Competitive swimmers complete 50‐m front crawl swimming without breathing or with a limited number of breaths. Breath holding during exercise can trigger diving reflex including bradycardia and diminished active muscle blood flow, whereas oxygen supply to vital organ such as brain is maintained. We hypothesized that swimmers achieving faster time in 50‐m front crawl with limited number of breaths demonstrate a blunted diving reflex of cardiac and active muscle blood flow responses with elevated cerebral perfusion to counteract peripheral and central fatigues. Twenty‐eight competitive swimmers (12 females) underwent a 50‐m front crawl swimming time trial with minimum respiratory interruptions, following which they were categorized into two groups: Fast (n = 13) and Slow (n = 15). Additionally, they performed knee extension exercises with maximal voluntary breath‐ holding, wherein leg blood flow (Doppler ultrasound), cardiac output (Modelflow), heart rate (electrocardiogram), and middle cerebral artery mean blood velocity (transcranial Doppler ultrasound) were evaluated. The pattern of leg blood flow response differed between the two groups (p = 0.031) with the Fast group experiencing a delayed onset of reductions in leg blood flow (p = 0.035). The onset of bradycardia was also delayed in the Fast group (p = 0.014), with this group demonstrating a higher value of the lowest heart rate (between‐trial difference in average: 15.9 [3.73, 28.2] beats/min) and cardiac output (between‐trial difference in median: 2.84 L/min) (both, p ≤ 0.013). Middle cerebral artery mean blood velocity was similar between the groups (all p ≥ 0.112). We show that swimmers with superior performance in 50‐m front crawl swim with limited breaths display a diminished diving reflex.

中文翻译：

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快速竞技游泳者表现出跳水反射减弱


竞技游泳运动员在没有呼吸或有限呼吸的情况下完成 50 米的前爬游泳。运动时屏气会触发潜水反射，包括心动过缓和活跃的肌肉血流减少，而大脑等重要器官的氧气供应得以维持。我们假设游泳者在呼吸次数有限的情况下在 50 m 前爬行中取得更快的时间，表现出心脏和主动肌肉血流反应的跳水反射迟钝，脑灌注升高以抵消外周和中枢疲劳。28 名竞技游泳运动员 （12 名女性） 接受了 50 m 前爬游泳计时赛，呼吸中断最少，之后她们被分为两组：快 （n = 13） 和慢 （n = 15）。此外，他们进行了膝关节伸展练习，最大自主屏气，其中评估了腿部血流 （多普勒超声）、心输出量 （Modelflow）、心率 （心电图） 和大脑中动脉平均血速 （经颅多普勒超声）。两组之间的腿部血流反应模式不同 （p = 0.031），Fast 组腿部血流减少的延迟开始 （p = 0.035）。Fast 组的心动过缓发作也延迟 （p = 0.014），该组表现出较低的心率值（试验间平均差异：15.9 [3.73， 28.2] 次/分钟）和心输出量（试验间中位数差异：2.84 L/min）（均，p ≤ 0.013）。两组之间大脑中动脉平均血流速度相似 （均 p ≥ 0.112）。我们表明，在呼吸受限的 50 m 前爬行游泳中表现优异的游泳者表现出跳水反射减弱。