橢圓機運動中踏板坡度與內偏角對下肢生物力學之影響

Abstract

介紹：橢圓機的設計概念為模仿步行且能減低對關節的衝擊力，由過去的文獻得知橢圓機運動與步行之生物力學效應有很大的不同，目前有許多新式橢圓機設計專利，企圖使橢圓機運動更趨近於步行或是其他日常運動，這些新設計對肌肉骨骼系統的影響還未曾被討論，本研究欲探討不同坡度及內偏角對橢圓機運動在生物力學上造成的影響，及其改善膝關節不適當生物力學環境的可能性。 方法：本研究收了8位年輕男性受試者，腿長範圍在85.5~92公分，在全身骨標記處貼反光球取得運動資料，六軸測力元裝置在橢圓機左側踏板上取得力學資料，以四種坡度模式（坡度一、二、三、四，各表γ= -1.08、-1.59、-2.36、-3.17°）及四種內偏角模式（α=0、5、10、12°）共16種情況進行橢圓機運動，步頻設定在60 rpm，阻值為30 watt，手握前端固定式手把。 結果：本研究顯示坡度對所有參數皆無顯著影響，但內偏角對三個平面都有發現顯著改變。增加內偏角可以減少第四期膝關節的彎曲角度，但同時會使踏板垂直反作用力變大，增加第四期最大膝關節伸直。增加內偏角使第一期及第四期踏板向內反作用力減少，但增加第二期及第三期踏板向內反作用力。為了配合踏板在內外方向的位置髖關節在T0附近呈現更內縮的角度，第二期及第三期呈現更外張的角度，整個運動過程中膝關節更加內轉，並減少膝關節外轉力矩。當α=10、12°時踏板向內作用力不穩定，造成額狀面及橫切面力矩發生劇烈抖動且快速變化。 結論：坡度不會顯著改變下肢生物力學在橢圓機運動的表現。內偏角也不如預期使橢圓機運動更相似於步行也無法降低膝關節伸直力矩，這是因為在步行中腳掌向身體中線移動，但腳掌都是呈現外八狀，在本研究的橢圓機運動在T3~T1腳掌皆呈內八狀，若能減少踏板內轉的角度可能可以改善下肢生物力學的表現。

Introduction：The concepts of elliptical trainer design were to simulate the motion of the human gait and avoid the impact force. The pervious papers showed the biomechanical environments of the gait and the elliptical exercise were totally different. Many new designs of the elliptical trainer were invented to approach the ambulation or other daily motions. However, the influences of those new designs on human musculoskeletal system have not been discussed. The purpose of this research is to investigate the effect of the slope and inward angle of pedal by quantifying lower limb dynamics. Method：Eight young-male subjects without any musculoskeletal impairments or disability were recruited to this study. The range of leg length between 85.5~92 cm. The passive optical markers and electrodes were placed on subjects. The load cell installed on the left pedal measured the pedal reaction force. The elliptical exercise was measured at four level of pedal slopes (slop1,2,3,4) and inward angles（α=0,5,10,12°）. Totally, sixteen conditions with the same cadence and resistance (60 rpm, 30 watt) were discussed. Result: The investigation shows that there are no significant influences on all parameters with slope. However, the inward angle significantly changes the lower limb biomechanics in three planes. Inward angle can reduce the knee flexion angle of phase IX, but it will increase vertical PRF at the same time and, therefore, will increase the knee extensor moment of phase IX. Medial PRF is decreased in phase I and IX but increased in II and III. Besides, hip adduction angle increases near T0 and hip abduction angle increases in phase II and III. Inward angle also increases knee internal rotator angle and reduces knee external rotator moment. In addition, when α= 10,12°, the medial PRF is not stable and induces disturbed moments on frontal plane and transverse plane. Conclusion: Pedal slope does not significantly affect the lower limb biomechanics. Inward angle can not make elliptical exercise more similar to walking and can not decrease knee extensor moment. The results may be caused by the fact that foot swings and closed to the center line of the body but toe out while walking, yet it is toe in during T3~T1 in the elliptical exercisr. Reducing the toe-in angle may improve the performance of lower limb biomechanics.