Cardiovasomobility: an integrative understanding of how disuse impacts cardiovascular and skeletal muscle health

Physiological and morphological impact of physical activity and nutritional interventions to offset disuse-induced skeletal muscle atrophy

Skeletal muscle tissue acts as a functional unit for physical movements, energy metabolism, thermogenesis, and metabolic homeostasis. In this literature review, the underlying mechanisms of skeletal muscle atrophy and the prevention strategies, including vigorous training and nutritional modifications are focused. Furthermore, the comparative analysis of multiple interventions is briefly explained. Ageing is an inevitable process often associated with cognitive impairment and physical decline due to muscular atrophy. Skeletal muscle atrophy is characterized by low muscle mass due to multiple underlying factors, i.e., genetic predisposition, ageing, inflammation, and trauma. The structural alterations include myofiber shrinkage, changes in myosin isoforms, decrease in myofiber diameter, and total protein loss. Furthermore, there is an imbalance in protein anabolic and catabolic reactions. This may be due to changes in multiple signal transduction pathways of protein degradation (i.e., caspase, calpain, ubiquitin protein degradation system, autophagy) and protein anabolism via the mTOR pathway. Consequently, certain pathophysiological factors associated with health disparities may reduce mobility and functional capacity to perform ADLs. To tackle this issue, novel strategies linked to physical movement, and dietary intake must be incorporated in life. Exercise poses multiple health benefits, including improved muscle mass and mobility. Diet diversification [particularly protein-rich meals] and the "whole food" approach (based on non-protein nutrients) may enhance intramuscular anabolic signaling and tissue remodeling. However, there is a pressing need to fund large-scale evidence-based trials based on modern machine learning techniques (AI-driven nutrition). Additionally, entrepreneurial platforms for commercialization of consumer-friendly food products must be initiated in future.

Effect of happiness and functional disability on older people's survival

The aim was to investigate survival and risk of death within a ten-year period according to physical functioning and frequency of the feeling of happiness in older people, conducting an analysis of the possible mediating effect of happiness on the association between physical functioning and mortality. A retrospective longitudinal study was conducted with 1,519 older people (≥ 60 years) interviewed for the 2008/2009 Health Survey in Campinas. A linkage was made between the databank of the survey and the Campinas Mortality Information System, with active search for confirmation of deaths and non-deaths from 2008 to 2018. Variables of interest were physical functioning (absence/presence of limitations) and frequency of feeling happiness. Kaplan-Meier survival curves were plotted and Cox regression analysis was performed to estimate hazard ratios (HR). A mediation analysis was also conducted using the Karlson-Holm-Breen (KHB) method. In the adjusted analysis, severe functional limitation (HR = 2.8; 95%CI: 2.0-3.8) and low frequency of happiness (HR = 1.6; 95%CI: 1.3-2.0) increased the risk of death in the period. Low frequency of happiness mediated the association between functioning and mortality by 14%. The results underscore the importance of strategies to maintain physical functioning during aging. Moreover, a greater frequency of the feeling of happiness increased the survival of the population. The findings also show that happiness plays an important mediating role in the association between functioning and mortality in older people.

Mathematical Modeling and Characterization of a Wearable Soft Robotic Device for Muscle Mechanotherapy

Treatments of disuse-induced muscle atrophy entail unmet clinical needs due to the lack of medical devices capable of mimicking physicians manual therapies. Therefore, in this paper we develop and model a wearable soft pneumatic elastomeric actuator to perform deep cyclic compression stimuli on human soft tissues for muscle rehabilitation by mechanotherapy. Static and dynamic characterization of the prototype demonstrate a 2.5 mm active deformation at 100 kPa with 600 mm3/s and a 5 Hz bandwidth. We estimate the transfer function of the experimentally acquired pressure, flow and deformation signals, processed by a Gaussian kernel-based approach. Our mathematical model accurately describes the actuator behavior and enables to extract its mechanical parameters. Then, through computational simulations, we illustrate its efficacy in emulating multiple complex bio-inspired movements. Our proposed methodology aims to improve the control efficiency in wearable soft robotics for muscle atrophy treatment.

Computational Analysis of Mechanical Interactions between a Soft Robotic Device and a Skin-Muscle Phantom for Mechanotherapy

Studying the soft robot-tissue mechanical interaction in muscle stimulation devices poses a significant challenge due to the complex behavior of the materials involved. To advance this field, this paper models computationally three types of soft elastomeric actuators designed to perform deep cyclic compression stimuli on human soft tissues for muscle rehabilitation by mechanotherapy. The analysis focuses on the interaction between a phantom representing transversely isotropic muscle and homogeneous skin, with a soft robotic device comprised of a hyperelastic actuator and a rigid support. Results from deformation, stress-strain and surface pressure analysis demonstrate efficient actuation, suggesting deep and focused stimulation on the muscle, while actuators exhibit reliable safety factors and load distribution, implying longer operational life. This lightweight and compact soft robotic device is suitable for integration into a wearable suit for targeted muscle groups stimulation in the lower limbs. Furthermore, this computational approach represents a significant advance in the biomechanical study of soft robot-human tissues interaction, with potential for generalization in similar biomedical device applications. Keywords-Soft Robotics, Mechanotherapy, Transversely Isotropic Muscle, Human-Robot interaction.

Attenuated reactive hyperemia after prolonged sitting is associated with reduced local skeletal muscle metabolism: insight from artificial intelligence

Blunted post-occlusive reactive hyperemia (PORH) after prolonged sitting (PS) has been used as evidence of microvascular dysfunction. However, it has not been determined if confounding variables are responsible for the reduction in PORH after PS. Therefore, the purpose of this study was to examine the PS-mediated changes in cardiovascular and metabolic factors that affect PORH using artificial intelligence (AI). We hypothesized that calf muscle metabolic rate (MMR) is attenuated after PS, which may reduce tissue hypoxia during an arterial occlusion (i.e., oxygen deficit) and PORH. Thirty-one subjects (male = 13, female = 18) sat for 2.5 h. A rapid-inflation cuff was placed around the thigh above the knee to generate an arterial occlusion. PORH was represented by the reoxygenation rate (RR) of the near-infrared spectroscopy (NIRS) tissue oxygenation index (TOI) after 5-min of arterial occlusion. An artificial intelligence model (AI) defined the stimulus-response relationship between the oxygen deficit (i.e., ΔTOI and TOI deficit), and RR with 65 previous PORH recordings. If the AI predicts the experimental RRs, then the change in RR is related to the change in the oxygen deficit. RR (Δ -0.27 ± 0.55 lnTOI%·s-1, P = 0.001), MMR (Δ -0.46 ± 0.61 lnTOI%·s-1, P < 0.001), ΔTOI (Δ -0.34 ± 0.62 lnTOI%, P < 0.001), and the TOI deficit (Δ -0.42 ± 0.68 lnTOI%·s, P < 0.001) were reduced after PS. In addition, strong linear associations were found between MMR and the TOI deficit (r2 = 0.900, P < 0.001) and ΔTOI (r2 = 0.871, P < 0.001). Furthermore, the AI accurately predicted the RRs pre- and post-PS (P = 0.471, P = 0.328, respectively). Therefore, blunted PORH after PS may be caused by attenuated MMR and not microvascular dysfunction.NEW & NOTEWORTHY Prolonged sitting reduces lower leg skeletal muscle metabolic rate in healthy individuals. Artificial intelligence revealed that impaired post-occlusive reactive hyperemia after prolonged sitting is related to a reduced stimulus for vasodilation and may not be evidence of microvascular dysfunction. Current post-occlusive reactive hyperemia protocols may be insufficient to assess micro- and macrovascular function after prolonged sitting.

Prolonged sitting and peripheral vascular function: potential mechanisms and methodological considerations

Sitting time is associated with increased risks for subclinical atherosclerosis and cardiovascular disease development, and this is thought to be partially due to sitting-induced disturbances in macro- and microvascular function as well as molecular imbalances. Despite surmounting evidence supporting these claims, contributing mechanisms to these phenomena remain largely unknown. In this review, we discuss evidence for potential mechanisms of sitting-induced perturbations in peripheral hemodynamics and vascular function and how these potential mechanisms may be targeted using active and passive muscular contraction methods. Furthermore, we also highlight concerns regarding the experimental environment and population considerations for future studies. Optimizing prolonged sitting investigations may allow us to not only better understand the hypothesized sitting-induced transient proatherogenic environment but to also enhance methods and devise mechanistic targets to salvage sitting-induced attenuations in vascular function, which may ultimately play a role in averting atherosclerosis and cardiovascular disease development.

The impact of aging and physical training on angiogenesis in the musculoskeletal system

Angiogenesis is the physiological process of capillary growth. It is strictly regulated by the balanced activity of agents that promote the formation of capillaries (pro-angiogenic factors) on the one hand and inhibit their growth on the other hand (anti-angiogenic factors). Capillary rarefaction and insufficient angiogenesis are some of the main causes that limit blood flow during aging, whereas physical training is a potent non-pharmacological method to intensify capillary growth in the musculoskeletal system. The main purpose of this study is to present the current state of knowledge concerning the key signalling molecules implicated in the regulation of skeletal muscle and bone angiogenesis during aging and physical training.

Capillary communication: the role of capillaries in sensing the tissue environment, coordinating the microvascular, and controlling blood flow

Historically, capillaries have been viewed as the microvascular site for flux of nutrients to cells and removal of waste products. Capillaries are the most numerous blood vessel segment within the tissue, whose vascular wall consists of only a single layer of endothelial cells and are situated within microns of each cell of the tissue, all of which optimizes capillaries for the exchange of nutrients between the blood compartment and the interstitial space of tissues. There is, however, a growing body of evidence to support that capillaries play an important role in sensing the tissue environment, coordinating microvascular network responses, and controlling blood flow. Much of our growing understanding of capillaries stems from work in skeletal muscle and more recent work in the brain, where capillaries can be stimulated by products released from cells of the tissue during increased activity and are able to communicate with upstream and downstream vascular segments, enabling capillaries to sense the activity levels of the tissue and send signals to the microvascular network to coordinate the blood flow response. This review will focus on the emerging role that capillaries play in communication between cells of the tissue and the vascular network required to direct blood flow to active cells in skeletal muscle and the brain. We will also highlight the emerging central role that disruptions in capillary communication may play in blood flow dysregulation, pathophysiology, and disease.