Effects of Exercise Training on Muscle Quality in Older Individuals: A Systematic Scoping Review with Meta-Analyses

Abstract

Background The quantity and quality of skeletal muscle are important determinants of daily function and metabolic health. Various forms of physical exercise can improve muscle function, but this effect can be inconsistent and has not been systematically examined across the health-neurological disease continuum. The purpose of this systematic scoping review with meta-analyses was to determine the effects and potential moderators of exercise training on morphological and neuromuscular muscle quality (MMQ, NMQ) in healthy older individuals. In addition and in the form of a scoping review, we examined the effects of exercise training on NMQ and MMQ in individuals with neurological conditions. Methods A systematic literature search was performed in the electronic databases Medline, Embase, and Web of Science. Randomized controlled trials were included that examined the effects of exercise training on muscle quality (MQ) in older individuals with and without neurological conditions. Risk of bias and study quality were assessed (Cochrane Risk of Bias Tool 2.0). We performed random-effects models using robust variance estimation and tested moderators using the approximate Hotelling–Zhang test. Results Thirty studies (n = 1494, 34% females) in healthy older individuals and no studies in individuals with neurological conditions were eligible for inclusion. Exercise training had small effects on MMQ (g = 0.21, 95% confidence interval [CI]: 0.03–0.40, p = 0.029). Heterogeneity was low (median I2 = 16%). Training and demographic variables did not moderate the effects of exercise on MMQ. There was no association between changes in MMQ and changes in functional outcomes. Exercise training improved NMQ (g = 0.68, 95% CI 0.35–1.01, p < 0.000) across all studies, in particular in higher-functioning older individuals (g = 0.72, 95% CI 0.38–1.06, p < 0.001), in lower extremity muscles (g = 0.74, 95% CI 0.35–1.13, p = 0.001), and after resistance training (g = 0.91; 95% CI 0.42–1.41, p = 0.001). Heterogeneity was very high (median I2 = 79%). Of the training and demographic variables, only resistance training moderated the exercise-effects on NMQ. High- versus low-intensity exercise moderated the exercise-effects on NMQ, but these effects were considered unreliable due to a low number of studies at high intensity. There was no association between changes in NMQ and changes in functional outcomes. Conclusion Exercise training has small effects on MMQ and medium-large effects on NMQ in healthy older individuals. There was no association between improvements in MQ and increases in muscle strength, mobility, and balance. Information on dose-response relations following training is currently lacking. There is a critical gap in muscle quality data for older individuals with lower function and neurological conditions after exercise training. Health practitioners should use resistance training to improve muscle function in older individuals. Well-designed studies are needed to examine the relevance of exercise training-induced changes in MQ in daily function in older individuals, especially to those with lower function and neurological conditions.

Research Progress on Cognitive Frailty in Older Adults with Chronic Kidney Disease

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Neuromuscular Component of Muscle Quality Assessment in Older Adults: Narrative Review

“…Muscle quality, a term used to characterize muscle's capacity for contraction, metabolic activity and electrical activity, plays a crucial role in various populations, particularly in low functioning older adults and those with muscle diseases like sarcopenia (Naimo et al, 2021). The concept of muscle quality encompasses both micro-and macroscopic aspects of muscle architecture and composition and has gained increasing attention with inclusion in the definition of sarcopenia, indicating the significance of muscle quality in evaluating muscle function and strength among older individuals (Cruz-Jentoft et al, 2019;Hortobágyi et al, 2023;Radaelli et al, 2021).…”

“…Additionally, muscle quality is not solely determined by the size and composition of the muscles, but also by the efficiency and effectiveness of the neuromuscular system. Therefore, it is comprised of two major components which describe different components (Hortobágyi et al, 2023): (i) characteristics of morphological component of the non-contractile tissue; and (ii) neuromuscular component defined as the ratio between force or torque and a measure of muscle size (thickness, volume, cross-sectional area or echo intensity) (Fragala et al, 2015;Lynch et al, 1999). So far, muscle quality has been most defined as a ratio between a measure of muscle strength and muscle mass, and in the earlier research it was suggested that muscle quality is an indicator of muscle function rather than muscle strength (Lynch et al, 1999).…”

Convolutional Neural Network-Based Automated Segmentation of Skeletal Muscle and Subcutaneous Adipose Tissue on Thigh MRI in Muscular Dystrophy Patients

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