Muscle quality in aging: analysis of non-invasive diagnostic methods, from morphological to functional approach, for routine community implementation and identification of key factors for an exercise protocol to enhance muscle quality
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2025-09-18
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Universidad de Deusto
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Current ageing paradigm reflects the extraordinary adaptive capacity of human beings and constitutes an unprecedented societal success. However, reforming health and social systems to meet the demands of this demographic shift remains a major public health challenge. In this context, musculoskeletal disorders, especially those exacerbating aging-related conditions like sarcopenia and frailty, are a public health priority due to their impact on adverse outcomes (Alkhodary et al., 2020; Cruz-Jentoft et al., 2019; Sayer & Cruz-Jentoft, 2022). Despite the knowledge about the negative consequences of these musculoskeletal pathologies, there are still barriers and knowledge gaps. Sarcopenia, in particular, has emerged as a major concern due to its association with loss of function, frailty and dependency. Over the last decade there have been significant advances incorporating the importance of muscle function and introducing the concept of muscle quality (MQ) (Cruz-Jentoft et al., 2019). MQ encompasses muscle composition factors, including microscopic and macroscopic alterations in muscle architecture, as well as functional performance per unit of muscle mass (de Lucena Alves et al., 2023; M. S. Fragala et al., 2015). However, its assessment remains an emerging area with diagnostic tools still under development, which hampers its clinical and community implementation (Cruz-Jentoft et al., 2019). This dissertation aligns with international and national sarcopenia guidelines, ensuring consistency with public health priorities and promoting comprehensive assessment of muscle quality and function (Basque Government, 2019, 2021; Cruz-Jentoft et al., 2019; Spain ministry of health, 2022; WHO, 2021). A key objective is to enhance the understanding and treatment of sarcopenia through a comprehensive evaluation of muscle quality and function, advocating for a shift from focusing solely on muscle mass to emphasizing strength, quality, and function. The guidelines highlight the need to advance non-invasive tools for assessing these parameters, establish optimal indicators, and determine which tools are accessible in different settings. However, their use is currently limited to research environments due to technical challenges. Therefore, a central objective is to identify the most effective and accessible tools for assessing MQ and to facilitate their implementation in clinical and community practice. Within the non-invasive tools for the assessment of MQ, two areas can be distinguished: morphological tools, which assess muscle composition and architecture, and functional ones, which assess strength in relation to muscle mass (de Lucena Alves et al., 2023; M. S. Fragala et al., 2015). Among direct non-invasive morphological assessment tools, computed tomography (CT) and magnetic resonance imaging (MRI) provide detailed information on muscle composition; however, their high cost and radiation exposure restrict their use to research settings. In contrast, ultrasound (US) has emerged as an accessible, non-invasive alternative with a significant correlation to these imaging modalities, though it faces challenges due to the lack of standardized protocols and operator-dependent variability. Other tools, such as bioimpedance analysis, electromyography, and tensiomyography, are being explored for MQ assessment, but their application requires more standardization (Virto, Río, Méndez-Zorrilla, et al., 2024). In this context, US is a promising technique for quantifying morphological MQ due to its accessibility, speed, and strong correlation with more precise imaging, making it valuable for both clinical practice and research (Virto, Río, Angulo-Garay, et al., 2024). However, in resource-limited settings, the assessment of muscle quality using ultrasound (US) presents accessibility challenges despite its advantages in accuracy and correlation with other imaging modalities. Therefore, although US is a precise tool with a high correlation to other techniques, this study aims to explore the integration and correlation of US with more accessible methods, such as functional muscle quantification tools. The pilot study establishes a correlation between ultrasound geometric variables and functional variables, suggesting a more accessible technique for community-based muscle quality assessment (Virto, Río, Angulo-Garay, et al., 2024). The analysis of functional MQ offers significant potential for daily use, as it involves fewer technical challenges, making it a practical tool in clinical and community settings with limited resources. As for functional methods, they allow a more accessible assessment of muscle quality, usually quantified through the relationship between strength and muscle mass (de Lucena Alves et al., 2023). A variety of non-invasive tools are available for assessing MQ, with handheld dynamometers and 1RM tests being practical for community use, while isokinetic dynamometers and power assessments are more specialized (Abe et al., 2016; American College of Sports Medicine et al., 2009; Baechle et al., 2000; Cruz-Jentoft et al., 2019; Grgic et al., 2020; Jenner et al., 2024). For muscle mass, MRI, CT and Dual-energy X-ray Absorptiometry (DXA) are highly accurate but costly, whereas Bioelectric Impedance Analysis (BIA) and US offer more accessible and cost-effective alternatives for community settings. In the following studies of this thesis work, accessible tools were selected, given their feasibility for use in resource-limited settings and their potential for widespread application in daily practice (Albano et al., 2020; Blake & Fogelman, 2007; Correa-de-Araujo et al., 2017; Cruz-Jentoft et al., 2019; Faron et al., 2020; Jain & Vokes, 2017; Niklasson et al., 2022; Oba et al., 2021; Sconfienza et al., 2018). The measurement of strength was performed by manual handgrip dynamometer and segmental bioimpedance analysis for body composition. Despite some variations from reference methods like MRI, DXA, or CT, these tools correlate well with them, making them suitable for community settings. The final studies of this dissertation explore in depth the multifactorial nature of sarcopenia, muscle quality, and functionality in older adults, highlighting the complex interactions among the factors involved. The results indicate that the primary determinants of sarcopenia include reduced muscle power, age, strength, body mass index (BMI), and sex, while balance, muscle and fat mass, and socioeconomic status also have a significant impact on its development and severity (Virto, Dequin, et al., 2024). Muscle quality, particularly in women, is influenced by age, BMI, muscle mass, fat mass, gait speed, squat test time (reflecting lower limb strength and power), balance, and socioeconomic level. Regarding functionality, which is closely related to gait speed and the neuromuscular and cognitive decline associated with aging, lower limb power and balance emerge as crucial factors (Virto, Río, Muñoz-Pérez, et al., 2024). In conclusion, this dissertation outlines guidelines for developing an exercise protocol to improve muscle quality and sarcopenia, based on previous studies. It also presents a protocol for selecting non-invasive muscle quality assessment tools, focusing on key parameters. This approach aims to deepen understanding of how different factors influence sarcopenia and muscle quality, with a focus on their assessment and targeted intervention in a more precise and accessible manner, thus contributing to improvements in the health and functionality of older adults in various contexts.
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Materias
Ciencias de la Vida
Fisiología humana
Fisiología del músculo
Fisiología humana
Fisiología del músculo