Skeletal Muscle Quality Research Articles

The preliminary effect of whole-body vibration intervention on improving the skeletal muscle mass index, physical fitness, and quality of life among older people with sarcopenia

BackgroundStudies have shown that sarcopenia easily leads to difficulty moving, disability, and poor quality of life. However, researches on the use of whole-body vibration for older adults with sarcopenia living in institutions have been lacking. Therefore, the main objective of the present study was to investigate the effect of whole-body vibration intervention on improving the skeletal muscle mass index, physical fitness, and quality of life of older adults with sarcopenia living in institutions.MethodsThis study adopted a quasi-experimental, single-group, pretest-posttest design. The whole-body vibration intervention was performed over a 3-month period, in which the older adults trained 3 times per week; each training lasted 60 s with a break of 30 s for 10 repetitions. The older adults’ skeletal muscle mass index, physical fitness and quality of life before and after the intervention of the whole-body vibration was collected. Concerning the statistical methods adopted, nonparametric method-based tests were employed.ResultsAccording to the results of analysis, after the intervention of the 12-week whole-body vibration, the skeletal muscle mass index (z = − 3.621, p = 0.000), physical fitness on standing on one foot (z = − 2.447, p = 0.014), shoulder–arm flexibility (z = − 3.159, p = 0.002), 8-ft up and go test (z = − 2.692, p = 0.009), hand grip strength (z = − 3.388, p = 0.009), and five repeated sit-to-stand tests (z = − 2.936, p = 0.003), all improved significantly. Furthermore, concerning the quality of life of the older adults in the pretest and posttest, the improvements were statistically significant (z = − 2.533, p = 0.011).ConclusionsThe study results showed the effect of whole-body vibration intervention on improving the skeletal muscle mass index, physical fitness, and quality of life of sarcopenic older people living in institutions and could serve as a crucial reference to health care professionals.

Efficacy of Age-Specific High-Intensity Stretch-Shortening Contractions in Reversing Dynapenia, Sarcopenia, and Loss of Skeletal Muscle Quality.

During the aging process, skeletal muscle performance and physiology undergoes alterations leading to decrements in functional capacity, health-span, and independence. Background: The utility and implementation of age-specific exercise is a paramount research agenda focusing on ameliorating the loss of both skeletal muscle performance and physiology; yet, to date, no consensus exists as to the most appropriate mechanical loading protocol design or overall exercise prescription that best meets this need. Thus, the purpose of this review is to highlight the most optimal type of exercise presently available and provide the most current, evidence-based findings for its efficacy. The hypothesis that high-intensity, stretch-shortening contractions (SSCs)—a form of “resistance-type exercise” training—present as the preferred exercise mode for serving as an intervention-based modality to attenuate dynapenia, sarcopenia, and decreased muscle quality with aging, even restoring the overall youthful phenotype, will be demonstrated. Conclusions: Appreciating the fundamental evidence supporting the use of high-intensity SSCs in positively impacting aging skeletal muscle’s responsivity and their use as a specific and sensitive countermeasure is crucial. Moreover, from an applied perspective, SSCs may improve skeletal muscle quality and rejuvenate health-span and, ultimately, lead to augmented functional capacity, independence, and quality of life concomitant with decreased morbidity.

Decreased Muscle Strength and Quality in Diabetes-Related Dementia

Background/Aims: Diabetes-related dementia (DrD), a dementia subgroup associated with specific diabetes mellitus (DM)-related metabolic abnormalities, is clinically and pathophysiologically different from Alzheimer disease (AD) and vascular dementia. We determined whether skeletal muscle strength, quality, and mass decrease in individuals with DrD. Methods: We evaluated grip and knee extension strength, muscle mass, and gait speed in 106 patients with probable AD and without type 2 DM (AD[–DM] group), 74 patients with probable AD and with DM (AD[+DM] group), and 36 patients with DrD (DrD group). Muscle quality was defined as the ratio of muscle strength to muscle mass. Results: Both female and male subjects with DrD showed significantly decreased muscle strength and quality in the upper extremities compared with the subjects with AD[–DM] or AD[+DM]. Female subjects with DrD showed significantly decreased muscle quality in the lower extremities compared with the subjects with AD[–DM]. Both female and male subjects with DrD had a significantly lower gait speed compared with the subjects with AD[–DM]. However, there were no significant differences in muscle mass and the prevalence of sarcopenia between the groups. Conclusion: Subjects with DrD showed decreased muscle strength and quality, but not muscle mass, and had a low gait speed.

Preoperative Low Muscle Mass and Low Muscle Quality Negatively Impact on Pulmonary Function in Patients Undergoing Hepatectomy for Hepatocellular Carcinoma

Background: Sarcopenia is a prognostic factor for mortality in digestive surgery. However, the correlation between preoperative cardiopulmonary function and sarcopenia in patients undergoing hepatectomy for hepatocellular carcinoma (HCC) remains unclear. Methods: The present study investigated the impact of preoperative sarcopenia on cardiopulmonary function in 402 patients who underwent first hepatectomy for HCC between April 2005 and April 2015. The quantity and quality of skeletal muscle were evaluated using psoas muscle index (PMI) and intramuscular adipose tissue content (IMAC), respectively, as determined from preoperative computed tomography imaging. Correlations between preoperative cardiopulmonary function and sarcopenic factors (PMI and IMAC) were evaluated. Results: No significant correlations were found between left ventricular ejection fraction and the two sarcopenic factors. On the other hand, preoperative vital capacity (VC) and forced expiratory volume in 1 s (FEV₁) correlated significantly with PMI (p < 0.001 each) in males and with IMAC (p < 0.001 each) in females. Moreover, VC and FEV₁ in the preoperative low PMI (p < 0.001 each) and high IMAC (p = 0.002 and p < 0.001, respectively) groups were significantly lower than in the normal group in males. In females, VC and FEV₁ were significantly lower in the preoperative high IMAC group than in the normal group (p < 0.001 each). Conclusion: Preoperative low muscle mass in males and low muscle quality in males and females were significantly associated with pulmonary dysfunction.

A Novel Preoperative Skeletal Muscle Measure as a Predictor of Postoperative Complications, Long-Term Survival and Tumor Recurrence for Patients with Gastric Cancer After Radical Gastrectomy.

Increasing numbers of studies have shown that skeletal muscle measures are closely associated with tumors. This study explored the relationship between skeletal muscle measures and short- and long-term outcomes after radical gastrectomy (RG) for gastric cancer (GC). The study analyzed 221 GC patients who underwent RG between December 2009 and December 2010. The total psoas area (TPA) and psoas density [Hounsfield unit average calculation (HUAC)] were measured. The total psoas gauge (TPG) was created by multiplying TPA×HUAC. Low TPA, low HUAC, and low TPG were defined in the categorical analyses as the lowest quartile. Logistic regression modeling, the Kaplan-Meier method, and three-step multivariate analysis were used. The median follow-up period was 64months. Compared with low TPA and low HUAC, only low TPG was an independent risk factor for postoperative complications. The univariate analysis showed that low TPA, low HUAC, and low TPG were predictors of overall survival (OS), recurrence-free survival (RFS), and cancer-specific survival (CCS) after surgery. The result of the three-step multivariate analysis demonstrated that low TPG was an independent risk factor for OS, RFS, and CCS. Moreover, the prognostic value of TPG was superior to that of TPA and HUAC. The patients with low TPG experienced significantly more postoperative liver recurrence than the patients with high TPG (p=0.011). Compared with preoperative skeletal muscle quantity (TPA) and quality (HUAC), TPG can more accurately predict complications and prognosis after RG. In addition, TPG may be an indicator for the early detection of liver recurrence after RG.

Animal-Derived Protein Consumption Is Associated with Muscle Mass and Strength in Community-Dwellers: Results from the Milan EXPO Survey.

Behavioral factors, including protein intake, influence the quantity and quality of skeletal muscle. The aim of this study was to explore the relationship between animal-derived protein intake and muscle mass and function in a large sample of unselected community-dwellers. The VIP (Very Important Protein) study, conducted during Expo 2015 in Milan, was a population survey aimed at assessing major health metrics in a population outside of the research setting, with a special focus on the relation between animal-derived protein intake and muscle mass and function. A brief questionnaire exploring lifestyle habits, dietary preferences and the consumption of selected foods was administered. Muscle mass was estimated by calf circumference (CC) and mid-arm muscle circumference (MAMC) of the dominant side. Muscle strength of upper and lower extremities was assessed through handgrip strength testing and repeated chair stand test, respectively. The mean age of the 1,853 participants was 50.3 years (standard deviation: 15.7; range: 18-98 years), of whom 959 (51.7%) were women. Participants in the highest tertile of protein consumption showed better performance at both the handgrip strength (p <0.001) and chair stand tests than those in the lowest tertile (p <0.01). The same results were found for CC (p <0.001) and MAMC (p <0.001). Participants with high protein intake and engaged in regular physical activity showed the higher scores in all the assessed domains. The results of the VIP survey suggest an association between animal-derived protein intake and muscle mass and strength across ages. Our findings also indicate a synergistic effect of animal-derived protein intake and physical activity on muscle-related parameters.

Muscle Deficits in Rheumatoid Arthritis Contribute to Inferior Cortical Bone Structure and Trabecular Bone Mineral Density.

Rheumatoid arthritis (RA) is associated with muscle loss, osteoporosis, and fracture. We examined associations between skeletal muscle mass, strength, and quality and trabecular and cortical bone deficits in patients with RA and healthy controls. Participants, ages 18-75 years, completed whole-body dual-energy x-ray absorptiometry and peripheral quantitative computed tomography (pQCT) of the tibia to quantify appendicular lean mass and fat mass indices (ALMI, FMI), muscle density at the lower leg, trabecular bone density, and cortical bone thickness. Age-, sex-, and race-specific Z scores were calculated based on distributions in controls. Associations between body composition and pQCT bone outcomes were assessed in patients with RA and controls. Linear regression analyses assessed differences in bone outcomes after considering differences in body mass index (BMI) and body composition. The sample consisted of 112 patients with RA (55 men) and 412 controls (194 men). Compared to controls, patients with RA had greater BMI Z score (p < 0.001), lower ALMI Z score after adjustment for FMI (p = 0.02), lower muscle strength Z score (p = 0.01), and lower muscle density Z score (p < 0.001). Among RA, ALMI Z scores were positively associated with trabecular density [β: 0.29 (0.062-0.52); p = 0.01] and cortical thickness [β: 0.33 (0.13-0.53; p = 0.002]. Associations were similar in controls. Bone outcomes were inferior in patients with RA after adjusting for BMI, but similar to controls when adjusting for body composition. Radiographic damage and higher adiponectin levels were independently associated with inferior bone outcomes. Patients with RA exhibit deficits in cortical bone structure and trabecular density at the tibia and a preserved functional muscle-bone unit. A loss of mechanical loading may contribute to bone deficits.

Effect of 12-month resistance and endurance training on quality, quantity, and function of skeletal muscle in older adults requiring long-term care

Older adults requiring long-term care will experience age-associated deterioration of the quality and quantity of skeletal muscle if no interventions are performed. Long-term training is considered a typical intervention method and is effective for improvement of both muscle quantity and physical function. However, how such training affects muscle quality [i.e., fat-to-muscle ratio as determined by echo intensity (EI)] in older adults requiring long-term care remains unclear. The purpose of this study was to investigate the effects of a 12-month physical training intervention on the quality and quantity of skeletal muscle, physical function, and blood chemistry in older adults requiring long-term care. Seventeen older adults requiring long-term care (Tr-group) and 15 healthy older adults (Cont-group) participated in this study. Patients in the Tr-group performed exercises consisting of resistance and endurance training once or twice a week for 12months. The EI and muscle thickness of the thigh were calculated from the rectus femoris and biceps femoris using B-mode transverse ultrasound images. Physical functions (isometric knee extension peak torque, sit-to-stand test, 5-m normal/maximal speed walking, handgrip strength, and timed up and go test) and blood lipid components including adipocytokines were measured at three points, i.e. baseline and 6 and 12months after. The thigh EI was significantly lower after 6months of training than baseline, and it returned to the initial level after 12months of training (baseline, 70.2±8.3a.u.; 6months, 64.1±11.2a.u.; 12months, 72.3±7.2a.u.). The thigh muscle thickness, 5-m maximal speed walking, and knee extension torque were significantly improved after 12months of training (P<0.05). The blood chemistry parameters did not significantly change. These results demonstrate that a 12-month training intervention contributes to improvement of muscle quantity and function with tentative changes in muscle quality but has no effect on blood chemistry in older adults requiring long-term care. We conclude that this type of training has the potential to restore the muscle functional abilities of older adults requiring long-term care.

SUN-P084: Influence of Both Skeletal Muscle Depletion and Low Muscle Quality on Prognosis of Locally Advanced Pancreatic Cancer Treated with Chemoradiotherapy: A Retrospective Study

SUN-P084: Influence of Both Skeletal Muscle Depletion and Low Muscle Quality on Prognosis of Locally Advanced Pancreatic Cancer Treated with Chemoradiotherapy: A Retrospective Study

Gastrointestinal Cancer

Gastrointestinal Cancer

Preoperative low muscle mass has a strong negative effect on pulmonary function in patients undergoing living donor liver transplantation.

This study investigated the effect of preoperative sarcopenia on cardiopulmonary function in patients undergoing living donor liver transplantation (LDLT). A retrospective analysis was performed of 207 patients who underwent LDLT between January 2008 and April 2015. The quantity and quality of skeletal muscle were evaluated by the psoas muscle mass index (PMI) and intramuscular adipose tissue content (IMAC), respectively, using preoperative computed tomography imaging. The correlations between preoperative cardiopulmonary function and sarcopenic factors (PMI, IMAC, and grip strength [GS]) were examined. Moreover, overall survival (OS) rates according to preoperative pulmonary function and risk factors were analyzed. No significant differences were found between ejection fraction (EF) and these sarcopenic factors. In contrast, preoperative vital capacity (VC) and forced expiratory volume (FEV) 1.0 were significantly correlated with PMI (P<0.001, P<0.001), IMAC (P=0.024, P=0.013), and GS (P=0.006, P=0.033) in males. Preoperative VC and FEV1.0 were significantly correlated with IMAC (P=0.002, P=0.001) and GS (P=0.002, P=0.001) in females. Moreover, %VC, VC, and FEV1.0 in the preoperative low muscle mass group were significantly lower than in the normal muscle mass group (P=0.004, P<0.001, P<0.001, respectively) in males. Multivariate analysis revealed that preoperative low PMI and preoperative restrictive ventilatory impairment were independent risk factors (P=0.046 and P=0.014, respectively). Preoperative low muscle mass was closely involved with pulmonary dysfunction in patients undergoing LDLT.

Human Muscle Precursor Cells Overexpressing PGC-1α Enhance Early Skeletal Muscle Tissue Formation

Muscle precursor cells (MPCs) are activated satellite cells capable of muscle fiber reconstruction. Therefore, autologous MPC transplantation is envisioned for the treatment of muscle diseases. However, the density of MPCs, as well as their proliferation and differentiation potential, gradually declines with age. The goals of this research were to genetically modify human MPCs (hMPCs) to overexpress the peroxisome proliferator-activated receptor γ coactivator (PGC-1α), a key regulator of exercise-mediated adaptation, and thereby to enhance early skeletal muscle formation and quality. We were able to confirm the sustained myogenic phenotype of the genetically modified hMPCs. While maintaining their viability and proliferation potential, PGC-1α-modified hMPCs showed an enhanced myofiber formation capacity in vitro. Engineered muscle tissues were harvested 1, 2, and 4 weeks after subcutaneous injection of cell–collagen suspensions, and histological analysis confirmed the earlier myotube formation in PGC-1α-modified samples, predominantly of slow-twitch myofibers. Increased contractile protein levels were detected by Western blot. In summary, by genetically modifying hMPCs to overexpress PGC-1α, we were able to promote early muscle fiber formation in vitro and in vivo, with an initial switch to slow-type myofibers. Therefore, overexpressing PGC-1α is a novel strategy to further enhance skeletal muscle tissue engineering.

Overweight in elderly people induces impaired autophagy in skeletal muscle

Sarcopenia is the gradual loss of skeletal muscle mass, strength and quality associated with aging. Changes in body composition, especially in skeletal muscle and fat mass are crucial steps in the development of chronic diseases. We studied the effect of overweight on skeletal muscle tissue in elderly people without reaching obesity to prevent this extreme situation. Overweight induces a progressive protein breakdown reflected as a progressive withdrawal of anabolism against the promoted catabolic state leading to muscle wasting. Protein turnover is regulated by a network of signaling pathways. Muscle damage derived from overweight displayed by oxidative and endoplasmic reticulum (ER) stress induces inflammation and insulin resistance and forces the muscle to increase requirements from autophagy mechanisms. Our findings showed that failure of autophagy in the elderly deprives it to deal with the cell damage caused by overweight. This insufficiently efficient autophagy leads to an accumulation of p62 and NBR1, which are robust markers of protein aggregations. This impaired autophagy affects myogenesis activity. Depletion of myogenic regulatory factors (MRFs) without links to variations in myostatin levels in overweight patients suggest a possible reduction of satellite cells in muscle tissue, which contributes to declined muscle quality. This discovery has important implications that improve the understanding of aged-related atrophy caused by overweight and demonstrates how impaired autophagy is one of the main responsible mechanisms that aggravate muscle wasting. Therefore, autophagy could be an interesting target for therapeutic interventions in humans against muscle impairment diseases.

Influence of anaerobic and aerobic exercise on age-related pathways in skeletal muscle

The aging process is characterized by the progressive loss of physiological stability, lower physical and cognitive reserve, and increased vulnerability to death. This progressive deterioration in organismal homeostasis is considered the underlying trigger of most chronic diseases like diabetes, neurodegenerative diseases and cancer. Experimental challenges that increase the rate of biological and cognitive decline are linked to accelerated aging while interventions that slow the aging process are accompanied by an extension in healthy lifespan (Lopez-Otin et al., 2013; Kennedy et al., 2014). Skeletal muscles perform several functions essential for locomotion and posture, and the loss of adequate mobility that occurs with aging causes the muscle to decrease its oxidative capacity and function. Gait speed represents an important integrative measure of muscle function and efficiency in the elderly (Peel et al., 2013) and its decline can be considered the best predictor of survival and health outcomes in humans (Perera et al., 2016). The age-associated decline in energy supply caused by mitochondrial dysfunction and/or reduction in the numbers of mitochondria adversely affects skeletal muscle function and homeostasis. One significant way to increase or preserve skeletal muscle quality and strength needed for healthy aging is through regular physical activity (Cartee et al., 2016). The present review addresses key facets of human aging and presents a summary of relevant metabolic sensors in skeletal muscle that coordinate the organismal response to exercise. We will explore various aspects of exercise that contribute to the regulation of metabolic pathways implicated in muscle strength and regeneration, as well as in mitochondria recycling and efficiency. The benefits of exercise as a universal therapeutic “pill” for healthy aging will also be discussed.

Relationships Among and Differences between Muscle Quality and Functional Performance in Younger and Older Women

The quality of skeletal muscle has been identified as an important factor that is used to describe intramuscular changes associated with muscle function in aging. Traditionally, muscle quality (MQ) has been calculated as maximal muscle strength expressed per unit of muscle mass. More recently, however, the echo intensity (EI) of skeletal muscle ultrasound images has been used as a surrogate measure of muscle quality. PURPOSE: The purpose of this study was to examine the relationships among and differences between commonly-used measures of MQ and functional performance in younger (YW) and older women (OW). METHODS: 15 YW (mean ± SD: 22 ± 2 yrs) and 15 OW (74 ± 5 yrs) completed this study. Muscle cross section area (mCSA) and EI of the rectus femoris were measured from ultrasound scans at the midpoint of the thigh. Each participant completed two maximal voluntary isometric knee extension contractions (MVICs) to determine MVIC strength. Each participant also completed three maximal velocity sit-to-stand movements, during which power and movement velocity were measured. MQ was calculated as MVIC strength ÷ mCSA. Independent samples t-tests were used to analyze differences between YW and OW and Pearson’s correlation coefficients were also used to analyze the relationships among the dependent variables in the YW and OW. RESULTS: MVIC strength (166 ± 37 vs 105 ± 28 Nm), mean velocity (0.6 ± 0.1 vs 0.4 ± 0.1 m/s), peak velocity (0.9 ± 0.2 vs 0.7 ± 0.1), mean power (435 ± 81 vs 299 ± 57 W), peak power (1070 ± 265 vs 597 ± 127 W) were greater and EI (39 ± 8 vs 52 ± 10 au) was lower in the YW than OW, respectively. There was no difference in muscle quality (p = 0.96). EI and MQ were not significantly related (r = 0.12) in the YW, but were significantly related in the OW (r = 0.54). EI was inversely related to mCSA in the YW (r = -0.53) and OW (r = -0.54). In addition, MVIC was significantly related to mCSA (r = 0.75) in the OW, and was not significantly related to EI or MQ in either the YW or OW. CONCLUSION: There were age-related differences in muscle strength, muscle size, echo intensity, and functional performance, but no age-related difference in traditionally measured MQ. EI was related to MQ in the OW, but not the YW. Although EI has been used as a surrogate for MQ, these data suggest that MQ and EI may reflect different qualities of skeletal muscle in aging.

Impact of Skeletal Muscle Mass Index, Intramuscular Adipose Tissue Content, and Visceral to Subcutaneous Adipose Tissue Area Ratio on Early Mortality of Living Donor Liver Transplantation.

Skeletal muscle depletion has been shown to be an independent risk factor for poor survival in various diseases. However, in surgery, the significance of other body components including visceral and subcutaneous adipose tissue remains unclear. This retrospective study included 250 adult patients undergoing living donor liver transplantation (LDLT) between January 2008 and April 2015. Using preoperative plain computed tomography imaging at the third lumbar vertebra level, skeletal muscle mass, muscle quality, and visceral adiposity were evaluated by the skeletal muscle mass index (SMI), intramuscular adipose tissue content (IMAC), and visceral to subcutaneous adipose tissue area ratio (VSR), respectively. The cutoff values of these parameters were determined for men and women separately using the data of 657 healthy donors for LDLT between 2005 and 2016. Impact of these parameters on outcomes after LDLT was analyzed. VSR was significantly correlated with patient age (P = 0.041), neutrophil-lymphocyte ratio (P < 0.001), body mass index (P < 0.001), and SMI (P = 0.001). The overall survival probability was significantly lower in patients with low SMI (P < 0.001), high IMAC (P < 0.001), and high VSR (P < 0.001) than in each respective normal group. On multivariate analysis, low SMI (hazard ratio [HR], 2.367, P = 0.002), high IMAC (HR, 2.096, P = 0.004), and high VSR (HR, 2.213, P = 0.003) were identified as independent risk factors for death after LDLT. Preoperative visceral adiposity, as well as low muscularity, was closely involved with posttransplant mortality.

Skeletal muscle loss and prognosis of breast cancer patients

The aim of this study was to clarify the changes in the cross-sectional area of skeletal muscle and muscle attenuation (MA) during 12-month period before death in breast cancer patients. Breast cancer patients who received treatment between September 2002 and July 2014 at Shizuoka Cancer Center or between December 2005 and July 2014 at Teikyo University Hospital were identified. Computed tomography (CT) scans during the 12-month period before death of consecutive female patients who died of breast cancer were reviewed. Skeletal muscle quantity and quality were evaluated by a cross-sectional area of skeletal muscle and MA, respectively, on CT scans taken 10-12months (T1), 7-9months (T2), 4-6months (T3), and within 3months (T4) prior to death. Wilcoxon signed rank test was used to compare the differences between the two-time points with Bonferroni correction (p=0.0083). The medical records of 99 patients (median age at death, 57years; range, 40-83years) were retrospectively analyzed. Both the cross-sectional area and MA continued to decrease during 12-month period before death. Statistically significant differences were observed in the cross-sectional areas between T1 and T4 (p=0.0011), T2 and T4 (p=0.0019), and T3 and T4 (p=0.0026), as well as in MA between T2 and T4 (p=0.0012) and T3 and T4 (p=0.0061). These results suggest that both quantity and quality of the skeletal muscle continued to decrease during 12-month period before death in breast cancer patients.

The need of operational paradigms for frailty in older persons: the SPRINTT project.

The exploration of frailty as a pre-disability geriatric condition represents one of the most promising research arenas of modern medicine. Frailty is today indicated as a paradigmatic condition around which the traditional healthcare systems might be re-shaped and optimized in order to address the complexities and peculiarities of elders. Unfortunately, the lack of consensus around a single operational definition has limited the clinical implementation of frailty in clinical practice. In these last years, growing attention (even beyond the traditional boundaries of geriatric medicine) has been given to physical performance measures. These instruments have shown to be predictive of negative health-related events and able to support an accurate estimation of the "biological age" in late life. The strong construct of physical performance measures also makes them particularly suitable for the assessment of the frailty status. Furthermore, the adoption of physical performance measures may help render the frailty condition more organ-specific (i.e., centred on the skeletal muscle quality) and less heterogeneous than currently perceived. The translation of the frailty concept by means of physical performance measures implicitly represents an attempt to go beyond traditional paradigms. In this context, the recently funded "Sarcopenia and Physical fRailty IN older people: multi-componenT Treatment strategies" (SPRINTT) project (largely based on such a novel approach) may indeed fill an important gap in the field and provide key insights for counteracting the disabling cascade in the elderly.

Impact of Aging and Exercise on Mitochondrial Quality Control in Skeletal Muscle.

Mitochondria are characterized by its pivotal roles in managing energy production, reactive oxygen species, and calcium, whose aging-related structural and functional deteriorations are observed in aging muscle. Although it is still unclear how aging alters mitochondrial quality and quantity in skeletal muscle, dysregulation of mitochondrial biogenesis and dynamic controls has been suggested as key players for that. In this paper, we summarize current understandings on how aging regulates muscle mitochondrial biogenesis, while focusing on transcriptional regulations including PGC-1α, AMPK, p53, mtDNA, and Tfam. Further, we review current findings on the muscle mitochondrial dynamic systems in aging muscle: fusion/fission, autophagy/mitophagy, and protein import. Next, we also discuss how endurance and resistance exercises impact on the mitochondrial quality controls in aging muscle, suggesting possible effective exercise strategies to improve/maintain mitochondrial health.

An Old Problem: Aging and Skeletal-Muscle-Strain Injury.

Understanding the fundamental evidence regarding how aging influences the responsivity of skeletal muscle to strain injury is vital for informing how clinicians approach and implement preventive strategies, as well as therapeutic interventions. From a practical perspective, maintaining or improving the overall health and tissue quality of skeletal muscle as one ages will positively affect skeletal muscle's safety threshold and responsivity, which may reduce incidence of injury, improve recovery time, and lessen overall fiscal burdens.