Atrophy and impaired muscle protein synthesis during prolonged inactivity and stress

The influence of immobility on muscle loss in older people with frailty and fragility fractures

This longitudinal study aimed to assess muscle morphological and functional changes in older patients admitted with fragility fractures managed by immobilisation of the affected limb for at least 6 weeks. Patients aged ≥ 70 hospitalised with non-weight bearing limb fractures, and functionally limited to transfers only, were recruited. Handgrip (HGS) and knee extensor strength (KES), Vastus Lateralis muscle thickness (VLMT) and cross-sectional area at ultrasound (VLCSA) were measured in the non-injured limb at hospital admission, 1, 3 and 6 weeks later. Barthel Index, mobility aid use and residential status were recorded at baseline and 16 weeks. Longitudinal changes in muscle measurements were analysed using one-way repeated measures ANOVA. In a sub-study, female patients' baseline measurements were compared to 11 healthy, female, non-frail, non-hospitalised control volunteers (HC) with comparable BMI, aged ≥ 70, using independent t tests. Fifty patients (44 female) participated. Neither muscle strength nor muscle size changed over a 6-week immobilisation. Dependency increased significantly from pre-fracture to 16 weeks. At baseline, the patient subgroup was weaker (HGS 9.2 ± 4.7 kg vs. 19.9 ± 5.8 kg, p < 0.001; KES 4.5 ± 1.5 kg vs. 7.8 ± 1.3 kg, p < 0.001) and had lower muscle size (VLMT 1.38 ± 0.47 cm vs. 1.75 ± 0.30 cm, p = 0.02; VLCSA 8.92 ± 4.37 cm2 vs. 13.35 ± 3.97 cm2, p = 0.005) than HC. The associations with lower muscle strength measures but not muscle size remained statistically significant after adjustment for age. Patients with non-weight bearing fractures were weaker than HC even after accounting for age differences. Although functional dependency increased after fracture, this was not related to muscle mass or strength loss, which remained unchanged.

Acute Sarcopenia: Mechanisms and Management

BACKGROUND

Acute sarcopenia refers to the swift decline in muscle function and mass following acute events such as illness, surgery, trauma, or burns that presents significant challenges in hospitalized older adults.

METHODS

narrative review to describe the mechanisms and management of acute sarcopenia.

RESULTS

The prevalence of acute sarcopenia ranges from 28% to 69%, likely underdiagnosed due to the absence of muscle mass and function assessments in most clinical settings. Systemic inflammation, immune-endocrine dysregulation, and anabolic resistance are identified as key pathophysiological factors. Interventions include early mobilization, resistance exercise, neuromuscular electrical stimulation, and nutritional strategies such as protein supplementation, leucine, β-hydroxy-β-methyl-butyrate, omega-3 fatty acids, and creatine monohydrate. Pharmaceuticals show variable efficacy.

CONCLUSIONS

Future research should prioritize serial monitoring of muscle parameters, identification of predictive biomarkers, and the involvement of multidisciplinary teams from hospital admission to address sarcopenia. Early and targeted interventions are crucial to improve outcomes and prevent long-term disability associated with acute sarcopenia.

Macrophages modulate skeletal muscle wasting and recovery in acute lung injury in mice

Skeletal muscle dysfunction in critical illnesses leaves survivors weak and functionally impaired. Macrophages infiltrate muscles; however, their functional role is unclear. We aim to examine muscle leukocyte composition and the effect of macrophages on muscle mass and function in the murine acute lung injury (ALI)-associated skeletal muscle wasting model. We performed flow cytometry of hindlimb muscle to identify myeloid cells pre-injury and time points up to 29 days after intratracheal lipopolysaccharide ALI. We evaluated muscle force and morphometrics after systemic and intramuscular clodronate-induced macrophage depletions between peak lung injury and recovery (day 5-6) versus vehicle control. Our results show muscle leukocytes changed over ALI course with day 3 neutrophil infiltration (130.5 ± 95.6cells/mg control to 236.3 ± 70.6cells/mg day 3) and increased day 10 monocyte abundance (5.0 ± 3.4%CD45+CD11b+ day 3 to 14.0 ± 2.6%CD45+CD11b+ day 10, p = 0.005). Although macrophage count did not significantly change, pro-inflammatory (27.0 ± 7.2% day 3 to 7.2 ± 3.8% day 10, p = 0.02) and anti-inflammatory (30.5 ± 11.1% day 3 to 52.7 ± 9.7% day 10, p = 0.09) surface marker expression changed over the course of ALI. Macrophage depletion following peak lung injury increased muscle mass and force generation. These data suggest muscle macrophages beyond peak lung injury limit or delay muscle recovery. Targeting macrophages could augment muscle recovery following lung injury.

Establishing Predictors of Acute Sarcopenia: A Proof-Of-Concept Study Utilising Network Analysis

Dynamic changes in sarcopenia status following stressor events are defined as acute sarcopenia; it is currently unknown how to stratify risk. Prospective observational study involving elective colorectal surgery, emergency abdominal surgery, and medical patients with infections aged ≥70 years-old. Handgrip strength, muscle quantity (ultrasound Bilateral Anterior Thigh Thickness, BATT, and Bioelectrical Impedance Analysis), and muscle quality (rectus femoris echogenicity) were measured preoperatively in the elective group, and within 48hours, 7days after, and 13weeks after admission/surgery. Serum/plasma samples were collected preoperatively (elective group) and within 48hours of admission/surgery (all groups). LASSO models adjusting for baseline sarcopenia status were performed. Seventy-nine participants were included (mean age 79.1, 39.2% female). Chronic Obstructive Pulmonary Disease (COPD) (48hours β 0.67, CI 0.59-0.75), and prescription of steroids during admission (48hours β 1.11, CI 0.98-1.24) were positively associated with sarcopenia at 7days. Delirium was negatively associated with change in BATT to 7days (7days β -0.47, CI -0.5- -0.44). COPD (Preoperative β 0.35, CI 0.12-0.58) and delirium (48hours β 0.13, CI 0.06-0.2) were positively associated with change in echogenicity to 7days in analysis including systemic biomarkers. Participants with sarcopenia at baseline had higher IL-7 concentrations during acute phase of illness (median 8.78pg/mL vs 6.52pg/mL; p=0.014). IL-1b within 48hours of admission/surgery was positively associated with sarcopenia status at 7days (β 0.24, CI 0.06-0.42). Patients most at risk of acute sarcopenia or reductions in muscle quantity and quality included those prescribed steroids, with COPD or delirium, or with heightened systemic inflammation.

The effect of protein or amino acid provision on immobilization-induced muscle atrophy in healthy adults: A systematic review and meta-analysis

Bed rest and limb immobilization are models of muscle disuse associated with skeletal muscle atrophy and reduced strength. The purpose of this systematic review was to examine the impact of protein or amino acid provision before and/or during a period of muscle disuse on muscle atrophy (primary outcome), strength and muscle protein synthesis (secondary outcomes) following a disuse period. We performed a systematic review of Embase, MEDLINE, Web of Science, PubMed and Clinical Trials in December 2022. Eligible studies were randomized controlled trials that combined a dietary protein or amino acid intervention versus control during an experimental model of disuse (bed rest or unilateral limb immobilization) in healthy individuals aged ≥18 years. Nine articles from eight independent trials were identified and rated for risk of bias by two authors. A meta-analysis of muscle mass data revealed no effect (standardized mean difference: 0.2; 95% confidence interval: -0.18 to 0.57, P = 0.31) of protein/amino acid intervention in preventing disuse-induced muscle atrophy. Although the meta-analysis was not conducted on strength or muscle protein synthesis data, there was insufficient evidence in the reviewed articles to support the use of protein/amino acid provision in mitigating the disuse-induced decline in either outcome measurement. Additional high-quality studies, including the reporting of randomization procedures and blinding procedures and the provision of statistical analysis plans, might be required to determine whether protein or amino acid provision serves as an effective strategy to attenuate muscle atrophy during periods of disuse.

Medical issues for female athletes returning to competition after childbirth

BACKGROUND

In recent years, the number of athletes who aim to return to competition after childbirth has increased. However, few international reports have investigated complications during pregnancy, and changes in physical function after childbirth in many athletes.

OBJECTIVE

To conduct a retrospective investigation of medical problems during pregnancy, and postpartum, in female athletes who aim to return to competition after childbirth, and to identify the barriers and facilitators for their return.

METHODS

A voluntary web-based survey was aimed at former female athletes who became pregnant with their first child and gave birth during their active sports career. The survey items included respondent background, their exercise activities during and after childbirth, perinatal complications, mode of delivery, symptoms and physical function after childbirth. The participants were divided into a vaginal delivery group and a cesarean section group.

RESULTS

Three hundred and twenty-eight (29.1 ± 5.1 years old) former athletes were included in the analysis, and about half reported undertaking exercise during pregnancy. The most common perinatal complication was anemia (27.4%). The appearance of any symptoms after childbirth, including low back pain (44.2%) and urinary incontinence (39.9%), was reported by 80.5%. The rate of urinary incontinence may be higher in the vaginal delivery than in the cesarean section group (p = 0.05). The most common physical decline after childbirth was in muscular strength, followed by speed and endurance.

CONCLUSION

Addressing pregnancy-associated anemia and managing low back pain is critical for athletes aiming to return to competition after childbirth. Additionally, interventions to reduce the risk for and treat urinary incontinence are important. In addition, in order to return to competition after childbirth, it is important to strengthen muscles, especially the lower limbs and trunk, as well as to create a training program that takes into account the sport/events.

Utility of growth differentiation factor-15 as a predictor of cardiovascular surgery outcomes: Current research and future directions

In a world increasingly confronted by cardiovascular diseases (CVDs) and an aging population, accurate risk assessment prior to cardiac surgery is critical. Although effective, traditional risk calculators such as the Japan SCORE, Society of Thoracic Surgeons score, and EuroSCORE II may not completely capture contemporary risks, particularly due to emerging factors such as frailty and sarcopenia. These calculators often focus on regional and ethnic specificity and rely heavily on evaluations based on age and underlying diseases. Growth differentiation factor-15 (GDF-15) is a stress-responsive cytokine that has been identified as a potential biomarker for sarcopenia and a tool for future cardiac risk assessment. Preoperative plasma GDF-15 levels have been associated with preoperative, intraoperative, and postoperative factors and short- and long-term mortality rates in patients undergoing cardiac surgery. Increased plasma GDF-15 levels have prognostic significance, having been correlated with the use of cardiopulmonary bypass during surgery, amount of bleeding, postoperative acute kidney injury, and intensive care unit stay duration. Notably, the inclusion of preoperative levels of GDF-15 in risk stratification models enhances their predictive value, especially when compared with those of the N-terminal prohormone of brain natriuretic peptide, which does not lead to reclassification. Thus, this review examines traditional risk assessments for cardiac surgery and the role of the novel biomarker GDF-15. This study acknowledges that the relationship between patient outcomes and elevated GDF-15 levels is not limited to CVDs or cardiac surgery but can be associated with variable diseases, including diabetes and cancer. Moreover, the normal range of GDF-15 is not well defined. Given its promise for improving patient care and outcomes in cardiovascular surgery, future research should explore the potential of GDF-15 as a biomarker for postoperative outcomes and target therapeutic intervention.

The Odds of One-Year Mortality in Bedridden Geriatric Patients Discharged from Acute Rehabilitation Ward Are Increased Eightfold If the Patients Have Three or More Complications

Low muscle strength, functional score at discharge, and complications during a ten-day rehabilitation hospital stay can affect mortality rates in bedridden geriatric patients. This was a prospective observational study in a cohort of 105 bedridden geriatric patients admitted to the Rehabilitation ward after a major illness or surgery. All participants had a severe dependency on another person (Barthel's Index < 60). The one-year mortality rate in this cohort was 15.2%, with further subdivision according to the number of complications: 61.5% in patients with ≥3 complications during hospitalization, 17.6% in patients with two complications, 9.5% with one complication, and 3% in patients with no complications. The Barthel Index at discharge (OR = 0.95; p = 0.003) and ≥3 medical complications (OR = 8.33; p = 0.005) during rehabilitation ward stay were significant predictors for one-year mortality. The odds of one-year mortality after discharge increased eightfold in patients with ≥3 medical complications. Sarcopenia, age, and sex were not significant predictors of mortality in this cohort. The 10-day acute rehabilitation was too short to achieve progress from severe to moderate independence in 60% of patients. The Barthel Index at discharge and a number of complications affect the mortality rate. These findings provide valuable insights into the complex dynamics of mortality and functional outcomes in bedridden geriatric patients.

The Structural Adaptations That Mediate Disuse-Induced Atrophy of Skeletal Muscle

The maintenance of skeletal muscle mass plays a fundamental role in health and issues associated with quality of life. Mechanical signals are one of the most potent regulators of muscle mass, with a decrease in mechanical loading leading to a decrease in muscle mass. This concept has been supported by a plethora of human- and animal-based studies over the past 100 years and has resulted in the commonly used term of 'disuse atrophy'. These same studies have also provided a great deal of insight into the structural adaptations that mediate disuse-induced atrophy. For instance, disuse results in radial atrophy of fascicles, and this is driven, at least in part, by radial atrophy of the muscle fibers. However, the ultrastructural adaptations that mediate these changes remain far from defined. Indeed, even the most basic questions, such as whether the radial atrophy of muscle fibers is driven by the radial atrophy of myofibrils and/or myofibril hypoplasia, have yet to be answered. In this review, we thoroughly summarize what is known about the macroscopic, microscopic, and ultrastructural adaptations that mediated disuse-induced atrophy and highlight some of the major gaps in knowledge that need to be filled.

Effects of unimodal or multimodal prehabilitation on patients undergoing surgery for esophagogastric cancer: a systematic review and meta-analysis

PURPOSE

To evaluate the effects of unimodal or multimodal prehabilitation on patients undergoing surgery for esophagogastric cancer.

METHODS

We conducted a systematic search of the PubMed, Embase, CINAHL, Web of Science, and Cochrane Library (CENTRAL) databases from database inception to May 5, 2023, for randomized controlled trials (RCTs) and cohort studies that investigated prehabilitation in the context of esophagogastric cancer. A random-effects model was used for meta-analysis.

RESULTS

We identified 2,994 records and eventually included 12 studies (6 RCTs and 6 cohort studies) with a total of 910 patients. According to random-effects pooled estimates, prehabilitation reduced the incidence of all complications (RR = 0.79, 95% CI: 0.66 to 0.93, P = 0.006), pulmonary complications (RR = 0.61, 95% CI: 0.47 to 0.79, P = 0.0002), and severe complications (RR = 0.63, 95% CI: 0.47 to 0.84, P = 0.002), and shortened the length of stay (MD = -1.92, 95% CI: -3.11 to -0.73, P = 0.002) compared to usual care. However, there were no statistically significant differences in 30-day readmission rates or in-hospital mortality. Subgroup analysis showed that multimodal prehabilitation was effective in reducing the risk of all complications and severe complications, while unimodal prehabilitation was not.

CONCLUSIONS

Our findings suggested that prehabilitation may be beneficial in reducing postoperative complications and length of stay. We recommend preoperative prehabilitation to improve postoperative outcomes and hasten recovery following esophagogastric cancer surgery, and multimodal prehabilitation seems to be more advantageous in reducing complications. However, further studies are needed to confirm these results.

High-protein diet with excess leucine prevents inactivity-induced insulin resistance in women

BACKGROUND AND AIMS

Muscle inactivity leads to muscle atrophy and insulin resistance. The branched-chain amino acid (BCAA) leucine interacts with the insulin signaling pathway to modulate glucose metabolism. We have tested the ability of a high-protein BCAA-enriched diet to prevent insulin resistance during long-term bed rest (BR).

METHODS

Stable isotopes were infused to determine glucose and protein kinetics in the postabsorptive state and during a hyperinsulinemic-euglycemic clamp in combination with amino acid infusion (Clamp + AA) before and at the end of 60 days of BR in two groups of healthy, young women receiving eucaloric diets containing 1 g of protein/kg per day (n = 8) or 1.45 g of protein/kg per day enriched with 0.15 g/kg per day of BCAAs (leucine/valine/isoleucine = 2/1/1) (n = 8). Body composition was determined by Dual X-ray Absorptiometry.

RESULTS

BR decreased lean body mass by 7.6 ± 0.3 % and 7.2 ± 0.8 % in the groups receiving conventional or high protein-BCAA diets, respectively. Fat mass was unchanged in both groups. At the end of BR, percent changes of insulin-mediated glucose uptake significantly (p = 0.01) decreased in the conventional diet group from 155 ± 23 % to 84 ± 10 % while did not change significantly in the high protein-BCAA diet group from 126 ± 20 % to 141 ± 27 % (BR effect, p = 0.32; BR/diet interaction, p = 0.01; Repeated Measures ANCOVA). In contrast, there were no BR/diet interactions on proteolysis and protein synthesis Clamp + AA changes in the conventional diet and the high protein-BCAA diet groups.

CONCLUSION

A high protein-BCAA enriched diet prevented inactivity-induced insulin resistance in healthy women.

Loss of body weight and lean mass in long-stay, hospitalized canine patients

A high prevalence of malnutrition occurs in human hospitals and has been associated with detrimental consequences. By comparison, much less is known in hospitalized veterinary patients. The aims of this study were to evaluate the prevalence of malnutrition and body composition changes in long-stay hospitalised patients using an isotopic dilution technique. An additional objective was to compare the changes in composition with commonly used methods measuring body fat and lean mass. The dogs consumed on average 77.5% of their estimated resting energy requirements during their stay. The majority (78.3%) of dogs lost body weight, of which a greater proportion was lean mass (61.8%) than fat mass (FM) (38.2%). There was a moderate correlation between body condition score and percentage FM measured at admission (Kendall's τ = 0.51; p = 0.002), and at discharge (Kendall's τ = 0.55; p = 0.001). However, there was no correlation between muscle condition score and fat-free mass at either admission or discharge (p > 0.1). Duration of stay was positively associated with loss of body weight (p < 0.001), but was not associated with changes in either lean or FM expressed as a percentage of body weight or in absolute terms (p > 0.1), which was presumed to be explained by small sample size and variation. Food intake was not found to a significant factor for lean or FM loss (p > 0.1). These findings indicate that weight loss is common in hospitalized canine patients, which is not explained by simple under-eating. Other factors such as inflammation and inactivity should be evaluated in future studies to determine their role in influencing muscle and FM changes in hospitalized canine patients.

Biological sex divergence in transcriptomic profiles during the onset of hindlimb unloading-induced atrophy

Disuse-induced muscle atrophy is a common clinical problem observed mainly in older adults, intensive care units patients, or astronauts. Previous studies presented biological sex divergence in progression of disuse-induced atrophy along with differential changes in molecular mechanisms possibly underlying muscle atrophy. The aim of this study was to perform transcriptomic profiling of male and female mice during the onset and progression of unloading disuse-induced atrophy. Male and female mice underwent hindlimb unloading (HU) for 24, 48, 72, and 168 h (n = 8/group). Muscles were weighed for each cohort and gastrocnemius was used for RNA-sequencing analysis. Females exhibited muscle loss as early as 24 h of HU, whereas males after 168 h of HU. In males, pathways related to proteasome degradation were upregulated throughout 168 h of HU, whereas in females these pathways were upregulated up to 72 h of HU. Lcn2, a gene contributing to regulation of myogenesis, was upregulated by 6.46- to 19.86-fold across all time points in females only. A reverse expression of Fosb, a gene related to muscle degeneration, was observed between males (4.27-fold up) and females (4.57-fold down) at 24-h HU. Mitochondrial pathways related to tricarboxylic acid (TCA) cycle were highly downregulated at 168 h of HU in males, whereas in females this downregulation was less pronounced. Collagen-related pathways were consistently downregulated throughout 168 h of HU only in females, suggesting a potential biological sex-specific protective mechanism against disuse-induced fibrosis. In conclusion, females may have protection against HU-induced skeletal muscle mitochondrial degeneration and fibrosis through transcriptional mechanisms, although they may be more vulnerable to HU-induced muscle wasting compared with males.NEW & NOTEWORTHY Herein, we have assessed the transcriptomic response across biological sexes during the onset and progression of unloading disuse-induced atrophy in mice. We have demonstrated an inverse expression of Fosb between males and females, as well as differentially timed patterns of expressing atrophy-related pathways between sexes that are concomitant to the accelerated atrophy in females. We also identified in females signs of mechanisms to combat disuse-induced mitochondrial degeneration and fibrosis.

A focus on leucine in the nutritional regulation of human skeletal muscle metabolism in ageing, exercise and unloading states

Muscle protein synthesis (MPS) and muscle protein breakdown (MPB) are influenced through dietary protein intake and physical (in)activity, which it follows, regulate skeletal muscle (SKM) mass across the lifespan. Following consumption of dietary protein, the bio-availability of essential amino acids (EAA), and primarily leucine (LEU), drive a transient increase in MPS with an ensuing refractory period before the next MPS stimulation is possible (due to the "muscle full" state). At the same time, MPB is periodically constrained via reflex insulin actions. Layering exercise on top of protein intake increases the sensitivity of SKM to EAA, therefore extending the muscle full set-point (∼48 h), to permit long-term remodelling (e.g., hypertrophy). In contrast, ageing and physical inactivity are associated with a premature muscle full set-point in response to dietary protein/EAA and contractile activity. Of all the EAA, LEU is the most potent stimulator of the mechanistic target of rapamycin complex 1 (mTORC1)-signalling pathway, with the phosphorylation of mTORC1 substrates increasing ∼3-fold more than with all other EAA. Furthermore, maximal MPS stimulation is also achieved following low doses of LEU-enriched protein/EAA, negating the need for larger protein doses. As a result, LEU supplementation has been of long term interest to maximise muscle anabolism and subsequent net protein accretion, especially when in tandem with resistance exercise. This review highlights current knowledge vis-à-vis the anabolic effects of LEU supplementation in isolation, and in enriched protein/EAA sources (i.e., EAA and/or protein sources with added LEU), in the context of ageing, exercise and unloading states.

Rice Germ Attenuates Chronic Unpredictable Mild Stress-Induced Muscle Atrophy

Chronic stress leads to hypothalamic-pituitary-adrenal axis dysfunction, increasing cortisol levels. Glucocorticoids (GCs) promote muscle degradation and inhibit muscle synthesis, eventually causing muscle atrophy. In this study, we aimed to evaluate whether rice germ supplemented with 30% γ-aminobutyric acid (RG) attenuates muscle atrophy in an animal model of chronic unpredictable mild stress (CUMS). We observed that CUMS raised the adrenal gland weight and serum adrenocorticotropic hormone (ACTH) and cortisol levels, and these effects were reversed by RG. CUMS also enhanced the expression of the GC receptor (GR) and GC-GR binding in the gastrocnemius muscle, which were attenuated by RG. The expression levels of muscle degradation-related signaling pathways, such as the Klf15, Redd-1, FoxO3a, Atrogin-1, and MuRF1 pathways, were enhanced by CUMS and attenuated by RG. Muscle synthesis-related signaling pathways, such as the IGF-1/AKT/mTOR/s6k/4E-BP1 pathway, were reduced by CUMS and enhanced by RG. Moreover, CUMS raised oxidative stress by enhancing the levels of iNOS and acetylated p53, which are involved in cell cycle arrest, whereas RG attenuated both iNOS and acetylated p53 levels. Cell proliferation in the gastrocnemius muscle was reduced by CUMS and enhanced by RG. The muscle weight, muscle fiber cross-sectional area, and grip strength were reduced by CUMS and enhanced by RG. Therefore, RG attenuated ACTH levels and cortisol-related muscle atrophy in CUMS animals.

Ursodeoxycholic acid induces sarcopenia associated with decreased protein synthesis and autophagic flux

BACKGROUND

Skeletal muscle generates force and movements and maintains posture. Under pathological conditions, muscle fibers suffer an imbalance in protein synthesis/degradation. This event causes muscle mass loss and decreased strength and muscle function, a syndrome known as sarcopenia. Recently, our laboratory described secondary sarcopenia in a chronic cholestatic liver disease (CCLD) mouse model. Interestingly, the administration of ursodeoxycholic acid (UDCA), a hydrophilic bile acid, is an effective therapy for cholestatic hepatic alterations. However, the effect of UDCA on skeletal muscle mass and functionality has never been evaluated, nor the possible involved mechanisms.

METHODS

We assessed the ability of UDCA to generate sarcopenia in C57BL6 mice and develop a sarcopenic-like phenotype in C₂C₁₂ myotubes and isolated muscle fibers. In mice, we measured muscle strength by a grip strength test, muscle mass by bioimpedance and mass for specific muscles, and physical function by a treadmill test. We also detected the fiber's diameter and content of sarcomeric proteins. In C₂C₁₂ myotubes and/or isolated muscle fibers, we determined the diameter and troponin I level to validate the cellular effect. Moreover, to evaluate possible mechanisms, we detected puromycin incorporation, p70S6K, and 4EBP1 to evaluate protein synthesis and ULK1, LC3 I, and II protein levels to determine autophagic flux. The mitophagosome-like structures were detected by transmission electron microscopy.

RESULTS

UDCA induced sarcopenia in healthy mice, evidenced by decreased strength, muscle mass, and physical function, with a decline in the fiber's diameter and the troponin I protein levels. In the C₂C₁₂ myotubes, we observed that UDCA caused a reduction in the diameter and content of MHC, troponin I, puromycin incorporation, and phosphorylated forms of p70S6K and 4EBP1. Further, we detected increased levels of phosphorylated ULK1, the LC3II/LC3I ratio, and the number of mitophagosome-like structures. These data suggest that UDCA induces a sarcopenic-like phenotype with decreased protein synthesis and autophagic flux.

CONCLUSIONS

Our results indicate that UDCA induces sarcopenia in mice and sarcopenic-like features in C₂C₁₂ myotubes and/or isolated muscle fibers concomitantly with decreased protein synthesis and alterations in autophagic flux.

Impacts of microgravity on amino acid metabolism during spaceflight

Spaceflight exerts an extreme and unique influence on human physiology as astronauts are subjected to long-term or short-term exposure to microgravity. During spaceflight, a multitude of physiological changes, including the loss of skeletal muscle mass, bone resorption, oxidative stress, and impaired blood flow, occur, which can affect astronaut health and the likelihood of mission success. In vivo and in vitro metabolite studies suggest that amino acids are among the most affected nutrients and metabolites by microgravity (a weightless condition due to very weak gravitational forces). Moreover, exposure to microgravity alters gut microbial composition, immune function, musculoskeletal health, and consequently amino acid metabolism. Appropriate knowledge of daily protein consumption, with a focus on specific functional amino acids, may offer insight into potential combative and/or therapeutic effects of amino acid consumption in astronauts and space travelers. This will further aid in the successful development of long-term manned space mission and permanent space habitats.

The more you have, the more you lose: Muscle mass changes in trauma patients with prolonged hospitalizations

INTRODUCTION

Sarcopenia is a clinically relevant loss of muscle mass with implications of increased morbidity and mortality in adult trauma populations.  Our study aimed to evaluate loss of muscle mass change in adult trauma patients with prolonged hospital stays.

METHODS

Retrospective analysis using institutional trauma registry to identify all adult trauma patients with hospital length of stay >14 days admitted to our Level 1 center between 2010 and 2017. All CT images were reviewed, and cross-sectional area (cm²) of the left psoas muscle was measured at the level of the third lumbar vertebral body to determine total psoas area (TPA) and Total Psoas Index (TPI) normalized for patient stature.  Sarcopenia was defined as a TPI on admission below gender specific thresholds of 5.45(cm²/m²) in men and 3.85(cm²/m²) in women.  TPA, TPI, and rates of change in TPI were then evaluated and compared between sarcopenic and non-sarcopenic adult trauma patients.

RESULTS

There were 81 adult trauma patients who met inclusion criteria. The average change in TPA was -3.8 cm² and TPI was -1.3 cm². On admission, 23% (n = 19) of patients were sarcopenic while 77% (n = 62) were not. Non-sarcopenic patients had a significantly greater change in TPA (-4.9 vs. -0.31, p<0.0001), TPI (-1.7 vs. -0.13, p<0.0001), and rate of decrease in muscle mass (p = 0.0002). 37% of patients who were admitted with normal muscle mass developed sarcopenia during admission.  Older age was the only risk factor independently associated with developing sarcopenia (OR: 1.04, 95%CI 1.00-1.08, p = 0.045).

CONCLUSION

Over a third of patients with normal muscle mass at admission subsequently developed sarcopenia with older age as the primary risk factor. Patients with normal muscle mass at admission had greater decreases in TPA and TPI, and accelerated rates of muscle mass loss compared to sarcopenic patients.

Combining exercise, protein supplementation and electric stimulation to mitigate muscle wasting and improve outcomes for survivors of critical illness-The ExPrES study

BACKGROUND

Neuromuscular electrical stimulation (NMES) with high protein supplementation (HPRO) to preserve muscle mass and function has not been assessed in ICU patients. We compared the effects of combining NMES and HPRO with mobility and strength rehabilitation (NMES+HPRO+PT) to standardized ICU care.

OBJECTIVES

To assess the effectiveness of combined NMES+HPRO+PT in mitigating sarcopenia as evidenced by CT volume and cross-sectional area when compared to usual ICU care. Additionally, we assessed the effects of the combined therapy on select clinical outcomes, including nutritional status, nitrogen balance, delirium and days on mechanical ventilation.

METHODS

Participants were randomized by computer generated assignments to receive either NMES+HPRO+PT or standard care. Over 14 days the standardized ICU care group (N = 23) received usual critical care and rehabilitation while the NMES+HPRO+PT group (N = 16) received 30 min neuromuscular electrical stimulation of quadriceps and dorsiflexors twice-daily for 10 days and mean 1.3 ± 0.4 g/kg body weight of high protein supplementation in addition to standard care. Nonresponsive participants received passive exercises and, once responsive, were encouraged to exercise actively. Primary outcome measures were muscle volume and cross-sectional area measured using CT-imaging. Secondary outcomes included nutritional status, nitrogen balance, delirium and days on mechanical ventilation.

RESULTS

The NMES+HPRO+PT group (N = 16) lost less lower extremity muscle volume compared to the standard care group (N = 23) and had larger mean combined thigh cross-sectional area. The nitrogen balance remained negative in the standard care group, while positive on days 5, 9, and 14 in the NMES+HPRO+PT group. Standard care group participants experienced more delirium than the NMES+HPRO+PT group. No differences between groups when comparing length of stay or mechanical ventilation days.

CONCLUSIONS

The combination of neuromuscular electrical stimulation, high protein supplementation and mobility and strength rehabilitation resulted in mitigation of lower extremity muscle loss and less delirium in mechanically ventilated ICU patients.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT02509520. Registered July 28, 2015.

Chronic Stress Induces Type 2b Skeletal Muscle Atrophy via the Inhibition of mTORC1 Signaling in Mice

Chronic stress induces psychological and physiological changes that may have negative sequelae for health and well-being. In this study, the skeletal muscles of male C57BL/6 mice subjected to repetitive water-immersion restraint stress to model chronic stress were examined. In chronically stressed mice, serum corticosterone levels significantly increased, whereas thymus volume and bone mineral density decreased. Further, body weight, skeletal muscle mass, and grip strength were significantly decreased. Histochemical analysis of the soleus muscles revealed a significant decrease in the cross-sectional area of type 2b muscle fibers. Although type 2a fibers also tended to decrease, chronic stress had no impact on type 1 muscle fibers. Chronic stress increased the expression of REDD1, FoxO1, FoxO3, KLF15, Atrogin1, and FKBP5, but did not affect the expression of myostatin or myogenin. In contrast, chronic stress resulted in a decrease in p-S6 and p-4E-BP1 levels in the soleus muscle. Taken together, these results indicate that chronic stress promotes muscle atrophy by inhibiting mammalian targets of rapamycin complex 1 activity due to the upregulation of its inhibitor, REDD1.

Incidence of muscle wasting in the critically ill: a prospective observational cohort study

Loss of muscle mass occurs rapidly during critical illness and negatively affects quality of life. The incidence of clinically significant muscle wasting in critically ill patients is unclear. This study aimed to assess the incidence of and identify predictors for clinically significant loss of muscle mass in this patient population. This was a single-center observational study. We used ultrasound to determine the rectus femoris cross-sectional area (RFcsa) on the first and seventh day of ICU stay. The primary outcome was the incidence of significant muscle wasting. We used a logistic regression model to determine significant predictors for muscle wasting. Ultrasound measurements were completed in 104 patients. Sixty-two of these patients (59.6%) showed ≥ 10% decreases in RFcsa. We did not identify any predictor for significant muscle wasting, however, age was of borderline significance (p = 0.0528). The 28-day mortality rate was higher in patients with significant wasting, but this difference was not statistically significant (30.6% versus 16.7%; p = 0.165). Clinically significant muscle wasting was frequent in our cohort of patients. Patient age was identified as a predictor of borderline significance for muscle wasting. The results could be used to plan future studies on this topic.Trial registration: ClinicalTrials.gov NCT03865095, date of registration: 06/03/2019.

(-)-Epicatechin and its colonic metabolite hippuric acid protect against dexamethasone-induced atrophy in skeletal muscle cells

Cocoa flavanols have been shown to improve muscle function and may offer a novel approach to protect against muscle atrophy. Hippuric acid (HA) is a colonic metabolite of (-)-epicatechin (EPI), the primary bioactive compound of cocoa, and may be responsible for the associations between cocoa supplementation and muscle metabolic alterations. Accordingly, we investigated the effects of EPI and HA upon skeletal muscle morphology and metabolism within an in vitro model of muscle atrophy. Under atrophy-like conditions (24h 100μM dexamethasone (DEX)), C2C12 myotube diameter was significantly greater following co-incubation with either 25μM HA (11.19±0.39μm) or 25μM EPI (11.01±0.21μm) compared to the vehicle control (VC; 7.61±0.16μm, both P < .001). In basal and leucine-stimulated states, there was a significant reduction in myotube protein synthesis (MPS) rates following DEX treatment in VC (P = .024). Interestingly, co-incubation with EPI or HA abrogated the DEX-induced reductions in MPS rates, whereas no significant differences versus control treated myotubes (CTL) were noted. Furthermore, co-incubation with EPI or HA partially attenuated the increase in proteolysis seen in DEX-treated cells, preserving LC3 α/β II:I and caspase-3 protein expression in atrophy-like conditions. The protein content of PGC1α, ACC, and TFAM (regulators of mitochondrial function) were significantly lower in DEX-treated versus. CTL cells (all P < .050). However, co-incubation with EPI or HA was unable to prevent these DEX-induced alterations. For the first time we demonstrate that EPI and HA exert anti-atrophic effects on C2C12 myotubes, providing novel insight into the association between flavanol supplementation and favourable effects on muscle health.

The Resilience and the Subsequent Hospitalization of Older People with Different Frailty Status: A Prospective Cohort Study

OBJECTIVE

To evaluate the difference in resilience across frailty status by measuring the impact of unplanned hospitalization across people with different frailty condition on (1) 2-year changes in lean mass, physical performance, and quality of life, and (2) subsequent hospitalization.

DESIGN

A prospective cohort study.

SETTING AND PARTICIPANTS

Three thousand seventeen older people (73.7 ± 4.9 years) were recruited from the community in Hong Kong.

METHODS

Frailty status was defined using the Cardiovascular Health Study scale at baseline. Unplanned hospitalization between the 2 visits was obtained from the Hong Kong Hospital Authority. The interaction of frailty and hospitalization status on the 2-year changes in lean mass, physical performance, and quality of life were examined using 2-way analysis of covariance. Risk of subsequent hospitalization was estimated using Poisson regression. The effect of prolonged hospitalization, which was defined as 6 or more total hospitalized days, was also examined.

RESULTS

Upon unplanned hospitalization, frail older people had significantly augmented decline than prefrail and robust people in appendicular skeletal mass (-0.44 ± 0.08 kg), height-adjusted appendicular skeletal mas (-0.13 ± 0.03 kg/m²), 5-time chair-stand (4.79 ± 0.60 s), and mental health (-3.72 ± 0.88). The reduction increased with the length of hospitalization. Unplanned hospitalization conferred an augmented risk of subsequent hospitalization for those who were prefrail and frail (RR = 1.44, 95% confidence interval = 1.30-1.59 and RR = 1.69, 95% confidence interval = 1.45-1.97, respectively).

CONCLUSIONS AND IMPLICATIONS

The resilience of older people varies according to their frailty status, and the poor resilience may translate to a higher chance of having subsequent hospitalization for prefrail and frail people. These findings emphasized the importance of having the frailty screening in making posthospitalization plans for older people depending on their frailty status and encouraging prefrail and frail older people to build up their resilience.

From the Ketogenic Diet to the Mediterranean Diet: The Potential Dietary Therapy in Patients with Obesity after CoVID-19 Infection (Post CoVID Syndrome)

PURPOSE OF REVIEW

This review primarily examines the evidence for areas of consensus and on-going uncertainty or controversy about diet and physical exercise approaches for in the post-CoVID. We propose an ideal dietary and physical activity approach that the patient with obesity should follow after CoVID-19 infection in order to reduce the clinical conditions associated with post-CoVID syndrome.

RECENT FINDINGS

The CoVID-19 disease pandemic, caused by the severe acute respiratory syndrome coronavirus-2, has spread all over the globe, infecting hundreds of millions of individuals and causing millions of death. It is also known to be is associated with several medical and psychological complications, especially in patients with obesity and weight-related disorders who in general pose a significant global public health problem, and in specific affected individuals are on a greater risk of developing poorer CoVID-19 clinical outcomes and experience a higher rate of mortality. Little is still known about the best nutritional approach to be adopted in this disease especially in the patients post-CoVID syndrome. To the best of our knowledge, no specific nutritional recommendations exist to manage in the patients post-CoVID syndrome. We report a presentation of nutritional therapeutic approach based on a ketogenic diet protocol followed by a transition to the Mediterranean diet in patients post-infection by CoVID, combined to a physical activity program to address conditions associated with post-CoVID syndrome.

COVID's Impact on Non-communicable Diseases: What We Do Not Know May Hurt Us

PURPOSE OF REVIEW

In this review, we outline the impacts of the COVID-19 pandemic on non-communicable diseases around the world.

RECENT FINDINGS

The mechanisms of COVID-19's impact on non-communicable diseases are both direct and indirect. The direct mechanisms include direct vascular and myocardial injury as well as pancreatic injury increasing incidence of new-onset diabetes. Indirect effects of the pandemic on non-communicable disease include delayed presentation for acute illness including STEMI and the impact of social distancing and quarantine policies on socialization, mental health, physical activity, and the downstream health impacts of inactivity and deconditioning. International focus has been on disease variants, infection control and management, healthcare system, and resource utilization and infection incidence. However, the impact of this pandemic on non-communicable diseases has been largely overlooked but will manifest itself in the coming years to decades.

The Perceived Impact of COVID-19 on Functional Activities Among Canadian Education Workers: A Cross-Sectional Study

Objective

This cross-sectional study examined the self-perceived impact of the COVID-19 pandemic on 2,378 education workers in Ontario, Canada, during the second wave.

Methods

We examined six domains of functioning as per the short version of the World Health Organization Disability Assessment Schedule-2.0. Participants selected if their functioning had improved, remained unchanged or worsened during the pandemic for each item.

Results

Educational workers described a general worsening of functional activities since the beginning of the pandemic. Moderate-to-extreme challenges were reported for all six functional domains. These challenges appeared to aggravate functional challenges for workers with disability, as indicated by pre-existing work accommodations. Older participants reported worse mobility than younger participants; however, they appeared to have better coping skills in learning new tasks and maintaining friendships. Women were more likely to report difficulties in maintaining household responsibilities.

Conclusions

We consider the role of mental health challenges and pre-existing inequality as predictors of pandemic-related difficulties. Recommendations include more longitudinal research in this population and policymakers to incorporate a health promotion lens to support their education workers more proactively.

Reliability of Multifrequency Bioelectrical Impedance Analysis to Quantify Body Composition in Patients After Musculoskeletal Trauma

BACKGROUND

Changes in body composition, especially loss of lean mass, commonly occur in the orthopedic trauma population due to physical inactivity and inadequate nutrition. The purpose of this study was to assess inter-rater and intra-rater reliability of a portable bioelectrical impedance analysis (BIA) device to measure body composition in an orthopedic trauma population after operative fracture fixation. BIA uses a weak electric current to measure impedance (resistance) in the body and uses this to calculate the components of body composition using extensively studied formulas.

METHODS

Twenty subjects were enrolled, up to 72 hours after operative fixation of musculoskeletal injuries and underwent body composition measurements by two independent raters. One measurement was obtained by each rater at the time of enrollment and again between 1-4 hours after the initial measurement. Reliability was assessed using intraclass correlation coefficients (ICC) and minimum detectable change (MDC) values were calculated from these results.

RESULTS

Inter-rater reliability was excellent with ICC values for body fat mass (BFM), lean body mass (LBM), skeletal muscle mass (SMM), dry lean mass (DLM), and percent body fat (PBF) of 0.993, 0.984, 0.984, 0.979, and 0.986 respectively. Intra-rater reliability was also high for BFM, LBM, SMM, DLM, and PBF, at 0.994, 0.989, 0.990, 0.983, 0.987 (rater 1) and 0.994, 0.988, 0.989, 0.985, 0.989 (rater 2). MDC values were calculated to be 4.05 kg for BFM, 4.10 kg for LBM, 2.45 kg for SMM, 1.21 kg for DLM, and 4.83% for PBF.

CONCLUSION

Portable BIA devices are a versatile and attractive option that can reliably be used to assess body composition and changes in lean body mass in the orthopedic trauma population for both research and clinical endeavors. Level of Evidence: III.

Disuse-induced skeletal muscle atrophy in disease and non-disease states in humans: mechanisms, prevention, and recovery strategies

Decreased skeletal muscle contractile activity (disuse) or unloading leads to muscle mass loss, also known as muscle atrophy. The balance between muscle protein synthesis (MPS) and muscle protein breakdown (MPB) is the primary determinant of skeletal muscle mass. A reduced mechanical load on skeletal muscle is one of the main external factors leading to muscle atrophy. However, endocrine and inflammatory factors can act synergistically in catabolic states, amplifying the atrophy process and accelerating its progression. Additionally, older individuals display aging-induced anabolic resistance, which can predispose this population to more pronounced effects when exposed to periods of reduced physical activity or mechanical unloading. Different cellular mechanisms contribute to the regulation of muscle protein balance during skeletal muscle atrophy. This review summarizes the effects of muscle disuse on muscle protein balance and the molecular mechanisms involved in muscle atrophy in the absence or presence of disease. Finally, a discussion of the current literature describing efficient strategies to prevent or improve the recovery from muscle atrophy is also presented.

Nutritional indices at admission are associated with mortality rates of patients in the intensive care unit

BACKGROUND

Malnutrition is a common occurrence in critically ill patients, and has been related to poor prognosis in various diseases. Here, we assess the prognostic value of malnutrition using nutritional indices in intensive care units (ICU) patients.

METHODS

We retrieved information on 2060 patients from the Medical Information Mart for Intensive Care III, and randomized the patients into training and validation cohorts, at a ratio of 7:3. We estimated their nutritional indices using prognostic nutritional index (PNI), geriatric nutritional risk index (GNRI), and controlling nutritional status (CONUT) score. Both multivariate regression analysis and the Kaplan-Meier (KM) survival curve were used to examine the prognostic role of nutritional indices in ICU mortality. Then we evaluated the additional predictive significance of each nutritional index beyond the baseline model including conventional risk factors.

RESULTS

Multivariate regression analysis revealed that PNI, GNRI, and CONUT were independent predictors of in-hospital and 1-year mortality (all P < 0.001). KM curves showed higher 1-year mortality rates in having nutritional risk patients (PNI ≤ 38 or GNRI ≤ 98 or CONUT ≥ 2). Moreover, subgroup analyses revealed a significant association between each nutritional index and 1-year mortality in patients with different comorbidities. We also observed a pronounced additional impact on the predictive value of 1-year mortality when PNI, GNRI, and CONUT were separately added to the baseline model. The additional role of each nutritional index was further verified in the validation cohort.

CONCLUSIONS

Our results revealed that the nutritional indices at admission are significantly correlated with increased mortality rates in ICU adult patients.

Three Nutritional Indices Are Effective Predictors of Mortality in Patients With Type 2 Diabetes and Foot Ulcers

Introduction

Malnutrition has been associated with mortality in various diseases. This retrospective cohort study aimed to investigate the relationship between three nutritional indices and all-cause mortality in patients with diabetic foot ulcers (DFUs).

Materials and Methods

A total of 771 patients diagnosed with DFUs in the First Affiliated Hospital of Wenzhou Medical University from 2015 to 2019 were included in this retrospective cohort study. Patients were classified as high nutritional risk groups or low nutritional risk groups according to the optimal cut-off values of the geriatric nutritional risk index (GNRI), prognostic nutritional index (PNI), and controlling nutritional status (CONUT), respectively. The associations of three nutritional indices with all-cause mortality were evaluated by multivariable Cox regression analyses.

Results

Log-rank tests indicated that patients with high nutritional risk had lower overall survival rates (all p < 0.001). The multivariable Cox regression revealed that low GNRI (adjusted HR 2.01, 95% CI: 1.37–2.96, P < 0.001), low PNI (adjusted HR 2.04, 95% CI: 1.29–3.23, P = 0.002) and high CONUT (adjusted HRs 1.54, 95% CI: 1.07–2.23, P = 0.021) were independently associated with high all-cause mortality. In subgroup analyses, only GNRI predicted higher all-cause mortality in patients with severe DFUs, while all of the three indices persisted as independent prognostic factors in patients with no severe DFUs.

Discussion

The present study demonstrated that three nutritional indices were effective predictors of all-cause mortality in patients with DFUs. Routine screening for malnutrition using any of the three nutritional indices might be a simple and effective way to identify high-risk patients with DFUs. GNRI can be used as an independent prognostic indicator in patients with severe DFUs.

Effect of C60 Fullerene on Recovery of Muscle Soleus in Rats after Atrophy Induced by Achillotenotomy

Biomechanical and biochemical changes in the muscle soleus of rats during imitation of hind limbs unuse were studied in the model of the Achilles tendon rupture (Achillotenotomy). Oral administration of water-soluble C₆₀ fullerene at a dose of 1 mg/kg was used as a therapeutic agent throughout the experiment. Changes in the force of contraction and the integrated power of the muscle, the time to reach the maximum force response, the mechanics of fatigue processes development, in particular, the transition from dentate to smooth tetanus, as well as the levels of pro- and antioxidant balance in the blood of rats on days 15, 30 and 45 after injury were described. The obtained results indicate a promising prospect for C₆₀ fullerene use as a powerful antioxidant for reducing and correcting pathological conditions of the muscular system arising from skeletal muscle atrophy.

Sarcopenia and motoric cognitive risk syndrome: a moderated mediation model

Background

Sarcopenia has been identified as a risk factor for cognitive impairment, and motoric cognitive risk syndrome (MCR) is a recently defined pre-dementia syndrome. It is not known whether they are related. We aimed to investigate the association and potential pathways between sarcopenia and MCR in the community elderly by establishing a moderated mediation model.

Methods

846 community residents aged ≥ 60 years were recruited from May 2021 to September 2021 and had a comprehensive geriatric evaluation. The diagnosis of sarcopenia followed the criteria issued by the Asian Working Group for Sarcopenia in 2019. MCR was defined as subjective cognitive decline and slow gait. Apathy symptoms and physical activity were assessed by the Apathy Evaluation Scale (AES) and the International Physical Activity Questionnaire (IPAQ). Logistic regression and moderated mediation analyses were conducted to explore the association between the four.

Results

60 (7.1%) had MCR among 846 participants. After full adjustment, sarcopenia (odds ratio [OR] = 3.81, 95% confidence interval [CI] = 1.69–8.60, P = 0.001), AES score (OR = 1.09, 95% CI = 1.04–1.14, P < 0.001), and IPAQ level (OR = 0.43, 95% CI = 0.28–0.66, P < 0.001) were associated with MCR. Apathy partially mediated the relationship between sarcopenia and MCR. Physical activity played a moderation role in the indirect pathway of the mediation model. The increase in physical activity can alleviate the indirect effect of sarcopenia on MCR.

Conclusion

We established a moderated mediation model to uncover the underlying association mechanism of sarcopenia and MCR preliminarily. These findings suggest that attention should be paid to the management of apathy and physical activity in the context of sarcopenia to prevent early dementia actively. Further validation is needed in future longitudinal studies.

Systemic ablation of vitamin D receptor leads to skeletal muscle glycogen storage disorder in mice

BACKGROUND

Vitamin D deficiency leads to pathologies of multiple organ systems including skeletal muscle. Patients with severe vitamin D deficiency exhibit muscle weakness and are susceptible to frequent falls. Mice lacking a functional vitamin D receptor (VDR) develop severe skeletal muscle atrophy immediately after weaning. But the root cause of myopathies when vitamin D signalling is impaired is unknown. Because vitamin D deficiency leads to metabolic changes as well, we hypothesized that the skeletal muscle atrophy in mice lacking VDR may have a metabolic origin.

METHODS

We analysed wild-type (WT) mice as well as vitamin D receptor null (vdr-/-) mice for skeletal muscle proteostasis, energy metabolism, systemic glucose homeostasis, and muscle glycogen levels. Dysregulation of signalling pathways as well as the glycogen synthesis and utilization machinery were also analysed using western blots. qRT-PCR assays were performed to understand changes in mRNA levels.

RESULTS

Skeletal muscles of vdr-/- exhibited higher expression levels of muscle-specific E3 ubiquitin ligases and showed increased protein ubiquitination, suggesting up-regulation of protein degradation. Foxo1 transcription factor was activated in vdr-/- while Foxo3 factor was unaffected. Fasting protein synthesis as well as mTORC1 pathways were severely down-regulated in vdr-/- mice. Skeletal muscle ATP levels were low in vdr-/- (0.58 ± 0.18 μmol/mL vs. 1.6 ± 0.0.14 μmol/mL, P = 0.006), leading to increased AMPK activity. Muscle energy deprivation was not caused by decreased mitochondrial activity as we found the respiratory complex II activity in vdr-/- muscles to be higher compared with WT (0.29 ± 0.007 mU/μL vs. 0.16 ± 0.005 mU/μL). vdr-/- mice had lower fasting blood glucose levels (95 ± 14.5 mg/dL vs. 148.6 ± 6.1 mg/dL, P = 0.0017) while they exhibited hyperlactataemia (7.42 ± 0.31 nmol/μL vs. 4.95 ± 0.44 nmol/μL, P = 0.0032), suggesting systemic energy deficiency in these mice. Insulin levels in these mice were significantly lower in response to intraperitoneal glucose injection (0.69 ± 0.08 pg/mL vs. 1.11 ± 0.09 pg/mL, P = 0.024). Skeletal muscles of these mice exhibit glycogen storage disorder characterized by increased glycogen accumulation. The glycogen storage disorder in vdr-/- muscles is driven by increased glycogen synthase activity and decreased glycogen phosphorylase activity. Increased glycogenin expression supports higher levels of glycogen synthesis in these muscles.

CONCLUSIONS

The results presented show that lack of vitamin D signalling leads to a glycogen storage defect in the skeletal muscles, which leads to muscle energy deprivation. The inability of vdr-/- skeletal muscles to use glycogen leads to systemic defects in glucose homeostasis, which in turn leads to proteostasis defects in skeletal muscles and atrophy.

Motives and Barriers to Exercise Training during Hospitalization in Patients with Type 2 Diabetes: A Cross-Sectional Study

Background: Exercise training during hospitalization may prevent loss of physical function and hyperglycemia in patients with type 2 diabetes. The aim of this study was to assess motives and barriers to exercise training in hospitalized patients with type 2 diabetes. Methods: Data were collected using a questionnaire about motives and barriers to exercise training during hospitalization. Additional data for clinical characteristics of the participants were collected from patient records. Results: 79 patients participated (mean ± SD age 72 ± 12 years; 42% women), of whom 25% had a low level of education and 46% lived alone. The median (IQR) length of the stay was 6 (4–10) days. A total of 67% of the participants wished to be more physically active. Walking as exercise was preferred by 51%. The most frequently reported barriers to exercise training were bodily pain (48%) and dizziness (42%). Low vs. high level of education, and living alone vs. being married/living with a partner were associated with reduced odds of a wish to be more physically active, odds ratio (OR) 0.15 [95% CI 0.03; 0.76], p = 0.022, and 0.21 [0.05; 0.82], p = 0.025, respectively. Conclusion: Two out of three hospitalized patients with type 2 diabetes wished to be more physically active during admission. Bodily pain was a barrier to exercise training and needs attention in training programs. As a low level of education was associated with reduced odds of a wish to be more active, a strategy to include all patients in training programs which considers social inequality is needed.

Pandemic decrease of in-person physiotherapy as a factor in parent perceived decline in function in children with neuromuscular disorders

PURPOSE

Restrictions related to the COVID-19 pandemic can negatively affect patients who require physiotherapy. This study aimed to analyze the consequences of limited physiotherapy on the functional state of children with neuromuscular diseases (NMD). In addition, the caregivers' well-being and caregiver opinions on physiotherapy were analyzed.

METHODS

A questionnaire was shared with parents of children with NMD immediately after the COVID-19 lockdown. The survey included questions regarding the physical and mental condition of children and parents before the pandemic and during lockdown as well as their views on physiotherapy and telephysiotherapy. Statistical analysis was performed using the Wilcoxon Matched-Pairs Signed Ranks test, Spearman's Rank Correlation test, McNemar test, and Chi-square test.

RESULTS

Parents of 235 children participated in the study. Results indicated that children devoted more time to physiotherapy before the pandemic than during the lockdown period, which was true for those living in cities and the countryside. The functional state of 50.2% of the children deteriorated during the lockdown, in the opinion of their parents. Significant correlations were found between limited physiotherapy time and the deterioration of children's functional condition, ability to maintain a standing position, and increased anxiety. The majority of parents reported increased levels of fear and anxiety (72.8%), fatigue (67.7%), and pain (53.2%). In-person physiotherapy was rated significantly higher than telephysiotherapy by parents.

CONCLUSIONS

Limited access to physiotherapy and shorter therapy times may lead to functional deterioration in children with NMD, but this assumption needs to be objectively confirmed. According to the parents' opinions, telephysiotherapy is less beneficial than direct physiotherapy but may support therapy conducted directly by a physiotherapist. Results based on subjective parental opinions may be helpful in planning future projects.

Post-COVID-19 acute sarcopenia: physiopathology and management

In this review, we discuss the pathophysiologic and management aspects of acute sarcopenia in relation to SARS-CoV-2 infection. COVID-19 is as a multi-organ infectious disease characterized by a severe inflammatory and highly catabolic status, influencing the deep changes in the body build, especially the amount, structure, and function of skeletal muscles which would amount to acutely developed sarcopenia. Acute sarcopenia may largely impact patients’ in-hospital prognosis as well as the vulnerability to the post-COVID-19 functional and physical deterioration. The individual outcome of the COVID-19 and the degree of muscle mass and functional loss may be influenced by multiple factors, including the patient’s general pre-infection medical and functional condition, especially in older adults. This paper gathers the information about how the SARS-CoV-2 hyper-inflammatory involvement exacerbates the immunosenescence process, enhances the endothelial damage, and due to mitochondrial dysfunction and autophagy, induces myofibrillar breakdown and muscle degradation. The aftermath of these acute and complex immunological SARS-CoV-2-related phenomena, augmented by anosmia, ageusia and altered microbiota may lead to decreased food intake and exacerbated catabolism. Moreover, the imposed physical inactivity, lock-down, quarantine or acute hospitalization with bedrest would intensify the acute sarcopenia process. All these deleterious mechanisms must be swiftly put to a check by a multidisciplinary approach including nutritional support, early physical as well cardio-pulmonary rehabilitation, and psychological support and cognitive training. The proposed holistic and early management of COVID-19 patients appears essential to minimize the disastrous functional outcomes of this disease and allow avoiding the long COVID-19 syndrome.

Preoperative physical performance as predictor of postoperative outcomes in patients aged 65 and older scheduled for major abdominal cancer surgery: A systematic review

BACKGROUND

Abdominal cancer surgery is associated with considerable morbidity in older patients. Assessment of preoperative physical status is therefore essential. The aim of this review was to describe and compare the objective physical tests that are currently used in abdominal cancer surgery in the older patient population with regard to postoperative outcomes.

METHODS

Medline, Embase, CINAHL and Web of Science were searched until 31 December 2020. Non-interventional cohort studies were eligible if they included patients ≥65 years undergoing abdominal cancer surgery, reported results on objective preoperative physical assessment such as Cardiopulmonary Exercise Testing (CPET), field walk tests or muscle strength, and on postoperative outcomes.

RESULTS

23 publications were included (10 CPET, 13 non-CPET including Timed Up & Go, grip strength, 6-minute walking test (6MWT) and incremental shuttle walk test (ISWT)). Meta-analysis was precluded due to heterogeneity between study cohorts, different cut-off points, and inconsistent reporting of outcomes. In CPET studies, ventilatory anaerobic threshold and minute ventilation/carbon dioxide production gradient were associated with adverse outcomes. ISWT and 6MWT predicted outcomes in two studies. Tests addressing muscle strength and function were of limited value. No study compared different physical tests.

DISCUSSION

CPET has the ability to predict adverse postoperative outcomes, but it is time-consuming and requires expert assessment. ISWT or 6MWT might be a feasible alternative to estimate aerobic capacity. Muscle strength and function tests currently have limited value in risk prediction. Future research should compare the predictive value of different physical instruments with regard to postoperative outcomes in older surgical patients.

Effects of long-term immobilisation on endomysium of the soleus muscle in humans

NEW FINDINGS

What is the central question of this study? While muscle fibre atrophy in response to immobilisation has been extensively examined, intramuscular connective tissue, particularly endomysium, has been largely neglected: does endomysium content of the soleus muscle increase during bed rest? What is the main finding and its importance? Absolute endomysium content did not change, and previous studies reporting an increase are explicable by muscle fibre atrophy. It must be expected that even a relative connective tissue accumulation will lead to an increase in muscle stiffness.

ABSTRACT

Muscle fibres atrophy during conditions of disuse. Whilst animal data suggest an increase in endomysium content with disuse, that information is not available for humans. We hypothesised that endomysium content increases during immobilisation. To test this hypothesis, biopsy samples of the soleus muscle obtained from 21 volunteers who underwent 60 days of bed rest were analysed using immunofluorescence-labelled laminin γ-1 to delineate individual muscle fibres as well as the endomysium space. The endomysium-to-fibre-area ratio (EFAr, as a percentage) was assessed as a measure related to stiffness, and the endomysium-to-fibre-number ratio (EFNr) was calculated to determine whether any increase in EFAr was absolute, or could be attributed to muscle fibre shrinkage. As expected, we found muscle fibre atrophy (P = 0.0031) that amounted to shrinkage by 16.6% (SD 28.2%) on day 55 of bed rest. ENAr increased on day 55 of bed rest (P < 0.001). However, when analysing EFNr, no effect of bed rest was found (P = 0.62). These results demonstrate that an increase in EFAr is likely to be a direct effect of muscle fibre atrophy. Based on the assumption that the total number of muscle fibres remains unchanged during 55 days of bed rest, this implies that the absolute amount of connective tissue in the soleus muscle remained unchanged. The increased relative endomysium content, however, could be functionally related to an increase in muscle stiffness.

Blood Flow Restriction Training for the Shoulder: A Case for Proximal Benefit

BACKGROUND

Although blood flow restriction (BFR) is becoming increasingly popular in physical therapy and athletic training settings, little is known about the effects of BFR combined with low-intensity exercise (LIX) on muscles proximal to the site of occlusion.

HYPOTHESIS/PURPOSE

Determine whether LIX combined with BFR applied distally to the shoulder on the brachial region of the arm (BFR-LIX) promotes greater increases in shoulder lean mass, rotator cuff strength, endurance, and acute increases in shoulder muscle activation compared with LIX alone. We hypothesized that BFR-LIX would elicit greater increases in rotator cuff strength, endurance, and muscle mass. We also hypothesized that the application of BFR would increase EMG amplitude in the shoulder muscles during acute exercise.

STUDY DESIGN

Controlled laboratory study.

METHODS

32 healthy adults were randomized into 2 groups (BFR group, 13 men, 3 women; No-BFR group, 10 men, 6 women) who performed 8 weeks of shoulder LIX (2 times per week; 4 sets [30/15/15/fatigue]; 20% maximum) using common rotator cuff exercises (cable external rotation [ER], cable internal rotation [IR], dumbbell scaption, and side-lying dumbbell ER). The BFR group also trained with an automated tourniquet placed at the proximal arm (50% occlusion). Regional lean mass (dual-energy x-ray absorptiometry), isometric strength, and muscular endurance (repetitions to fatigue [RTF]; 20% maximum; with and without 50% occlusion) were measured before and after training. Electromyographic amplitude (EMGa) was recorded from target shoulder muscles during endurance testing. A mixed-model analysis of covariance (covaried on baseline measures) was used to detect within-group and between-group differences in primary outcome measures (α = .05).

RESULTS

The BFR group had greater increases in lean mass in the arm (mean ± 95% CI: BFR, 175 ± 54 g; No BFR, -17 ± 77 g; P < .01) and shoulder (mean ± 95% CI: BFR, 278 ± 90 g; No BFR, 96 ± 61 g; P < .01), isometric IR strength (mean ± 95% CI: BFR, 2.9 ± 1.3 kg; No BFR, 0.1 ± 1.3 kg; P < .01), single-set RTF volume (repetitions × resistance) for IR (~1.7- to 2.1-fold higher; P < .01), and weekly training volume (weeks 4, 6-8, ~5%-22%; P < .05). Acute occlusion (independent of group or timepoint) yielded increases in EMGa during RTF (~10%-20%; P < .05).

CONCLUSION

Combined BFR-LIX may yield greater increases in shoulder and arm lean mass, strength, and muscular endurance compared with fatiguing LIX alone during rotator cuff exercises. These findings may be due, in part, to a greater activation of shoulder muscles while using BFR.

CLINICAL RELEVANCE

The present study demonstrates that BFR-LIX may be a suitable candidate for augmenting preventive training or rehabilitation outcomes for the shoulder.

Muscle follistatin gene delivery increases muscle protein synthesis independent of periodical physical inactivity and fasting

Blocking of myostatin and activins effectively counteracts muscle atrophy. However, the potential interaction with physical inactivity and fasting in the regulation of muscle protein synthesis is poorly understood. We used blockade of myostatin and activins by recombinant adeno-associated virus (rAAV)-mediated follistatin (FS288) overexpression in mouse tibialis anterior muscle. To investigate the effects on muscle protein synthesis, muscles were collected 7 days after rAAV-injection in the nighttime or in the daytime representing high and low levels of activity and feeding, respectively, or after overnight fasting, refeeding, or ad libitum feeding. Muscle protein synthesis was increased by FS288 independent of the time of the day or the feeding status. However, the activation of mTORC1 signaling by FS288 was attenuated in the daytime and by overnight fasting. FS288 also increased the amount of mTOR colocalized with lysosomes, but did not alter their localization toward the sarcolemma. This study shows that FS288 gene delivery increases muscle protein synthesis largely independent of diurnal fluctuations in physical activity and food intake or feeding status, overriding the physiological signals. This is important for eg cachectic and sarcopenic patients with reduced physical activity and appetite. The FS288-induced increase in mTORC1 signaling and protein synthesis may be in part driven by increased amount of mTOR colocalized with lysosomes, but not by their localization toward sarcolemma.

The effect of indirect calorimetry guided isocaloric nutrition on mortality in critically ill patients-a systematic review and meta-analysis

Indirect calorimetry (IC)-guided nutrition might positively affect the clinical outcome of critically ill patients. In this systematic review and meta-analysis, our objective was to assess the benefit of isocaloric nutrition guided by IC, compared to hypocaloric nutrition, for critically ill patients admitted to the intensive care unit (ICU). We performed a systematic review of all randomized controlled trials published through January 2021, assessing the benefit of isocaloric nutrition guided by IC. The primary outcome was 28-day all-cause mortality. Secondary outcomes were ICU and 90-day all-cause mortality, rate of nosocomial infections, and adverse events. Four trials evaluating 1052 patients were included. Patients treated with isocaloric nutrition had a lower 28-day mortality rate (risk ratio (RR) 0.79, 95% confidence interval (CI) 0.63-0.99, P = 0.04). No between-group difference was found in ICU and 90-day mortality (RR 0.92, 95% CI 0.68-1.23, P = 0.56 and RR 0.88, 95% CI 0.72-1.07; P = 0.2, respectively) and in the rate of nosocomial infections (RR 1.15, 95% CI 0.77-1.72, P = 0.51). A pooled analysis of studies that evaluated the benefit of isocaloric nutrition guided by IC, for critically ill patients in the ICU, has shown reduced 28-day mortality. However, there was no difference in 90-day mortality and nosocomial infection rate.

6-Month Respiratory Outcomes and Exercise Capacity of COVID-19 Acute Respiratory Failure Patients Treated With CPAP

Background

COVID‐19 long‐term sequelae are ill‐defined since only a few studies have explored the long‐term consequences of this disease so far.

Aims

To evaluate the 6‐month respiratory outcome and exercise capacity of COVID‐19 acute respiratory failure (ARF) patients treated with continuous positive airway pressure (CPAP) during the first wave of the ongoing COVID‐19 pandemic.

Methods

A retrospective observational study included COVID‐19 patients with ARF. Interventions included CPAP during hospitalisation and 6‐month follow up. Frailty assessment was carried out through frailty index (FI), pO₂/FiO₂ during hospitalisation and at follow up, respiratory parameters, 6‐min walking test (6MWT) and the modified British Medical Research Council (mMRC) and Borg scale at follow up.

Results

More than half of the patients had no dyspnoea according to the mMRC scale. Lower in‐hospital pO₂/FiO₂ correlated with higher Borg scale levels after 6MWT (ρ 0.27; P 0.04) at the follow‐up visit. FI was positively correlated with length of hospitalisation (ρ 0.3; P 0.03) and negatively with the 6MWT distance walked (ρ −0.36; P 0.004).

Conclusions

Robust and frail patients with COVID‐19 ARF treated with CPAP outside the intensive care unit setting had good respiratory parameters and exercise capacity at 6‐month follow up, although more severe patients had slightly poorer respiratory performance compared with patients with higher PaO₂/FiO₂ and lower FI.

Blood Flow Restriction Combined with Electrical Stimulation Attenuates Thigh Muscle Disuse Atrophy

PURPOSE

This study aimed to investigate the effects of blood flow restriction (BFR) combined with electrical muscle stimulation (EMS) on skeletal muscle mass and strength during a period of limb disuse.

METHODS

Thirty healthy participants (22 ± 3 yr; 23 ± 3 kg·m-2) were randomly assigned to control (CON; n = 10), BFR alone (BFR; n = 10), or BFR combined with EMS (BFR + EMS; n = 10). All participants completed unloading of a single leg for 14 d, with no treatment (CON), or while treated with either BFR or BFR + EMS (twice daily, 5 d·wk-1). BFR treatment involved arterial three cycles of 5-min occlusion using suprasystolic pressure, each separated by 5 min of reperfusion. EMS (6 s on, 15 s off; 200 μs; 60 Hz; 15% maximal voluntary contraction [MVC]) was applied continuously throughout the three BFR cycles. Quadriceps muscle mass (whole-thigh lean mass via dual-energy x-ray absorptiometry and vastus lateralis [VL] muscle thickness via ultrasound) and strength (via knee extension MVC) were assessed before and after the 14-d unloading period.

RESULTS

After limb unloading, whole-thigh lean mass decreased in the control group (-4% ± 1%, P < 0.001) and BFR group (-3% ± 2%, P = 0.001), but not in the BFR + EMS group (-0.3% ± 3%, P = 0.8). VL muscle thickness decreased in the control group (-4% ± 4%, P = 0.005) and was trending toward a decrease in the BFR group (-8% ± 11%, P = 0.07) and increase in the BFR + EMS group (+5% ± 10%, P = 0.07). Knee extension MVC decreased over time (P < 0.005) in the control group (-18% ± 15%), BFR group (-10% ± 13%), and BFR + EMS group (-18% ± 15%), with no difference between groups (P > 0.5).

CONCLUSION

Unlike BFR performed in isolation, BFR + EMS represents an effective interventional strategy to attenuate the loss of muscle mass during limb disuse, but it does not demonstrate preservation of strength.

Social Distancing in Chronic Migraine during the COVID-19 Outbreak: Results from a Multicenter Observational Study

BACKGROUND

The restrictions taken to control the rapid spread of COVID-19 resulted in a sudden, unprecedented change in people's lifestyle, leading to negative consequences on general health. This study aimed to estimate the impact of such changes on migraine severity during 2020 March-May lockdown.

METHODS

Patients affected by migraine with or without aura, diagnosed by expert physicians, completed a detailed interview comprehensive of: assessment of migraine characteristics; measure of physical activity (PA) levels; measure of the intake frequency of main Italian foods; the Insomnia Severity Index (ISI) questionnaire investigating sleep disorders.

RESULTS

We included 261 patients with a mean age of 44.5 ± 12.3 years. During social distancing, 72 patients (28%) reported a headache worsening, 86 (33%) an improvement, and 103 (39%) a stable headache frequency. A significant decrease of the PA levels during COVID-19 quarantine in the whole study sample was observed (median total metabolic equivalent task (METs) decreased from 1170 to 510; p < 0.001). Additionally, a significant difference was reported on median ISI scores (from 7 to 8; p < 0.001), which were increased in patients who presented a stable or worsening headache.

CONCLUSIONS

Our study confirmed that the restrictions taken during the pandemic have affected the practice of PA levels and sleep quality in migraine. Hence, PA and sleep quality should be assessed to find strategies for an improvement in quality of life.

Mitochondrial Dysfunction Is a Common Denominator Linking Skeletal Muscle Wasting Due to Disease, Aging, and Prolonged Inactivity

Skeletal muscle is the most abundant tissue in the body and is required for numerous vital functions, including breathing and locomotion. Notably, deterioration of skeletal muscle mass is also highly correlated to mortality in patients suffering from chronic diseases (e.g., cancer). Numerous conditions can promote skeletal muscle wasting, including several chronic diseases, cancer chemotherapy, aging, and prolonged inactivity. Although the mechanisms responsible for this loss of muscle mass is multifactorial, mitochondrial dysfunction is predicted to be a major contributor to muscle wasting in various conditions. This systematic review will highlight the biochemical pathways that have been shown to link mitochondrial dysfunction to skeletal muscle wasting. Importantly, we will discuss the experimental evidence that connects mitochondrial dysfunction to muscle wasting in specific diseases (i.e., cancer and sepsis), aging, cancer chemotherapy, and prolonged muscle inactivity (e.g., limb immobilization). Finally, in hopes of stimulating future research, we conclude with a discussion of important future directions for research in the field of muscle wasting.

Skeletal Muscle Energetics and Mitochondrial Function Are Impaired Following 10 Days of Bed Rest in Older Adults

Background

Older adults exposed to periods of inactivity during hospitalization, illness, or injury lose muscle mass and strength. This, in turn, predisposes poor recovery of physical function upon reambulation and represents a significant health risk for older adults. Bed rest (BR) results in altered skeletal muscle fuel metabolism and loss of oxidative capacity that have recently been linked to the muscle atrophy program. Our primary objective was to explore the effects of BR on mitochondrial energetics in muscle from older adults. A secondary objective was to examine the effect of β-hydroxy-β-methylbuturate (HMB) supplementation on mitochondrial energetics.

Methods

We studied 20 older adults before and after a 10-day BR intervention, who consumed a complete oral nutritional supplement (ONS) with HMB (3.0 g/d HMB, n = 11) or without HMB (CON, n = 9). Percutaneous biopsies of the vastus lateralis were obtained to determine mitochondrial respiration and H₂O₂ emission in permeabilized muscle fibers along with markers of content. RNA sequencing and lipidomics analyses were also conducted.

Results

We found a significant up-regulation of collagen synthesis and down-regulation of ribosome, oxidative metabolism and mitochondrial gene transcripts following BR in the CON group. Alterations to these gene transcripts were significantly blunted in the HMB group. Mitochondrial respiration and markers of content were both reduced and H₂O₂ emission was elevated in both groups following BR.

Conclusions

In summary, 10 days of BR in older adults causes a significant deterioration in mitochondrial energetics, while transcriptomic profiling revealed that some of these negative effects may be attenuated by an ONS containing HMB.

The effect of acute sleep deprivation on skeletal muscle protein synthesis and the hormonal environment

Chronic sleep loss is a potent catabolic stressor, increasing the risk of metabolic dysfunction and loss of muscle mass and function. To provide mechanistic insight into these clinical outcomes, we sought to determine if acute sleep deprivation blunts skeletal muscle protein synthesis and promotes a catabolic environment. Healthy young adults (N = 13; seven male, six female) were subjected to one night of total sleep deprivation (DEP) and normal sleep (CON) in a randomized cross‐over design. Anabolic and catabolic hormonal profiles were assessed across the following day. Postprandial muscle protein fractional synthesis rate (FSR) was assessed between 13:00 and 15:00 and gene markers of muscle protein degradation were assessed at 13:00. Acute sleep deprivation reduced muscle protein synthesis by 18% (CON: 0.072 ± 0.015% vs. DEP: 0.059 ± 0.014%·h^‐1, p = .040). In addition, sleep deprivation increased plasma cortisol by 21% (p = .030) and decreased plasma testosterone by 24% (p = .029). No difference was found in the markers of protein degradation. A single night of total sleep deprivation is sufficient to induce anabolic resistance and a procatabolic environment. These acute changes may represent mechanistic precursors driving the metabolic dysfunction and body composition changes associated with chronic sleep deprivation.

Age-related degeneration of lumbar muscle morphology in healthy younger versus older men

AIM

The aim of this study was to evaluate age-related changes in lumbar paravertebral muscle (LPM) morphology in healthy younger and older adult men.

METHODS

T2-weighted axial MRI of the lumbar spine were obtained for 12 healthy older (67.3 ± 6.0 years) and younger (24.7 ± 3.1 years) men. Normalised muscle volume (NMV) and muscle fat infiltrate (MFI) were determined bilaterally for the psoas (PS), quadratus lumborum (QL), erector spinae (ES) and multifidus (MF). MANOVA was used to compare NMV and MFI between age groups. Follow-up ANOVA compared NMV and MFI for each muscle between age groups, with physical activity (PA) as a covariate. Stepwise regression was used to explore the association between muscle morphology.

RESULTS

NMV of the ES and QL were significantly lower in the older group (OG) (p = 0.040 and p < 0.001, respectively). MFI across all muscles was significantly greater in the OG (p < 0.001). PA did not moderate the relationship between aging and muscle degeneration. Non-dominant handgrip strength was associated with NMV (p = 0.003).

CONCLUSIONS

Age-related atrophy is muscle specific in the lumbar spine; changes in lumbar musculature is independent of PA, handgrip strength may reflect morphological changes in the postural muscles with age. This study supports establishing effective targeted exercise interventions in the lumbar musculature.