全身性震動(whole-body vibration)可誘發肌肉張力性震動反射收縮(tonic vibration reflex)，藉此改善高齡者下肢肌力及平衡能力。雖然研究指出職業運動員於30Hz及40Hz震動採半蹲姿勢時股外側肌活性較大，全身性震動訓練未必適用於不同身體活動程度之較高齡者。本研究目的在探討不同震動頻率與身體活動量對中高齡男性下肢肌電訊號的影響。36位50~65歲健康男性使用國際身體活動量表(International Physical Activity Questionnaire)，依活動量分為運動不足及運動充足組，於震動平臺上以靜態半蹲進行0Hz（無震動）、20Hz、30Hz、40Hz各30秒，膝蓋彎曲角度100度，記錄下慣用腳肌電圖反應。本研究結果：兩組受試者基本資料無顯著差異，運動不足組在0Hz無震動時，股外側肌及腓腸肌之肌電訊號顯著較高，而在各頻率震動情形之腓腸肌及20Hz震動之脛前肌亦有相似的組間差異。運動充足組除40Hz震動情形之脛前肌外，在各頻率震動情形下皆有較大的肌電訊號。運動不足組僅在20Hz震動有此效果，而30Hz震動可顯著增加股外側肌及腓腸肌之肌電訊號強度，40Hz震動則提高小腿肌電訊號強度。本研究結論：身體活動程度會影響中高齡男性等長收縮及反射收縮時下肢肌肉活化，各震動頻率幾乎都能增加運動充足組下肢肌肉活化，運動不足組局部肌肉則僅在20Hz震動才有此效果，而20Hz震動對所有中高齡者下肢肌肉刺激最大，且較能徵召拮抗肌群協同作用。本研究僅檢測單次震動刺激，未來可探討長期震動訓練效果及其作用機轉。

Whole-body vibration (WBV) has been suggested to ameliorate muscle strength and balance via tonic vibration reflex in the elderly. Although researches have shown that WBV at 30 and 40 Hz in half-squat position could induce higher reflex response of the vastuslateralis in professional athletes, yet the training effect might not be applied to people of older age with different levels of physical activity (PA). This study aimed to investigate the effect of WBV at different frequencies on muscle activity of lower-limb between different levels of physical activity in middle-aged male adults. Thirty-six healthy middle-aged male adults (50-65 years) divided into the PA insufficient (PAI) and PA sufficient (PAS) groups according to definition from the International Physical Activity Questionnaire (IPAQ). All subjects were underwent WBV at 0-Hz (no vibration) and random vibrating frequencies (20, 30 and 40 Hz) in static half-squat position with knees bent at 100°. Muscle activities of the dominant lower-limb were recorded for 30 sec using electromyography (EMG). The results showed no significant group differences in baseline subject characteristics. In the 0-Hz condition, the PAI group had significantly greater muscle activity in the vastuslateralis and gastrocnemius than the PAS group. WBV also significantly induced greater muscle activity of the gastrocnemius for all vibrating frequencies and the tibia anterior at 20 Hz in the PAI group. Except for 40 Hz in the tibia anterior, greater muscle activities were found in all muscles for the PAS group at all frequencies. For the PAI group, similar greater muscle activities were found at 20 Hz frequency in all four muscle groups. However, 30 Hz vibration led to greater muscle activities at for the vastuslateralis and gastrocnemius and at 40 Hz for the calf muscle as compared to the 0-Hz condition. The study indicated that PA could affect muscle activities of lower-limb during isometric and reflex contraction in middle-aged male adults. For the PAS group, WBV at each frequency could induce greater muscle activities in the four major muscle groups of the lower-limb. In contrast, for the PAI group, greater muscle activities were found only in the 20 Hz condition. WBV at 20 Hz could induce the highest muscle activities of the lower-limb and synchronize more antagonists for the both groups. On account of a single bout investigation, further research is needed to study the long-term effect and mechanism of WBV for people of older age.