Watanabe Yasunori, Wakayoshi Kohji, Nomura Teruo
Faculty of Sports Science, Sendai University, Miyagi, Japan.
Faculty of Human Sciences, Osaka University of Economics, Osaka, Japan.
PLoS One. 2017 May 9;12(5):e0177368. doi: 10.1371/journal.pone.0177368. eCollection 2017.
This study aims to investigate the effect of changes in buoyancy when a swimmer respires in a horizontal posture. We attempted to evaluate the levelness of swimmers' streamline posture by simultaneously measuring the lung capacity and buoyancy under water. The buoyancy was measured based on the changes in the vertical loads of the upper and lower limbs on the subjects' streamline posture under water. The horizontal x-axis as lung ventilation and the vertical y-axis as buoyancy forms a linear equation y = ax + b. The relation between hand (upper-limb) buoyancy and lung ventilation is defined as y = a1x + b1 and that between foot (lower-limb) buoyancy and lung ventilation as y = a2x + b2. Horizontal levelness was calculated as a ratio by dividing a2 by a1 using the inclination (a) values from these formulas for an underwater streamline posture. We defined this ratio as the breathing-balance (BB) ratio. Although the performance levels in the present study did not show any difference in the absolute quantity of air that humans can inhale in a streamline posture, the BB ratio was higher in a statistically significant manner in junior swimmers competing at international levels compared with the other groups of subjects (P < 0.001). This statistical difference in horizontal levelness, despite the absence of a noticeable difference in the absolute quantity of inhaled air, may be attributable to the way in which each person inhales and exhales air. Top-level junior swimmers that exhibited a high BB ratio might have inhaled in a way that would counteract the sinking of the lower limbs, for example, through abdominal respiration. When exhaling, on the other hand, they might have let out air gradually to mitigate the acceleration force involved in submerging the lower limbs.
本研究旨在调查游泳者在水平姿势呼吸时浮力变化的影响。我们试图通过同时测量水下肺活量和浮力来评估游泳者流线型姿势的平稳程度。浮力是根据水下受试者流线型姿势上下肢垂直负荷的变化来测量的。以肺通气量为水平x轴，浮力为垂直y轴，形成线性方程y = ax + b。手部（上肢）浮力与肺通气量的关系定义为y = a1x + b1，足部（下肢）浮力与肺通气量的关系定义为y = a2x + b2。通过使用这些公式计算水下流线型姿势的倾斜度（a）值，将a2除以a1，以比率形式计算水平平稳度。我们将这个比率定义为呼吸平衡（BB）比率。尽管本研究中的表现水平在流线型姿势下人类可吸入的空气绝对量方面没有显示出任何差异，但与其他受试组相比，国际水平比赛的初级游泳者的BB比率在统计学上显著更高（P < 0.001）。尽管吸入空气的绝对量没有明显差异，但水平平稳度的这种统计差异可能归因于每个人吸入和呼出空气的方式。表现出高BB比率的顶级初级游泳者可能以一种抵消下肢下沉的方式吸气，例如通过腹式呼吸。另一方面，呼气时，他们可能会逐渐呼出空气，以减轻下肢浸入水中时的加速力。
