Hull M L, Kautz S, Beard A
Department of Mechanical Engineering, University of California, Davis 95616.
J Biomech. 1991;24(7):577-86. doi: 10.1016/0021-9290(91)90290-4.
The contributions of this article are twofold. One is procedure for determining the angular velocity profile in seated cycling that maintains the total mechanical energy of both legs constant. A five-bar linkage model (thigh, shank, foot, crank and frame) of seated (fixed hip) cycling served for the derivation of the equations to compute potential and kinetic energies of the leg segments over a complete crank cycle. With experimentally collected pedal angle data as input, these equations were used to compute the total combined mechanical energy (sum of potential and kinetic energies of the segments of both legs) for constant angular velocity pedalling at 90 rpm. Total energy varied indicating the presence of internal work. Motivated by a desire to test the hypothesis that reducing internal work in cycling will reduce energy expenditure, a procedure was developed for determining the angular velocity profile that eliminated any change in total energy. Using data recorded from five subjects, this procedure was used to determine a reference profile for an average equivalent cadence of 90 rpm. The phase of this profile is such that highest and lowest angular velocities occur when the cranks are near vertical and horizontal respectively. The second contribution is the testing of the hypothesis that the reference angular velocity profile serves to effectively reduce internal work for the subjects whose data were used to develop this profile over the range of pedalling rates (80-100 rpm) naturally preferred. In this range, the internal work was decreased a minimum of 48% relative to the internal work associated with constant angular velocity pedalling. The acceptance of this hypothesis has relevance to the protocol for future experiments which explore the effect of reduced internal work on energy expenditure in cycling.
本文的贡献有两个方面。一是确定坐姿骑行中角速度分布的程序，该程序能使双腿的总机械能保持恒定。坐姿（固定髋关节）骑行的五杆连杆模型（大腿、小腿、脚、曲柄和车架）用于推导计算腿部各节段在一个完整曲柄周期内势能和动能的方程。以实验收集的踏板角度数据作为输入，这些方程用于计算以90转/分钟的恒定角速度踩踏时双腿各节段的总机械能（势能和动能之和）。总能量发生变化，表明存在内部功。出于测试减少骑行内部功将降低能量消耗这一假设的愿望，开发了一种确定角速度分布的程序，该程序消除了总能量的任何变化。使用从五名受试者记录的数据，该程序用于确定平均等效踏频为90转/分钟的参考分布。该分布的相位使得最高和最低角速度分别出现在曲柄接近垂直和水平位置时。第二个贡献是对以下假设的测试：对于在自然偏好的踩踏速率范围（80 - 100转/分钟）内使用其数据来制定此分布的受试者，参考角速度分布有助于有效减少内部功。在此范围内，相对于与恒定角速度踩踏相关的内部功，内部功至少减少了48%。这一假设的接受与未来探索减少内部功对骑行能量消耗影响的实验方案相关。
