優秀的高爾夫選手在下桿時，會鬆弛上身的雙臂以讓下身先行扭轉後桿頭才觸球，所以本研究的目的在於分析下桿時上身與下身的動作順序，以及對桿頭速度的影響，亦即由足部的重心轉移對地表作用，而地表給予反作用力導致桿頭速度的明顯增加。下桿時體重在右足的最大垂直分力，的時間至左足最大垂直分力的時間，稱為下桿的「作用階段時間」(action phase), 而左足最大垂直分力的時間作至桿頭觸球的時間，稱為「反作用階段時間」(reaction phase)，背闊肌開始收縮的時間至胸大肌開始收縮的時間，稱為「肌肉工作時間差」(time difference of contraction)。實驗場地的儀器包括，測力板、桿頭測速器、肌電儀以及設計於測力板上的揮桿草皮。以Kistler系統1000Hz的取樣頻率來獲取最大垂直分力資料，置於桿身尖端(tip)的桿頭測速器的單位為公尺／秒，兩片肌電訊號偵測器(electrode detectors)分別置於背闊肌與胸大肌表面，肌肉收縮活動的訊號以Acqknowledge分析軟體進行分析，取樣頻率為1000Hz。三名國家代表隊的優秀選手設定為A組，四名初學者設定為B組，進行每人30下的揮桿測試，桿頭速度為依變數並進行依變速與自變數的統計分析。在下身引導上身的背闊肌早於胸大肌收縮情形下，發現A組的作用階段時間(0.250±0.087sec)比B組(0.478±0.290sec)快，A組的反作用階段時間(0.058±0.01 sec)比B組(0.049±0.25sec)長，選手A組的肌肉工作時間差(0.448±0.18sec)比初學者B(0.691±0.370sec)短，同時選手A組的桿頭速度(44.83±1.14m/sec)比初學者B組(37.27±3.80sec)快，在上身引導下身的胸大肌早於背闊肌收縮的情形下出現初學者的78次揮桿，其桿頭速度明顯降低至28.74±2.02m/se。比較兩組各變相的獨立樣本t考驗，顯示初學組的作用階段時間未達顯著關係外，其它皆達極顯著關係。檢定選手組表現在各項變數的相關性質，則顯示作用階段時間、反作用階段時間、肌肉工作時間差，與桿頭速度呈現極相關水準(P<.01)以上顯示必需有下身引導上身的下桿順序，始能使桿頭明顯加速。

Elite golfers soften their arms as to let lower body twist before club head impact the ball, so the intent of this study was to find out the sequential movement of down swing and its affection on the club-head velocity. The contribution of achieving maximum club head velocity is the result of a culmination of forces origination at the feet. The time between the maximum vertical force on back and front foot named "action phase", on front foot and impact named "reaction phase". The start time between latissimus dorsi and pectoralis major contraction named “time difference of contraction”. Two separate force plates, club head speed meter, EMG and an artificial swing mate on force plate were arranged in laboratory. Samples of vertical force were collected with 1000 Hz rate in Kistler system, speed meter (m/sec) was put on the neck of club head, and the muscles activity data with 1000 Hz rate in Bio-Pac system and AcqKnowledge software were obtained from electrode detectors on latissimus dorsi and pectoralis major. Three elite golfers from national team members and four beginners were tested and named A group, B group. We found action phase of A group was 0.250±0.087sec and of B was 0.478±0.290sec, reaction phase of A group was 0.058±0.01 sec and of B was 0.049±0.25sec sec, time difference of contraction of A was 0.448±0.18 sec and of B was0.691 ± 0.370sec sec and club head speed of A was 44.83 ± 1.14 ni/sec and of B was 37.27 ± 3.80m/sec. Moreover, there were 78 times of B group to play the un-correct sequential movement during down swing which caused the contraction time of pectoralis major prior to latissimus dorsi and reduce the club head speed to 28.74±2.02 m/sec. The T test of two group shown the significant difference on all factors but action phase of B group (.06), and the correlation test of A group shown that action phase, reaction phase, and time difference of contraction were most significant relation with club head speed (p<.01). It shown that the correct sequential movement could increase the club head speed during golf down swing.