Fletcher Jared R, MacIntosh Brian R
Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Canada; W21C Research and Innovation Centre, O'Brien Institute for Public Health, Cumming School of Medicine, University of Calgary, Canada.
Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Canada.
J Biomech. 2018 May 17;73:73-79. doi: 10.1016/j.jbiomech.2018.03.023. Epub 2018 Mar 27.
We have recently demonstrated that the triceps surae muscles energy cost (EC) represents a substantial portion of the total metabolic cost of running (E). Therefore, it seems relevant to evaluate the factors which dictate EC, namely the amount and velocity of shortening, since it is likely these factors will dictate E. E and triceps surae morphological and AT mechanical properties were obtained in 46 trained and elite male and female distance runners using ultrasonography and dynamometry. EC (J·stride) at the speed of lactate threshold (sLT) was estimated from AT force and crossbridge mechanics and energetics. To estimate the relative impact of these factors on EC, mean values for running speed, body mass, resting fascicle length (L), Achilles tendon stiffness and moment arm and maximum isometric plantarflexion torque were obtained. EC was calculated across a range (mean ± 1 sd) of values for each independent factor. Average sLT was 233 m·min. At this speed, EC was 255 J·stride. Estimated fascicle shortening velocity was 0.08 V and the level of muscle activation was 84.7% of maximum isometric torque. Compared to the EC calculated from the lowest range of values obtained for each independent factor, higher AT stiffness was associated with a 39% reduction in EC 81% reduction in fascicle shortening velocity and a 31% reduction in muscle activation. Longer AT moment arms and elevated body masses were associated with an increase in EC of 18% and 23%, respectively. These results demonstrate that a low EC is achieved primarily from a high AT stiffness and low body mass, which is exemplified in elite distance runners.
我们最近证明，小腿三头肌的能量消耗（EC）占跑步总代谢成本（E）的很大一部分。因此，评估决定EC的因素似乎很有必要，即缩短的量和速度，因为这些因素很可能也决定E。我们使用超声检查和测力法，对46名训练有素的精英男女长跑运动员的E、小腿三头肌形态和跟腱力学性能进行了测定。根据跟腱力量、横桥力学和能量学，估算了乳酸阈速度（sLT）下的EC（焦耳·步幅）。为了评估这些因素对EC的相对影响，我们获取了跑步速度、体重、静息肌纤维长度（L）、跟腱刚度、力臂和最大等长跖屈扭矩的平均值。针对每个独立因素，在一系列值（平均值±1标准差）范围内计算EC。平均sLT为233米·分钟。在此速度下，EC为255焦耳·步幅。估计肌纤维缩短速度为0.08V，肌肉激活水平为最大等长扭矩的84.7%。与根据每个独立因素获得的最低值范围计算出的EC相比，较高的跟腱刚度与EC降低39%、肌纤维缩短速度降低81%以及肌肉激活降低31%相关。较长的跟腱力臂和增加的体重分别与EC增加18%和23%相关。这些结果表明，低EC主要源于高跟腱刚度和低体重，这在精英长跑运动员身上得到了体现。
