Broker J P, Gregor R J
Sports Science and Technology Division, United States Olympic Training Center, Colorado Springs, CO 80906.
Med Sci Sports Exerc. 1994 Jan;26(1):64-74.
Conservation of energy suggests that during cycling the constrained lower extremity is capable of delivering energy to the bicycle without expending energy to move the limbs. The purpose of this study was to characterize the management of mechanical energy during cycling and, specifically, to evaluate the potential for system energetic conservatism. Mechanical energy contributions derived from lower extremity energy sources were computed for 12 experienced male cyclists riding at five combinations of cadence and power output. The knee joint dominated (> 50%) in contributing to system energy and a moderate amount of energy was derived from hip joint reaction forces (> 6%). Energy generations and dissipations at the sources were sensitive to power output and, within the range of conditions studied, insensitive to cadence. Two energy models estimated mechanical energy expenditure under hypothetical single-joint and multijoint muscle operating conditions. When multijoint muscles were incorporated into the energy management analysis, a significant reduction in mechanical work relative to the single-joint muscle operation occurred. Energy savings associated with multijoint muscle energy transfers were enhanced at higher bicycle power levels, suggesting that conservation of mechanical energy is plausible given appropriate actions of two-joint muscles.
能量守恒表明，在骑行过程中，受约束的下肢能够在不消耗能量来移动肢体的情况下向自行车传递能量。本研究的目的是描述骑行过程中机械能的管理情况，特别是评估系统能量保守性的潜力。计算了12名经验丰富的男性自行车手在五种踏频和功率输出组合下骑行时，来自下肢能量源的机械能贡献。膝关节在系统能量贡献中占主导地位（>50%），并且有相当数量的能量来自髋关节反作用力（>6%）。能量源处的能量产生和耗散对功率输出敏感，在所研究的条件范围内，对踏频不敏感。两个能量模型估计了假设的单关节和多关节肌肉工作条件下的机械能消耗。当将多关节肌肉纳入能量管理分析时，相对于单关节肌肉工作，机械功显著减少。在较高的自行车功率水平下，与多关节肌肉能量转移相关的能量节省有所增加，这表明在双关节肌肉采取适当行动的情况下，机械能守恒是合理的。
