Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah.
Geriatric Research, Education, and Clinical Center, Salt Lake City, Utah.
J Appl Physiol (1985). 2021 Dec 1;131(6):1691-1700. doi: 10.1152/japplphysiol.00400.2021. Epub 2021 Oct 21.
This study investigated the impact of dietary nitrate supplementation on peripheral hemodynamics, the development of neuromuscular fatigue, and time to task failure during cycling exercise. Eleven recreationally active male participants (27 ± 5 yr, V̇o: 42 ± 2 mL/kg/min) performed two experimental trials following 3 days of either dietary nitrate-rich beetroot juice (4.1 mmol NO/day; DNS) or placebo (PLA) supplementation in a blinded, counterbalanced order. Exercise consisted of constant-load cycling at 50, 75, and 100 W (4 min each) and, at ∼80% of peak power output (218 ± 12 W), to task-failure. All participants returned to repeat the shorter of the two trials performed to task failure, but with the opposite supplementation regime (iso-time comparison; ISO). Mean arterial pressure (MAP), leg blood flow (Q; Doppler ultrasound), leg vascular conductance (LVC), and pulmonary gas exchange were continuously assessed during exercise. Locomotor muscle fatigue was determined by the change in pre to postexercise quadriceps twitch-torque (ΔQ) and voluntary activation (ΔVA; electrical femoral nerve stimulation). Following DNS, plasma [nitrite] (∼670 vs. ∼180 nmol) and [nitrate] (∼775 vs. ∼11 μmol) were significantly elevated compared with PLA. Unlike PLA, DNS lowered both Q and MAP by ∼8% ( < 0.05), but did not alter LVC ( = 0.31). V̇O across work rates, as well as cycling time to task-failure (∼7 min) and locomotor muscle fatigue following the ISO-time comparison were not different between the two conditions (ΔQ ∼42%, ΔVA ∼4%). Thus, despite significant hemodynamic changes, DNS did not alter the development of locomotor muscle fatigue and, ultimately, cycling time to task failure. This study sought to characterize the impact of dietary nitrate supplementation on the hemodynamic response, locomotor muscle fatigue, and time to task failure during cycling exercise. Although nitrate supplementation lowered mean arterial pressure and exercising leg blood flow, leg vascular conductance and oxygen utilization were unaffected. Despite significant hemodynamic changes, there was no effect of dietary nitrate on neuromuscular fatigue development and, ultimately, cycling time to task failure.
本研究旨在探讨饮食硝酸盐补充对周期性运动时外周血液动力学、神经肌肉疲劳发展和任务失败时间的影响。11 名有规律运动的男性参与者（27 ± 5 岁，V̇o：42 ± 2 毫升/公斤/分钟）在服用 3 天饮食硝酸盐丰富的甜菜根汁（4.1 毫摩尔 NO/天；DNS）或安慰剂（PLA）补充剂后，以盲法、平衡方式进行了两次实验性试验。运动包括在 50、75 和 100 W 下进行恒定负荷的自行车运动（每 4 分钟一次），并在约 80%的峰值功率输出（218 ± 12 W）下，直到任务失败。所有参与者都返回重复进行的两项试验中较短的一项，但补充剂方案相反（等时比较；ISO）。在运动过程中连续评估平均动脉压（MAP）、腿部血流量（Q；多普勒超声）、腿部血管传导率（LVC）和肺气体交换。运动肌肉疲劳通过股四头肌抽搐扭矩（ΔQ）和自愿激活（ΔVA；电股神经刺激）前后的变化来确定。与 PLA 相比，DNS 后血浆[亚硝酸盐]（670 对180 毫摩尔）和[硝酸盐]（775 对11 微摩尔）显著升高。与 PLA 不同，DNS 降低了腿部血流量和 MAP 约 8%（<0.05），但没有改变 LVC（=0.31）。两种条件下的工作率 V̇O 以及 ISO 时间比较后的自行车运动至任务失败时间（7 分钟）和运动肌肉疲劳没有差异（ΔQ42%，ΔVA~4%）。因此，尽管存在显著的血液动力学变化，但 DNS 并未改变运动肌肉疲劳的发展，最终也未改变自行车运动至任务失败的时间。本研究旨在描述饮食硝酸盐补充对周期性运动时血液动力学反应、运动肌肉疲劳和任务失败时间的影响。尽管硝酸盐补充降低了平均动脉压和运动腿部血流量，但腿部血管传导率和氧气利用率不受影响。尽管血液动力学发生了显著变化，但饮食硝酸盐对神经肌肉疲劳发展和最终自行车运动至任务失败时间没有影响。
