緒論：快走是以較平常走路更快速度的行走方式，常被建議作為增進體適能的運動。肌肉柔軟度不足會限制關節活動而影響行走動作。腓腸肌緊縮是常見肌肉柔軟度不足的問題。利用靜態牽拉可改善肌肉柔軟度不足，但過去文獻指出牽拉可能對肌力和一些運動表現有負面影響。本研究目的在探討靜態牽拉對腓腸肌緊縮者快走步態與腓腸肌長度的立即影響。方法：本研究徵召20位腓腸肌緊縮者隨機分為緊縮牽拉組和緊縮無牽拉組，和10位健康且腓腸肌柔軟度的正常人作為正常控制組。所有實驗參與者在牽拉前後均測量腓腸肌柔軟度。緊縮牽拉組接受10次靜態牽拉，每次牽拉2分鐘休息30秒。緊縮無牽拉組和正常控制組休息沒有牽拉。步態測試於牽拉後進行，以動作分析系統和測力板測量與計算出快走的時空參數、下肢關節角度和地面反力。腓腸肌長度是依過去文獻建立的數學模式，以踝背屈彎曲角度和膝伸直角度推算。結果：緊縮牽拉組於牽拉後柔軟度測試的腓腸肌長度明顯較緊縮無牽拉組長。緊縮牽拉組和緊縮無牽拉組在快走時下肢各關節的角度、腓腸肌長度和地面反力變化無明顯差異。快走動作在當腓腸肌到達最大長度時，在髖關節和膝關節的關節角度方面，緊縮牽拉組相較正常控制組有明顯較大的彎曲角度。結論：靜態牽拉可改善緊縮腓腸肌的柔軟度，但是對快走時的步態與腓腸肌長度沒有顯著影響。與正常控制組相比，腓腸肌緊縮者在牽拉後仍有較大髖關節和膝關節彎曲的不正常步態。

Introduction: Fast walking is faster than stroll or pedestrian walking and is often recommended for fitness. Poor muscular flexibility can restrict joint motion and affect walking movement. Gastrocnemius is a common tight muscles found in lower limbs. Static stretching is frequently recommended to elongate tight muscle. However, some previous evidences suggested that acute muscle stretching might impair muscle strength and other components of sports performance. Thus, the purpose of the study is to investigate the acute effects of stretching on the gait performance and gastrocnemius muscle length during fast walking for people with tight gastrocnemius. Methods: Twenty volunteers with tight gastrocnemius were randomly assigned to a stretch or no-stretch group. Ten healthy volunteers with normal gastrocnemius flexibility were assigned to normal control group. Gastrocnemius tightness measurements were performed before and after stretching. The stretch group underwent ten gastrocnemius stretches for 2 minutes each with 30-second rest periods. The no-stretch and normal control group would rest instead of stretch. The gait data were collected using a motion analysis system and two force plates after stretching. The spatiotemporal parameters, joint angles in the lower extremity and ground reaction forces were computed and analyzed. The regression model of previous study was used to estimate gastrocnemius length from measurements of joint angle in ankle dorsifleixon and knee extension. Results: Compared with the no-stretch group, a greater gastrocnemius length in flexibility test was found after stretching for the participants with tight gastrocnemius. The joint angles in lower limbs, ground forces and gastrocnemius length in fast walking were not significantly different in stretch group as compared to no-stretch group. Compared with the normal control group, significantly greater flexion angles of the hip and knee were detected in stretch group during fast walking. Conclusion: Static stretch can improve the flexibility of tight gastrocnemius. However, the stretch has no significant effect on gait movement and gastrocnemius length during fast walking for people with tight gastrocnemius. Compared with the normal controls, participants with tight gastrocnemius adopt a flexed hip and knee gait after stretching during fast walking.