Swing Speed Research Articles

Warming Up With a Dynamic Moment of Inertia Bat Can Increase Bat Swing Speed in Competitive Baseball Players.

While most baseball players' warm-up with a weighted bat/donut, there is evidence to suggest the swing speed decreases after the warm-up even though the bat feels lighter. Warming up with a dynamic moment of inertia bat may not decrease the swing speed and therefore improve the performance of baseball players. The hypothesis is that a dynamic moment of inertia bat will negate the effect of the kinesthetic illusion observed with a weighted bat. To measure the difference in bat swing speed between warming up with the dynamic moment of inertia bat compared with a weighted bat. Thirty-nine competitive baseball players participated in the study. All players were randomly assigned a warm-up tool that could be either a dynamic moment of inertia bat or a weighted bat. After the players' warm-up, they swung their normal bat, and the bat swing speed was measured using a high-speed camera. We used motion analysis software to calculate the swing speed which measured the linear displacement during the last 15 frames before ball contact. The process was then repeated so that each player had the chance to try both warm-up bats. The post warm-up swing speeds using the dynamic moment of inertia bat were significantly faster compared with a weighted bat warm-up. There was a 0.56 (0.78)m/s (1.26 [1.74]mph) increase in swing speed when using the dynamic moment of inertia bat (P = .0001), which is an average increase of 2.10% compared with a weighted bat warm-up. Our findings suggest that using a dynamic moment of inertia bat before an at-bat can increase swing speed compared with a weighted warm-up. Future studies are needed to determine if using a dynamic moment of inertia bat as part of rehabilitation can facilitate returning to competition after injury by focusing on swing speed.

TREINAMENTO DE VELOCIDADE DE REAÇÃO NO VOLEIBOL

ABSTRACT Introduction: Volleyball is a team sport where winning the confrontation at the net largely determines characteristics. Volleyball players must constantly strive to improve team cooperation, defensive ability, and speed skills to improve their ability to perform over the net. Objective: Establish a fixed intensity load model for speed training on the athlete's visual response in volleyball. Methods: This paper selected several volleyball players as research subjects, randomly divided into two groups (regular training and experimental groups). The experimental group was subjected to a visual response speed training protocol based on routine training. Mathematical statistics were employed to analyze the athletes’ reaction speed and defensive ability against the net. Results: The qualities analyzed, mainly movement speed, swing speed, agility, and endurance for fast swing and fast movement, showed a significant differential after the intervention. The speed response was concentrated in the center of body balance. The lower limbs increased the endurance for speed. After visual reaction speed training, the experimental group's ability to cope with attacks on the net was statistically superior (P<0.05). Conclusion: The proposed protocol can improve the reaction speed training of volleyball players. Volleyball players should reinforce reaction speed training daily to perform better close to the net. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

EFEITOS DO EXERCÍCIO DE FLEXIBILIDADE DOS MEMBROS INFERIORES SOBRE A APTIDÃO FÍSICA DOS JOGADORES DE TÊNIS DE MESA

ABSTRACT Introduction: the main fitness requirements of table tennis players are highly automated motor skills and a strong body control ability; this combination is believed to benefit from flexibility exercises. Objective: Study the effects of lower limb flexibility training on physical fitness in table tennis players. Methods: The controlled experiment randomly divided 20 volunteers into two groups with no statistical differences between them. The control group continued using the existing table tennis teaching program, while the experimental group adopted the optimized lower limb flexibility training program. The course design was organized according to the physical education teacher's table tennis player talent training plan. Results: In the experimental group, the number of right body turns for throwing and blocking increased to 60.41 ± 4.67 times after the experiment; the number of right body turns increased to 64.045 ± 5.22; in the control group, the number of right push and blocks increased to 56.78 ± 3.67 times after the experiment. After the experiment, the number of fixed point swing speed of the whole station increased to 64.66 ± 3.95 (P<0.05). Conclusion: Adding lower limb flexibility exercises to table tennis flexibility training has been shown to improve athletes’ static and dynamic flexibility, positively optimizing players’ fitness. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

Improving static balance ability with trainings supported by somatosensory-based feedback system

To support trainings for static balance ability improvement, in this study, we developed a somatosensory-based feedback system (SFS) using Kinect technology. Three training tasks such as knees crouch, rotating upper body and rotating upper body with a ball in hands were designed according to the static balance ability training method. Forty-four participants volunteered to participate in the study. The participants completed these tasks by performing three movements during a six-week period. Feedback, either positive or negative, on the participants’ static balance performance was provided by the SFS to adjust their posture and static balance. We tested the effectiveness of the SFS on improving the static balance ability in an experiment. The participants were randomly assigned to a control group (n = 22) and an experimental group (n = 22). The participants in the experimental group completed the training tasks with the support of the SFS, whereas the participants in the control group completed the training tasks without any feedback. A static balance ability pretest was administered before the training and a static balance ability posttest after the training. Differences between two groups on tests’ results were compared. In addition, the participants in the experimental group completed intermediate tests (the same test as the pre- and post-test) during the training. Three main findings were obtained. First, there was no difference between the two groups in the static balance ability pretest; however, the experimental group outperformed the control group on the static balance ability posttest. Second, the participants’ scores for the single barefoot standing using the dominant leg with eyes opened (SFOE) and single barefoot standing using the dominant leg with eyes closed (SFCE) testing tasks were higher than those in the double barefoot standing with eyes opened (DFOE) and double barefoot standing with eyes closed (DFCE) testing tasks. Third, there were improvements in swing path, swing speed, swing amplitude, and area research variables. According to interviews with the participants, the SFS was useful, as it provided feedback to the static balance performance and they used it to adjust their postures and balance. Based on the results, we suggest applying the SFS to trainings for static balance ability as it can improve the static balance ability.

Effect analysis on thermohydraulic characteristics of microchannel direct liquid cooling under swing condition

In this paper, the thermohydraulic characteristics of direct liquid cooling in rectangular microchannels were studied under swing condition. Deionized water was used as the coolant. The effects of coolant flow rate, coolant inlet temperature, microchannel equivalent diameter and heating power on the thermohydraulic performances were studied. In addition, the wall temperature uniformity and axial heat conduction effect were discussed. Furthermore, the influence of swing speed on the performances of microchannel direct liquid cooling was studied. The performance factor was defined to evaluate the microchannel comprehensive thermohydraulic performance. The results show that the transition Reynolds number of microchannels with equivalent diameters of 0.9–1.6 mm is between 500 and 2000. The wall temperature uniformity is improved with the increase of coolant flow and the decrease of coolant inlet temperature. The axial heat conduction demonstrates a great influence on the microchannels, which accounts for about 40%-50% to the total heat. With the increase of swing speed, the drag coefficient decreases slowly within 4%. Meanwhile, the flow rate should be in 0.14–0.2 L/min to obtain an optimal effect of the performance factor.

대학 골프선수의 팔 체력과 클럽 스피드의 관계

This study defined the relationship between the arm strength and club speed of college female golf players and determined a standard value of arm strength for club speed. To this end, by applying the significance sampling method among non-probability sampling methods, 56 players were selected as subjects who, as of 2022, participated in official golf matches as college students. In addition, arm strength, muscular endurance and flexibility, and club head speed (carry swing speed, ball speed) were measured and analyzed, and the following results were identified.BR First, in the relationship between arm strength and club speed of college female golf players, arm strength had a positive effect on club speed. Second, in the relationship between arm muscular endurance and club speed of college female golf players, arm muscular endurance had a positive effect on the carry factor of club speed. Third, it was found that there was no significant effect on the relationship between arm flexibility and club speed of college female golf players. Fourth, in setting the arm strength standard for club speed of college female golf players, in terms of muscle strength and muscular endurance, the validity of the baseline setting was established, the baseline for strength was set at .802, and the baseline for muscular endurance was set at .344.

Septic arthritis in an in vivo murine model induced by Staphylococcus aureus : a comparison between actions of the haemolysin toxin and the effects of the host immune response.

Aims Staphylococcus aureus is a major cause of septic arthritis, and in vitro studies suggest α haemolysin (Hla) is responsible for chondrocyte death. We used an in vivo murine joint model to compare inoculation with wild type S. aureus 8325-4 with a Hla-deficient strain DU1090 on chondrocyte viability, tissue histology, and joint biomechanics. The aim was to compare the actions of S. aureus Hla alone with those of the animal’s immune response to infection.MethodsAdult male C57Bl/6 mice (n = 75) were randomized into three groups to receive 1.0 to 1.4 × 107 colony-forming units (CFUs)/ml of 8325-4, DU1090, or saline into the right stifle joint. Chondrocyte death was assessed by confocal microscopy. Histological changes to inoculated joints were graded for inflammatory responses along with gait, weight changes, and limb swelling.ResultsChondrocyte death was greater with 8325-4 (96.2% (SD 5.5%); p < 0.001) than DU1090 (28.9% (SD 16.0%); p = 0.009) and both were higher than controls (3.8% (SD 1.2%)). Histology revealed cartilage/bone damage with 8325-4 or DU1090 compared to controls (p = 0.010). Both infected groups lost weight (p = 0.006 for both) and experienced limb swelling (p = 0.043 and p = 0.018, respectively). Joints inoculated with bacteria showed significant alterations in gait cycle with a decreased stance phase, increased swing phase, and a corresponding decrease in swing speed.ConclusionMurine joints inoculated with Hla-producing 8325-4 experienced significantly more chondrocyte death than those with DU1090, which lack the toxin. This was despite similar immune responses, indicating that Hla was the major cause of chondrocyte death. Hla-deficient DU1090 also elevated chondrocyte death compared to controls, suggesting a smaller additional deleterious role of the immune system on cartilage.Cite this article: Bone Joint Res 2022;11(9):669–678.

Manifestations Of Anxiety In Gait

PURPOSE: The purpose of this study was to employ machine learning (ML) in order to identify individuals who currently report feelings of anxiety using self-paced walking gait and balance assessments. METHODS: Participants (n = 87) completed the testing in a single session. Self-reported feelings of anxiety were measured using the Profile of Mood States- Short Form (POMS-SF), the modified Clinical Test of Sensory Interaction and Balance (mCTSIB) was used to assess balance in 4 conditions (eyes open (EO), feet on ground (FI), eyes closed (EC) FI, EO foam surface (FO) and EC FO) and a self-paced 2-minute walking gait around a 6 m track was measured using the APDM mobility monitors. Participants were grouped into anxious (A) (n = 36, age = 23.31 ± 3.69 yrs, height = 174.13 ± 9.76 cm, weight = 74.86 ± 14.26 kg, male = 14), and not anxious (NA) (n = 51, age = 25.20 ± 4.24, height = 174.13 ± 9.76 cm, weight = 73.00 ± 15.83 kg, male = 21). The models were trained using classifiers with all features and top 5 features (using a 0.024 cut-off for feature importance). The models were trained in a 10-fold cross-validation manner in order to avoid problems such as overfitting or selection bias. Data was then randomly split into training set (90%) and test set (10%) and ran through each of the ML models 10,000 times. RESULTS: The top model was a Random Forrest with the top 5 features. The median accuracy of that model was 75% and the mean was 69.7%. Approximately 3% of the models had 100% accuracy. The top five features were mean angles of turns, variance of neck bending in the frontal plane, variance in arm swing speed, movement of the lumbar region in the sagittal plane and the maximal lumbar rotation in the transverse plane. CONCLUSIONS: The findings of this study suggest that gait variables are the most important variables in identifying individuals who report feelings of anxiety. The median accuracy of the models suggests that studies with a larger pool of subjects may yield significantly better models in order to identify individuals who feel anxious when using walking gait analysis.

Applied Assessment Method for Varus Thrust during Walking in Patients with Knee Osteoarthritis Using Acceleration Data Measured by an Inertial Measurement Unit.

We developed a novel quantitative method to assess varus thrust during walking using acceleration data obtained from an inertial measurement unit (IMU). This study aimed to examine the reliability of the developed index and to evaluate its ability to distinguish patients with knee osteoarthritis (OA) with varus thrust from healthy adults. Overall, 16 patients with knee OA and 16 healthy adults walked on a treadmill with IMUs attached to the tibial tuberosity and lateral femoral condyle. As an index of varus thrust, we used the root mean square (RMS) of acceleration in the mediolateral direction. This value was adjusted by dividing it by swing speed while walking (adjusted RMS, A-RMS) because the RMS of the acceleration was strongly coupled with the speed of motion. The intraclass correlation coefficients of A-RMS of the tibia and femur were 0.85 and 0.73, respectively. Significant differences were observed in the A-RMSs of the tibia and femur, with large effect sizes between the patients with knee OA and healthy adults (Cohen’s d: 1.23 and 0.97, respectively). Our results indicate that A-RMS has good test–retest reproducibility and can differentiate patients with varus thrust from healthy adults.

Measuring the bat-ball impact location from bat acceleration

This study describes a novel method to identify the bat-ball impact location from accelerations measured at the bat knob. The magnitude of mode 1 and mode 2 accelerations were normalized by the swing speed and found as a function of the impact location. The impact location was identified by minimizing the error of normalized acceleration from impacts of batters swinging at different speeds. Impact locations from the accelerations were then compared with locations measured by high-speed video. Good agreement was found for bats with an asymmetric acceleration signature.

Data Analysis of Sport Specific Variables for Performance Consistency Evaluation in Critical Moments of College Tennis Matches

Performance under pressure typically represents a significant factor in achieving desired athletic goals and competition outcomes. Dealing with performance under pressure can be an extremely challenging task for many athletes as competitions are not necessarily decided by talent or technique alone, but also by performance quality under pressure conditions. Even though coaches and fans can be quick to claim that recognition of suboptimal or superior performance under pressure is simple, clear definitions of individual performance patterns under pressure have not yet been established. This work introduces an approach for the identification of crucial moments in college tennis matches, presents a data collection methodology designed to capture measurements and observations of college tennis specific variables, and proposes data analysis procedures designed to evaluate performance quality in crucial moments of college tennis competitions. The crucial moments of college tennis matches were defined as a newly introduced variable, called the crucial point, and its identification was based on match scores. The study data were collected with 15 college tennis players in 60 tennis sessions using two wearable sensors. College tennis specific parameters evaluated in the study were swing speed and heartrate variables. The obtained results showed specific performance data pattern relationships between the study variables and the identified crucial points. The results provide evidence that the presented performance under pressure evaluation model, if developed further, could help college tennis coaches and players to develop individually tailored game plans and strategies to improve their chances for success in crucial moments of their college tennis competitions.

Intermittent hypoxia promotes the recovery of motor function in rats with cerebral ischemia by regulating mitochondrial function.

Hypoxia preconditioning is neuroprotective, but the therapeutic effects of intermittent hypoxia were not fully considered. The present study investigated the neuroprotective effect and mechanism of intermittent hypoxia on motor function after cerebral ischemia and explored alternative clinical treatment options. In total, 36 8-week-old male Sprague-Dawley rats were subjected to 60 min of transient middle cerebral artery occlusion (tMCAO) and then randomly divided into a sham-operated group (SHAM), tMCAO-sedentary group (SED), and tMCAO-intermittent hypoxia group (IH). The intervention was performed 1 week after tMCAO and lasted 4 weeks. Rats in the IH group were placed in an animal hypoxic chamber (altitude 5000 m and oxygen concentration of 13%) for 4 h/day and 7 days/week, and rats in the SED group were placed in a normoxic environment for 4 weeks. Body weights, neurological deficit scores, cerebral infarction volume ratios, gait analyses, mitochondrial structure, adenosine triphosphate (ATP) content and AMO-activated protein kinase (AMPK), peroxisome proliferator-activated receptor γ co-activator-1α (PGC-1α), and silencing regulatory protein 3 (Sirt3) expression in the peri-ischemic region brain tissues were detected during the intervention. Compared with the SED group, the body weight of the IH group gradually recovered, and the neurological deficit scores were significantly reduced (P < 0.05). The gait analysis results showed that the pressure of the affected paw and the maximum content area, swing speed, stride length, and other parameters were significantly restored (P < 0.05). The cerebral infarction volume ratio was significantly reduced (P < 0.01). Mitochondrial morphological structure damage in the peri-ischemic region brain tissues recovered, the number was significantly increased (P < 0.05), and the expression of AMPK, PGC-1α, and Sirt3 proteins (P < 0.05), and ATP content were significantly increased (P < 0.05). Intermittent hypoxia may activate the AMPK-PGC-1α-Sirt3 signaling pathway, promote mitochondrial biogenesis, repair mitochondrial ultrastructural damage, and improve mitochondrial function to reduce brain damage and promote motor function recovery in rats with cerebral ischemia.

Torso dynamics during follow through in baseball batting

ABSTRACT The purpose of this study was to clarify the relationship between the bat swing speed immediately after the ball impact and the dynamics of the torso during the follow through in baseball batting. The batting motion and ground reaction forces acting on each foot for 29 collegiate baseball players were recorded using a motion capture system and two force plates. The biomechanical variables of the torso joint (i.e., the virtual joint that divides the torso between upper and lower) were calculated. For right-handed batters, the torque power of the right rotation in the torso joint was negative. Additionally, the bat head speed immediately after the ball impact was significantly correlated with the negative (i.e., right) peak rotation torque of the torso joint (r = −.635, p < 0.001) and the negative peak power in the right rotation torque of the torso joint (r = −.590, p = 0.001). These results suggest that the left external abdominal oblique muscle is in eccentric contraction during the follow through in baseball batting. Moreover, the results imply that the higher the bat head speed immediately after the ball impact, the higher the possibility to strain the abdominal oblique muscle.

A single smartwatch-based segmentation approach in human activity recognition

The development of smart wearable devices has driven the rapid progress of activity recognition. However, existing activity recognition methods are still struggling to recognize single arm swings due to coarse-grained sensor data segmentation. Refined arm-swing-wise data segmentation is vital in some specific cases, such as the rehabilitation of disabled patients. In this paper, we propose a smartwatch-based arm-swing-wise data segmentation approach for human activity recognition, which converts original sensor signals into square-wave signals to detect the cut-off points of each arm swing. Particularly, our method can adaptively adjust the window size and step size of a sliding window without considering the change of swing speed. Empirical evaluation on two datasets, a self-collected dataset and a publicly-available benchmark dataset, shows superior performance of our approach over other methods under different settings, such as classifiers, features, and wearing positions.

Different Effects of 12-Week Speed or Accuracy Training on Obstacle-Crossing Foot Motion in Healthy Elderly.

Preventing falls is important in the elderly. One reason for falling is tripping or stumbling; hence, it is important to improve the crossing motion. This study aimed to compare speed- and accuracy-oriented crossing training and establish a useful training method. To investigate the effects of crossing motion training, we conducted a randomized controlled trial. Twenty healthy elderly individuals (aged 71.7 ± 1.5 years) were randomly assigned to two groups: speed training and accuracy training groups. They practiced initiating their crossing motion faster or more accurately for 12 weeks. Using a three-dimensional motion analysis system, the data on the crossing motion was captured before and after the training period. We set four conditions (normal speed, fast, leaning stance, and leaning stance and fast) and two directions (anterior and lateral) to analyze the crossing motion. The crossing motion of the speed training group became significantly faster compared to baseline (p < 0.05); however, the accuracy of the crossing motion of the accuracy training group was not statistically significant. Speed training in this study had clear effects on crossing motion. It is surprising that crossing motion training from a normal upright stance can also improve swing speed from the leaning stance. We believe that this training is easy and useful in the elderly population.

Anthropomorphic Prosthetic Hand Inspired by Efficient Swing Mechanics for Sports Activities

Swinging-generating high impact by maximizing the speed of motion-is essential in sports activities. However, designing prosthetic hands suitable for swinging is still a challenge. Herein, in this article, we propose a swing-dedicated prosthetic hand that adopts the anatomical features of humans for an efficient swing. Our design, inspired by the joint arthrokinematics and tendon routing of fingers, enables a diagonal power “squeeze” grip robust to impact while increasing the reach of the clubhead. The swing speed is further increased by radio/ulnar deviation of the wrist and its nonlinear stiffness change achieved by the passive clutch mechanism. We evaluated our prosthetic hand through golf and found that it sustained high impact with diagonal grip, and clubhead speed increased by 19% at 90 r/min, with the radio/ulnar deviation nonlinearly correlated with arm angle. Our prosthetic hand design will contribute to improving amputees’ quality of life by allowing them to participate in sports activities.

Kinetic Analysis of the Dwigongjungdorachagi in Taekwondo

Purpose: The purpose of this study is to provide the basic data for technical performance by analyzing and presenting the differences in major kinematic factors in the jumping phase, flight phase, and finally striking phase for national team and non-national team male demonstration members. Method: As for the subjects of this study, 6 members of the national team and 6 members of the non-national team who had more than 3 years of demonstration experience were selected and tested. Before entering the ex-periment, a consent was secured from each subject, the experimental procedure was explained, and kinematic data were collected by using 14 high-speed digital cameras. For the statistical processing of this study, the mean and standard deviation (M±SD) were calculated by using Excel 2018, and the statistical program (SPSS 22.0, SPSS Inc., Chicago, IL, USA) was used to verify the difference in kinematic variables of dwigongjungdorachagi motion. The Shapiro-Wilk verification was conducted to confirm the normality of the collected data, and according to the results, an independent sample test (independent t-test), test (Mann-Whitney U-test), and the correlation analysis were performed. Results: There was a statistically significant difference in P3 (p<.05) of the required time phase. There was a statistically significant difference in E4 (p<.05) of the (Z) movement displacements. There was a statistically significant difference in the right E4 (p<.05) of the right ankle joint angle. The correlation coefficient between the body center’s displacement and flight time showed a high correlation and showed a statistically significant difference (r=.953, P=.001). The correlation coefficient between the angular velocity and the body center’s displacement showed a high correlation and showed a statistically significant difference (r=.809, p=.001). The correlation coefficient between the angular velocity and flight time showed a high correlation and a statistically significant differ-ence (r=.809, p=.001). Conclusion: As a result of the experiment, the swing speed of the arm and the angle of the knee joint before jumping during dwigongjungdorachagi provided a great force to project the human body into the air and also had the effect of increasing vertical ascent. Hence, it is apparent that the coordination of movements is a very important factor.

The effects of 10-week light and heavy ball mixed training on the performance in young baseball players

&lt;p&gt;目的 : 探討 10週輕重球混合投擲訓練對青少年棒球選手的上肢肌力與投球表現之影響。方法：受試者為 24位國中甲組棒球隊選手，分為混合組 (正常球：145g；輕球：125g；重球：175g)與控制組 (正常球：145g)，進行 10週每週三次的訓練。訓練前後測量上肢肌力(坐姿推鉛球擲遠能力、握力、指力)與投球表現(投擲球速、準度、擲遠能力與瞬間揮臂速度)。結果：10週訓練後混合組投球球速、擲遠能力以及瞬間揮臂速度均顯著進步 (p &lt; .05)，其餘依變項則無顯著改變；控制組的所有依變項均無顯著進步或改變。結論：10週每週三次投擲不同重量棒球的混合訓練，對於體型、體能、技術正在發展中的青少棒選手，能顯著改善投擲速度、擲遠能力及投球出手瞬間揮臂速度，建議青少棒選手可進行輕、重球混合的訓練，以提升投球表現。&lt;/p&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;&lt;p&gt;Purpose: To explore the effects of 10-week light and heavy ball mixed training on the upper limb muscle strength and pitching performance in young baseball players. Methods: The subjects were 24 middle school baseball players who were randomly assigned to the mixed group (normal ball: 145g; light ball: 125g; heavy ball: 175g) and the control group (normal ball: 145g) for 10 weeks each Training three times a week. Before and after training, the muscle strength of the upper limbs (the ability to throw shots in a sitting position, grip strength, and finger strength) and throwing performance (the speed of throwing the ball, accuracy, ability to throw the distance and instant arm swing speed) were measured. Results: After 10 weeks of training, the mixed group’s pitching speed, throwing ability and instant arm swing speed all improved significantly (p&lt;.05), and the other dependent variables did not change significantly; all dependent variables of the control group showed no significant improvement or change. Conclusion: The mixed training of throwing different weight baseballs three times a week for 10 weeks can significantly improve the throwing speed, the ability of throwing distance, and the speed of throwing the ball. It is recommended that young baseball players can practice mixed light and heavy ball training to improve their pitching performance.&lt;/p&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;

Accuracy and Error Trends of Commercially Available Bat Swing Sensors in Baseball.

In baseball, the swing speed and swing angle of the bat just before ball impact are important to increase the speed and horizontal distance of a batted ball. This study investigated the accuracies and error trends of four commercially available bat sensors to measure these parameters. The hitting motions of seven healthy participants were measured simultaneously using the bat sensors and an optical motion capture system, and the swing speeds and swing angles were compared. The swing speed was measured with high accuracy, as indicated by the high intraclass correlation coefficient (ICC) between the bat sensor and the motion capture system measurements (mean ICC = 0.78). However, the ICC for the swing angle was lower (mean ICC = 0.58) than that of the swing speed for all but one bat sensor, indicating low accuracy. Moreover, in the high swing speed range, the accuracy of the swing speed tended to decrease for three bat sensors, but the trend of the swing angle was different among bat sensors. Significant systematic biases or proportional errors were found for all bat sensors, indicating the possibility of error correction. The sensor used in this study can help to evaluate the differences between players with different competition levels and hitting motions. Coaches need to be cautious in taking measurements of players with high swing speeds and in assessing slight changes within an individual.

Effect of Training to Hammer Swing on Swing Speed in Baseball Batting

Effect of Training to Hammer Swing on Swing Speed in Baseball Batting