Center for Health and Sports Science, Kyushu Sangyo University, 2-3-1 Matsukadai, Higashi-ku, Fukuoka, 813-8503, Japan.
Faculty of Health and Sports Science, Doshisha University, 1-3 Miyakodani, Kyotanabe-shi, Kyoto, 610-0394, Japan.
J Physiol Anthropol. 2018 Jun 19;37(1):18. doi: 10.1186/s40101-018-0177-7.
Energy cost of transport per unit distance (CoT) against speed shows U-shaped fashion in walking and linear fashion in running, indicating that there exists a specific walking speed minimizing the CoT, being defined as economical speed (ES). Another specific gait speed is the intersection speed between both fashions, being called energetically optimal transition speed (EOTS). We measured the ES, EOTS, and muscle activities during walking and running at the EOTS under hyperoxia (40% fraction of inspired oxygen) on the level and uphill gradients (+ 5%).
Oxygen consumption [Formula: see text] and carbon dioxide output [Formula: see text] were measured to calculate the CoT values at eight walking speeds (2.4-7.3 km h) and four running speeds (7.3-9.4 km h) in 17 young males. Electromyography was recorded from gastrocnemius medialis, gastrocnemius lateralis (GL), and tibialis anterior (TA) to evaluate muscle activities. Mean power frequency (MPF) was obtained to compare motor unit recruitment patterns between walking and running.
[Formula: see text], [Formula: see text], and CoT values were lower under hyperoxia than normoxia at faster walking speeds and any running speeds. A faster ES on the uphill gradient and slower EOTS on both gradients were observed under hyperoxia than normoxia. GL and TA activities became lower when switching from walking to running at the EOTS under both FiO conditions on both gradients, so did the MPF in the TA.
ES and EOTS were influenced by reduced metabolic demands induced by hyperoxia. GL and TA activities in association with a lower shift of motor unit recruitment patterns in the TA would be related to the gait selection when walking or running at the EOTS.
UMIN000017690 ( R000020501 ). Registered May 26, 2015, before the first trial.
单位距离能量消耗（CoT）与速度的关系在步行时呈 U 形，在跑步时呈线性，表明存在一个特定的步行速度可以使 CoT 最小化，这个速度被定义为经济速度（ES）。另一个特定的步态速度是两种模式的交点速度，称为能量最优转换速度（EOTS）。我们在平地上和上坡时（+5%）测量了 17 名年轻男性在高氧（40%吸入氧分数）下 EOTS 时的 ES、EOTS 和肌肉活动，在 8 个步行速度（2.4-7.3km/h）和 4 个跑步速度（7.3-9.4km/h）下测量了氧气消耗[公式：见正文]和二氧化碳输出[公式：见正文]，以计算 CoT 值。从比目鱼肌内侧、比目鱼肌外侧（GL）和胫骨前肌（TA）记录肌电图，以评估肌肉活动。获得平均功率频率（MPF）以比较步行和跑步时运动单位募集模式。
在更快的步行速度和任何跑步速度下，高氧条件下的 CoT 值比常氧条件下更低。在上坡时，ES 更快，在两个梯度上 EOTS 更慢。在两种 FiO 条件下，从步行切换到跑步时，EOTS 下 GL 和 TA 的活动降低，TA 的 MPF 也降低。
ES 和 EOTS 受到高氧诱导的代谢需求降低的影响。与 TA 中运动单位募集模式的较低转变相关的 GL 和 TA 活动可能与在 EOTS 时选择步行或跑步有关。
UMIN000017690（R000020501）。于 2015 年 5 月 26 日，在第一次试验前注册。
