Strutzenberger Gerda, Wunsch Tobias, Kroell Josef, Dastl Jacqueline, Schwameder Hermann
Sports Biomech. 2014 Jun;13(2):97-108. doi: 10.1080/14763141.2014.908946.
Non-circular chainrings theoretically enhance cycling performance by increasing effective chainring diameter and varying crank velocity, but research has failed to consistently reproduce the benefits in cycling trials. The aim of this study was (1) to investigate the effect of different chainring shapes on sagittal knee joint moment and sagittal lower limb joint powers and (2) to investigate whether alterations are affected by cadence and workload. Fourteen elite cyclists cycled in six conditions (70, 90 and 110 rpm, each at 180 and 300 W), for 2 min each, using three chainrings of different ovalities (1.0-1.215). Kinematic data and pedal forces were collected. For most conditions, only the chainring with the highest ovality (1.215) was characterised by smaller sagittal knee joint moments, smaller relative sagittal knee joint power contribution and larger relative sagittal hip joint power contribution, which suggests a change from maximising efficiency to maximising power production. Effect sizes increased with higher cadences, but not with higher workload. This study has application for athletes, clinicians and sports equipment industry as a non-circular chainring can change joint-specific power generation and decrease knee joint moment, but certain ovality seems to be necessary to provoke this effect.
非圆形链轮理论上可通过增加有效链轮直径和改变曲柄速度来提高骑行性能，但研究未能在骑行试验中始终重现这些益处。本研究的目的是：（1）研究不同链轮形状对矢状面膝关节力矩和矢状面下肢关节功率的影响；（2）研究这些变化是否受踏频和工作量的影响。14名精英自行车运动员在六种条件下骑行（70、90和110转/分钟，每种转速分别对应180瓦和300瓦），每种条件骑行2分钟，使用三种不同椭圆度（1.0 - 1.215）的链轮。收集运动学数据和踏板力。在大多数条件下，只有椭圆度最高（1.215）的链轮表现出矢状面膝关节力矩较小、矢状面膝关节相对功率贡献较小以及矢状面髋关节相对功率贡献较大，这表明从效率最大化转变为功率输出最大化。效应量随踏频增加而增大，但不随工作量增加而增大。本研究对运动员、临床医生和体育器材行业具有应用价值，因为非圆形链轮可改变特定关节的功率产生并降低膝关节力矩，但似乎需要一定的椭圆度才能引发这种效果。
