Fonda Borut, Sarabon Nejc, Li François-Xavier
a School of Sport, Exercise and Rehabilitation Sciences , University of Birmingham , Birmingham , UK.
J Sports Sci. 2014;32(10):940-6. doi: 10.1080/02640414.2013.868919. Epub 2014 Feb 6.
The most common bike fitting method to set the seat height is based on the knee angle when the pedal is in its lowest position, i.e. bottom dead centre (BDC). However, there is no consensus on what method should be used to measure the knee angle. Therefore, the first aim of this study was to compare three dynamic methods to each other and against a static method. The second aim was to test the intra-session reliability of the knee angle at BDC measured by dynamic methods. Eleven cyclists performed five 3-min cycling trials; three at different seat heights (25°, 30° and 35° knee angle at BDC according to static measure) and two at preferred seat height. Thirteen infrared cameras (3D), a high-speed camera (2D), and an electrogoniometer were used to measure the knee angle during pedalling, when the pedal was at the BDC. Compared to 3D kinematics, all other methods statistically significantly underestimated the knee angle (P = 0.00; η(2) = 0.73). All three dynamic methods have been found to be substantially different compared to the static measure (effect sizes between 0.4 and 0.6). All dynamic methods achieved good intra-session reliability. 2D kinematics is a valid tool for knee angle assessment during bike fitting. However, for higher precision, one should use correction factor by adding 2.2° to the measured value.
设置座椅高度最常见的自行车调整方法是基于踏板处于最低位置（即下止点，BDC）时的膝盖角度。然而，对于应使用何种方法测量膝盖角度，目前尚无共识。因此，本研究的首要目的是将三种动态方法相互比较，并与一种静态方法进行比较。第二个目的是测试通过动态方法测量的下止点处膝盖角度在会话内的可靠性。11名骑自行车的人进行了5次3分钟的骑行试验；三次在不同的座椅高度（根据静态测量，下止点处膝盖角度为25°、30°和35°），两次在偏好的座椅高度。在踏板处于下止点时，使用13台红外摄像机（3D）、一台高速摄像机（2D）和一个电子测角仪测量蹬踏过程中的膝盖角度。与3D运动学相比，所有其他方法在统计学上均显著低估了膝盖角度（P = 0.00；η(2) = 0.73）。与静态测量相比，所有三种动态方法均存在显著差异（效应大小在0.4至0.6之间）。所有动态方法在会话内均具有良好的可靠性。2D运动学是自行车调整过程中评估膝盖角度的有效工具。然而，为了获得更高的精度，应通过在测量值上加上2.2°来使用校正因子。
