Gottschall Jinger S, Kram Rodger
Department of Integrative Physiology, University of Colorado, Boulder, USA.
J Appl Physiol (1985). 2005 Jul;99(1):23-30. doi: 10.1152/japplphysiol.01190.2004.
To investigate the metabolic cost and muscular actions required for the initiation and propagation of leg swing, we applied a novel combination of external forces to subjects walking on a treadmill. We applied a forward pulling force at each foot to assist leg swing, a constant forward pulling force at the waist to provide center of mass propulsion, and a combination of these foot and waist forces to evaluate leg swing. When the metabolic cost and muscle actions were at a minimum, the condition was considered optimal. We reasoned that the difference in energy consumption between the optimal combined waist and foot force trial and the optimal waist force-only trial would reflect the metabolic cost of initiating and propagating leg swing during normal walking. We also reasoned that a lower muscle activity with these assisting forces would indicate which muscles are normally responsible for initiating and propagating leg swing. With a propulsive force at the waist of 10% body weight (BW), the net metabolic cost of walking decreased to 58% of normal walking. With the optimal combination, a propulsive force at the waist of 10% BW plus a pulling force at the feet of 3% BW the net metabolic cost of walking further decreased to 48% of normal walking. With the same combination, the muscle activity of the iliopsoas and rectus femoris muscles during the swing phase was 27 and 60% lower, respectively, but the activity of the medial gastrocnemius and soleus before swing did not change. Thus our data indicate that approximately 10% of the net metabolic cost of walking is required to initiate and propagate leg swing. Additionally, the hip flexor muscles contribute to the initiation and propagation leg swing.
为了研究腿部摆动起始和推进所需的代谢成本及肌肉活动，我们对在跑步机上行走的受试者施加了一种新型的外力组合。我们在每只脚上施加向前的拉力以辅助腿部摆动，在腰部施加恒定的向前拉力以提供质心推进力，并结合这些脚部和腰部的力来评估腿部摆动。当代谢成本和肌肉活动处于最低水平时，该条件被认为是最佳的。我们推断，最佳的腰部和脚部联合施力试验与仅最佳腰部施力试验之间的能量消耗差异，将反映正常行走过程中起始和推进腿部摆动的代谢成本。我们还推断，使用这些辅助力时较低的肌肉活动将表明哪些肌肉通常负责起始和推进腿部摆动。当腰部推进力为体重（BW）的10%时，行走的净代谢成本降至正常行走的58%。在最佳组合下，即腰部推进力为10% BW加上脚部拉力为3% BW时，行走的净代谢成本进一步降至正常行走的48%。在相同组合下，摆动期髂腰肌和股直肌的肌肉活动分别降低了27%和60%，但摆动前内侧腓肠肌和比目鱼肌的活动没有变化。因此，我们的数据表明，起始和推进腿部摆动大约需要行走净代谢成本的10%。此外，髋屈肌对起始和推进腿部摆动有贡献。
