Muscle fiber size and function in elderly humans: a longitudinal study

Age-specific differences in the time-frequency representation of surface electromyographic data recorded during a submaximal cyclic back extension exercise: a promising biomarker to detect early signs of sarcopenia

PURPOSE

Motivated by the goal of developing new methods to detect early signs of sarcopenia, we investigated if surface electromyographic (SEMG) data recorded during the performance of cyclic, submaximal back extensions are marked by age-specific differences in their time and frequency characteristics. Furthermore, day-to-day retest reliability of the EMG measures was examined.

METHODS

A total of 86 healthy volunteers used a back dynamometer to perform a series of three maximal voluntary contractions (MVC) consisting of isometric back extensions, followed by an isometric back extension at 80% MVC, and finally 25 slow cyclic back extensions at 50% MVC. SEMG data was recorded bilaterally at L1, L2, and L5 from the iliocostalis lumborum, longissimus, and multifidus muscles, respectively. Tests were repeated two days and six weeks later. A linear mixed-effects model with fixed effects "age, sex, test number" and the random effect "person" was performed to investigate age-specific differences in both the initial value and the time-course (as defined by the slope of the regression line) of the root mean square (RMS-SEMG) values and instantaneous median frequency (IMDF-SEMG) values calculated separately for the shortening and lengthening phases of the exercise cycles. Generalizability Theory was used to examine reliability of the EMG measures.

RESULTS

Back extensor strength was comparable in younger and older adults. The initial value of RMS-SEMG and IMDF-SEMG as well as the RMS-SEMG time-course did not significantly differ between the two age groups. Conversely, the IMDF-SEMG time-course showed more rapid changes in younger than in older individuals. Absolute and relative reliability of the SEMG time-frequency representations were comparable in older and younger individuals with good to excellent relative reliability but variable absolute reliability levels.

CONCLUSIONS

The IMDF-SEMG time-course derived from submaximal, cyclic back extension exercises performed at moderate effort showed significant differences in younger vs. older adults even though back extension strength was found to be comparable in the two age groups. We conclude that the SEMG method proposed in this study has great potential to be used as a biomarker to detect early signs of sarcopenic back muscle function.

Age- and sex-specific effects in paravertebral surface electromyographic back extensor muscle fatigue in chronic low back pain

The impact of aging on the back muscles is not well understood, yet may hold clues to both normal aging and chronic low back pain (cLBP). This study sought to investigate whether the median frequency (MF) surface electromyographic (SEMG) back muscle fatigue method—a proxy for glycolytic muscle metabolism—would be able to detect age- and sex-specific differences in neuromuscular and muscle metabolic functions in individuals with cLBP in a reliable way, and whether it would be as sensitive as when used on healthy individuals. With participants seated on a dynamometer (20° trunk anteflexion), paraspinal SEMG activity was recorded bilaterally from the multifidus (L5), longissimus (L2), and iliolumbalis (L1) muscles during isometric, sustained back extensions loaded at 80% of maximum from 117 younger (58 females) and 112 older (56 female) cLBP individuals. Tests were repeated after 1–2 days and 6 weeks. Median frequency, the SEMG variable indicating neuromuscular fatigue, was analyzed. Maximum back extensor strength was comparable between younger and older participants. Significantly less MF-SEMG back muscle fatigue was observed in older as compared to younger, and in older female as compared to older male cLBP individuals. Relative reliability was excellent, but absolute reliability appeared large for this SEMG-fatigue measure. Findings suggest that cLBP likely does not mask the age-specific diagnostic potential of the MF-SEMG back extensor fatigue method. Thus, this method possesses a great potential to be further developed into a valuable biomarker capable of detecting back muscle function at risk of sarcopenia at very early stages.

A new approach to the classification of muscle health: preliminary investigations

OBJECTIVE

Upper leg skeletal or lean tissue mass (LTM), strength and muscle quality have emerged as time-sensitive indices of muscular health. The aim of this study was to generate a comparative data set based on these indices, in healthy young (n  =  30, 29.0  ±  3.0 y old) and older (n  =  32, 58.7  ±  2.8 years old) adults, in order to evaluate their construct validity in establishing cut-points for muscle health.

APPROACH

Whole body and upper leg LTM was obtained (iDXATM; GE Healthcare, Madison, WI) prior to the assessment of maximal voluntary isometric torque of the knee extensors and flexors (Cybex Isokinetic Dynamometer; Humac Norm, USA).

MAIN RESULTS

Peak isometric upper leg torque showed the greatest age-related difference (-29.0%), followed by muscle quality (-19.1%) and upper leg LTM (-9.8%).

SIGNIFICANCE

Cut-points based on Z and T-scores generated from the young adult mean suggest muscle quality demonstrates the greatest construct validity toward the aim of classifying the muscular health of adults. Data generated from large, representative and sex-specific samples are required to adequately classify the muscular health of adults.

The Importance of Resistance Exercise Training to Combat Neuromuscular Aging

Older adults undergoing age-related decrements in muscle health can benefit substantially from resistance exercise training, a potent stimulus for whole muscle and myofiber hypertrophy, neuromuscular performance gains, and improved functional mobility. With the use of advancing technologies, research continues to elucidate the mechanisms of and heterogeneity in adaptations to resistance exercise training beyond differences in exercise prescription. This review highlights the current knowledge in these areas and emphasizes knowledge gaps that require future attention of the field.

Aging and Imaging Assessment of Body Composition: From Fat to Facts

The aging process is characterized by the chronic inflammatory status called "inflammaging", which shares major molecular and cellular features with the metabolism-induced inflammation called "metaflammation." Metaflammation is mainly driven by overnutrition and nutrient excess, but other contributing factors are metabolic modifications related to the specific body composition (BC) changes occurring with age. The aging process is indeed characterized by an increase in body total fat mass and a concomitant decrease in lean mass and bone density, that are independent from general and physiological fluctuations in weight and body mass index (BMI). Body adiposity is also re-distributed with age, resulting in a general increase in trunk fat (mainly abdominal fat) and a reduction in appendicular fat (mainly subcutaneous fat). Moreover, the accumulation of fat infiltration in organs such as liver and muscles also increases in elderly, while subcutaneous fat mass tends to decrease. These specific variations in BC are considered risk factors for the major age-related diseases, such as cardiovascular diseases, type 2 diabetes, sarcopenia and osteoporosis, and can predispose to disabilities. Thus, the maintenance of a balance rate of fat, muscle and bone is crucial to preserve metabolic homeostasis and a health status, positively contributing to a successful aging. For this reason, a detailed assessment of BC in elderly is critical and could be an additional preventive personalized strategy for age-related diseases. Despite BMI and other clinical measures, such as waist circumference measurement, waist-hip ratio, underwater weighing and bioelectrical impedance, are widely used as a surrogate measure for body adiposity, they barely reflect the distribution of body fat. Because of the great advantages offered by imaging tools in research and clinics, the attention of clinicians is now moving to powerful imaging techniques such as computed tomography, magnetic resonance imaging, dual-energy X-ray absorptiometry and ultrasound to obtain a more accurate estimation of BC. The aim of this review is to present the state of the art of the imaging techniques that are currently available to measure BC and that can be applied to the study of BC changes in the elderly, outlining advantages and disadvantages of each technique.

Quality of life and subjective health status according to handgrip strength in the elderly: a cross-sectional study

OBJECTIVES

The purpose of this cross-sectional study was to examine potential associations between handgrip strength and health-related quality of life, or subjective health status, in the elderly.

METHOD

We performed secondary data analysis on 2377 elderly individuals aged >65 years. Raw data from the Korea National Health and Nutrition Examination Survey VI (2014-2015), were drawn from a representative national sample.

RESULTS

Of those aged ≥65 years or older, 25.4% had low handgrip strength. After adjusting for confounding variables, the odds ratios of elderly individuals with low handgrip strength were 1.30 (95% confidence interval [CI]: 1.00-1.69) for mobility, 2.18 (95% CI: 1.47-3.22) for self-care, 1.70 (95% CI: 1.30-2.23) for usual activities, 1.30 (95% CI: 1.01-1.67) for pain/discomfort, 1.03 (95% CI: 0.74-1.44) for anxiety/depression, 1.44 (95% CI: 1.10-1.87) for the EQ-5D index, and 1.37 (95% CI: 1.08-1.73) for subjective health status.

CONCLUSION

Health-related quality of life and subjective health status differ according to handgrip strength. Therefore, handgrip strength should be addressed to improve quality of life in elderly individuals. Elderly individuals require exercise education and adequate nutritional intake to increase handgrip strength.

Physical Activity and Incidence of Heart Failure in Postmenopausal Women

OBJECTIVES

This study prospectively examined physical activity levels and the incidence of heart failure (HF) in 137,303 women, ages 50 to 79 years, and examined a subset of 35,272 women who, it was determined, had HF with preserved ejection fraction (HFpEF) and HF with reduced EF (HFrEF).

BACKGROUND

The role of physical activity in HF risk among older women is unclear, particularly for incidence of HFpEF or HFrEF.

METHODS

Women were free of HF and reported ability to walk at least 1 block without assistance at baseline. Recreational physical activity was self-reported. The study documented 2,523 cases of total HF, and 451 and 734 cases of HFrEF and HFpEF, respectively, during a mean 14-year follow-up.

RESULTS

After controlling for age, race, education, income, smoking, alcohol, hormone therapy, and hysterectomy status, compared with women who reported no physical activity (reference group), inverse associations were observed across incremental tertiles of total physical activity for overall HF (hazard ratio [HR]: Tertile 1 = 0.89, Tertile 2 = 0.74, Tertile 3 = 0.65; trend p < 0.001), HFpEF (HR: 0.93, 0.70, 0.68; p < 0.001), and HFrEF (HR: 0.81, 0.59, 0.68; p = 0.01). Additional controlling for potential mediating factors included attenuated time-varying coronary heart disease (CHD) (nonfatal myocardial infarction, coronary revascularization) diagnosis but did not eliminate the inverse associations. Walking, the most common form of physical activity in older women, was also inversely associated with HF risks (overall: 1.00, 0.98, 0.93, 0.72; p < 0.001; HFpEF: 1.00, 0.98, 0.87, 0.67; p < 0.001; HFrEF: 1.00, 0.75, 0.78, 0.67; p = 0.01). Associations between total physical activity and HF were consistent across subgroups, defined by age, body mass index, diabetes, hypertension, physical function, and CHD diagnosis. Analysis of physical activity as a time-varying exposure yielded findings comparable to those of baseline physical activity.

CONCLUSIONS

Higher levels of recreational physical activity, including walking, are associated with significantly reduced HF risk in community-dwelling older women.

Influence of a periodized circuit training protocol on intermuscular adipose tissue of patients with knee osteoarthritis: protocol for a randomized controlled trial

BACKGROUND

The objective of this study is to analyze the influence of a 14-week periodized circuit training protocol on patients with knee osteoarthritis (OA), in randomized intervention groups, on thigh intermuscular adipose tissue (interMAT), body composition, systemic inflammation, cartilage degradation, and its repercussion on pain, functional performance and quality of life.

METHODS

This study presents a protocol for a randomized controlled trial. Sixty selected participants diagnosed with knee OA grades II and III, 40-65 years old and BMI < 30 kg/m2, will be randomly divided into three groups:periodized circuit training, strength training, and educational protocol. The circuit training and strength training protocols consist of 14-week training protocols conducted 3 times a week. The circuit training group will perform selected exercises previously stratified as light, moderate, and intense, arranged progressively in a circuit model, the strength group will perform regular strength exercises, and the educational protocol group will participate in a 14-week protocol with lectures twice a month about healthy lifestyles. Baseline and follow-up evaluations will be conducted for thigh interMAT (computed tomography), body composition (DXA), inflammation (IL-1β, IL-6, IL-10, TNF-α, leptin, and adiponectin), and joint degradation biomarkers (uCTX-II and sCOMP), performance-based tests (30s Chair Stand Test, 40 m Fast-paced Walk Test and Stair Climb Test), quadriceps and hamstring maximal isometric voluntary contraction (MIVC), and questionnaires (WOMAC and pain catastrophizing scale). Repeated measures ANOVA will be used to compare differences between groups (circuit training X strength training X educational protocol) at the different times of assessment (baseline x follow-up or baseline x during protocol x follow-up) for each of the dependent variables. When significant main effects were found, the pots hoc Bonferroni test will be used to identify statistical differences. A significance level of 5% (p < 0.05) will be adopted.

DISCUSSION

This will be the first randomized controlled trial to assess the effects of a circuit training protocol on patients with knee OA on thigh intermuscular adipose tissue (interMAT). Given the prevalence and impact of OA and the widespread availability of this intervention, assessing the efficacy of a low-cost, non-pharmacological, and non-invasive treatment for knee OA patients has the potential for immediate and high clinical impact.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02761590 , registered in May 4, 2016.

Impaired Muscle Efficiency but Preserved Peripheral Hemodynamics and Mitochondrial Function With Advancing Age: Evidence From Exercise in the Young, Old, and Oldest-Old

Muscle weakness in the elderly has been linked to recurrent falls and morbidity; therefore, elucidating the mechanisms contributing to the loss of muscle function and mobility with advancing age is critical. To this aim, we comprehensively examined skeletal muscle metabolic function and hemodynamics in 11 young (23 ± 2 years), 11 old (68 ± 2 years), and 10 oldest-old (84 ± 2 years) physical activity-matched participants. Specifically, oxidative stress markers, mitochondrial function, and the ATP cost of contraction as well as peripheral hemodynamics were assessed during dynamic plantar flexion exercise at 40 per cent of maximal work rate (WRmax). Both the PCr recovery time constant and the peak rate of mitochondrial ATP synthesis were not significantly different between groups. In contrast, the ATP cost of dynamic contractions (young: 1.5 ± 1.0, old: 3.4 ± 2.1, oldest-old: 6.1 ± 3.6 mM min-1 W-1) and systemic markers of oxidative stress were signficantly increased with age, with the ATP cost of contraction being negatively correlated with WRmax (r = .59, p < .05). End-of-exercise blood flow per Watt rose significantly with increasing age (young: 37 ± 20, old: 82 ± 68, oldest-old: 154 ± 93 mL min-1 W-1). These findings suggest that the progressive deterioration of muscle contractile efficiency with advancing age may play an important role in the decline in skeletal muscle functional capacity in the elderly.

Effects of elevated H+ and Pi on the contractile mechanics of skeletal muscle fibres from young and old men: implications for muscle fatigue in humans

KEY POINTS

The mechanisms responsible for the loss in muscle power and increased fatigability with ageing are unresolved. We show that the contractile mechanics of fibres from the vastus lateralis of old men were well-preserved compared to those of young men, but the selective loss of fast myosin heavy chain II muscle was strongly associated with age-related decrements in whole-muscle strength and power. We reveal that the combination of acidosis (H+ ) and inorganic phosphate (Pi ) is an important mediator of muscle fatigue in humans by inhibiting the low- to high-force state of the cross-bridge cycle and peak power, but the depressive effects of these ions on cross-bridge function were similar in fibres from young and old men. These findings suggest that the age-related loss in muscle power is primarily determined by the atrophy of fast fibres, but the age-related increased fatigability cannot be explained by an increased sensitivity of the cross-bridge to H+ and Pi .

ABSTRACT

The present study aimed to identify the mechanisms responsible for the loss in muscle power and increased fatigability with ageing by integrating measures of whole-muscle function with single fibre contractile mechanics. After adjusting for the 22% smaller muscle mass in old (73-89 years, n = 6) compared to young men (20-29 years, n = 6), isometric torque and power output of the knee extensors were, respectively, 38% and 53% lower with age. Fatigability was ∼2.7-fold greater with age and strongly associated with reductions in the electrically-evoked contractile properties. To test whether cross-bridge mechanisms could explain age-related decrements in knee extensor function, we exposed myofibres (n = 254) from the vastus lateralis to conditions mimicking quiescent muscle and fatiguing levels of acidosis (H+ ) (pH 6.2) and inorganic phosphate (Pi ) (30 mm). The fatigue-mimicking condition caused marked reductions in force, shortening velocity and power and inhibited the low- to high-force state of the cross-bridge cycle, confirming findings from non-human studies that these ions act synergistically to impair cross-bridge function. Other than severe age-related atrophy of fast fibres (-55%), contractile function and the depressive effects of the fatigue-mimicking condition did not differ in fibres from young and old men. The selective loss of fast myosin heavy chain II muscle was strongly associated with the age-related decrease in isometric torque (r = 0.785) and power (r = 0.861). These data suggest that the age-related loss in muscle strength and power are primarily determined by the atrophy of fast fibres, but the age-related increased fatigability cannot be explained by an increased sensitivity of the cross-bridge to H+ and Pi .

Quantification of Muscle Tissue Properties by Modeling the Statistics of Ultrasound Image Intensities Using a Mixture of Gamma Distributions in Children With and Without Cerebral Palsy

OBJECTIVES

To investigate whether quantitative ultrasound (US) imaging, based on the envelope statistics of the backscattered US signal, can describe muscle properties in typically developing children and those with cerebral palsy (CP).

METHODS

Radiofrequency US data were acquired from the rectus femoris muscle of children with CP (n = 22) and an age-matched cohort without CP (n = 14) at rest and during maximal voluntary isometric contraction. A mixture of gamma distributions was used to model the histogram of the echo intensities within a region of interest in the muscle.

RESULTS

Muscle in CP had a heterogeneous echo texture that was significantly different from that in healthy controls (P < .001), with larger deviations from Rayleigh scattering. A mixture of 2 gamma distributions showed an excellent fit to the US intensity, and the shape and rate parameters were significantly different between CP and control groups (P < .05). The rate parameters for both the single gamma distribution and mixture of gamma distributions were significantly higher for contracted muscles compared to resting muscles, but there was no significant interaction between these factors (CP and muscle contraction) for a mixed-model analysis of variance.

CONCLUSIONS

Ultrasound tissue characterization indicates a more disorganized architecture and increased echogenicity in muscles in CP, consistent with previously documented increases in fibrous infiltration and connective tissue changes in this population. Our results indicate that quantitative US can be used to objectively differentiate muscle architecture and tissue properties.

Skeletal Muscle Function in the Oldest-Old: The Role of Intrinsic and Extrinsic Factors

Although skeletal muscle function is diminished with advanced age, single muscle fiber function seems to be preserved. Therefore, this review examines the hypothesis that the skeletal muscle fiber, per se, is not the predominant factor responsible for the reduction in force-generating capacity in the oldest-old, but, rather, is attributable to a combination of factors external to the muscle fibers.

Physiologic Changes of the Musculoskeletal System with Aging: A Brief Review

Aging is one of the important challenges of modern society. Advanced adult age is associated with changes in many physiologic systems. Of particular interest is the musculoskeletal system because it directly contributes to mobility and functional independence. Skeletal muscle mass and strength decline with age. These changes are mostly due to a reduction in the number of muscle fibers and cellular and molecular changes that reduce the force-generation process. Bone mass and architecture are compromised and may result in fractures. Tendons and ligaments undergo significant biochemical alterations that directly compromise their biomechanical function.

Fat infiltration in the gluteus minimus muscle in older adults

Purpose

Fat infiltration (FI) in the gluteus minimus muscle (GMin) has been reported as being restricted to the anterior part. The aim of this study was to verify whether FI is localized only to the anterior part of the GMin through the dissection of large number of elderly cadavers and to clarify the underlying mechanism of FI localized to a specific region.

Materials and methods

Thirty-eight hips from 20 embalmed elder cadavers were dissected for verification of FI localization. The samples of three regions – the fat infiltrated region of the anterior part (FI), the region without FI (non-FI), and the posterior region – were harvested from nine hips for the histological fiber type assessment.

Results

The FI area was distributed at 2.6°–38° from the anterior border within the anterior part, of which function is responsible for hip extension and internal rotation and is likely reduced by disuse following aging. The number of type I fibers was lowest in FI, followed by non-FI, while the number of type I fibers was highest in the posterior. Meanwhile, the number of type II fibers was equivalent across the three regions. Atrophic type II fibers were observed in overall samples of the three regions, and grouped atrophy, which is evidence of denervation, was observed in FI and non-FI samples. Type grouping, which suggests to be reinnervated, was found in the non-FI and posterior samples but very little in the FI samples.

Conclusion

FI in the GMin in older adults restricted to deep within the anterior part is secondary to disuse and is strongly related to impaired denervation–reinnervation process.

Effect of a resistance exercise program for sarcopenic elderly women: quasi-experimental study

Abstract Introduction: Resistance training is quoted as one of the best pathways to manage sarcopenia and progressive resistance training is supposed to improve muscle mass, strength and performance in older adults. Objective: The aim was to examine the impact of a progressive resistance exercise program (PREP) on muscle and function performance in sarcopenic community-dwelling elder women. Methods: Quasi-experimental study (pre - post intervention). Participated 18 sarcopenic community-dwelling elder women (65 years or older). PREP based on 75% of the participant’s maximum load (12/wk, 3 times/wk). Main outcome measures: muscle strength of knee extensors (isokinetic dynamometry), muscle mass (dual-x ray absorptiometry - DXA), functional performance (Short Physical Performance Battery - SPPB). Paired t-test was used to evaluate differences pre and post intervention. Results: Improvements on power (p = 0.01) and peak torque (p = 0.01) were observed when measured by the isokinetic dynamometer at low speed (60º/s). Improvements on DXA (pre PREP: 5.49 kg/m2 vs. post PREP: 6.01 kg/m2; p = 0.03) and SPPB scores (pre PREP: 9.06 vs. post PREP: 10.28; p = 0.01) were also observed. Conclusion: The PREP was able to improve muscle and functional performance in sarcopenic community-dwelling elder women. This program should be considered in clinical practice.

High-intensity interval training improves insulin sensitivity in older individuals

AIM

Metabolic health may deteriorate with age as a result of altered body composition and decreased physical activity. Endurance exercise is known to counter these changes delaying or even preventing onset of metabolic diseases. High-intensity interval training (HIIT) is a time efficient alternative to regular endurance exercise, and the aim of this study was to investigate the metabolic benefit of HIIT in older subjects.

METHODS

Twenty-two sedentary male (n = 11) and female (n = 11) subjects aged 63 ± 1 years performed HIIT training three times/week for 6 weeks on a bicycle ergometer. Each HIIT session consisted of five 1-minute intervals interspersed with 1½-minute rest. Prior to the first and after the last HIIT session whole-body insulin sensitivity, measured by a hyperinsulinaemic-euglycaemic clamp, plasma lipid levels, HbA1c, glycaemic parameters, body composition and maximal oxygen uptake were assessed. Muscle biopsies were obtained wherefrom content of glycogen and proteins involved in muscle glucose handling were determined.

RESULTS

Insulin sensitivity (P = .011) and maximal oxygen uptake increased (P < .05) in both genders, while plasma cholesterol (P < .05), low-density lipoprotein (P < .05), visceral fat mass (P < .05) and per cent body fat (P < .05) decreased after 6 weeks of HIIT. HbA1c decreased only in males (P = .001). Muscle glycogen content increased in both genders (P = .001) and in line GLUT4 (P < .05), glycogen synthase (P = .001) and hexokinase II (P < .05) content all increased.

CONCLUSION

Six weeks of HIIT significantly improves metabolic health in older males and females by reducing age-related risk factors for cardiometabolic disease.

Shear wave sonoelastography of skeletal muscle: basic principles, biomechanical concepts, clinical applications, and future perspectives

Imaging plays an important role in the diagnosis and therapeutic response evaluation of muscular diseases. However, one important limitation is its incapacity to assess the in vivo biomechanical properties of the muscles. The emerging shear wave sonoelastography technique offers a quantifiable spatial representation of the viscoelastic characteristics of skeletal muscle. Elastography is a non-invasive tool used to analyze the physiologic and biomechanical properties of muscles in healthy and pathologic conditions. However, radiologists need to familiarize themselves with the muscular biomechanical concepts and technical challenges of shear wave elastography. This review introduces the basic principles of muscle shear wave elastography, analyzes the factors that can influence measurements and provides an overview of its potential clinical applications in the field of muscular diseases.

Association between muscle function, cognitive state, depression symptoms and quality of life of older people: evidence from clinical practice

BACKGROUND

Although low muscle function/strength is an important predictor of poor clinical outcome in older patients, information on its impact on mental health in clinical practice is still lacking.

AIMS

The aim of this report is to measure the impact of low muscle function measured by handgrip strength on mental health of older people during both acute illness and recovery.

METHODS

Four hundred and thirty-two randomly selected hospitalized older patients had their baseline demographic and clinical characteristics assessed within 72 h of admission, at 6 weeks and at 6 months. Low muscle strength-handgrip was defined using the European Working Group criteria. Mental health outcome measures including cognitive state, depression symptoms and quality of life were also measured.

RESULTS

Among the 432 patients recruited, 308 (79%) had low muscle strength at baseline. Corresponding figures at 6 weeks and at 6 months were 140 (73%) and 158 (75%). Patients with poor muscle strength were significantly older with increased disability and poor nutritional status compared with those with normal muscle strength. After adjustment for age, gender, disability, comorbidity including severity of acute illness and body mass index patients with low muscle strength had worse cognitive function, quality of life and higher depression symptoms compared with those with normal muscle strength over a 6-month period (p < 0.05).

CONCLUSION

Poor muscle strength in older people is associated with poor cognitive state and quality of life and increased depression symptoms during both acute illness and recovery.

The vitamin D receptor expression in skeletal muscle of women with distal radius fracture

We evaluated the vitamin D receptor (VDR) expression in the forearm flexor muscle of women with distal radius fracture. High VDR expression was associated with low appendicular lean mass index.

INTRODUCTION

We aimed to evaluate the relationship between the VDR expression in the muscle cell and the muscle mass in women with a distal radius fracture (DRF).

METHODS

We prospectively recruited 45 women over 50 years of age (mean age, 66 years) with DRF and acquired biopsy of the forearm flexor muscle. The muscle cross-sectional area (CSA) and VDR expression were measured using immunohistochemistry staining. The clinical parameters including grip strength, gait speed, body mass index (BMI), bone mineral density (BMD), and serum vitamin D levels were compared between patients grouped by appendicular lean mass index and were correlated with the VDR expression.

RESULTS

Twelve patients (27%) showed a decreased appendicular lean mass index, less than the cut-off value of 5.4 kg/m2 which was suggested by the Asian Working Group for Sarcopenia. Patients with a low appendicular lean mass index had significantly lower muscle CSA (p = 0.037), but a higher VDR expression (p = 0.045) than those with higher indices. VDR expression was negatively correlated with BMI (r = - 0.417, p = 0.004) and appendicular lean mass index (r = - 0.316, p = 0.044).

CONCLUSIONS

DRF patients with low appendicular lean mass index presented high VDR expression and low CSA in forearm muscle cells. This suggests that the VDR expression might be upregulated in the attempt to compensate for the decreasing muscle mass. Further studies are necessary to explore the role of VDR in the progression of sarcopenia.

Human neuromuscular aging: Sex differences revealed at the myocellular level

Age-related muscle loss (sarcopenia) is a major clinical problem affecting both men and women - accompanied by muscle weakness, dysfunction, disability, and impaired quality of life. Current definitions of sarcopenia do not fully encompass the age-related changes in skeletal muscle. We therefore examined the influence of aging and sex on elements of skeletal muscle health using a thorough histopathological analysis of myocellular aging and assessments of neuromuscular performance. Two-hundred and twenty-one untrained males and females were separated into four age cohorts [mean age 25 y (n = 47), 37 y (n = 79), 61 y (n = 51), and 72 y (n = 44)]. Total (-12%), leg (-17%), and arm (-21%) lean mass were lower in both 61 y and 72 y than in 25 y or 37 y (P < 0.05). Knee extensor strength (-34%) and power (-43%) were lower (P < 0.05) in the older two groups, and explosive sit-to-stand power was lower by 37 y (P < 0.05). At the histological/myocellular level, type IIx atrophy was noted by 37 y and type IIa atrophy by 61 y (P < 0.05). These effects were driven by females, noted by substantial and progressive type IIa and IIx atrophy across age. Aged female muscle displayed greater within-type myofiber size heterogeneity and marked type I myofiber grouping (~5-fold greater) compared to males. These findings suggest the predominant mechanisms leading to whole muscle atrophy differ between aging males and females: myofiber atrophy in females vs. myofiber loss in males. Future studies will be important to better understand the mechanisms underlying sex differences in myocellular aging and optimize exercise prescriptions and adjunctive treatments to mitigate or reverse age-related changes.

Measurement of muscle health in aging

Muscle health is a critical component in the struggle against physical frailty and the efforts to maintain metabolic health until the limit of chronological age. Consensus opinion is to evaluate muscle health in terms of muscle mass, strength and functional capability. There has been considerable variability in the components of muscle health which have been investigated in addition to variability in the tools of assessment and protocol for measurement. This is in stark contrast to the validated measurement of bone health across the adult life span. The purpose of this review was to identify indices of muscle mass, strength and functional capability most responsive to change with ageing and where possible to provide an estimate of the rate of change. We suggest lean tissue mass (LTM) or skeletal muscle (SM) is best evaluated from the thigh region due to its greater responsiveness to ageing compared to the whole body. The anterior compartment of the thigh region undergoes a preferential age-related decline in SM and force generating capacity. Therefore, we suggest that knee extensor torque is measured to represent the force generating capacity of the thigh and subsequently, to express muscle quality (strength per unit tissue). Finally, we suggest measures of functional capability which allow participants perform to a greater maximum are most appropriate to track age-related difference in functional capacity across the adult lifespan. This is due to their ability encompass a broad spectrum of abilities. This review suggests indices of muscular health for which reference ranges can be generated across the lifespan.

Both Light Intensity and Moderate-to-Vigorous Physical Activity Measured by Accelerometry Are Favorably Associated With Cardiometabolic Risk Factors in Older Women: The Objective Physical Activity and Cardiovascular Health (OPACH) Study

BACKGROUND

The relationship between light intensity physical activity (PA), which is common in older adults, and cardiovascular disease (CVD) risk factors is unclear. This study examined associations of accelerometer-measured PA intensity with CVD risk factors in older women of different race-ethnicities.

METHODS AND RESULTS

Cross-sectional analyses were conducted in 4832 women (mean age 78.9 years; 52.5% white, 30.5% black, 17.1% Hispanic) who were without known CVD and wore triaxial accelerometers a minimum of 4 of 7 days with ≥10 hours/d awake wear-time. Vector magnitude counts per 15-s epoch were used to define time spent in low light (19-225 counts/15 s), high light (226-518), and moderate-to-vigorous; ≥519) intensity PA. Fasting CVD biomarkers, resting blood pressure, waist girth, body mass index, and 10-year predicted CVD risk (Reynolds Risk Score) were measured. After adjusting for age, wear time, race-ethnicity, and potential confounders, each PA measure was favorably associated with mean high-density lipoprotein, triglyceride, glucose, C-reactive protein, body mass index, waist girth, and Reynolds Risk Score (P<0.05, all). Associations with mean blood pressure, insulin, and total and low-density lipoprotein cholesterol were variable. A 30-minute/d increment in PA was associated, on average, with odds ratios for high predicted CVD risk (Reynolds Risk Score ≥20) of 0.96 (95% confidence interval, 0.92, 1.00), 0.88 (0.83, 0.94), and 0.85 (0.79, 0.91) for low light, high light, and moderate-to-vigorous, respectively, and remained significant with further mutual control for PA intensity.

CONCLUSIONS

PA measured by accelerometry, including light intensity PA, was associated with lower CVD risk factor levels in race-ethnically diverse older women.

Near Retirement Age (≥55 Years) Self-Reported Physical Symptoms and Use of Computers/Mobile Phones at Work and at Leisure

The aim of this research is to study the symptoms and use of computers/mobile phones of individuals nearing retirement age (≥55 years). A questionnaire was sent to 15,000 Finns (aged 18–65). People who were ≥55 years of age were compared to the rest of the population. Six thousand one hundred and twenty-one persons responded to the questionnaire; 1226 of them were ≥55 years of age. Twenty-four percent of the ≥55-year-old respondents used desktop computers daily for leisure; 47.8% of them frequently experienced symptoms in the neck, and 38.5% in the shoulders. Workers aged ≥55 years had many more physical symptoms than younger people, except with respect to symptoms of the neck. Female daily occupational users of desktop computers had more physical symptoms in the neck. It is essential to take into account that, for people aged ≥55 years, the use of technology can be a sign of wellness. However, physical symptoms in the neck can be associated with the use of computers.

Impact of poor muscle strength on clinical and service outcomes of older people during both acute illness and after recovery

Background

Although Low muscle strength is an important predictor of functional decline in older people, however information on its impact on clinical and service outcomes in acute care settings is still lacking. The aim of this study is to measure the impact of low muscle strength on clinical and service outcomes in older adults during both acute illness and recovery.

Methods

Randomly selected 432 hospitalised older patients had their clinical characteristics and nutritional status assessed within 72 h of admission, at 6 weeks and at 6 months. Low muscle strength-hand grip was defined using the European Working Group criteria. Health outcome measures including nutritional status, length of hospital stay, disability, discharge destination, readmission and mortality were also measured.

Results

Among the 432 patients recruited, 308 (79%) had low muscle strength at baseline. Corresponding figures at 6 weeks and at 6 months were 140 (73%) and 158 (75%). Patients with poor muscle strength were significantly older, increasingly disabled, malnourished and stayed longer in hospital compared with those with normal muscle strength. A significantly higher number of patients with normal muscle strength discharged home independently compared with those with poor muscle strength (p < 0.05). One-year death rate was lower in patients with normal muscle strength 5(6%), compared with those with poor muscle strength 52(15%), however, results were not statistically significant after adjusting for other poor prognostic indicators [adjusted hazard ratio 0.74 (95% CI: 0.14–3.87), p = 0.722].

Conclusion

Poor muscle strength in older people is associated with poor clinical service outcomes during both acute illness and recovery.

Discrepancies between Skinned Single Muscle Fibres and Whole Thigh Muscle Function Characteristics in Young and Elderly Human Subjects

We aimed to analyse the mechanical properties of skinned single muscle fibres derived from the vastus lateralis (VL) muscle in relation to those of the whole intact thigh muscle and to compare any difference between young and older adults. Sixteen young men (29.25 ± 4.65 years), 11 older men (71.45 ± 2.94 years), 11 young women (29.64 ± 4.88 years), and 7 older women (67.29 ± 1.70 years) were recruited. In vivo analyses were performed for mechanical properties such as isokinetic performance, isometric torque, and power. Specific force and maximum shortening velocity (Vo) were measured with single muscle fibres. Sex difference showed greater impact on the functional properties of both the whole muscle (p < 0.01) and single muscle fibres than aging (p < 0.05). Sex difference, rather than aging, yielded more remarkable differences in gross mechanical properties in the single muscle fibre study in which significant differences between young men and young women were found only in the cross-sectional area and Vo (p < 0.05). Age and sex differences reflect the mechanical properties of both single muscle fibres and whole thigh muscle, with the whole muscle yielding more prominent functional properties.

Improved single muscle fiber quality in the oldest-old

We examined single muscle fiber contractile function of the oldest-old (3F/2M, 89 ± 1 yr old) enrolled in The Health, Aging, and Body Composition Study (The Health ABC Study). Vastus lateralis muscle biopsies were obtained and single muscle fiber function was determined (n = 105) prior to myosin heavy chain (MHC) isoform identification with sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Cross-sectional area of MHC I muscle fibers (5,576 ± 333 μm²; n = 58) was 21% larger (P < 0.05) than MHC IIa fibers (4,518 ± 386 μm²; n = 47). Normalized power (an indicator of muscle fiber quality incorporating size, strength, and speed) of MHC I and IIa muscle fibers was 2.3 ± 0.1 and 17.4 ± 0.8 W/l, respectively. Compared with previous research from our lab using identical procedures, MHC I normalized power was 28% higher than healthy 20 yr olds and similar to younger octogenarians (∼80 yr old). Normalized power of MHC IIa fibers was 63% greater than 20 yr olds and 39% greater than younger octogenarians. These comparative data suggest that power output per unit size (i.e., muscle quality) of remaining muscle fibers improves with age, a phenomenon more pronounced in MHC IIa fibers. Age-related single muscle fiber quality improvements may be a compensatory mechanism to help offset decrements in whole muscle function.

Therapeutic potential of eccentric exercises for age-related muscle atrophy

Recent studies have focused on evidence-based interventions to prevent mobility decline and enhance physical performance in older adults. Several modalities, in addition to traditional strengthening programs, have been designed to manage age-related functional decline more effectively. In this study, we reviewed the current relevant literatures to assess the therapeutic potential of eccentric exercises for age-related muscle atrophy (sarcopenia). Age-related changes in human skeletal muscle, and their relationship with physical performance, are discussed with reference to in vitro physiologic and human biomechanics studies. An overview of issues relevant to sarcopenia is provided in the context of the recent consensus on the diagnosis and management of the condition. A decline in mobility among the aging population is closely linked with changes in the muscle force-velocity relationship. Interventions based specifically on increasing velocity and eccentric strength can improve function more effectively compared with traditional strengthening programs. Eccentric strengthening programs are introduced as a specific method for improving both muscle force and velocity. To be more effective, exercise interventions for older adults should focus on enhancing the muscle force-velocity relationship. Exercises that can be performed easily, and that utilize eccentric strength (which is relatively spared during the aging process), are needed to improve both muscle force and velocity.

Original Research: Central and peripheral quadriceps fatigue in young and middle-aged untrained and endurance-trained men: A comparative study

This study aimed to compare quadriceps function (i.e. strength, endurance, central, and peripheral fatigue) of young (Young-UnTr) and middle-aged (MidAge-UnTr) untrained men and young endurance-trained men (Young-Tr). Twenty-four male subjects (eight Young-UnTr (26 ± 4 yr), eight Young-Tr (29 ± 3 yr), and eight MidAge-UnTr (56 ± 4 yr) performed a maximal cycling test to assess their fitness level. On a separate visit, subjects performed sets of 10 intermittent (5-s on/5-s off) isometric contractions starting at 10% maximum voluntary contraction (MVC), with 10% MVC increments from one set to another until exhaustion. Electrophysiological and mechanical (e.g. twitch) evoked responses elicited with magnetic femoral nerve stimulation in the relaxed muscle and during MVC (i.e. estimation of voluntary activation using the interpolated twitch technique) were measured at baseline and after each set to assess peripheral and central fatigue, respectively. Endurance (= total number of contractions) was also evaluated. Young-UnTr exhibited larger reductions in evoked quadriceps mechanical responses than MidAge-UnTr and Young-Tr after identical standardized muscle loading (e.g. after the 50% MVC set, reduction in single potentiated twitch was -36 ± 9%, -21±16%, and -2 ± 4%, respectively). At both 50% MVC set and exhaustion, MidAge-UnTr exhibited similar reduction in maximal voluntary activation and displayed similar endurance compared to Young-UnTr. Young-Tr exhibited greater endurance than Young-UnTr without significant changes in maximal voluntary activation throughout the test. This study provides robust comparative data regarding the influence of chronic exposure to endurance training and middle-aged on central and peripheral quadriceps fatigability and endurance. Endurance-trained subjects showed smaller level of peripheral fatigue and displayed no significant central fatigue, even at exhaustion and despite greater endurance performance. Our findings also demonstrate that men in the sixth decade exhibit significant alterations in quadriceps function typically observed in much older subjects. These data emphasize the need for developing normative data for both central and peripheral quadriceps fatigability.

Age-related functional changes and susceptibility to eccentric contraction-induced damage in skeletal muscle cell

Depending upon external loading conditions, skeletal muscles can either shorten, lengthen, or remain at a fixed length as they produce force. Fixed-end or isometric contractions stabilize joints and allow muscles to act as active struts during locomotion. Active muscles dissipate energy when they are lengthened by an external force that exceeds their current force producing capacity. These unaccustomed eccentric activities often lead to muscle weakness, soreness, and inflammation. During aging, the ability to produce force under these conditions is reduced and appears to be due to not only reductions in muscle mass but also to alterations in the basic mechanisms of contraction. These alterations include impairments in the excitation–contraction process, and the action of the cross-bridges. Also, it is well known that age-related skeletal muscle atrophy is characterized by a preferential atrophy of fast fibers, and increased susceptibility to fast muscle fiber when aged muscles are exposed to eccentric contraction followed by the impaired recovery process has been reported. Taken together, the selective loss of fast muscle fiber in aged muscle could be affected by eccentric-induced muscle damage, which has significant implication to identify the etiology of the age-related functional changes. Therefore, in this review the alteration of age-related muscle function and its impact to/of eccentric induced muscle damage and recovery will be addressed in detail.

Age-related decline in muscle mass and muscle function in Flemish Caucasians: a 10-year follow-up

Aging is a complex process that is accompanied with changes in both muscle mass and muscle function (strength and performance). Therefore, the current longitudinal study aimed to provide a better insight in 10-year aging-related changes in whole-body muscle mass and strength performance of the leg extensors during the adult life span. Data were gathered within the framework of the first- (2002-2004: baseline) and third-generation Flemish Policy Research Center Sport (2012-2014: follow-up). Results are based on muscle characteristics data of 591 Flemish Caucasian adults (19-73 years, 381 men). Skeletal muscle mass (SMM) was determined with bioelectrical impedance analysis. Biodex Medical System 3® dynamometer was used to measure isometric (PTstatic120°) and isokinetic (PTdynamic60° and PTdynamic240°) strength, ballistic movement speed (S 20 %), and muscular endurance (work) of the knee extensors. Overall strength performance was higher at both evaluation moments in men compared to women (p < 0.01). But only S 20 % declined significantly faster in men compared to women (p < 0.01). Age and baseline strength performance were negatively related with the change in strength performance, even when corrected for SMM, protein intake, and energy expenditure during sports (E sport). In conclusion, strength performance was not associated with E sport in this study, but protein intake was associated with isometric strength in men, and with ballistic and isokinetic strength in women. Changes in S 20 % were significantly greater in men compared to women. Baseline values of strength performance and age were associated with changes in strength performance parameters, even after correction for SMM, protein intake, and E sport.

Effect of Lifestyle Intervention on the Hormonal Profile of Frail, Obese Older Men

OBJECTIVE

Obesity-associated hypogonadism is hypothesized to be due to the suppressive effect of high estradiol (from an increase in aromatase activity present in the abundant adipose tissue) on the hypothalamic-pituitary-gonadal unit resulting in low testosterone production. Although weight loss has been found to be effective in reducing estradiol and raising testosterone levels in studies of younger men, its effect in frail, obese older men is understudied. Thus, the objective of this study was to determine the effect of lifestyle intervention on hormone levels in frail, obese older men.

DESIGN

Randomized controlled trial of lifestyle intervention in frail, obese older men (≥65 yo) for 1 year.

SETTING

University hospital.

METHODS

Forty frail, obese elderly men were randomized, for a 52-week study, to any of the following treatment groups: (1) control group, (2) diet-induced weight loss group (diet group), (3) exercise training group (exercise group), and (4) diet-induced weight loss and exercise training group (diet-exercise group). The objective was to achieve a ~10 % weight loss at 6 months and maintain this weight for an additional 6 months. Physical function was assessed by the modified physical performance testing (modified PPT). Estradiol was measured by radioimmunoassay, testosterone by automated immunoassay, and sex hormone-binding globulin by enzyme-linked immunoassay.

RESULTS

After 12 months of intervention, diet alone resulted in a weight loss of -10.1 ± 1.9 kg in the diet group and -9.1 ± 0.9 kg in the diet-exercise group. This resulted in a significant decrease (both p<0.05) in total estradiol compared to baseline among subjects in the diet (-2.5 ± 1.3 pg/ml) and diet-exercise group (-2.2 ± 4.0 pg/ml). Free estradiol index also significantly decreased (both p <0.05) in both the diet (-0.39 ± 0.14 pmol/nmol) and diet-exercise (-0.52 ± 0.12 pmol/nmol) group. Total testosterone significantly increased (p<0.05) in response to diet (71.0 ± 21.0 ng/dl) and diet-exercise (49.9 ± 15.5 pg/ml) resulting in values of 287.0 ± 28.1 ng/dl in the diet and 317.6 ± 33.1 ng/dl in the diet-exercise group. However, because there was a significant increase in sex hormone-binding globulin levels in both the diet and diet-exercise groups, free testosterone index and the changes in free testosterone index were not significant compared to baseline. Regardless of changes in hormonal levels, patients in the diet, exercise, and diet-exercise groups experienced significant improvements in the modified PPT from baseline.

CONCLUSION

Weight loss from lifestyle intervention resulted in significant decreases in total and free estradiol levels in frail, obese older men, but this did not result in a clinically important increase in total testosterone nor a significant increase in free testosterone. Thus, alternative forms of treatment in addition to lifestyle intervention may be necessary to improve the hormonal profile among these patients. Nevertheless, whether further improvement in hormonal profile would result in better physical performance than what can be achieved by lifestyle alone in these subjects remains uncertain.

Neuromuscular dysfunction in type 2 diabetes: underlying mechanisms and effect of resistance training

Diabetic patients are at higher risk of developing physical disabilities than non-diabetic subjects. Physical disability appears to be related, at least in part, to muscle dysfunction. Several studies have reported reduced muscle strength and power under dynamic and static conditions in both the upper and lower limbs of patients with type 2 diabetes. Additional effects of diabetes include a reduction in muscle mass, quality, endurance and an alteration in muscle fibre composition, though the available data on these parameters are conflicting. The impact of diabetes on neuromuscular function has been related to the co-existence of long-term complications. Peripheral neuropathy has been shown to affect muscle by impairing motor nerve conduction. Also, vascular complications may contribute to the decline in muscle strength. However, muscle dysfunction occurs early in the course of diabetes and affects also the upper limbs, thus suggesting that it may develop independently of micro and macrovascular disease. A growing body of evidence indicates that hyperglycaemia may cause an alteration of the intrinsic properties of the muscle to generate force, via several mechanisms. Recently, resistance exercise has been shown to be an effective strategy to counteract the deterioration of muscular performance. High-intensity exercise seems to provide greater benefits than moderate-intensity training, whereas the effect of a power training is yet unknown. This article reviews the available literature on the impairment of muscle function induced by diabetes, the underlying mechanisms, and the effect of resistance training on this defect. Copyright © 2015 John Wiley & Sons, Ltd.

Age-related neuromuscular changes affecting human vastus lateralis

KEY POINTS

Skeletal muscle size and strength decline in older age. The vastus lateralis, a large thigh muscle, undergoes extensive neuromuscular remodelling in healthy ageing, as characterized by a loss of motor neurons, enlargement of surviving motor units and instability of neuromuscular junction transmission. The loss of motor axons and changes to motor unit potential transmission precede a clinically-relevant loss of muscle mass and function.

ABSTRACT

The anterior thigh muscles are particularly susceptible to muscle loss and weakness during ageing, although how this is associated with changes to neuromuscular structure and function in terms of motor unit (MU) number, size and MU potential (MUP) stability remains unclear. Intramuscular (I.M.) and surface electromyographic signals were recorded from the vastus lateralis (VL) during voluntary contractions held at 25% maximal knee extensor strength in 22 young (mean ± SD, 25.3 ± 4.8 years) and 20 physically active older men (71.4 ± 6.2 years). MUP size, firing rates, phases, turns and near fibre (NF) jiggle were determined and MU number estimates (MUNEs) were made by comparing average surface MUP with maximal electrically-evoked compound muscle action potentials. Quadriceps cross-sectional area was measured by magnetic resonance imaging. In total, 379 individual MUs were sampled in younger men and 346 in older men. Compared to the MU in younger participants, those in older participants had 8% lower firing rates and larger MUP size (+25%), as well as increased complexity, as indicated by phases (+13%), turns (+20%) and NF jiggle (+11%) (all P < 0.0005). The MUNE values (derived from the area of muscle in range of the surface-electrode) in older participants were ∼70% of those in the young (P < 0.05). Taking into consideration the 30% smaller cross-sectional area of the VL, the total number of MUs in the older muscles was between 50% and 60% lower compared to in young muscles (P < 0.0005). A large portion of the VL MU pool is lost in older men and those recruited during moderate intensity contractions were enlarged and less stable. These MU changes were evident before clinically relevant changes to muscle function were apparent; nevertheless, the changes in MU number and size are probably a prelude to future movement problems.

Multi-atlas-based fully automatic segmentation of individual muscles in rat leg

OBJECTIVE

To quantify individual muscle volume in rat leg MR images using a fully automatic multi-atlas-based segmentation method.

MATERIALS AND METHODS

We optimized a multi-atlas-based segmentation method to take into account the voxel anisotropy of numbers of MRI acquisition protocols. We mainly tested an image upsampling process along Z and a constraint on the nonlinear deformation in the XY plane. We also evaluated a weighted vote procedure and an original implementation of an artificial atlas addition. Using this approach, we measured gastrocnemius and plantaris muscle volumes and compared the results with manual segmentation. The method reliability for volume quantification was evaluated using the relative overlap index.

RESULTS

The most accurate segmentation was obtained using a nonlinear registration constrained in the XY plane by zeroing the Z component of the displacement and a weighted vote procedure for both muscles regardless of the number of atlases. The performance of the automatic segmentation and the corresponding volume quantification outperformed the interoperator variability using a minimum of three original atlases.

CONCLUSION

We demonstrated the reliability of a multi-atlas segmentation approach for the automatic segmentation and volume quantification of individual muscles in rat leg and found that constraining the registration in plane significantly improved the results.

Diagnostic ultrasound estimates of muscle mass and muscle quality discriminate between women with and without sarcopenia

Introduction: Age-related changes in muscle mass and muscle tissue composition contribute to diminished strength in older adults. The objectives of this study are to examine if an assessment method using mobile diagnostic ultrasound augments well-known determinants of lean body mass (LBM) to aid sarcopenia staging, and if a sonographic measure of muscle quality is associated with muscle performance.

Methods: Twenty community-dwelling female subjects participated in the study (age = 43.4 ± 20.9 years; BMI: 23.8, interquartile range: 8.5). Dual energy X-ray absorptiometry (DXA) and diagnostic ultrasound morphometry were used to estimate LBM. Muscle tissue quality was estimated via the echogenicity using grayscale histogram analysis. Peak force was measured with grip dynamometry and scaled for body size. Bivariate and multiple regression analyses were used to determine the association of the predictor variables with appendicular lean mass (aLM/ht²), and examine the relationship between scaled peak force values and muscle echogenicity. The sarcopenia LBM cut point value of 6.75 kg/m² determined participant assignment into the Normal LBM and Low LBM subgroups.

Results: The selected LBM predictor variables were body mass index (BMI), ultrasound morphometry, and age. Although BMI exhibited a significant positive relationship with aLM/ht² (adj. R² = 0.61, p < 0.001), the strength of association improved with the addition of ultrasound morphometry and age as predictor variables (adj. R² = 0.85, p < 0.001). Scaled peak force was associated with age and echogenicity (adj. R² = 0.53, p < 0.001), but not LBM. The Low LBM subgroup of women (n = 10) had higher scaled peak force, lower BMI, and lower echogenicity values in comparison to the Normal LBM subgroup (n = 10; p < 0.05).

Conclusions: Diagnostic ultrasound morphometry values are associated with LBM, and improve the BMI predictive model for aLM/ht² in women. In addition, ultrasound proxy measures of muscle quality are more strongly associated with strength than muscle mass within the study sample.