Verma Ajay K, Xu Da, Garg Amanmeet, Blaber Andrew P, Tavakolian Kouhyar
School of Electrical Engineering and Computer Science, University of North Dakota, Grand Forks, ND, United States.
Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada.
Front Physiol. 2019 Jul 16;10:845. doi: 10.3389/fphys.2019.00845. eCollection 2019.
Activation of leg muscles is an important component in the regulation of blood pressure during standing, failure of which could result in syncope and falls. Our previous work demonstrated baroreflex mediated activation of leg muscles (muscle-pump baroreflex) as an important factor in the regulation of blood pressure during standing; however, the effect of aging on the muscle-pump baroreflex of individual leg muscles during standing remains to be understood. Here, the interaction between systolic blood pressure (SBP) and the activation of lateral gastrocnemius (LG), medial gastrocnemius (MG), tibialis anterior (TA), and soleus (SOL) muscles during standing was quantified. Beat-to-beat heart period (RR interval), SBP, electromyography impulse (EMG) were derived from continuously acquired electrocardiography, finger blood pressure, and calf-electromyography, respectively. The cardiac baroreflex (SBP→RR) causality (0.88 ± 0.08 vs. 0.94 ± 0.03, = 0.01), percent time with significant coherence (%SC: 50.95 ± 23.31 vs. 76.75 ± 16.91, = 0.001), and gain (4.39 ± 4.38 vs. 13.05 ± 8.11, < 0.001) was lower in older (69 ± 4 years) compared to young (26 ± 2 years) persons. Muscle-pump baroreflex (SBP→EMG) causality of LG (0.81 ± 0.08 vs. 0.88 ± 0.05, = 0.01) and SOL (0.79 ± 0.11 vs. 0.88 ± 0.04, = 0.01) muscles was lower in older compared to young persons. %SC was lower for all muscles in the older group (LG, < 0.001; MG, = 0.01; TA, = 0.01; and SOL, < 0.001) compared to young. The study outcomes highlighted impairment in muscle-pump baroreflex with age in addition to cardiac baroreflex. The findings of the study can assist in the development of an effective system for monitoring orthostatic tolerance via cardiac and muscle-pump baroreflexes to mitigate syncope and falls.
站立时腿部肌肉的激活是血压调节的重要组成部分，其功能失效可能导致晕厥和跌倒。我们之前的研究表明，压力反射介导的腿部肌肉激活（肌肉泵压力反射）是站立时血压调节的一个重要因素；然而，衰老对站立时单个腿部肌肉的肌肉泵压力反射的影响仍有待了解。在此，我们对站立时收缩压（SBP）与外侧腓肠肌（LG）、内侧腓肠肌（MG）、胫骨前肌（TA）和比目鱼肌（SOL）肌肉激活之间的相互作用进行了量化。逐搏心动周期（RR间期）、SBP、肌电图冲动（EMG）分别来自连续采集的心电图、手指血压和小腿肌电图。与年轻人（26±2岁）相比，老年人（69±4岁）的心脏压力反射（SBP→RR）因果关系（0.88±0.08对0.94±0.03，P = 0.01）、显著相干百分比（%SC：50.95±23.31对76.75±16.91，P = 0.001）和增益（4.39±4.38对13.05±8.11，P < 0.001）较低。与年轻人相比，老年人LG肌（0.81±0.08对0.88±0.05，P = 0.01）和SOL肌（0.79±0.11对0.88±0.04，P = 0.01）的肌肉泵压力反射（SBP→EMG）因果关系较低。与年轻人相比，老年组所有肌肉的%SC均较低（LG，P < 0.001；MG，P = 0.01；TA，P = 0.01；SOL，P < 0.001）。研究结果突出了除心脏压力反射外，肌肉泵压力反射也随年龄增长而受损。该研究结果有助于开发一种有效的系统，通过心脏和肌肉泵压力反射来监测直立耐力，以减轻晕厥和跌倒。
