| Summary: | 碩士 === 臺北巿立體育學院 === 運動器材研究所 === 100 === Purpose: The aim of this study was to investigate subjective fatigue effect on softball pitching performance and biomechanics of stride leg after long-term pitching. Methods: Seven collegiate women’s softball pitchers were recruited to throw 15 pitches per inning with interval of rest for 3 minutes under an actual softball game atmosphere in biomechanics lab. Repeated pitching was ended by subjective fatigue (RPE ≧ 17) or achieving 150 pitches. Speed gun and video records were collected pitching performance, including of ball velocity and pitching accuracy. Motion analysis system was captured kinematics of stride leg as well as a force plate was gathered ground reaction force during acceleration phase of pitching. Surface electromyography was detected hip and thigh muscles activities. All parameters were examined by nonparametric method (Wilcoxon signed ranks test) between pre and post fatigue pitching. Results: Ball velocity slightly decrease by 2mph after repeatedly pitching until subjective fatigue, but the error distance from pitching target was significantly enlarged from 21.91 ± 1.82cm to 28.74 ± 3.93cm. Both range of motion (ROM) of knee flexion and hip flexion during eccentric landing phase increased with significance from 11.34 ± 4.97° to 13.91 ± 5.84° and 3.15 ± 8.26°to 4.62 ± 8.17° in sequence. ROM of trunk forward tilting from 3.77 ± 1.73° was significant larger to 5.53 ± 3.80°. Pre-activation of rectus femoris muscle before the leg stride had decreased with significance by 26%, however, gluteus medius muscle activation was significantly greater by 34% during landing to pitching. Conclusion: Pitching accuracy was decreased by long-term pitching and knee of stride leg bent more during landing phase, for the reason that more muscle activities were recruited among hip extensor and abductors to keep stability of pelvis and trunk. We recommend that pitchers should strengthen lower extremity and coaches should properly arrange training programs including recovery time from fatigue to preserve pitching performance and avoid sports injuries.
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