Castillo Eric R, Lieberman Graham M, McCarty Logan S, Lieberman Daniel E
Department of Human Evolutionary Biology, Harvard University, Cambridge, Massachusetts;
Harvard University Medical School, Boston, Massachusetts; and.
J Appl Physiol (1985). 2014 Sep 1;117(5):507-17. doi: 10.1152/japplphysiol.00119.2014. Epub 2014 Jul 3.
This study investigates whether a flexible pole can be used as an energy-saving method for humans carrying loads. We model the carrier and pole system as a driven damped harmonic oscillator and predict that the energy expended by the carrier is affected by the compliance of the pole and the ratio between the pole's natural frequency and the carrier's step frequency. We tested the model by measuring oxygen consumption in 16 previously untrained male participants walking on a treadmill at four step frequencies using two loaded poles: one made of bamboo and one of steel. We found that when the bamboo pole was carried at a step frequency 20% greater than its natural frequency, the motions of the centers of mass of the load and carrier were approximately equal in amplitude and opposite in phase, which we predicted would save energy for the carrier. Carrying the steel pole, however, resulted in the carrier and loads oscillating in phase and with roughly equal amplitude. Although participants were less economical using poles than predicted costs using conventional fixed-load techniques (such as backpacks), the bamboo pole was on average 5.0% less costly than the steel pole. When allowed to select their cadence, participants also preferred to carry the bamboo pole at step frequencies of ∼2.0 Hz. This frequency, which is significantly higher than the preferred unloaded step frequency, is most economical. These experiments suggest that pole carriers can intuitively adjust their gaits, or choose poles with appropriate compliance, to increase energetic savings.
本研究调查了柔性杆是否可作为人类负重时的一种节能方式。我们将携带者和杆系统建模为一个受迫阻尼简谐振荡器，并预测携带者消耗的能量受杆的柔顺性以及杆的固有频率与携带者步频之比的影响。我们通过测量16名此前未经训练的男性参与者在跑步机上以四种步频行走时的耗氧量来测试该模型，他们使用两根负重杆：一根是竹竿，一根是钢杆。我们发现，当以比竹竿固有频率高20%的步频携带竹竿时，负载和携带者质心的运动幅度大致相等且相位相反，我们预测这会为携带者节省能量。然而，携带钢杆时，携带者和负载同相振荡且幅度大致相等。尽管参与者使用杆子时的经济性不如使用传统固定负载技术（如背包）时预测的成本，但竹竿平均比钢杆成本低5.0%。当允许参与者选择他们的节奏时，他们也更喜欢以约2.0赫兹的步频携带竹竿。这个频率明显高于无负载时的首选步频，是最节能的。这些实验表明，使用杆负重的人可以直观地调整他们的步态，或者选择具有适当柔顺性的杆，以增加能量节省。
