Muscle Quality Index Research Articles

The muscle quality index and mortality among males and females

PurposeThe muscle quality index (MQI) was proposed as a measure to quantify age-related alterations in muscle function. It is unknown if the MQI predicts mortality. MethodsThis was a population-based cohort study from the Third National Health and Nutrition Survey (NHANES III; 1988–1994). The MQI was quantified using a timed sit-to-stand test, body mass, and leg length. Vital status was obtained through the National Center for Health Statistics. We fit multivariable-adjusted regression models to estimate the hazard ratio (HR) and 95% confidence interval (CI) between the MQI and mortality. ResultsDuring 14.6 years of follow-up, 3299 (73.1%) of 4510 study participants died. Lower MQI was associated with a higher risk of mortality (Ptrend <.001). The multivariable-adjusted HR for mortality was 1.50 (95% CI, 1.15–1.96) for those in the lowest quintile of MQI compared to the highest quintile. The association between MQI and mortality was stronger among males (highest vs. lowest quintile of MQI, HR = 1.37 [95% CI, 1.00–1.87]; Ptrend = .001) compared to females (highest vs. lowest quintile of MQI, HR = 1.27 (95% CI, 0.89–1.83); Ptrend = .044; Pinteraction = .005]. ConclusionsThe MQI predicts mortality and may differ between males and females. Additional research examining the MQI is warranted.

Muscle quality in aging: a multi-dimensional approach to muscle functioning with applications for treatment.

Aging is often accompanied by declines in physical functioning which impedes older adults' quality of life, sense of independence, and ability to perform daily tasks. Age-related decreases in skeletal muscle quantity, termed sarcopenia, have traditionally been blamed for these physical decrements. However, recent evidence suggests that the quality of muscle tissue may be more functionally relevant than its quantity. 'Muscle quality' has been emerging as a means to elucidate and describe the intricate intramuscular changes associated with muscle performance in the context of aging and sarcopenia. While muscle quality has most commonly been defined in terms of muscle composition or relative strength, at the core, muscle quality really describes muscle's ability to function. Skeletal muscle displays a strong structure-function relationship by which several architectural characteristics factor into its functional capacity. This review describes the structural, physiological, and functional determinants of muscle quality at the tissue and cellular level, while also introducing other novel parameters such as sarcomere spacing and integrity, circulating biomarkers, and the muscle quality index. Muscle qualitative features are described from the perspective of how physical exercise may improve muscle quality in older adults. This broad, multidimensional perspective of muscle quality in the context of aging and sarcopenia offers comprehensive insights for consideration and integration in developing improved prognostic tools for research and clinical care, while also promoting translational approaches to the design of novel targeted intervention strategies designed to maintain function and mobility into late life.

Age-related site-specific muscle loss in the thigh and zigzag walking performance in older men and women

To investigate the relationships between site-specific muscle loss in the thigh, muscle quality and zigzag walking performance, 40 men and 41 women aged 65-79 years had muscle thickness (MTH) measured by ultrasound at nine sites on the anterior and posterior aspects of the body. Skeletal muscle mass (SM) was estimated from an ultrasound-derived prediction equation. Site-specific thigh sarcopenia was calculated using ultrasound-measured MTH at the anterior/posterior aspects of the thigh (AP-MTH ratio). Zigzag walking time (ZWT) and maximum isometric knee extension (KE) and flexion (KF) torques were measured. Muscle quality (torque/thigh SM) and knee joint strength index (torque/body mass) were calculated. There were no significant correlations between SM index and ZWT. However, AP-MTH ratio was inversely correlated (P < 0.05) to ZWT in men (r = -0.335) and women (r = -0.309). ZWT was also inversely correlated (P < 0.05) to KE-strength index in both sexes (men, r = -0.328; women, r = -0.372). Similarly, ZWT was correlated to KF-strength index (r = -0.497) and muscle quality (r = -0.322) in women, but not in men. After adjusting for age, height and body mass, AP-MTH ratio was inversely correlated to ZWT in men (r = -0.325) and tended to be correlated to ZWT in women (r = -0.263). Zigzag walking performance may be associated with site-specific thigh sarcopenia in older men and women.

Sex- and age-related differences in mid-thigh composition and muscle quality determined by computed tomography in middle-aged and elderly Japanese.

Sex- and age-related differences in mid-thigh composition and muscle quality remain unclear. The present study aimed to clarify these differences using computed tomography in middle-aged and elderly Japanese. A total of 2310 participants (age 40-89 years), who were randomly selected from the local residents, underwent computed tomography examination of the right mid-thigh. Thigh circumference and cross-sectional areas of the thigh, muscle, quadriceps, non-quadriceps, fat, and bone were measured. Knee extension strength and muscle quality index (knee extension strength/quadriceps cross-sectional area) were also assessed. Sex- and age-related differences in these indices were analyzed. The thigh cross-sectional area in men and women decreased by 0.6% and 0.5%/year, respectively, because of a decrease in muscle cross-sectional area (men 75.2%, women 40.6%), fat cross-sectional area (men 24.4%, women 59.6%) and bone cross-sectional area (men 0.5%, women -0.2%). Muscle cross-sectional area in men and women decreased by 0.6% and 0.4%/year, respectively, because of a decrease in quadriceps cross-sectional area (men 65.6%, women 81.6%) and non-quadriceps cross-sectional area (men 34.4%, women 18.4%). Muscle quality in men and women decreased by 0.4% and 0.3%/year, respectively. Thigh cross-sectional area decreased with age mainly because of a decrease in muscle cross-sectional area in men and fat cross-sectional area in women. The rate of decrease in muscle cross-sectional area was 1.5-fold higher in men than in women. Muscle cross-sectional area decreased with age mainly because of a decrease in quadriceps cross-sectional area, especially in women. Decrease in muscle quality with age was similar in both sexes.

Muscle quality index improves with resistance exercise training in older adults

IntroductionSarcopenia is currently best described as an age-related decline in skeletal muscle mass and function. However, no consensus exists as to how to best quantify muscle function in older adults. The muscle quality index (MQI) was recently recommended as an ideal evidence-based assessment of functional status in older adults. Nevertheless, the usefulness of MQI to assess physical function is limited by whether it is reflective of muscle qualitative changes to an intervention. Thus, the purpose of this investigation was to determine whether MQI changes in response to resistance exercise training and detraining and how such changes correspond to other recommended measures of physical function proposed by suggested definitions of sarcopenia. MethodsTwenty-five older adults (70.6±6.1y; BMI=28.1±5.4kg·m−2) completed a 6-week resistance training program in a wait-list controlled, cross-over design. MQI was determined as power output from timed sit to stand (STS), body mass, and leg length. Gait speed, hand grip strength, get-up-and-go and lean body mass (LBM) were evaluated before and after exercise training and detraining. MQI and functional changes to training and detraining were evaluated with repeated measures ANOVA and clinical interpretations of magnitude based inferences. ResultsShort term resistance training significantly and clinically improved MQI (203.4±64.31 to 244.3±82.92W), gait time (1.85±0.36 to 1.66±0.27s) and sit to stand performance (13.21±2.51 to 11.05±1.58s). Changes in LBM and hand grip strength were not significant or clinically meaningful. De-training for 6-weeks did not result in significant changes in any measure from post-training performance.

Myosteatosis and myofibrosis: Relationship with aging, inflammation and insulin resistance

The mechanisms impairing muscle quality and leading to myofibrosis (MF) and myosteatosis (MS) are incompletely known. In biopsies of paraspinous muscle (PM) of 16 elderly men undergoing elective vertebral surgery, we histologically determined the area of MF and MS expressed as muscle quality index (MQI), in order to investigate the relation between them, as well as the main predictors of muscle quality. Total PM area and intermuscular adipose tissue (IMAT) were evaluated by MRI and body composition by DXA. Circulating fasting glucose, insulin, hs-CRP, leptin, adiponectin and IL-6 were measured and HOMA index calculated. Quantification of gene expression in PM and in subcutaneous adipose tissue (SAT) overlying the muscle was performed by rt-PCR. The degree of MS and MF was significantly and positively related to each other and positively associated with BMI, waist, FM and FM% as well as with IMAT. The area of PM was negatively related with MF even after adjustment for weight. Leptin was positively associated with MF and MS, whereas hs-CRP to MF. In backward regression analyses, larger waist and smaller PM area explained 90% of MF variance, whereas leptin about 80% of MS variance. IL-6 expression in SAT was significantly higher in participants with higher MQI values. In PM biopsies we found significantly higher expression of SOCS-3 and a trend toward higher expression of myostatin with greater degrees of MQI. MS and MF are related phenomena that concur to alter muscle quality and both should be considered in further studies on the evolution of sarcopenia.

How to assess functional status: a new muscle quality index.

Aging is associated with decreases in muscle mass, muscle strength and muscle power, with muscle strength declining at a higher rate than muscle mass, but at a lower rate than muscle power. This progressive mismatch suggests a deterioration of muscle "quality" that may lead to functional incapacities. Although it may be difficult to synthesize the concept of muscle quality, the aim of the present paper was to propose a clinical definition of muscle quality in regard to the functional status. Accordingly, the muscle strength or muscle power per unit of muscle mass ratios appear to be clinically relevant markers of muscle quality. Several mechanisms susceptible to influence these ratios have been described, among which age, gender, sex hormones, obesity, physical activity and fibrosis. Various methods to assess muscle quality in both the clinical and research fields have also been listed, with a particular interest for the tests used to measure muscle power. Finally, we proposed a clinical screening tool to detect individuals at risk of functional incapacities. Briefly, the muscle quality score is based on handgrip strength assessment by hand dynamometer, muscle mass measurement by bioelectrical analysis, and leg muscle power estimation using a chair stand test.