as well as essential physical parameters in soccer players is still controversial. Therefore, the aim of this study was to determine the effect of caffeine supplementation on vertical jump (VJ), sprint, reaction time, balance, change of direction (COD), and ball-kicking speed in soccer players. In a double-blind, cross-over design, nine moderately trained male soccer players (21.11 ± 2.02 years, 171.22 ± 6.14 cm, 71.78 ± 10.02 kg) consumed caffeine (6 mg/kg) or a placebo 60 min before completing balance, reaction time, vertical jump, agility, 30 m sprint, and ball-kicking speed tests. Greater VJ height (p = 0.01) and power (p = 0.08), and faster completion time according to the Illinois Agility Test (p = 0.08) were found following caffeine supplementation compared to placebo. Elapsed time (p = 0.01), average (p = 0.01) time, and the slowest reaction times (p = 0.016) were significantly reduced after caffeine consumption compared to placebo supplementation. Caffeine intake significantly improved VJ, agility, and reaction time (p < 0.05) but did not affect 30 m sprint, ball-kicking speed, balance, and RPE values in soccer players (p > 0.05). Although non-significant, caffeine intake also improved sprint (0.67%) and ball kicking (2.7%) performance percentages. Also, caffeine consumption did not induce dehydration, and the athletes' body hydration levels were normal. These findings support the use of caffeine supplementation as an effective nutritional ergogenic aid to enhance anaerobic performance, at least for vertical jumps, COD speed, and reaction time, in trained male soccer players.

Sequencing Effects of Concurrent Strength and Endurance Training on Selected Measures of Physical Fitness in Young Male Soccer Players: A Randomized Matched-Pairs Trial

BackgroundVarious physical fitness qualities such as muscle strength, speed and endurance are related to soccer performance. Accordingly, the combination of strength and endurance training (i.e., concurrent training [CT]) is an often-encountered training regimen in soccer. Less is known about the effects of CT sequencing on performance in young soccer players. The aim of this study was to assess the sequencing effects of strength and intermittent endurance training applied within the same training session (intrasession) on measures of physical fitness and soccer performance in young soccer players.MethodsFifty male adolescent soccer players volunteered to participate in this study which was conducted in the Netherlands in 2019. Players were randomly assigned to a strength-endurance (SE) or an endurance-strength (ES) group in matched pairs based on their countermovement jump (CMJ) performance at baseline. Both groups completed a 12-weeks in-season training program with two weekly CT sessions. Training sessions consisted of 15 min plyometric exercises and 15 min soccer-specific intermittent endurance training. Both groups performed the same training volumes and the only difference between the groups was the CT intrasession sequencing scheme (SE vs. ES). Pre and post intervention, proxies of muscle power (CMJ, squat jump [SJ]), linear sprint speed (30-m sprint test), agility (Illinois test with / without ball), and soccer performance (ball kicking velocity) were tested.ResultsData from 38 players aged 14.8 ± 1.0 years (body height 172.9 ± 8.1 cm, body mass: 57.0 ± 7.2 kg, soccer experience: 8.8 ± 2.8 years, age from peak-height-velocity [PHV]: +1.2 ± 1.0 years) were included. Significant main time effects were found for CMJ (p = 0.002, d = 0.55), SJ (p = 0.004, d = 0.51), the Illinois agility test with ball (p = 0.016, d = 0.51), and ball kicking velocity (p = 0.016, d = 0.51). Significant group-by-time interactions were observed for 30-m linear sprint speed (p < 0.001, d = 0.76) with ES showing greater improvements (p = 0.006, d = 0.85, Δ-5%).ConclusionsBoth CT-sequencing types improved performance in the tests administered. The intrasession CT sequencing (SE vs. ES) appears not to have a major impact on physical fitness adaptations, except for linear sprint speed which was in favor of ES.

The Role of Upper Body Motions in Stationary Ball-Kicking Motion: A Systematic Review

AbstractA ball-kicking motion requires a coordinated sequencing of all body segments for maximum ball release speed. Evidence of the role of upper body rotations and motor coordination during a ball-kicking motion is inconsistent among existing evidence. This study aimed to systematically review the role of upper body rotations on all modes of ball kicking and performance metrics. A comprehensive search of seven electronic databases from the inception was conducted. Studies reporting on the relationships between upper body rotation, and ball-kicking performance were included. From 1486 potentially relevant studies, we analysed 27 studies involving 457 participants. These studies encompassed instep soccer kicks (n = 21), inside-of-the-foot soccer kicks (n = 1), rugby place kicks (n = 4) with a stationary ball, and a volley kick (n = 1). Methodological quality assessment was performed using Standard Quality Assessment Criteria. Our results provide moderate evidence that increasing thoracolumbar rotations along the longitudinal axis and the transverse plane can enhance ball-releasing velocity through a "whip-like effect" based on the kinetic link principle. However, to gain a comprehensive understanding, further research is needed to explore the effects of timing and the ranges of motion of all relevant upper and lower body segments on ball release velocity and its potential influence on ball release accuracy. The current coaching manuals do not emphasise the significance of upper body rotation, indicating a pressing requirement for revisions in training guidelines to enhance ball-kicking performance.

Holistic approach to testing ball kicking mechanics and outcome metrics in soccer: methodological aspects, observation and intervention (PhD Academy Award)

Holistic approach to testing ball kicking mechanics and outcome metrics in soccer: methodological aspects, observation and intervention (PhD Academy Award)

Impact of Task Oriented Training on Activities of Daily Living in Post Stroke Rehabilitation: A Single Arm Randomised Controlled Trial

Introduction: There are several complications following the stroke including reduced functional independence, inability to maintain adequate posture, alterations in daily activities and several others. Physical therapy intervention aims at improving the stated complications targeting the task-oriented approach. This study investigated the effect of task-oriented training in post stroke patients on activities of daily living. Methodology: In this single-arm randomized controlled trial, 10 post-stroke males with hemiparesis and functional limitations in activities of daily living (ADL) were recruited following informed consent. The study implemented a structured intervention including activities like Forward Reach and Grasping Pen in sitting, Ball squeeze, stacking rings, piling up the Cones, Pegboard activities, Ball kicking, and Stepping drill. Each activity had a different dosage based on the specific drill performed. Pre and post-test evaluations were conducted on Day 0 and Day 21, utilizing the Functional Independence Measure (FIM) and Barthel Index (BI). Results: Within the group comparisons revealed statistically significant differences (p&lt; 0.05). The pre and post-test readings for FIM were evaluated as 52.50±15.130 and 69.0±11.972 respectively and for BI were observed as 61.0±14.870 and 74.50±7.619 respectively. Conclusion: Task-oriented training is an effective and viable method for enhancing functional independence and strength in activities of daily living (ADLs) in patients with hemiparesis following stroke.

A Comprehensive Study on Optimized Mechanical and Kinematic Design for Holonomic Drive Rugby Ball Kicking and Passing Robots

A Comprehensive Study on Optimized Mechanical and Kinematic Design for Holonomic Drive Rugby Ball Kicking and Passing Robots

Positional Comparison of Footballers' Ball Kicking Techniques, Leg Strength and Shooting Accuracy Percentages

The aim of the study was to investigate the differences of foot pressure points, shot accuracy percentages, leg strength values of footballers at the moment of kicking the ball with different techniques according to their positions. The research group consisted of U-17 and U-19 football players of Erzurumspor FK team. W-INSHOE brand device was used to determine the knee and hip strength of the footballers at 60o angular velocity and foot pressure points at the moment of kicking the ball. SPSS v20 package programme was used for data analysis and statistical significance was accepted as p&amp;lt;0.05. The normal distribution of continuous variables was analysed by Shapiro Wilk-W test, Kolmogorov Simirnov test, Q-Q graph, skewness and kurtosis. According to the results, it was determined that there was a statistical difference in favour of defenders in the pressure parameter in the L2 and L5 sensors inside the foot and in the L2 sensor outside the foot, in favour of forwards in the L6 sensor above the foot, in favour of forwards in the technical score parameter the second score when kicking the ball outside the foot and in the total score outside the foot, in the knee and hip strength parameter, in the peak torque extension movement in the hip joint, in favour of forwards. As a result, it is seen that the strikers who participated in the study are better in both technical scoring and hip strength in line with the needs of the position they play compared to other positions.

Asymmetry in Ball Kicking Speed between Preferred and Non-preferred Leg in Young Soccer Players

Kicking ability is one of the most important skills in soccer. It is very important to have a good kicking ability with both feet. The main goal of this research was to determine a ball kicking asymmetry (KA) between preferred and non-preferred leg in young soccer players for the U-15 and the U-17 age category. The second goal was to determine differences in kicking asymmetry (KA) between players of different playing positions. 183 young players in U-15 category as well as 87 players from U-17 age category were tested with simple soccer specific test to evaluate kicking velocity (km/h) with preferred and non-preferred leg using Pocket radar. Testing took place on the artificial grass during dry and warm weather and ball was kicked while stationary at the 11-m spot. Results obtained with Student’s T-test showed that differences in the maximum kicking velocity with the preferred and non-preferred leg were statistically significant (p≤0.05) in both age groups (90.2±8.8 km/h /78.5±9.8 km/h for U-15) and (102.7±6.4 km/h /89.5±9.4 km/h for U-17) which confirmed KA is present. Additionally, univariate analysis of variance (ANOVA) showed that there were significant differences in KA between different playing positions in U-17 group (KA=14.57/9.72/14.1 for defenders, midfielders and attackers, respectively). Soccer kicking can be a quality indicator for assessing the soccer kicking ability. By assessing kicking ability, relevant results can be obtained in a fast, and efficient way and can be utilized in the selection process of young talents.

Warm-up stretching exercises and physical performance of youth soccer players.

This study aims to compare the effects of standard warm-up versus warm-up using stretching exercises on the physical performance of male youth soccer players. Eighty-five male soccer players (age: 10.3 ± 4.3years; body mass index: 19.8 ± 4.3kg/m2) were assessed for countermovement jump height (CMJ, cm), 10m, 20m and 30m running sprint speed (s) and ball kicking speed (km/h) for the dominant and non-dominant leg under five (randomized) warm-up conditions. Using 72h of recovery between conditions, the participants completed a control condition (CC) and four experimental conditions, including static stretching (SSC), dynamic stretching (DSC), ballistic stretching (BSC), and proprioceptive neuromuscular facilitation (PNFC) exercises. All warm-up conditions had a duration of 10minutes. The main results indicate that no significant differences (p > 0.05) were found between warm-up conditions compared to CC in CMJ (CC = 28.1 ± 4.9; SSC = 28.4 ± 4.9; DSC = 30.9 ± 4.8; BSC = 30.9 ± 5.2; PNFC = 28.4 ± 5.0), 10m sprint (CC = 2.42 ± 0.4; SSC = 2.50 ± 0.4; DSC = 2.30 ± 0.3; BSC = 2.27 ± 0.3; PNFC = 2.53 ± 0.4), 20m sprint (CC = 5.42 ± 0.9; SSC = 5.59 ± 0.9; DSC = 5.37 ± 0.9; BSC = 5.40 ± 0.9; PNFC = 5.44 ± 0.9), 30m sprint (CC = 8.05 ± 1.3; SSC = 8.27 ± 1.3; DSC = 8.01 ± 1.3; BSC = 8.00 ± 1.3; PNFC = 8.12 ± 1.3), ball kicking speed for dominant (CC = 56.2 ± 4.9; SSC = 55.3 ± 5.2; DSC = 56.9 ± 5.8; BSC = 57.3 ± 5.8; PNFC = 55.7 ± 5.2) and non-dominant leg (CC = 52.8 ± 3.4; SSC = 51.8 ± 4.6; DSC = 53.5 ± 5.4; BSC = 53.6 ± 4.9; PNFC = 52.5 ± 4.0). In conclusion, compared to standard warm-up, stretching-based warm-up exerts no effect on male youth soccer players jump height, sprint speed and ball kicking speed.

Association between motor competence, and the rating of perceived exertion in male young adults

The purpose of this study was two-fold: (i) to analyze the relationship between motor competence (i.e., a person’s ability to be proficient in different gross motor skills) and the rating of perceived exertion (RPE), which represents the physiological and psychological responses during training, in young adults, and (ii) to compare RPE between participants with high and low motor competence. Forty-eight male young adults (22.01 ± 2.43 years) participated in this study. Participants were randomly divided into several teams of three players to perform a small-sided game for 25 min (Goalkeeper+ 2 × 2 + Goalkeeper) in which the RPE was collected. Then, motor competence was assessed through six tests assessing three main components: stability (Jumping Sideways and Shifting Platforms); locomotor (Standing Long Jump and Shuttle Run), and manipulative (Velocity of Ball Kicking and Throwing). Motor competence was negatively associated with RPE (r = −0.64; p &lt; 0.001). Moreover, locomotor, stability, and manipulative components were negatively associated with RPE (all, p &lt; 0.05). Furthermore, upon comparing groups with low and high levels of motor competence, we observed significantly higher RPE values (p &lt; 0.001; d = 0.32) in the low motor competence group. The findings from this study suggest that individuals with higher levels of motor competence may report a lower RPE during exercise. This information is valuable for coaches as improving levels of motor competence may potentially lead to increases in on-field performance.

IMPACTOS DO TREINO COM CARGAS ELEVADAS SOBRE A FORÇA EXPLOSIVA NOS JOGADORES DE FUTEBOL

ABSTRACT Introduction: The soccer athlete must complete the confrontation, dribbling, and shooting actions in a short time. This requires a high quality of explosive strength. Training with loads is useful for this purpose, but there still needs to be more evidence of the results of applying high loads. Objective: Study the influence of high-load training on the explosive quality of soccer players. Methods: Twenty soccer athletes were selected and divided into experimental and control groups. The experimental group completed their training with a high-load protocol added to their daily soccer training. In contrast, the ten control group athletes continued their existing daily training without changes. The experiment lasted six weeks. Pertinent data were collected and statistically analyzed to analyze the intervention results. Results: The stationary ball kick distance elevation in the experimental group was 49.74±1.42 m, while that of the control was 46.16±3.01 m, p&lt;0.05. The rate of change in the experimental group was 8.07%, higher than the 1.54% in the control group. Conclusion: Introducing the high-load training module into the soccer daily training system can effectively optimize soccer athletes’ explosive muscle strength quality, increasing their competitive performance in games. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

GENÇ FUTBOLCULARDA DİRENÇ BANDI EGZERSİZLERİNİN BAZI PERFORMANS PARAMETRELERİNE ETKİSİ

The aim of this study was to investigate the acute effect of resistance band exercises on some performance parameters in young football players. Active and trained 16 male football players (age: 15.18 ± .40 years; height: 170.81 ± 7.21 cm; weight: 59.43 ± 8.61 kg; body mass index (BMI): 20.26 ± 1.60 kg/m2) voluntarily participated in this study. Subjects performed two different warmup protocols including jogging+dynamic stretching exercises and jogging+dynamic stretching+resistance band exercises on non-consecutive days. Following the warm-up protocols and then three minutes of passive recovery, subjects were tested on the balance test, reaction time test, vertical jump and anaerobic power test, Illinois agility test, 30-m sprint, and ball kicking speed. Data were checked for normality by using Shapiro-Wilk test. Comparison between groups was analyzed with paired sample t-test. Besides, Cohen’s d was utilized in calculation of effect size. Statistical analyses and interpretations of the data were accepted as p&amp;lt;0.05. In comparison of the balance, vertical jump, 30-m sprint, and Illinois agility tests results between two groups, resistance band exercises were found to have positive effects on performance in all tests. However, statistically significant differences were detected in balance, agility, and sprint tests (p&amp;lt;0.05). In conclusion, balance, vertical jump, 30-m sprint, and Illinois agility test performance parameters of football players improved following the resistance band exercises. Accordingly, it is recommended that coaches and athletes incorporate resistance band exercises into sport-specific warmup protocols, and resistance band exercises should be performed in pre-training warm up session for achieving high performance in football players.

Reliability levels of motor competence in youth athletes

This study aimed to analyze the reliability of the tests included in the motor competence assessment (MCA) battery and compare the effects of the number of trials per test. Thirty female volleyball players (14.6 ± 1.3 years of age) were tested. The participants performed two or three trials of each test. Intra-class correlation (ICC) was calculated, and a paired sample t-test analyzed the variations between trials (1st vs. 2nd vs. 3rd). Results revealed a significant difference between the first and the second trials for jumping sideways [t(29) = -4.108, p < 0.01], standing long jump [t(29) = -3.643, p < 0.01], and shuttle run [t(29) = -3.139, p < 0.01]. No significant result was registered in the shifting platforms, ball throwing and kicking between the first and second trials. Hence, any difference was recorded between the second and third trial. High ICC values were registered in lateral jumps, among the three repetitions of ball kicking and ball throwing, and between the last two repetitions of shuttle run. Almost perfect values were recorded for the shifting platforms and standing long jump. Nevertheless, there seems to be a learning effect between the first and the second repetition—no differences were registered only considering the two manipulative tests. In conclusion, except for jumping sideways, the MCA tests are reliable and only need to be performed two times instead of three.

Ventricular fibrillation arrest after blunt chest trauma in a 33-year-old man, commotio cordis?

BackgroundCommotio cordis is an event in which a blunt, non-penetrating blow to the chest occurs, triggering a life-threatening arrhythmia and often sudden death. This phenomenon is often seen in young, male athletes and has become increasingly well-known over the past few decades. We present a unique case in which ventricular fibrillation occurs in an older male athlete after blunt trauma.Case presentationPatient with no known medical history was brought to the ER after being found unconscious after a soccer ball kick to the chest. He was found to be in ventricular fibrillation and successfully resuscitated on the soccer field. Patient was admitted to the hospital and lab workup and initial imaging were unremarkable, except elevated troponin and lactate, which returned to normal levels. An echocardiogram showed global left ventricular systolic dysfunction with a visually estimated ejection fraction of 45–50%. Coronary showed angiographically nonobstructive coronary arteries. The patient was diagnosed with commotio cordis and discharged from the hospital in stable condition. Follow-up echocardiogram continued to show low ejection fraction and event monitor demonstrated frequent polymorphic ventricular tachycardia with periods of asystole.ConclusionThis case is unique in that blunt trauma to the chest from a soccer ball immediately triggered ventricular fibrillation in a patient with a possible cardiomyopathy. It is possible that the blunt trauma caused primary commotio cordis that led to cardiomyopathy in a previous healthy man, or that an underlying cardiomyopathy made it more likely for this to occur. Overall, increased awareness and prevention efforts of blunt chest trauma are required to reduce the high mortality associated life-threatening arrhythmias. There is limited data regarding the interplay between these two entities.

Inviting Self-Efficacy in Children

The predictive power of self-efficacy beliefs of children aged 4 to 10 was investigated using common schoolyard activities. Participants were 24 elementary school-aged children and 4 pre-kindergarten-aged children. Age-appropriate tasks included the standing broad jump for both groups, a targeted ball kick for the older group and basketball dribbling for the younger group. Results indicated that until around the fifth birthday, the age at which most children begin formal education, the ability to predict performance was not reliable. The school-aged children were more accurate in their predictions and, as a group, illustrated the role of peer support and selfconfidence in developing self-efficacy.

Development of modular multi-degree-of-freedom hybrid joints and robotic flexible legs via fluidic elastomer actuators

Soft actuators with high safety, adaptivity, and energy-to-weight ratio have the potential to be used in developing more adaptive legged robots. In this work, we incorporate soft actuators into rigid parallel mechanisms and develop multi-degree-of-freedom (multi-DOF) soft-rigid hybrid joints that can actively achieve 1, 2, and 3 DOFs actuated by 2, 4, and 8 bellows-type fluidic elastomer actuators (FEAs), respectively. The FEAs exhibit large axial strain (ϵ e max = 176%, ϵ c max = 25%), small radial expansion (ϵ r max = 12%) at 70 kPa, and are light weight, and the rigid parallel mechanisms constrain motions of the joints to the desired DOFs. We characterize the proposed joints’ kinematic and static performances by measuring their range of motion and blocked torque upon actuation. Results show that these joints successfully achieve all desired DOFs and are of high torque to weight ratio (4.07 N·m·kg−1). A bucking prediction model is established to evaluate the critical buckling pressure. As a demonstration for legged robots, we use the proposed joints and develop two types of multi-DOF legs based on inspirations from the DOF configuration of legged mammals’ musculoskeletal systems. Preliminary results demonstrate that FEAs-based multi-DOF legs can perform fundamental biomimetic movements (e.g. leg swing) through pressure adjustment, and high-speed tasks (e.g. ball kicking and jumping) through high-pressure and short-pulse actuation.

Automatic Markerless Motion Detector Method against Traditional Digitisation for 3-Dimensional Movement Kinematic Analysis of Ball Kicking in Soccer Field Context.

Kicking is a fundamental skill in soccer that often contributes to match outcomes. Lower limb movement features (e.g., joint position and velocity) are determinants of kick performance. However, obtaining kicking kinematics under field conditions generally requires time-consuming manual tracking. The current study aimed to compare a contemporary markerless automatic motion estimation algorithm (OpenPose) with manual digitisation (DVIDEOW software) in obtaining on-field kicking kinematic parameters. An experimental dataset of under-17 players from all outfield positions was used. Kick attempts were performed in an official pitch against a goalkeeper. Four digital video cameras were used to record full-body motion during support and ball contact phases of each kick. Three-dimensional positions of hip, knee, ankle, toe and foot centre-of-mass (CMfoot) generally showed no significant differences when computed by automatic as compared to manual tracking (whole kicking movement cycle), while only z-coordinates of knee and calcaneus markers at specific points differed between methods. The resulting time-series matrices of positions (r2 = 0.94) and velocity signals (r2 = 0.68) were largely associated (all p < 0.01). The mean absolute error of OpenPose motion tracking was 3.49 cm for determining positions (ranging from 2.78 cm (CMfoot) to 4.13 cm (dominant hip)) and 1.29 m/s for calculating joint velocity (0.95 m/s (knee) to 1.50 m/s (non-dominant hip)) as compared to reference measures by manual digitisation. Angular range-of-motion showed significant correlations between methods for the ankle (r = 0.59, p < 0.01, large) and knee joint displacements (r = 0.84, p < 0.001, very large) but not in the hip (r = 0.04, p = 0.85, unclear). Markerless motion tracking (OpenPose) can help to successfully obtain some lower limb position, velocity, and joint angular outputs during kicks performed in a naturally occurring environment.

Reliability of Physical Fitness Assessment for Children Aged 4-6 Years

PURPOSE: Physical fitness is a powerful health marker for the well-being of children and adolescence as well as a vital predictor of health later in life. In this regard, the assessment of physical fitness in young people is important from a clinical and public health point of view. The purpose of this study was to examine the test-retest reliability of a National Fitness Award Battery for preschool children.METHODS:A total of 141 preschoolers aged 4-6 years participated in this study. Anthropometry, muscle strength, endurance, flexibility, cardiorespiratory fitness, balance, speed, agility and coordination were assessed by measuring or testing their height and weight, handgrip, curl-up, sit and reach, 10 m shuttle run, one leg stand, standing long jump, 5 m×4 shuttle run, ball throw, ball kick and button-pushing respectively. Each test was performed twice with a two-week interval and test-retest reliability was evaluated using intraclass correlation coefficients (ICC). Bland-Altman plots were used to measure agreement.RESULTS:The results indicated that the test items were excellently reliable (height, weight, handgrip, curl-up, sit and reach, 10 m shuttle run, standing long jump, 5 m×4 shuttle run and button-pushing) except for one leg stand, ball throw and ball kick tests.CONCLUSIONS: National Fitness Award Battery for preschool children is a reliable tool to assess their physical fitness yet one leg stand, and ball throw, ball kick tests showed poor reliability. In order to find substitute items, further study will be required.