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  • 學位論文

智慧型手機不同操作姿勢下之肌肉活動量、輸入表現與偏好評估

The Ergonomic Concerns for Smartphone Users: Assessment of Muscular Activity, Input Performance and Preference by Various Postures

指導教授 : 黃耀輝
共同指導教授 : 梁蕙雯(Huey-Wen Liang)

摘要


實驗背景與動機: 智慧型手機持有率於近年來大幅上升,但相關人因參數之客觀量測研究仍不多。本研究旨在探討使用不同姿勢操作智慧型手機,其肌肉活動量、關節活動度、輸入表現及自覺偏好度並與電腦操作相比較看是否有所不同。同時分析與比較不同手機操作姿勢之差異性,以期能了解智慧型手機使用者的人因暴露危險因子,並藉此給予使用者適當的建議。 方法: 本實驗使用4吋螢幕之智慧型手機,請受測者使用五種不同手機操作姿勢進行文字輸入,並與以桌上型電腦進行鍵盤輸入的表現情形相比較。 上述五種手機操作姿勢如下: (a) 右手握機,拇指操作(ST), (b) 左手懸空握機,右手食指操作(SI), (c) 雙手握機,雙手拇指操作(D), (d) 同上,但前臂靠在腿上(DL), (e) 雙手握機至視線水平高,雙手拇指操作(H)。 在受測者進行文字輸入時,同時以表面肌電圖量測其肌肉活動量,並以電子量角器量測其關節活動度。測量的肌肉群以手機操作時,用於穩定手腕/手肘、手指彎曲伸展活動、支持頭部與肩膀等動作的相關肌肉為主,包含屈拇短肌、屈指淺肌、伸指總肌、肱二頭肌與上斜方肌。關節活動度量測的部位包含頸部、手肘與手腕關節。受測者輸入表現以每分鐘最快正確按鍵數來代表。並請受測者以問卷填答相關肌肉不適與姿勢偏好度。 結果與討論: (1)肌肉活動量 平均來說,在多數手機操作姿勢組別中,上肢肩頸肌肉群活動量普遍較電腦操作時為大,特別是屈拇短肌、肱二頭肌與上斜方肌這三條肌肉。其中屈拇短肌之活動量可達最大自主收縮值(MVC)的11.3%。而伸指總肌則是在電腦操作時肌肉活動量較多數手機操作姿勢時為大(7.7% MVC)。整體而言,單手拇指操作(ST)此一手機操作姿勢,多數肌肉活動量皆明顯較大。 (2)關節活動度 在頸部關節活動度中,其前屈角度(flexion angle)與電腦操作時相較,有三種常見手機操作姿勢(雙手拇指(D), 單手拇指(ST), 單手食指(SI))較電腦操作時為大,角度相差約15-18度。手肘關節部位在電腦操作時其屈曲活動度最小。與電腦操作時的手肘屈曲角度相較,所有手機操作姿勢下的手肘屈曲角度皆較電腦操作時為大,相差約7-31度。特別是常見手機操作姿勢(雙手拇指(D), 單手拇指(ST), 單手食指(SI))中,平均手肘關節活動度皆大於90度。在手腕關節活動度中,電腦操作與五種不同手機操作姿勢皆處於伸展之角度(extension)。但手機操作時手腕關節活動角度與電腦操作時相較,除了單手食指操作(SI)手腕角度較大可達伸展27度外,其餘手機操作姿勢手腕伸展角度皆較電腦操作時為小。 (3)輸入速度 受測者英文打字輸入速度在不同操作姿勢下手機的正確按鍵數為每分鐘91-115字元,約為電腦操作時每分鐘218字元的一半。 (4)姿勢偏好度與自覺肌肉不適度 受測者最喜歡的文字輸入姿勢依序為電腦操作(C)、雙手拇指操作(D)、單手食指操作(SI)、雙手前傾操作(DL)、單手拇指操作(ST)、雙手拿高操作(H)。其中單手拇指操作(ST)與雙手拿高(H)操作手機的姿勢讓受測者自覺肌肉不適度較高。 結論: 本研究提供了不同手機操作姿勢時受測者肌肉活動量、關節活動度、輸入表現、受測者姿勢偏好度及自覺肌肉不適度的客觀量測證據。本研究證實手機操作時,上肢關節處於不良的姿勢,頸部與手肘前彎角度皆相當明顯,且相應之上肢肌群肌肉活動量多數較電腦操作時大,特別是屈拇短肌、肱二頭肌與上斜方肌這三條肌肉。若計算打字輸入速度,手機操作輸入每分鐘最快正確按鍵數約為電腦操作時的一半,且以單手拇指操作(ST)與雙手拿高(H)操作手機時受測者自覺肌肉不適度較高。因此,本實驗建議若要做大量訊息輸入時,應考慮使用電腦操作,避免使用手機作長時間之操作。同時,長時間操作手機時應間歇性變換不同姿勢,以減少肌肉與關節負荷。

並列摘要


Background: In recent years, the demand for smartphones has dramatically increased. However, the health-related ergonomics parameters for smartphone use were not well studied yet. The purpose of this study was therefore set to compare user's muscle activities, range of motion of joints, text entry performance and posture preference among computer use and smartphone use with various postures. Materials and Methods: For comparison, study subjects were asked to type on desktop computer with comfortable sitting posture and on 4-inch-screen smartphone with five different designated postures, respectively, including (1) holding smartphone with right hand without support and typing with right thumb (ST), (2) holding smartphone with suspended left hand and typing with right index finger (SI), (3) holding smartphone with both hands and typing with bilateral thumbs (D), (4) same as (3) but trunk bending forward with forearm lean against leg (DL), and (5) holding smartphone with both hands up to eye level and typing with bilateral thumbs (H). As the study subjects perform typing, surface electromyogram and goniometers were applied to measure their muscle activities and range of joint motions, respectively, at neck, elbow and wrist. The monitored muscles include flexor pollicis brevis, flexor digitorum superficialis, extensor digitorum communis, biceps brachii, and upper trapezius, which are typically used to flex and extend fingers, to stabilize wrists and elbows, or to support necks and shoulders. Typing performance of the study subject was recorded as maximum correctly typed characters per minute (cpm). Likert’s scale was used to evaluate the muscle symptoms and the preferred postures were ranked in order by the study subject themselves. Results and Discussions: (1) Muscle activity In average, as compared to computer use, the muscle loads for smartphone use with various postures were larger, especially for flexor pollicis brevis, biceps brachii and upper trapezius muscles. Among them, the muscle activity of flexor pollicis brevis muscle was up to 11.3 % maximal voluntary contraction (MVC). As to extensor digitorum communis, the muscle activity for computer use was the highest (7.7 % MVC). In general, users holding smartphone with right hand and typing with right thumb (ST) tended to have much more muscle exertions at various studied muscles. (2) Range of motion of joints The angles of cervical flexion of the smartphone users holding with right hand and typing with right thumb (ST), holding with suspended left hand and typing with right index finger (SI) and holding with both hands and typing with bilateral thumbs (D) were generally greater by 15 to 18 degrees as compared with computer use. As to elbow range of motion, the flexion angles for smartphone users with various designated postures were all greater than those for computer use, ranging from 7 to 31 degrees. Especially for those common postures for smartphone use, i.e., holding with right hand and typing with right thumb (ST), holding with suspended left hand and typing with right index finger (SI), and holding with both hands and typing with bilateral thumbs (D), the average ranges of elbow motion were even greater than 90 degrees. As to wrist range of motion, the wrist was always extended either for computer use or for smartphone use with various designated postures. The greatest wrist extension angle, 27 degrees, was found for smartphone use by holding with suspended left hand and typing with right index finger (SI). The wrist extension angles for smartphone use with all other four designated postures were less than that computer use. (3) Text entry performance The typing speed of the study subjects when using smartphone ranged from 91 to 115 characters per minute (cpm), which were around half as fast as they did with computer. (4) Preference The most preferred posture for typing was computer use(C), followed by smartphone use, holding with both hands and typing with bilateral thumbs (D), then holding with suspended left hand and typing with index finger (SI), holding with both hands and typing with bilateral thumbs, but trunk bending forward with forearm lean against leg (DL), holding with right hand and typing with right thumb (ST), holding with both hands up to eye level and typing with bilateral thumbs (H). Conclusions: This study provided objective measurements to illustrate relatively awkward postures while using smartphones, especially the markedly flexed cervical spines and elbows. The corresponding muscle loads for smartphone use were found mostly greater than that for computer use, especially for flexor pollicis brevis, biceps brachii and upper trapezius muscles. Besides, study subjects typed with smartphone about half as fast as they did with computer. The two most uncomfortable postures for smartphone use were holding with right hand and typing with right thumb (ST) and holding smartphone with both hands up to eye level and typing with bilateral thumbs (H). Therefore, when performing large text entry task, computer use is recommended to avoid continuous smartphone use. Meanwhile, it is suggested to intermittently change smartphone-holding postures in order to minimize muscle and joint loads.

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