Skeletal Muscle Pump Drives Control of Cardiovascular and Postural Systems

Ajay K Verma,Andrew P Blaber,Reza Fazel-Rezai,Kouhyar Tavakolian,Michelle Bruner,Da Xu,Amanmeet Garg

doi:10.1038/srep45301

Ajay K Verma, Andrew P Blaber + Show 5 more

Open Access

https://doi.org/10.1038/srep45301

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Abstract

The causal interaction between cardio-postural-musculoskeletal systems is critical in maintaining postural stability under orthostatic challenge. The absence or reduction of such interactions could lead to fainting and falls often experienced by elderly individuals. The causal relationship between systolic blood pressure (SBP), calf electromyography (EMG), and resultant center of pressure (COPr) can quantify the behavior of cardio-postural control loop. Convergent cross mapping (CCM) is a non-linear approach to establish causality, thus, expected to decipher nonlinear causal cardio-postural-musculoskeletal interactions. Data were acquired simultaneously from young participants (25 ± 2 years, n = 18) during a 10-minute sit-to-stand test. In the young population, skeletal muscle pump was found to drive blood pressure control (EMG → SBP) as well as control the postural sway (EMG → COPr) through the significantly higher causal drive in the direction towards SBP and COPr. Furthermore, the effect of aging on muscle pump activation associated with blood pressure regulation was explored. Simultaneous EMG and SBP were acquired from elderly group (69 ± 4 years, n = 14). A significant (p = 0.002) decline in EMG → SBP causality was observed in the elderly group, compared to the young group. The results highlight the potential of causality to detect alteration in blood pressure regulation with age, thus, a potential clinical utility towards detection of fall proneness.

Highlights

Postural stability is dependent on input from visual, cognitive, somatosensory, and vestibular systems[11,13,14]
The resampled EMG, center of pressure (COPr), and systolic blood pressure (SBP) signals were input to the false nearest neighbor (FNN) algorithm
Τ= 20 and E = 4 was used for Convergent cross mapping (CCM) causality analysis between cardio-postural-musculoskeletal systems and all CCM results presented in this article were obtained using such parameters unless mentioned otherwise

Summary

Introduction

Postural stability is dependent on input from visual, cognitive, somatosensory, and vestibular systems[11,13,14]. In the absence of such input, an alteration in postural stability along with blood pressure and muscle activity is observed[15] This is indicative of inter-relationship between cardio-postural-musculoskeletal systems[16]. This inter-relationship has been recently validated during quiet standing by exhibiting the presence of significant coherence (linear coupling) between variables belonging to respective systems[15,16,17]. The established knowledge of causality between dynamical systems could be exploited for physiological system performance monitoring, as; a significant deviation in the behavior of causally linked systems from the established norm could be symptomatic of system impairment To this end, the commonly applied Granger causality method measures the ability of one signal to predict the future of other to establish causal behavior. With evidence of success in the literature, CCM is expected to accurately unearth dynamics of underlying physiological interactions between cardio-postural-musculoskeletal systems (cardio-postural control loop), a pivotal intersystem interaction required for maintaining stable upright posture

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