Muscle architecture and its relationship with lower extremity muscle strength in multiple sclerosis

White matter volume and microstructural integrity are associated with fatigue in relapsing multiple sclerosis

Multiple sclerosis (MS) is a prevalent neurological disorder marked by inflammation and demyelination, with fatigue being one of the most reported and debilitating symptoms. While fatigue occurs across various neurological conditions and even in healthy individuals, the specific mechanisms contributing to fatigue in each context remain unclear. In this study, we conducted a cross-sectional analysis involving 32 people with relapsing MS (PwRMS) and 29 healthy controls who reported fatigue. Participants underwent MRI scans, including T1-weighted and diffusion-weighted imaging. Additionally, the Modified Fatigue Impact Scale was utilized. We employed Bayesian LASSO and Spike-and-Slab LASSO regression models to investigate the hypothesis that fatigue correlates differently with brain structures in PwRMS. Our findings revealed brain regions associated with general and cognitive fatigue. In particular, reduced white matter volume and compromised microstructural integrity in specific areas-such as the cingulate gyrus, inferior frontal gyrus, and the banks of the superior temporal sulcus-showed significant associations with fatigue scores in PwRMS. These results suggest that alterations in specific brain regions may play a critical role in the clinical manifestation of fatigue in MS. Understanding these insights could help differentiate general mechanisms of fatigue from those affecting people with relapsing MS, which may guide future therapeutic strategies.

Experimental autoimmune encephalomyelitis causes skeletal muscle dysfunction in mice

Multiple sclerosis (MS) is a neuroinflammatory disease affecting the brain and spinal cord and characterized by demyelination, neurodegeneration and chronic inflammation. More than 90% of people with MS present with peripheral muscle dysfunction and a progressive decline in mobility. Current treatments attenuate the inflammatory processes but do not prevent disease progression. Therefore, there remains an unmet medical need for new and/or additional therapeutic approaches that specifically improve muscle function in this patient population. The development of novel treatments targeting skeletal muscle dysfunction in MS will depend on suitable preclinical models that can mimic the human musculoskeletal manifestations of MS. Using a non-invasive approach to assess muscle function, we demonstrate in vivo that Experimental Autoimmune Encephalomyelitis (EAE) impairs skeletal muscle strength. Our data reveal a 28.3% (p < 0.0001) lower muscle force in animals with EAE compared to healthy control mice during electrically evoked tetanic muscle contractions that occur at intervals of 0.25 s and thus mimic fatiguing tasks. As we conduct force measurements by direct transcutaneous muscle stimulation in anesthetized animals, our setup allows for the repeated evaluation of muscle function, and in the absence of primary fatigue or reduced nerve input which constitute important confounding factors in MS. Taken together, our data highlight important similarities between MS in humans and EAE in mice with regards to skeletal muscle contractile impairments, and provide first evidence for a non-invasive in-vivo setup that will enable the preclinical profiling of novel drug candidates directed at specifically improving muscle function in MS.

The therapeutic potential of exercise for improving mobility in multiple sclerosis

Multiple sclerosis (MS) is a chronic autoimmune disease characterized by inflammation and demyelination in the central nervous system (CNS) with subsequent axonal and neuronal degeneration. These changes are associated with a broad range of symptoms including skeletal muscle dysfunction. Importantly, musculoskeletal impairments manifest in various ways, compromise the quality of life and often precede the later development of mobility disability. As current standard disease modifying therapies for MS predominantly act on neuroinflammation, practitioners and patients face an unmet medical need for adjunct therapies specifically targeting skeletal muscle function. This review is intended to detail the nature of the skeletal muscle dysfunctions common in people with MS (pwMS), describe underlying intramuscular alterations and outline evidence-based therapeutic approaches. Particularly, we discuss the emerging role of aerobic and resistance exercise for reducing the perception of fatigue and increasing muscle strength in pwMS. By integrating the most recent literature, we conclude that both exercise interventions should ideally be implemented as early as possible as they can address MS-specific muscle impairments. Aerobic exercise is particularly beneficial for pwMS suffering from fatigue and metabolic impairments, while resistance training efficiently counters muscle weakness and improves the perception of fatigue. Thus, these lifestyle interventions or possible pharmacological mimetics have the potential for improving the general well-being and delaying the functional declines that are relevant to mobility.

Blood Flow Restriction and Veterans With Multiple Sclerosis and Advanced Disability: Protocol for a Randomized Controlled Trial

OBJECTIVE

The purpose of this study will be to determine the efficacy of low intensity lower extremity resistance training with and without blood flow restriction (BFR) on quadriceps muscle strength and thickness in veterans with advanced multiple sclerosis (MS).

METHODS

This will be an assessor-blinded, 2-group (1 to 1 allocation) randomized controlled trial targeting an enrollment of 58 participants with advanced MS as defined by Patient-Determined Disease Steps scale levels 4 to 7. Both groups will complete 10 weeks of twice weekly low-load resistance training (20%-30% of 1-repetition max) targeting knee and hip extension, knee flexion, and ankle plantarflexion. The intervention group will perform all training using BFR, with limb occlusion pressures between 60% and 80% of maximal limb occlusion pressure. Primary outcomes will be quadriceps muscle strength and thickness. Secondary outcomes will include knee flexion and ankle plantarflexion strength, functional mobility, physical activity, and patient-reported measures. All outcomes will be assessed at baseline before the intervention, immediately after the intervention, and at a 2-month follow-up assessment. The change between groups postintervention and after the 2-month follow-up will be reported for all outcomes. All analyses will assume a 2-sided test of hypothesis (α = .05).

IMPACT

There is very little evidence for the efficacy of exercise interventions in people with MS who have advanced mobility disability. Resistance training with BFR may be an important approach for people with advanced MS who may not tolerate more conventional, moderate-to-high intensity resistance training. The results of this study will inform clinicians regarding exercise decisions for people with advanced MS and future investigations on the role of BFR in people with MS.

The Association of Age, Sex, and BMI on Lower Limb Neuromuscular and Muscle Mechanical Function in People with Multiple Sclerosis

(1) Background: The countermovement jump (CMJ) on a force plate could be a sensitive assessment for detecting early lower-limb muscle mechanical deficits in the early stages of multiple sclerosis (MS). CMJ performance is known to be influenced by various anthropometric, physiological, and biomechanical factors, mostly investigated in children and adult athletes. Our aim was to investigate the association of age, sex, and BMI with muscle mechanical function using CMJ to provide a comprehensive overview of lower-limb motor function in people with multiple sclerosis (pwMS). (2) Methods: A cross-sectional study was conducted with pwMS (N = 164) and healthy controls (N = 98). All participants performed three maximal CMJs on a force plate. Age, sex, and BMI were collected from all participants. (3) Results: Significant age, sex, and BMI effects were found for all performance parameters, flight time, and negative and positive power for pwMS and HC, but no significant interaction effects with the group (pwMS, HC) were detected. The highest significant effects were found for sex on flight time (η2 = 0.23), jump height (η2 = 0.23), and positive power (η2 = 0.13). PwMS showed significantly lower CMJ performance compared to HC in middle-aged (31-49 years), with normal weight to overweight and in both women and men. (4) Conclusions: This study showed that age, sex, and BMI are associated with muscle mechanical function in pwMS and HC. These results may be useful in developing reference values for CMJ. This is a crucial step in integrating CMJ into the diagnostic assessment of people with early MS and developing individualized and effective neurorehabilitative therapy.

Architectural Ultrasound Pennation Angle Measurement of Lumbar Multifidus Muscles: A Reliability Study

The pennation angle has been shown to be a relevant parameter of muscle architecture. This parameter has not previously been measured in the lumbar multifidus musculature, and it is for this reason that it has been considered of great interest to establish an assessment protocol to generate new lines of research in the future. Objective: The objective of this study was to establish a protocol for measuring the pennation angle of the multifidus muscles, with a study of intra-rater and interrater reliability values. Design: This was a reliability study following the recommendations of the Guidelines for Reporting Reliability and Agreement Studies (GRRAS). Setting: The study was carried out at University of Alcalá, Department of Physiotherapy. Subjects: Twenty-seven subjects aged between 18 and 55 years were recruited for this study. Methods: Different ultrasound images of the lumbar multifidus musculature were captured. Subsequently, with the help of ImageJ software, the pennation angle of this musculature was measured. Finally, a complex statistical analysis determined the intra- and interrater reliability. Results: The intra-rater reliability of the pennation angle measurement protocol was excellent for observer 1 in the measurement of the left-sided superficial multifidus 0.851 (0.74, 0.923), and for observer 2 in the measurement of the right-sided superficial 0.711 (0.535, 0.843) and deep multifidus 0.886 (0.798, 0.942). Interrater reliability was moderate to poor, and correlation analysis results were high for thickness vs. pennation angle. Conclusions: The designed protocol for ultrasound measurement of the pennation angle of the lumbar multifidus musculature has excellent intra-rater reliability values, supporting the main conclusions and interpretations. Normative ranges of pennation angles are reported. High correlation between variables is described.

The pathophysiology of motor fatigue and fatigability in multiple sclerosis

Multiple Sclerosis (MS) is a heterogeneous immune mediated disease of the central nervous system (CNS). Fatigue is one of the most common and disabling symptom of MS. It interferes with daily activities on the level of cognition and motor endurance. Motor fatigue can either result from lesions in cortical networks or motor pathways (“primary fatigue”) or it may be a consequence of detraining with subsequent adaptions of muscle and autonomic function. Programmed exercise interventions are used frequently to increase physical fitness in MS-patients. Studies investigating the effects of training on aerobic capacity, objective endurance and perceived fatigability have yielded heterogenous results, most likely due to the heterogeneity of interventions and patients, but probably also due to the non-uniform pathophysiology of fatigability among MS-patients. The aim of this review is to summarize the current knowledge on the pathophysiology of motor fatigability with special reference to the basic exercise physiology that underlies our understanding of both pathogenesis and treatment interventions.