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Lin K.-H.,National Tsing Hua University | Huang Y.-M.,National Taiwan Sport University | Tang W.-T.,National Taiwan Sport University | Chang Y.-J.,Chang Gung University | And 3 more authors.
Isokinetics and Exercise Science | Year: 2013

BACKGROUND: Trunk muscle endurance training is used by most high school baseball or softball coaches. However, evidence demonstrating a relationship between trunk muscle endurance and batting performance is lacking. OBJECTIVE: This study aimed to establish a relationship between trunk muscle endurance and bat swing velocity in a high school baseball team. METHOD: Sixty-one high school (15-18 years old) baseball players, taken from the same team, with 6.5 ± 1.3 years of training experience, participated in the following tests: static trunk flexion/extension endurance tests, dynamic trunk flexion/extension endurance tests and a maximum bat swing velocity test. RESULTS: Bat swing velocity showed significant low-to-moderate negative correlations with static trunk flexor endurance (P=0.001, r=-0.404), dynamic trunk flexor endurance (P=0.016, r= -0.308) and the ratio of static flexor/extensor endurance (P=0.021, r=-0.298). CONCLUSIONS: These findings support the concept that better trunk flexor endurance might not benefit batting performance. Trunk flexor endurance training should not be over-emphasized when the targeted training goal is to enhance bat swing velocity. © 2013 - IOS Press and the authors. All rights reserved.

Chan M.-S.,National Taiwan Normal University | Huang S.-L.,Graduate Institute of Sports Equipment Technology | Shih Y.,National Taiwan Normal University | Chen C.-H.,National Taiwan Normal University | Shiang T.-Y.,National Taiwan Normal University
Sports Biomechanics | Year: 2013

In addition to vertical ground reaction force (GRF), anterior-posterior GRF with a greater external moment arm may be another repetitive impact force that contributes to overuse running injuries. In this study, a shear cushion device was placed between the sole of a shoe and the ground to reduce not only the vertical loading, but also the anterior-posterior loading while walking and running. For this study, 15 healthy male runners classified as heel strikers (height: 173.2 ± 4.7 cm, mass: 68.5 ± 5.6 kg) were recruited. Participants were required to walk (2.5 m/s), jog (3.5 m/s), and run (4.2 m/s) while wearing shoes with three different sole groove designs (conventional, straight groove, and 45° groove). Both the straight and 45° groove soles provided significant shear shift during walking, jogging, and running, as well as delayed the time to first peak anterior-posterior GRF during walking. The straight groove sole reduced the vertical loading rate during jogging (p = 0.010) and running (p = 0.010), and delayed the time to first peak vertical GRF in all gait conditions. These findings suggest that the vertical loading rate and the time to the first peak anterior-posterior GRF can be changed by the sole groove design under various gait conditions. © 2013 © 2013 Taylor & Francis.

Yang W.-W.,Graduate Institute of Sports Equipment Technology | Yang W.-W.,National Yang Ming University | Liu Y.-C.,Chung Hua University | Lu L.-C.,Graduate Institute of Sports Equipment Technology | And 4 more authors.
Journal of Strength and Conditioning Research | Year: 2013

Compared with regulation-weight baseballs, lightweight baseballs generate lower torque on the shoulder and elbow joints without altering the pitching movement and timing. This study investigates the throwing accuracy, throwing velocity, arm swing velocity, and maximum shoulder external rotation (MSER) of adolescent players after 10 weeks of pitching training with appropriate lightweight baseballs. We assigned 24 adolescent players to a lightweight baseball group (group L) and a regulation-weight baseball group (group R) based on their pretraining throwing velocity. Both groups received pitching training 3 times per week for 10 weeks with 4.4- and 5-oz baseballs. The players' throwing accuracy, throwing velocity, arm swing velocity, and MSER were measured from 10 maximum efforts throws using a regulation-weight baseball before and after undergoing the pitching training. The results showed that the players in group L significantly increased their throwing velocity and arm swing velocity (p < 0.05) after 10 weeks of pitching training with the 4.4-oz baseball, whereas group R did not (p > 0.05). Furthermore, the percentage change in the throwing velocity and arm swing velocity of group L was significantly superior to that of group R (p < 0.05). Thus, we concluded that the 10 weeks of pitching training with an appropriate lightweight baseball substantially enhanced the arm swing velocity and throwing velocity of the adolescent baseball players. These findings suggest that using a lightweight baseball, which can reduce the risk of injury without altering pitching patterns, has positive training effects on players in the rapid physical growth and technique development stage. © 2013 National Strength and Conditioning Association.

Chen C.-H.,National Taiwan Normal University | Liu C.,Graduate Institute of Sports Equipment Technology | Chuang L.-R.,Chinese Culture University | Chung P.-H.,Graduate Institute of Sports Equipment Technology | Shiang T.-Y.,National Taiwan Normal University
Journal of Science and Medicine in Sport | Year: 2014

Previous studies on vibration training have all been based on protocols at different combinations of frequencies and amplitudes without controlling the loading intensity. Objectives: This study investigated the effect of an 8-week vibration training program, under identical acceleration loads with various frequencies and amplitudes, on jumping performance, muscle activation and body balance. Design: Fifty young adults were randomly assigned to an high-frequency (32. Hz, 1. mm, and 4. g), low-frequency (18. Hz, 3. mm, and 4. g), or a control group. The high-frequency and low-frequency groups underwent 60. s of squats exercise on the specific vibration platform three times a week, whereas the control group was trained without vibration. Methods: A force platform was used to measure the center of pressure of a static single leg stance, and the heights and impulse of two consecutive countermovement jumps before and after intervention. The activation of the rectus femoris and biceps femoris were also measured synchronously by surface electromyography. Results: The heights and impulse of both the first and second countermovement jumps were significantly increased and the area of center of pressure was significantly decreased after training in both the high-frequency and low-frequency groups (P<.05). Consequently, activation of the rectus femoris during the first countermovement jump was significantly lower than the pre-training value in the HF group but increased in the low-frequency group after training (P< .05). Conclusions: An 8-week identical acceleration vibration training regimen with various frequencies and amplitudes can significantly improve jumping performance and body balance, but the specific neuromuscular adaptation is possibly induced by different training settings. © 2013 Sports Medicine Australia.

Lin K.-F.,Graduate Institute of Sports Equipment Technology | Chen Y.-C.,Graduate Institute of Sports Equipment Technology
2010 International Conference on System Science and Engineering, ICSSE 2010 | Year: 2010

This study is to analyze the upper and lower extremity's reaction while riding bicycle in 3 different speed and 3 different gradients on both fixed and non-fixed training platform, We used 6 physically healthy male as our subjects, who are aged 23.46±3.21 with an average height 171.26±6.39cm, average weight 64.43±7.48kg, average time of working out per week 13 hours, and no physical obstacles and surgery record. We used Bio-MP150 system along with the data retrieving software ACQ Knowledge Version 3.8.1 to analyze the distribution of extremity's muscle used. Different speed and gradient could activate different muscles of extremity; by the way, the strength of RE and UF in non-fixed are less than fixed training platform. It is very interesting, because there will be comfortably when we ride bike with non-fixed training platform. This study provides professional cyclists useful information for training purpose. © 2010 IEEE.

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