Kwak Minyoung, Benitez Brian, Mitchinson Clara J, Snell Erik R, Bergstrom Haley C
Department of Kinesiology and Health Promotion, University of Kentucky, Lexington, KY 40502, USA.
Department of Kinesiology and Health Promotion, University of Kentucky, Lexington, KY 40502, USA.
Microvasc Res. 2025 Sep;161:104839. doi: 10.1016/j.mvr.2025.104839. Epub 2025 Jul 2.
This study investigated fatigability, reflected by torque responses and time to task failure (TTF), and time course of muscle oxygenation (SmO) dynamics, as well as microvascular function assessed by near-infrared spectroscopy-vascular occlusion test (NIRS-VOT), in response to low-intensity, isometric forearm flexion anchored to a constant rating of perceived exertion (RPE) level of 3 (0-10 scale).
Twenty-five healthy young adults (22.9 ± 4.8 yr) completed a pre-exercise VOT, maximal voluntary isometric contraction (MVIC), and RPE-clamp exercise (RPE = 3), followed by post-exercise MVIC and VOT. Initial torque, TTF, and SmO dynamics were recorded during the RPE-clamp exercise. The time course of SmO was analyzed in 5 % TTF segments. During the VOTs, slope 1 (desaturation rate), minimum SmO, slope 2 (reperfusion rate), maximum SmO, and area under the curve (AUC) were recorded.
MVIC torque significantly decreased from pre- to post-exercise (-13.9 % ± 14.0 %; p < 0.001). Initial torque was 23.3 ± 10.3 % MVIC, and TTF was 436.3 ± 252.0 s. SmO declined significantly from 0 % to 5 % TTF (p = 0.005), but returned to the initial value and remained stable across subsequent time intervals. Compared to pre-VOT, post-VOT exhibited significantly lower slope 1 (p < 0.001) and minimum SmO (p = 0.002), and greater maximum SmO (p = 0.013), while slope 2 (p = 0.065) and AUC (p = 0.379) were unchanged.
During the RPE-clamp exercise, the voluntary reduction in torque to maintain the assigned RPE likely resulted in stable muscle oxygen availability, preventing the development of hypoxic stimulus needed to enhance microvascular responsiveness. However, the low-intensity isometric RPE-clamp exercise combined with a post-VOT may enhance muscle aerobic metabolism through sustained oxygen utilization.
本研究调查了以扭矩反应和任务失败时间（TTF）反映的疲劳性、肌肉氧合（SmO）动力学的时间进程，以及通过近红外光谱 - 血管闭塞试验（NIRS - VOT）评估的微血管功能，这些指标是针对以3级（0 - 10级）的恒定主观用力程度（RPE）水平进行的低强度等长前臂屈曲运动的反应。
25名健康年轻成年人（22.9 ± 4.8岁）完成了运动前的VOT、最大自主等长收缩（MVIC）和RPE钳夹运动（RPE = 3），随后进行运动后的MVIC和VOT。在RPE钳夹运动期间记录初始扭矩、TTF和SmO动力学。在TTF的5%时间段内分析SmO的时间进程。在VOT期间，记录斜率1（去饱和率）、最小SmO、斜率2（再灌注率）、最大SmO和曲线下面积（AUC）。
MVIC扭矩从运动前到运动后显著降低（-13.9% ± 14.0%；p < 0.001）。初始扭矩为MVIC的23.3% ± 10.3%，TTF为436.3 ± 252.0秒。SmO在TTF的0%至5%显著下降（p = 0.005），但在随后的时间间隔内恢复到初始值并保持稳定。与运动前VOT相比，运动后VOT的斜率1显著降低（p < 0.001）和最小SmO显著降低（p = 0.002），而最大SmO增加（p = 0.013），而斜率2（p = 0.065）和AUC（p = 0.379）无变化。
在RPE钳夹运动期间，为维持指定RPE而自愿降低扭矩可能导致肌肉氧供应稳定，防止增强微血管反应性所需的缺氧刺激的发展。然而，低强度等长RPE钳夹运动与运动后VOT相结合可能通过持续的氧利用增强肌肉有氧代谢。
