A parasympathetic reactivation is an underlying mechanism mediating the rapid fall in heart rate (HR) at the onset of post-exercise ischemia (PEI) in humans. Herein, we tested the hypothesis that, compared to men, women present a slower HR recovery at the cessation of isometric handgrip exercise (i.e., onset of PEI) due to an attenuated cardiac vagal reactivation. Forty-seven (23 women) young and healthy volunteers were recruited. Subjects performed 90s of isometric handgrip exercise at 40% of maximal voluntary contraction followed by 3-min of PEI. The onset of PEI was analyzed over the first 30s in 10s windows. Cardiac vagal reactivation was indexed using the HR fall and by HR variability metrics (e.g., RMSSD and SDNN) immediately after the cessation of the exercise. HR was significantly increased from rest during exercise in men and women and increases were similar between sexes. However, following the cessation of exercise, the HR recovery was significantly slower in women compared to men regardless of the time point (women vs. men: ∆-14 ± 8 vs. ∆-18 ± 6 beats.min-1 at 10s; ∆-20 ± 9 vs. ∆-25 ± 8 beats.min-1 at 20s; ∆-22 ± 10 vs. ∆-27 ± 9 beats.min-1 at 30s; P = .027). RMSSD and SDNN increased at the cessation of exercise in greater magnitude in men compared to women. These findings demonstrate that women had a slower HR recovery at the cessation of isometric handgrip exercise and onset of PEI compared to men, suggesting a sex-related difference in cardiac vagal reactivation in healthy young humans.

中文翻译：

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从等长握力运动结束和肌肉代谢反射隔离开始时心脏迷走神经再激活的性别差异

副交感神经再激活是介导人类运动后缺血 (PEI) 开始时心率 (HR) 快速下降的潜在机制。在此，我们检验了以下假设：与男性相比，由于心脏迷走神经再激活减弱，女性在停止等长握力运动（即 PEI 开始）时心率恢复较慢。招募了四十七名（23 名女性）年轻健康的志愿者。受试者以 40% 的最大自主收缩率进行 90 年代的等长握力运动，然后进行 3 分钟的 PEI。在 10 秒窗口中的前 30 秒内分析了 PEI 的发作。心脏迷走神经再激活在运动停止后立即使用心率下降和心率变异性指标（例如，RMSSD 和 SDNN）进行索引。男性和女性在运动期间休息时 HR 显着增加，并且两性之间的增加相似。然而，在停止运动后，无论时间点如何，女性的心率恢复都明显慢于男性（女性与男性：Δ-14 ± 8 与 Δ-18 ± 6 beats.min-1 at 10s； ∆-20 ± 9 vs. ∆-25 ± 8 beats.min-1 at 20s；∆-22 ± 10 vs. ∆-27 ± 9 beats.min-1 at 30s；P = .027）。与女性相比，男性在停止运动时 RMSSD 和 SDNN 的增加幅度更大。这些发现表明，与男性相比，女性在停止等长握力运动和 PEI 开始时的心率恢复较慢，这表明健康年轻人心脏迷走神经再激活的性别相关差异。无论时间点如何，女性的 HR 恢复均明显慢于男性（女性与男性：Δ-14 ± 8 与 Δ-18 ± 6 beats.min-1 at 10s；Δ-20 ± 9 与 Δ -25 ± 8 beats.min-1 at 20s；∆-22 ± 10 vs. ∆-27 ± 9 beats.min-1 at 30s；P = .027）。与女性相比，男性在停止运动时 RMSSD 和 SDNN 的增加幅度更大。这些发现表明，与男性相比，女性在停止等长握力运动和 PEI 开始时的心率恢复较慢，这表明健康年轻人心脏迷走神经再激活的性别相关差异。无论时间点如何，女性的 HR 恢复均明显慢于男性（女性与男性：Δ-14 ± 8 与 Δ-18 ± 6 beats.min-1 at 10s；Δ-20 ± 9 与 Δ -25 ± 8 beats.min-1 at 20s；∆-22 ± 10 vs. ∆-27 ± 9 beats.min-1 at 30s；P = .027）。与女性相比，男性在停止运动时 RMSSD 和 SDNN 的增加幅度更大。这些发现表明，与男性相比，女性在停止等长握力运动和 PEI 开始时心率恢复较慢，这表明健康年轻人心脏迷走神经再激活的性别相关差异。与女性相比，男性在停止运动时 RMSSD 和 SDNN 的增加幅度更大。这些发现表明，与男性相比，女性在停止等长握力运动和 PEI 开始时心率恢复较慢，这表明健康年轻人心脏迷走神经再激活的性别相关差异。与女性相比，男性在停止运动时 RMSSD 和 SDNN 的增加幅度更大。这些发现表明，与男性相比，女性在停止等长握力运动和 PEI 开始时的心率恢复较慢，这表明健康年轻人心脏迷走神经再激活的性别相关差异。