橢圓齒盤對公路自行車騎乘效率及下肢肌電訊號之影響

The effect of non-circular chainring on road bike riding efficiency and lower extremity electromyography

汪旖文(Yi-wen Wang)

指導教授 ： 謝伸裕

國立臺灣師範大學/運動與休閒學院/體育學系/碩士(2012年)

摘要

橢圓齒盤(non-circular chainring)是一項為了增進踩踏效率而發展出的產品，其原理是改進原本兩腿作圓周運動踩踏時，接近上下死點處雙腿輸出功率較小的缺點，利用減少踩踏週期中這兩處齒片切線點到中軸的半徑，增加扭矩、減少齒數，並讓上下死點附近的施力齒快速通過。同理，當雙腳前後死點時，踩踏力量最大時，此時橢圓齒盤增加前齒片的切線點到中軸的半徑，增加齒數，讓施力時連貫，以期踩踏時發揮最大功率。目的：比較受試者在使用一般圓形齒盤及橢圓齒盤時的攝氧量，以評估其工作效率。比較受試者在使用一般圓形齒盤及橢圓齒盤時的下肢肌群肌電訊號（股直肌、股二頭肌、脛前肌、腓腸肌）之活動情形。方法：以8位國內男性優秀公路自行車選手（年齡：24.50 ± 4.23歲；身高：172.67 ± 5.1公分；體重：67.50 ± 10.0公斤；最大攝氧量：67.14 ± 5.80 ml/kg/min），自行車齡3年以上，每週訓練時間20小時以上或週訓練量600公里以上，以平衡次序法使用一般齒盤或橢圓齒盤進行以無氧閾值(AT)為基準的三種強度（AT+ 10%、AT、AT- 20%）之騎乘，每種強度騎5分鐘，記錄其間的攝氧量及肌電訊號。結果：使用一般齒盤與橢圓齒盤在3種運動強度下之攝氧量並無顯著差異。在AT+ 10%強度下，股直肌在使用橢圓齒盤時的均方根肌電訊號顯著低於一般齒盤；在其餘強度時，股直肌、股二頭肌、脛前肌及腓腸肌在使用兩種不同齒盤時，肌電訊號皆無顯著差異。結論：橢圓齒盤無法提升專業自行車手進行次最大運動強度測驗時的運動經濟性。肌電訊號部分，於強度AT+ 10%下，使用橢圓齒盤時股直肌肌肉活化程度較小，表示較省力。但是無法減少其餘肌肉的肌肉活化程度，無法達到省力的效果。

關鍵字

橢圓齒盤 ； 運動經濟性 ； 肌電圖

並列摘要

Non-circular chainring is a product created for improving cycling performance. The principle of non-circular chainring is based on the modification of the gear ration of the chainring. While pedaling at the top and bottom dead point, the distance between buttom bracket and the point of tangency of the chainring becomes shorter. Therefore, the radius of chainring was decreased, the torque of the pedaling was increase, and the number of teeth was reduced virtually. In the same way, while pedaling to the circumstance of maximal power (3 O’clock), the design could increase the diameter of chainring, increase the number of teeth virtually, to have the more power output. Purpose: To investigate the effect of using non-circular chaining on road bike riding efficiency and electromyography( EMG) of lower extremity muscles ( rectus femoris, biceps femoris, tibial anterior, & gastrocnemius). Methods: Eight male elite cyclists (age: 24.50 ± 4.23 yrs old, height: 172.67 ± 5.1cm, weight: 67.50 ± 10.0kg, VO2max: 67.14 ± 5.80 ml/kg/min ) with more than 3 years cycling experience were recruited in this study. All of them train at least 20 hours or 600 km per week. Subjects randomly use conventional circular chainring or non-circular chainring to perform 3 riding trials for 5 minutes respectively under 3 different intensities which were 10% above anaerobic threshold (AT+10%), anaerobic threshold (AT), 20% below anaerobic threshold (AT-20%). VO2 and EMG were recorded during these 5 minutes tests. Results: There’s no significant difference on VO2 between using conventional chainring and non-circular chainring. At the intensity AT+ 10%, the EMG activity of rectus femoris using non-circular chainringwas significantly lower than using conventional chainring. However, there were no significant difference in other muscles between using these two different chainrings. Conclusion: For elite cyclists, non-circular chainring cannot enhance their riding efficiency at sub-maximal workload. At the intensity AT+ 10%, using non-circular chaining may reduce rectus femoris muscle activation.

並列關鍵字

non-circular chainring ； efficiency ； electromyography

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