DXA-Derived Adiposity and Lean Indices for Management of Cardiometabolic and Musculoskeletal Frailty: Data Interpretation Tricks and Reporting Tips

The proper assessment and follow-up of obesity and sarcopenia are relevant for the proper management of the complications of cardiometabolic and musculoskeletal frailty. A total body dual-energy X-ray absorptiometry (DXA) scan should be systematically incorporated in the rehabilitative routine management of patients with obesity and sarcopenia. In the former patients, the total body DXA can be used to assess the fat tissue amount and distribution, while in the latter patients, it can be used to quantify the reduction of appendicular lean mass and to investigate the inter-limb lean mass asymmetry. This tutorial article provides an overview of different DXA-derived fat and lean indices and describes a step-by-step procedure on how to produce a complete DXA report. We suggest that the systematic incorporation of these indices into routine examinations of the patients with obesity and sarcopenia can be useful for identifying the patients at risk for cardiometabolic and neuromuscular impairment-related comorbidities and for evaluating the effectiveness of pharmacological and rehabilitative interventions.

The Dynamic Motor Control Index as a Marker of Age-Related Neuromuscular Impairment

Biomarkers that can identify age-related decline in walking function have potential to promote healthier aging by triggering timely interventions that can mitigate or reverse impairments. Recent evidence suggests that changes in neuromuscular control precede changes in walking function; however, it is unclear which measures are best suited for identifying age-related changes. In this study, non-negative matrix factorization of electromyography data collected during treadmill walking was used to calculate two measures of the complexity of muscle co-activations during walking for 36 adults: (1) the number of muscle synergies and (2) the dynamic motor control index. Study participants were grouped into young (18–35 years old), young-old (65–74 years old), and old–old (75+ years old) subsets. We found that the dynamic motor control index [χ2(2) = 9.41, p = 0.009], and not the number of muscle synergies [χ2(2) = 5.42, p = 0.067], differentiates between age groups [χ2(4) = 10.62, p = 0.031, Nagelkerke R2 = 0.297]. Moreover, an impairment threshold set at a dynamic motor control index of 90 (i.e., one standard deviation below the young adults) was able to differentiate between age groups [χ2(2) = 9.351, p = 0.009]. The dynamic motor control index identifies age-related differences in neuromuscular complexity not measured by the number of muscle synergies and may have clinical utility as a marker of neuromotor impairment.

Neuromuscular impairment after high-intensity running and vertical jump exercise protocols

BACKGROUND: Repetitive stretch-shortening cycle exercises generate high rates of mechanical work and consequently induce substantial muscular fatigue related to delayed neuromuscular functions. OBJECTIVE: To investigate the neuromuscular impairment after high-intensity exercise protocols involving different gravity loads in stretch-shortening cycle – running (RUN) and vertical jumps (VJ). METHODS: Twenty-two healthy men, divided into two groups, VJ and RUN participated in this study. The individuals performed a training session involving six bouts of 30 s of VJ or RUN. The isokinetic PM (PM) of the knee extensors and flexor muscles, rate of perceived exertion and delayed onset muscle soreness (DOMS) were evaluated at pre, post, 24 h and 48 h post-training. RESULTS: The concentric and eccentric PM of the extensor in the RUN group was reduced until 24 h, while in the VJ a decrement was observed until 48 h. Following running, the PM of the flexors decreased until 48 h, while for VJ there was an eccentric PM decrement at 48 h. The DOMS increased at the anterior thigh and only after VJ training for 48 h. CONCLUSION: Acute and delayed neuromuscular impairment may be observed after both exercise regimens, but high-intensity training using vertical jumps seems to induce a more pronounced impairment than running.

Investigating the Nonlinear Dynamics of Human Balance Using Topological Data Analysis

Understanding the mechanisms behind human balance has been a subject of interest as various postural instabilities have been linked to neuromuscular diseases (e.g., Parkinson's, multiple sclerosis, and concussion). This paper presents a method to characterize an individual's postural stability and estimate of their neuromuscular feedback control parameters. The method uses a generated topological mapping between a subject's experimental data and a dataset consisting of time-series realizations generated using an inverted pendulum mathematical model of upright balance. The performance of the method is quantified using a set of validation time-series realizations with known stability and neuromuscular control parameters. The method was found to have an overall sensitivity of 85.1% and a specificity of 91.9%. Furthermore, the method was most accurate when identifying limit cycle oscillations (LCOs) with a sensitivity of 91.1% and a specificity of 97.6%. Such a method has the capability of classifying an individual's stability and revealing possible neuromuscular impairment related to balance control, ultimately providing useful information to clinicians for diagnostic and rehabilitation purposes.

Analysis of postural balance in older adult practitioners and non-practitioners of Pilates

Background: The aging process causes physiological changes on psychic and functional aspects. In this sense, there is a decline in functional capacities such as strength, balance, proprioception and flexibility, caused by neuromuscular impairment. Aim: This study aimed to analyze the effect of Pilates practice on postural balance in older adults. Methods: The study included 34 elderly (25 female and 9 male) distributed into two groups: Practitioners and Control (non-Pilates practitioners). At first, a socio-demographic questionnaire was performed to characterize the sample. Following, the variables analyzed were the items and scores obtained in the BESTest sections, and the scores of the Mini-Mental and Baecke questionnaires (adapted version for older adults). Results: No statistical differences were found between Pilates and Non-Pilates groups for the following items: age, falls, height, body mass, BMI, Mini-Mental and Baecke. However, there was a statistical difference for BESTest, the Pilates group presented a higher overall score when compared to control group, representing a superior difference of 14.68%. Conclusion: We concluded that Pilates practice seems to promote benefits in dynamic balance in the elderly and can be an important tool to minimize the risk of falls.Keywords: balance, aging, older adults, Pilates.

Mutation in the MICOS subunit gene APOO (MIC26) associated with an X-linked recessive mitochondrial myopathy, lactic acidosis, cognitive impairment and autistic features

BackgroundMitochondria provide ATP through the process of oxidative phosphorylation, physically located in the inner mitochondrial membrane (IMM). The mitochondrial contact site and organising system (MICOS) complex is known as the ‘mitoskeleton’ due to its role in maintaining IMM architecture. APOO encodes MIC26, a component of MICOS, whose exact function in its maintenance or assembly has still not been completely elucidated.MethodsWe have studied a family in which the most affected subject presented progressive developmental delay, lactic acidosis, muscle weakness, hypotonia, weight loss, gastrointestinal and body temperature dysautonomia, repetitive infections, cognitive impairment and autistic behaviour. Other family members showed variable phenotype presentation. Whole exome sequencing was used to screen for pathological variants. Patient-derived skin fibroblasts were used to confirm the pathogenicity of the variant found in APOO. Knockout models in Drosophila melanogaster and Saccharomyces cerevisiae were employed to validate MIC26 involvement in MICOS assembly and mitochondrial function.ResultsA likely pathogenic c.350T>C transition was found in APOO predicting an I117T substitution in MIC26. The mutation caused impaired processing of the protein during import and faulty insertion into the IMM. This was associated with altered MICOS assembly and cristae junction disruption. The corresponding mutation in MIC26 or complete loss was associated with mitochondrial structural and functional deficiencies in yeast and D. melanogaster models.ConclusionThis is the first case of pathogenic mutation in APOO, causing altered MICOS assembly and neuromuscular impairment. MIC26 is involved in the assembly or stability of MICOS in humans, yeast and flies.