棒球捕手沙發護墊對下肢運動生物力學之影響

The effects of baseball catcher's knee saver on biomechanical parameters in lower limb

緒論：沙發護墊是棒球捕手的新式器材，廣受捕手使用，但未有學術探討其功效，因此，研究目的為瞭解沙發護墊對捕手運動表現的影響，經由比較捕手於不同蹲捕姿勢下，有無穿戴沙發護墊對於捕手接捕及傳球動作表現、下肢運動學、膝關節力矩以及肌肉活化之影響。方法：六名業餘成棒甲組球隊捕手之平均年齡21.67±3.78歲、身高173.17±6.31公分、體重82.00±10.02公斤，隨機方式穿戴沙發護墊與無穿戴沙發護墊，進行低蹲姿和高蹲姿的蹲捕動作。收集穩定站姿5秒、穩定蹲姿5秒、接球起身傳球動作。以Motion Analysis System三維動作分析系統收集運動學參數，以AMTI測力板量測地面反作用力，並利用OrthoTrak計算膝關節力矩，並使用Biovision表面肌電儀擷取下肢股直肌、脛前肌、腿後肌、外側腓腸肌肌肉活性。結果：經相依樣本t考驗後，發現有穿戴沙發護墊的低蹲姿時，起身動作時間（0.55±0.08秒vs. 0.59±0.09秒）與牽制動作時間（0.89±0.09秒vs. 0.91±0.09秒）皆顯著較短，並能顯著減少穩定蹲姿期的股直肌肌肉活性（9.76±8.46% MVC vs. 13.26±8.94% MVC），顯示有穿著沙發護墊能在低蹲姿時，增加起身-牽制的動作表現，並有助於捕手長時間蹲捕時較不易造成股直肌的肌肉疲勞。然而，在高蹲姿時，有無穿戴沙發護墊在各項參數均未達顯著差異，顯示沙發護墊在高蹲姿時無效益。結論：市售捕手專用之沙發護墊能於低蹲姿時，僅能為捕手帶來一些生物力學上的正面效益，但在高蹲姿時則未有任何效益。

Introduction: The Knee Saver is a new equipment for baseball catchers. However, the biomechanical advantage is still unclear when catchers wear it. The study compared the catching-to-throwing movement time, lower limb kinematics, knee joint moments, and muscle activation under different squatting conditions between wearing with and without the Knee Saver. Methods: Six elite amateur catchers (age: 21.67±3.78 years; height: 173.17±6.31 cm; mass: 82.00±10.02 kg) voluntarily participated in this study. Each catcher randomly wore with and without the Knee Saver and performed low and high squatting conditions, respectively. Data collection included five seconds of stable standing, five seconds of stable squatting, and the receiving-to-throwing movement. Kinematical parameters were detected using the Motion Analysis System, ground reaction forces were measured through the AMTI force plates, and knee joint moments were calculated using the OrthoTrak software. The muscle activations of the rectus femoris, tibialis anterior, hamstrings, and lateral gastrocnemius were recorded using Biovision surface electromyography. Results: After using paired t-test, wearing the Knee Saver in the low squatting condition significantly reduced the standing movement time (0.55±0.08 sec vs. 0.59±0.09 sec), the throwing movement time (0.89±0.09 sec vs. 0.91±0.09 sec), and the Rectus Femoris muscle activation during the stable squatting phase was significantly lower (9.76±8.46% MVC vs. 13.26±8.94% MVC) compared to those of without wearing it. These findings suggested that the Knee Saver enhanced the catching-to-throwing performance and prevented muscle fatigue during prolonged squatting only in the low squatting condition. Furthermore, there were no significant differences across all parameters in the high squatting condition between wearing with and without the Knee Saver. Conclusion: The commercially available Knee Saver might only provide a few biomechanical advantages in low squatting conditions. However, no positive effect was revealed in high squatting conditions.