INTRODUCTION Individuals with Down syndrome (DS) exhibit autonomic dysfunction, which contributes to reduced work capacity. The metaboreflex produces exercise-induced sympathoexcitation and can be assessed via post-exercise muscle ischemia (PEMI). Blunted sympathoexcitation is common in individuals with DS and contributes to the physiological basis for reduced work capacity observed this population, but the influence of the metaboreflex is unknown. Using unilateral isometric knee extension exercise with PEMI, we hypothesized that individuals with DS would demonstrate a reduced metaboreflex compared to individuals without DS. METHODS Twenty-four individuals with DS (M/F: 13/11; 24 ± 5 years; 30.3 ± 6.2 kg/m2) and without DS (M/F: 13/11; 25 ± 4 years; 26.5 ± 4.5 kg/m2) performed a unilateral isometric knee extension at 30% of their maximal voluntary contraction (MVC) on a leg dynamometer. Following 2-min of contraction, a thigh-cuff was rapidly inflated to 220 mmHg on the exercised leg for 3-min to isolate the activation of the muscle metaboreflex via PEMI. Beat-to-beat mean and systolic blood pressure (MAP, SBP) were assessed using finger photoplethysmography. Heart rate (HR) was collected via 3-lead electrocardiogram. RESULTS Despite similar baseline values of all variables in both groups, individuals with DS demonstrated a blunted pressor response to unilateral isometric knee extension compared to individuals without DS (MAP; DS: 103 ± 14 vs. Non-DS: 125 ± 19 mmHg), and the blunted MAP response was maintained with PEMI (MAP; DS: 95 ± 13 vs. Non-DS: 106 ± 18 mmHg; groupXtime interaction, p < 0.001). Individuals with DS also exhibited reduced HR 2-min into contraction compared to individuals without DS (HR; DS: 90 ± 16 vs. Non-DS: 114 ± 22 bpm; groupXtime interaction, p < 0.001). CONCLUSIONS Individuals with DS demonstrated a diminished metaboreflex response compared to their peers without DS, during a task known to induce sympathoexcitation. Our findings suggest that reduced influence of the metaboreflex contributes to the reduced exercise pressor response in individuals with DS. Such exercise-specific peripheral autonomic alterations extend beyond our previous cardiac autonomic findings demonstrating blunted sympathoexcitatory perturbations in individuals with DS, which may contribute to reduced work capacity observed in this population.

中文翻译：

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唐氏综合症患者对等长膝关节伸展和运动后缺血的运动升压反应迟钝。


引言 唐氏综合症 （DS） 患者表现出自主神经功能障碍，这会导致工作能力下降。代谢反射产生运动诱导的交感神经兴奋，可以通过运动后肌肉缺血 （PEMI） 进行评估。钝感神经兴奋在 DS 个体中很常见，并有助于观察到该人群的工作能力降低的生理基础，但代谢反射的影响尚不清楚。使用带有 PEMI 的单侧等长膝关节伸展练习，我们假设与没有 DS 的个体相比，患有 DS 的个体会表现出代谢反射降低。方法 24 名患有 DS （M/F： 13/11;24 ± 5 岁;30.3 ± 6.2 kg/m2） 和无 DS （M/F： 13/11;25 ± 4 岁;26.5 ± 4.5 kg/m2） 的个体在腿部测力计上以最大自主收缩 （MVC） 的 30% 进行单侧等长膝关节伸展。收缩 2 分钟后，将大腿袖带在锻炼的腿上快速充气至 220 mmHg，持续 3 分钟，以隔离通过 PEMI 激活肌肉代谢反射。使用手指光电容积脉搏波描记法评估心跳平均心率和收缩压 （MAP， SBP）。通过 3 导联心电图收集心率 （HR）。结果 尽管两组所有变量的基线值相似，但与没有 DS 的个体相比，DS 个体对单侧等长膝关节伸展的升压反应减弱 （MAP;DS：103 ± 14 与非 DS：125 ± 19 mmHg），并且用 PEMI 维持迟钝的 MAP 反应（MAP;DS：95 ± 13 vs. 非 DS：106 ± 18 mmHg;groupXtime 交互，p < 0.001）。与没有 DS 的个体相比，DS 个体在宫缩 2 min 时也表现出 HR 降低（HR;DS：90 ± 16 对 非 DS：114 ± 22 次/分;groupXtime 交互，p < 0.001）。结论 在已知会诱发交感神经兴奋的任务中，与没有 DS 的同龄人相比，患有 DS 的个体表现出代谢反射反应减弱。我们的研究结果表明，代谢反射影响的降低有助于 DS 个体的运动加压反应降低。这种运动特异性外周自主神经改变超出了我们之前的心脏自主神经发现，表明 DS 个体的交感神经兴奋性扰动变钝，这可能导致在该人群中观察到的工作能力降低。