壹、緒論
一、問題背景
在許多的運動動作中，執行跑跳動作的跳躍著地過程中，人體的下肢肌肉骨 骼會呈現一個類似彈簧的特性，對人體下肢肌肉骨骼等組織結構建立一個彈簧質 量模型(spring-mass model)，因此該模型是由身體質量和支撐身體質量的線性彈簧 所組成的（Farley, and Ferris, 1998; Blickhan, 1989; Butler, Crowell, & Davis, 2003）。 下肢勁度表示在著地面接觸期間整個肌肉骨骼系統的平均勁度，下肢勁度在著地 期間受到最大地面垂直反作用和重心垂直下降的位移的相互影響（Farley, & Morgenroth, 1999; Hobara, Kimura, Omuro, Gomi, Muraoka, Iso, & Kanosue, 2008）， 也就是說，重心垂直的位移量減少，則有較大的下肢勁度。關節角勁度的計算是 下肢在著地時最大淨關節力矩變化量除以最大下肢關節彎曲角位移量。下肢勁度 會受到下肢重心垂直下降位移量的影響，相對地下肢重心垂直下降位移量也會影 響到關節角勁度的下肢各關節角度的變化量，並且下肢各關節肌群淨力矩的變化 量亦會影響最大地面反作用力之形成，所以下肢勁度與關節角勁度兩者之間的調 節應有所關聯。(Farley, & Morgenroth,1999)
貳、研究方法及步驟
一、研究對象 本研究受詴者為 6 名大專男子公開組第一級籃球隊隊員，平均年齡：21.5±1.9 歲；身高：188.5±4.6 公分；體重：81.8±4.5 公斤。所有受者在實驗期間或之前均 無疾病和下肢骨骼肌肉之病痛等相關症狀，對於本研究之研究目的及整個實驗流 程均有所了解，而且簽署受詴者同意書及個人基本資料。 二、實驗儀器圖 1 反光球黏貼位置示意圖
四、資料分析
不同頻率連續垂直跳需跳 15 下，取第 6 下至第 10 下做為本研究分析的資料。 可得到反作用力、垂直跳頻率、著地時間、空中時間及重心位移的距離等參數。
運動學的資料分析使用 Visual 3D (C-Motion, Inc., Rockville, MD, USA) 軟體 進行，反光球軌跡原始數據用截止頻率 8 Hz 的 Butterworth 2nd Zero-lag 低通濾波 來修勻去除雜訊。利用彈簧-質量模型來計算下肢勁度，在連續垂直跳期間，最大 垂直地面反作用力和下肢重心的位移量同時發生在地面接觸期的中間，下肢勁度 為最大垂直地面反作用力和下肢重心的位移量的比率（Farley, & Morgenroth, 1999; Hobara, et al., 2008），其計算公式如下：Kleg = Fpeak / △L。關節勁度的計算也是在地
面接觸期中間的最大關節力矩與關節角位移的比率（Farley, & Morgenroth, 1999）， 其計算公式如下：Kjoint = △Mjoint / △θjoint 。下肢關節力矩是使用逆動力學分析力矩
及人體肢段參結合計算出來的（Dempster, 1955）。將垂直地面反作用力除以受詴者 體重給予標準化，以計算出下肢勁度和關節勁度。本研究所有的參數皆取三次成 功實驗之平均值進行統計分析。
五、統計分析
(Hobara, et al., 2009, 2011）。人體的下肢對環境條件變化會產生調整和適應，並根 據運動頻率採用不同的控制策略來穩定跳躍，對於最佳的運動表現是很重要。
肆、結論與建議
一、結論 本研究利用將彈簧質量模型來評估下肢勁度，探討人體在不同頻率連續垂直 跳對下肢勁度的影響。隨著連續垂直跳頻率的增加，著地時間、空中時間、重心 位移和下肢各關節角位移也隨著減少，在 3.0 Hz 連續垂直跳時，有最小的最大地 面反作用力和重心位移，以及最大的下肢勁度；隨著垂直跳頻率增加，在著地期 間下肢各關節比較伸直(髖、膝關節較為伸直)，且關節角位移也相對較小，有較大 的踝關節角勁度。因此，在不同頻率連續垂直跳造成下肢勁度的差異，是由於增 加關節角勁度，且受到著地瞬間角度改變較小，下肢關節屈曲的程度也較小。將 人體視為一個簡單的彈簧質量模型，下肢勁度和重心位移度可以透過控制肌肉激 活或通過力學特性來調整，或者是依運動速率採用不同的控制策略來穩定彈跳步 態(Riese, et al., 2013; Yen, & Chang, 2010)。故人體會因應不同的工作項目及外在環 境條件變化，適時地調節下肢勁度，以獲得更佳的運動表現。二、建議
在進行下一步的研究時調查不同運動選手之間，以追踪在自我調控和節拍器 控制下的不同頻率，下肢勁度的變化是否隨時間變化或保持穩定。
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Effects of hopping with different frequencies on leg stiffness
Su-wei Lee12 / Chen-Fu Huang1Department of Physical Education, National Taiwan Normal University1 / Lee-Ming Institute of Technology2
Abstract
The purpose of this study was to investigate how humans adjust leg stiffness over a range of hopping frequencies. Six male basketball subjects performed in place hopping on two legs (age: 21.5 ± 1.9 years; height: 188.5 ± 4.6 cm; weight: 81.8 ± 4.5 kg). They were instructed to hop in place at five frequencies (1.5, 2.1, and 3.0 Hz, perform hopping with maximal effort and Self-selected frequencies). Ten Vicon Motion System cameras (250Hz), two Kistler force plates (1000Hz) and Vicon Nexus software were used simultaneously to capture kinematic and kinetic variables of hopping. Visual 3D software was used for calculations. A one-way repeated-measure ANOVA was performed for statistical analysis and LSD post-hoc were adopted to analyze the statistical difference with an alpha level of .05. The results showed that contact time, air time, COM displacement, hip and knee angular displacement decreased with an increase in hopping frequency. At the 3.0 Hz hopping frequency, there were greater leg stiffness and ankle stiffness. The subject’s hip and knee joints are straighter with increased hopping frequency during landing. These results suggest that over the range of hopping frequencies we evaluated, humans adjust leg stiffness by altering ankle stiffness. Therefore, when evaluating the leg stiffness of hopping at different frequencies, the human body can be adjusted through the ankle joint stiffness to obtain better exercise performance.
