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1.
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2.
According to recent motor control studies, it is important to know probabilistic structure of his/her own motor errors to choose an optimal motor plan (i.e., where you aim at) to maximise the expected gain. In this study, we questioned if pitching form determines the probabilistic structure of pitching errors in baseball pitchers. Eighteen collegiate baseball pitchers with various pitching forms including right- and left-handed overarm, sidearm and underarm throwers threw 100 pitches aiming at a target located 90 cm above the ground. Two dimensional distribution of pitch location was fitted by using bivariate normal distribution and 95% confidence ellipse was calculated. In order to quantify the pitching form, the direction of the throwing arm trajectory in frontal plane was calculated. The direction of the long axis was dependent on each participant’s pitching form (e.g., right overarm pitchers pitched along a right-up–left-down ellipse and left overarm pitchers pitched along a left-up–right-down ellipse). This was confirmed by circular correlation analysis (P = 0.98). These results suggest that different mechanisms, potentially errors in pitching mechanics and errors in ball release timing, might contribute to errors along the long axis and those along the short axis.  相似文献   

3.
By manipulating stimulus variation in terms of opponent pitcher actions, this study investigated the capability of expert (n = 30) and near-expert (n = 95) professional baseball batters to adapt anticipation skill when using the video simulation temporal occlusion paradigm. Participants watched in-game footage of two pitchers, one after the other, that was temporally occluded at ball release and various points during ball flight. They were required to make a written prediction of pitch types and locations. Per cent accuracy was calculated for pitch type, for pitch location, and for type and location combined. Results indicated that experts and near-experts could adapt their anticipation to predict above guessing level across both pitchers, but adaptation to the left-handed pitcher was poorer than the right-handed pitcher. Small-to-moderate effect sizes were found in terms of superior adaptation by experts over near-experts at the ball release and early ball flight occlusion conditions. The findings of this study extend theoretical and applied knowledge of expertise in striking sports. Practical application of the instruments and findings are discussed in terms of applied researchers, practitioners and high-performance staff in professional sporting organisations.  相似文献   

4.
While 10% of the general population is left-handed, 27% of professional baseball pitchers are left-handed. Biomechanical differences between left- and right-handed college pitchers have been previously reported, but these differences have yet to be examined at the professional level. Therefore, the purpose of this study was to compare pitching biomechanics between left- and right-handed professional pitchers. It was hypothesised that there would be significant kinematic and kinetic differences between these two groups. Pitching biomechanics were collected on 96 left-handed pitchers and a group of 96 right-handed pitchers matched for age, height, mass and ball velocity. Student t-tests were used to identify kinematic and kinetic differences (p < 0.05). Of the 31 variables tested, only four were found to be significantly different between the groups. Landing position of the stride foot, trunk separation at foot contact, maximum shoulder external rotation and trunk forward tilt at ball release were all significantly greater in right-handed pitchers. The magnitude of the statistical differences found were small and not consistent with differences in the two previous, smaller studies. Thus, the differences found may be of minimal practical significance and mechanics can be taught the same to all pitchers, regardless of throwing hand.  相似文献   

5.
ABSTRACT

Conceptually, an efficient baseball pitch demonstrates a proximal-to-distal transfer of segmental angular velocity. Such a timing pattern (or kinematic sequence) reduces stress on musculoskeletal structures of the throwing arm and maximises ball velocity. We evaluated the variability of kinematic sequences in 208 baseball pitches. 3D biomechanical pitch analyses were performed on 8–10 fastball pitches from 22 baseball pitchers (5 high school, 11 collegiate and 6 professional). The kinematic sequence patterns – time of peak angular velocity of five body segments: pelvis, trunk, arm, forearm and hand – were measured. None of the pitches analysed demonstrated an entirely proximal-to-distal kinematic sequence. Fourteen different kinematic sequence patterns were demonstrated, with the most prevalent sequence being pelvis → trunk → arm → hand → forearm. Fewer than 10% of the pitchers performed only one kinematic sequence pattern across the sampled pitches. The variability of the kinematic sequence was similar in high-school pitchers and professionals. Previous studies report that deviation from the proximal-to-distal kinematic sequence is associated with increased injury risk. As a method of evaluating the efficient transfer of energy to the hand, the kinematic sequence may provide insight to injury risk in the future. The ideal kinematic sequence and ideal variability of the sequence when throwing have yet to be determined.  相似文献   

6.
The purposes of this research were to quantify the kinematics of the lacrosse shot, based on arm dominance and player experience level. Male players (N = 39; 14–30 years; high school [n = 24], collegiate [n = 9], professional [n = 6]), performed overhead shots using dominant and non-dominant sides. Motion was captured using a high-speed, 12-camera optical system and high-speed filming. Body segment rotational velocities and joint angles were determined at key points in the shot cycle from foot contact (0% of shot) to ball release (100% of shot). All players shot with less anterior trunk lean, less transverse shoulder rotation, and slower trunk-shoulder rotational velocities with the non-dominant side than the dominant side (all p < 0.05). Professional players produced crosse angular velocities 21% faster than high school or collegiate players (p < 0.05). Transverse shoulder rotation range of motion on both dominant and non-dominant and trunk rotation sides was highest in the professional players (p < 0.05). These kinematic features enable professional players to produce faster ball speeds than younger players (138 ± 7 km/h vs. 112 ± 15 km/h, respectively; p < 0.05). Less anterior lean or suboptimal rotation sequence could increase proximal shoulder forces that could contribute to injury as in other throwing sports.  相似文献   

7.
The purpose of this study was to quantify trunk axial rotation and angular acceleration in pitching and batting of elite baseball players. Healthy professional baseball pitchers (n = 40) and batters (n = 40) were studied. Reflective markers attached to each athlete were tracked at 240 Hz with an eight-camera automated digitizing system. Trunk axial rotation was computed as the angle between the pelvis and the upper trunk in the transverse plane. Trunk angular acceleration was the second derivative of axial rotation. Maximum trunk axial rotation (55 ± 6°) and angular acceleration (11,600 ± 3,100 °/s2) in pitching occurred before ball release, approximately at the instant the front foot landed. Maximum trunk axial rotation (46 ± 9°) and angular acceleration (7,200 ± 2,800 °/s2) in batting occurred in the follow-through after ball contact. Thus, the most demanding instant for the trunk and spine was near front foot contact for pitching and after ball contact for batting.  相似文献   

8.
Controversy continues whether curveballs are stressful for young baseball pitchers. Furthermore, it is unproven whether professional baseball pitchers have fewer kinematic differences between fastballs and off-speed pitches than lower level pitchers. Kinematic and kinetic data were measured for 111 healthy baseball pitchers (26 youth, 21 high school, 20 collegiate, 26 minor league, and 18 major league level) throwing fastballs, curveballs, and change-ups in an indoor biomechanics laboratory with a high-speed, automated digitising system. Differences between pitch types and between competition levels were analysed with repeated measures ANOVA. Shoulder and elbow kinetics were greater in fastballs than in change-ups, while curveball kinetics were not different from the other two types of pitches. Kinematic angles at the instant of ball release varied between pitch types, while kinematic angles at the instant of lead foot contact varied between competition levels. There were no significant interactions between pitch type and competition level, meaning that kinetic and kinematic differences between pitch types did not vary by competition level. Like previous investigations, this study did not support the theory that curveballs are relatively more stressful for young pitchers. Although pitchers desire consistent kinematics, there were differences between pitch types, independent of competition level.  相似文献   

9.
Power is a fundamental component for many sporting activities; while the load that elicits peak power during different exercises and differences between sexes remains unclear. This study aims to determine the effect of sex and load on kinematic and kinetic variables during the mid-thigh clean pull. Men (n = 10) and women (n = 10) performed the mid-thigh clean pull at intensities of 40%, 60%, 80%, 100%, 120%, and 140% of one repetition maximum (1RM) power clean in a randomised and counter-balanced order, while assessing bar velocity, bar displacement, power, force, and impulse. Two-way analysis of variance revealed that men demonstrated significantly greater (p < 0.05) values for all variables across loads, excluding bar velocity. Men demonstrated significantly greater (p < 0.05) bar velocities with 40–80% 1RM; in contrast, women demonstrated significantly (p < 0.05) higher velocities with 120–140% 1RM. Irrespective of sex significantly greater (p < 0.05), system peak power, bar velocity, and displacement occurred with 40% 1RM. In contrast, peak force and impulse were significantly (p < 0.05) greater with 140% 1RM. When performing the mid-thigh clean pull, to maximise system power or bar velocity, lower loads (40–60% 1RM) are recommended. When training force production or impulse, higher loads (120–140% 1RM) are recommended, when using the mid-thigh clean pull.  相似文献   

10.
The purpose of the present study was to document crucial factors associated with students’ learning of biomechanical concepts, particularly between high- and-low achieving students. Students (N = 113) from three introductory biomechanics classes at two public universities volunteered for the study. Two measures of students’ learning were obtained, final course grade and improvement on the Biomechanics Concept Inventory version 3 administered before and after the course. Participants also completed a 15-item questionnaire documenting student learning characteristics, effort, and confidence. Partial correlations controlling for all other variables in the study, confirmed previous studies that students’ grade point average (p < 0.01), interest in biomechanics, (p < 0.05), and physics credits passed (p < 0.05) are factors uniquely associated with learning biomechanics concepts. Students’ confidence when encountering difficult biomechanics concepts was also significantly (p < 0.05) associated with final grade. There were significant differences between top 15% and bottom 15% achievers on these variables (p < 0.05), as well as on readings completed, work to pay for college per week, and learning epistemology. Consequently, instructors should consider strategies to promote students’ interest in biomechanics and confidence in solving relevant professional problems in order to improve learning for both low- and high-ability students.  相似文献   

11.
Task-specific auditory training can improve sensorimotor processing times of the auditory reaction time (RT). The majority of competitive swimmers do not conduct habitual start training with the electronic horn used to commence a race. We examined the effect of four week dive training interventions on RT and block time (BT) of 10 male adolescent swimmers (age 14.0 ± 1.4 years): dive training with auditory components (speaker and electronic horn) (n = 5) and dive training without auditory components (n = 5). Auditory stimulus dive training significantly reduced swimming start RT, compared with dive training without auditory components (p < 0.01), with a group mean RT reduction of 13 ± 9 ms. Four of the five swimmers that received auditory stimulus training showed medium to large effect size reductions in RT (d = 0.74; 1.32; 1.40; 1.81). No significant changes to swimmers’ BTs were evident in either dive training intervention. The adolescent swimmers’ results were compared against six male elite swimmers (age 19.8 ± 1.0 years). The elite swimmers had significantly shorter BTs (p < 0.05) but no significant difference in RTs. Auditory stimulus dive training should be explored further as a mechanism for improving swimming start performance in elite swimmers who have pre-established optimal BTs.  相似文献   

12.
To investigate characteristic upper limb muscle use between two common tug of war (TOW) gripping styles, 20 elite athletes from two high school TOW teams were recruited. Under conditioned attack pulling (with 90% maximal force) on a tug machine, participants used their own habitual gripping style to pull for five 15-s trials. Force and kinematic measurements showed a significantly better force performance and higher centre-of-gravity tilting angle with the gripping style one than with the gripping style two (GS2) (both p < 0.05). However, an overall higher and more symmetrical muscle activation detected by normalised surface electromyography signal amplitude was found in the GS2 group (both p < 0.05). In both groups, the distal and flexor muscles were more activated than the proximal and extensor muscles, respectively (p < 0.05). Higher co-contraction ratio was found in the wrist joints of the latter arm in both groups (p < 0.05). As higher muscle activation level and co-contraction indicate higher muscle and joint injury incidences, we suggest that gripping style factors should be considered in training to prevent muscle and joint injury. Future study concerning segmental kinematics, ground reaction force, moment arm and muscle endurance during the defence phase are warranted.  相似文献   

13.
The purpose of this study was to compare the lower extremity inter-joint coordination of different collision forces runners during running braking phase. A dynamical system approach was used to analyse the inter-joint coordination parameters. Data were collected with six infra-red cameras and two force plates. According to the impact peak of the vertical ground reaction force, twenty habitually rearfoot-strike runners were categorised into three groups: high collision forces runners (HF group, n = 8), medium collision forces runners (MF group, n = 5), and low collision forces runners (LF group, n = 7). There were no significant differences among the three groups in the ankle and knee joint angle upon landing and in the running velocity (p > 0.05). The HF group produced significantly smaller deviation phase (DP) of the hip flexion/extension-knee flexion/extension during the braking phase compared with the MF and LF groups (p < 0.05). The DP of the hip flexion/extension-knee flexion/extension during the braking phase correlated negatively with the collision force (p < 0.05). The disparities regarding the flexibility of lower extremity inter-joint coordination were found in high collision forces runners. The efforts of the inter-joint coordination and the risk of running injuries need to be clarified further.  相似文献   

14.
Cross-country mountain bike suspension reportedly enhances comfort and performance through reduced vibration and impact exposure. This study analysed the effectiveness of three different front fork systems at damping accelerations during the crossing of three isolated obstacles (stairs, drop, and root). One participant completed three trials on six separate occasions in a randomised order using rigid, air-sprung, and carbon leaf-sprung forks. Performance was determined by time to cross obstacles, while triaxial accelerometers quantified impact exposure and damping response. Results identified significant main effect of fork type for performance time (p < 0.05). The air-sprung and leaf-sprung forks were significantly slower than the rigid forks for the stairs (p < 0.05), while air-sprung suspension was slower than the rigid for the root protocol (p < 0.05). There were no differences for the drop protocol (p < 0.05). Rigid forks reduced overall exposure (p < 0.05), specifically at the handlebars for the stairs and drop trials. More detailed analysis presented smaller vertical accelerations at the handlebar for air-sprung and leaf-sprung forks on the stairs (p < 0.05), and drop (p < 0.05) but not the root. As such, it appears that the suspension systems tested were ineffective at reducing overall impact exposure at the handlebar during isolated aspects of cross-country terrain features which may be influenced to a larger extent by rider technique.  相似文献   

15.
Abstract

The aim of this study was to analyse the talent identification process of a professional soccer club. A preselection of players (n = 64) aged 9–10 years and a final selection (n = 21) were performed by the technical staff through the observation during training sessions and matches. Also, 34 age-matched players of an open soccer camp (CampP) acted as controls. All participants underwent anthropometric, maturity and performance measurements.

Preselected outfield players (OFs) were older and leaner than CampP (P < 0.05). Besides, they performed better in velocity, agility, endurance and jump tests (P < 0.05). A discriminant analysis showed that velocity and agility were the most important parameters. Finally, selected OFs were older and displayed better agility and endurance compared to the nonselected OFs (P < 0.05). Goalkeepers (GKs) were taller and heavier and had more body fat than OFs; also, they performed worse in the physical tests (P < 0.05). Finally, selected GKs were older and taller, had a higher predicted height and advanced maturity and performed better in the handgrip (dynamometry) and jump tests (P < 0.05).

Thus, the technical staff selected OFs with a particular anthropometry and best performance, particularly agility and endurance, while GKs had a different profile. Moreover, chronological age had an important role in the whole selection process.  相似文献   

16.
Abstract

Physical fitness performance is an important health correlate yet is often unrelated to sedentary behaviour in early adolescence. In this study, we examined the association of sedentary behaviour (i.e. screen time) with weight-related health markers and blood pressure, after controlling for cardiorespiratory fitness performance. American middle school students (N = 153, 56% females) aged 11–15 years (mean 12.6 years, s = 0.5) completed assessments of cardiorespiratory fitness performance, screen time, weight status (BMI percentile, waist-to-height ratio), and blood pressure. Multivariate analysis of covariance, controlling for cardiorespiratory fitness performance, found those who met the daily recommendation of 2 h or less of screen time (n = 36, 23.5%) had significantly lower BMI (p < 0.05) and systolic blood pressure (p < 0.01) compared with those who exceeded this recommendation. Findings suggest specific intervention programmes may be designed to target both cardiorespiratory fitness and sedentary behaviours to maximize early adolescent health because these behaviours are likely to have unique and independent effects on youth health markers.  相似文献   

17.
The purpose of this study was to compare kinetic, kinematic, and performance variables associated with full and shortened modern backswings in a skilled group of modern swing (one-plane) golfers. Shortening the modern golf backswing is proposed to reduce vertebral spine stress, but supporting evidence is lacking and performance implications are unknown. Thirteen male golfers performed ten swings of each swing type using their own 7-iron club. Biomechanical-dependent variables included the X-Factor kinematic data and spine kinetics. Performance-related dependent variables included club head velocity (CHV), shot distance, and accuracy (distance from the target line). Data were analysed with repeated measures ANOVA with an a priori alpha of 0.05 (SPSS 22.0, IBM, Armonk, NY, USA). We found significant reductions for the X-Factor (p < 0.05) between the full and shortened swings. The shortened swing condition ameliorated vertebral compression force from 7.6 ± 1.4 to 7.0 ± 1.7 N (normalised to body weight, p = 0.01) and significantly reduced CHV (p < 0.05) by ~2 m/s with concomitant shot distance diminution by ~10 m (p < 0.05). Further research is necessary to examine the applicability of a shortened swing for golfers with low back pain.  相似文献   

18.
The purpose of this study was to examine the relationship between dynamic hip rotational range of motion and upper extremity kinematics during baseball pitching. Thirty-one youth baseball pitchers (10.87 ± 0.92 years; 150.03 ± 5.48 cm; 44.83 ± 8.04 kg) participated. A strong correlation was found between stance hip rotation and scapular upward rotation at maximum shoulder external rotation (r = 0.531, P = 0.002) and at ball release (r = 0.536, P = 0.002). No statistically significant correlations were found between dynamic hip rotational range of motion and passive hip range of motion. Hip range of motion deficits can constrain pelvis rotation and limit energy generation in the lower extremities. Shoulder pathomechanics can then develop as greater responsibility is placed on the shoulder to generate the energy lost from the proximal segments, increasing risk of upper extremity injury. Additionally, it appears that passive seated measurements of hip range of motion may not accurately reflect the dynamic range of motion of the hips through the progression of the pitch cycle.  相似文献   

19.
The potential to use the vertical jump (VJ) to assess both athletic performance and risk of anterior cruciate ligament (ACL) injury could have widespread clinical implications since VJ is broadly used in high school, university, and professional sport settings. Although drop jump (DJ) and VJ observationally exhibit similar lower extremity mechanics, the extent to which VJ can also be used as screening tool for ACL injury risk has not been assessed. This study evaluated whether individuals exhibit similar knee joint frontal plane kinematic and kinetic patterns when performing VJs compared with DJs. Twenty-eight female collegiate athletes performed DJs and VJs. Paired t-tests indicated that peak knee valgus angles did not differ significantly between tasks (p = 0.419); however, peak knee internal adductor moments were significantly larger during the DJ vs. VJ (p < 0.001). Pearson correlations between the DJ and VJ revealed strong correlations for knee valgus angles (r = 0.93, p < 0.001) and for internal knee adductor moments (r = 0.82, p < 0.001). Our results provide grounds for investigating whether frontal plane knee mechanics during VJ can predict ACL injuries and thus can be used as an effective tool for the assessment of risk of ACL injury in female athletes.  相似文献   

20.
Abstract

The present study aimed to analyse the influence of speed and power abilities in goal situations in professional football.

During the second half of the season 2007/08, videos of 360 goals in the first German national league were analysed by visual inspection. For the assisting and the scoring player the situations immediately preceding the goal were evaluated. The observed actions were categorised as: no powerful action, rotation (around the body's centre-line), straight sprint, change-in-direction sprint, jump, or a combination of those categories.

Two hundred and ninety-eight (83%) goals were preceded by at least one powerful action of the scoring or the assisting player. Most actions for the scoring player were straight sprints (n = 161, 45% of all analysed goals, P < 0.001) followed by jumps (n = 57, 16%), rotations and change-in-direction sprints (n = 22, 6% each). Most sprints were conducted without an opponent (n = 109, P < 0.001) and without the ball (n = 121, P < 0.001). Similarly, for the assisting player the most frequent action was a straight sprint (n = 137, P < 0.001) followed by rotations (n = 28), jumps (n = 22) and change-in-direction sprints (n = 18). The straight sprints were mostly conducted with the ball (n = 93, P = 0.003).

In conclusion, straight sprinting is the most frequent action in goal situations. Power and speed abilities are important within decisive situations in professional football and, thus, should be included in fitness testing and training.  相似文献   

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