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NCT Number: NCT07373704

Respiratory Muscle Strength and Endurance Cut-Offs in Multiple Sclerosis

Multiple sclerosis (MS) is a chronic and progressive autoimmune disease of the central nervous system characterized by inflammation, demyelination, and axonal degeneration. Depending on lesion localization and disease severity, individuals with MS may develop a wide range of neurological manifestations affecting motor and sensory functions.

Current evidence indicates that pulmonary function impairments may occur in individuals with MS even in the absence of overt respiratory symptoms. Compared with healthy individuals, people with MS have been reported to exhibit significantly reduced values in several respiratory parameters, particularly respiratory muscle strength. Moreover, these reductions appear to become more pronounced in parallel with increasing Expanded Disability Status Scale (EDSS) scores, regardless of disease duration. Indeed, previous studies have demonstrated that even individuals with MS who have mild disability levels (EDSS 0-4.5) experience significant declines in respiratory muscle strength, pulmonary function, and functional exercise capacity compared with healthy controls.

These findings suggest that the respiratory system may be affected not only in the advanced stages of MS but also during the early phases of the disease, with functional impairments emerging before clinically evident respiratory complaints arise. Despite this, the existing literature lacks studies that define clear, clinically applicable cut-off values for respiratory muscle strength and endurance that can discriminate disability levels in individuals with MS. This gap highlights the absence of objective criteria that clinicians can rely on for early detection and for planning targeted rehabilitation interventions.

The present study aims to address this gap by identifying optimal cut-off points for respiratory muscle strength and endurance in individuals with MS to facilitate early and accurate discrimination of disability status. By doing so, this research seeks to make an original contribution to the literature. The findings are expected to support the standardization of respiratory assessment processes in clinical practice, thereby improving patient quality of life and enhancing the efficiency of healthcare services. Furthermore, the results will provide a strong scientific basis for integrating respiratory function assessments into MS follow-up protocols and will offer a methodological framework for future intervention-oriented studies.

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Key information

Conditions

Multiple Sclerosis Autoimmune Diseases Autoimmune Diseases of the Nervous System Demyelinating Autoimmune Diseases, CNS Demyelinating Diseases Immune System Diseases Nervous System Diseases

Age range

18 year and older

Sex eligibility

All sexes

Study type

Observational

Primary location

Selcuk University Faculty of Medicine Hospital MS Life Center

Konya, Selcuklu, 42130, Turkey (Türkiye)

Location contact

Mehmet K ALTUNOK, PHD(c) in PT

CONTACT

[email protected]

5558175133 ext. +90

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Diagnosed with multiple sclerosis,
  • Aged 18 years or older,
  • Able to communicate effectively (able to speak, understand, read, and comprehend Turkish),
  • No relapse within the past three months,
  • Clinically stable for at least the past one month,
  • No participation in respiratory-based rehabilitation programs within the past six months,
  • Voluntary participation in the study.

Exclusion criteria

  • Presence of neurological disorders other than multiple sclerosis,
  • Presence of autoimmune diseases other than multiple sclerosis (e.g., rheumatoid arthritis, type 1 diabetes mellitus, systemic lupus erythematosus),
  • Presence of chronic cardiac or pulmonary diseases that may affect respiratory muscle strength or pulmonary function, such as chronic obstructive pulmonary disease (COPD), asthma, interstitial lung disease, or heart failure,
  • Pregnancy or breastfeeding,
  • Inability to comply with the testing procedures.

Treatment and study plan

Respiratory Muscle Strength and Endurance Assessment

Other

Participants will undergo a comprehensive assessment of respiratory muscle function, including respiratory muscle strength measured by maximal inspiratory and expiratory pressures and respiratory muscle endurance evaluated using an incremental threshold loading protocol. Pulmonary function will be assessed by spirometry. These assessments will be conducted to determine optimal cut-off values of respiratory muscle strength and endurance for discriminating disability status in individuals with multiple sclerosis and to examine their associations with clinical outcomes.

Primary outcomes

  1. Respiratory Muscle Strength (Maximal Inspiratory and Expiratory Pressures)

    Time frame: Baseline

    Respiratory muscle strength will be assessed by measuring maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) using an electronic mouth pressure device. Optimal cut-off values of respiratory muscle strength for discriminating disability status will be determined based on EDSS levels.

  2. Respiratory Muscle Endurance

    Time frame: Baseline

    Respiratory muscle endurance will be evaluated using an incremental threshold loading protocol. The highest load sustained for at least one minute and the endurance index will be used to determine optimal cut-off values for distinguishing disability status in individuals with multiple sclerosis.

Secondary outcomes

  1. Expanded Disability Status Scale (EDSS)

    Time frame: Baseline

    Disability status will be assessed using the Expanded Disability Status Scale (EDSS), a widely used measure of neurological disability in multiple sclerosis. The EDSS score ranges from 0 to 10, with higher scores indicating greater disability. A score of 0 represents normal neurological function, while a score of 10 indicates death due to multiple sclerosis. EDSS will be used as the reference standard for discrimination analyses.

  2. Pulmonary Function: Forced Expiratory Volume in 1 Second (FEV₁)

    Time frame: Baseline

    Forced Expiratory Volume in one second (FEV₁) will be assessed using spirometry and reported in liters and as a percentage of predicted values. FEV₁ reflects expiratory airflow and pulmonary function.

  3. Pulmonary Function: Forced Vital Capacity (FVC)

    Time frame: Baseline

    Forced Vital Capacity (FVC) will be measured using spirometry according to standardized American Thoracic Society and European Respiratory Society guidelines. FVC represents the maximum volume of air that can be forcibly exhaled after full inspiration and will be reported in liters and as a percentage of predicted values.

  4. Pulmonary Function: FEV₁/FVC Ratio

    Time frame: Baseline

    The ratio of Forced Expiratory Volume in one second to Forced Vital Capacity (FEV₁/FVC) will be calculated from spirometric measurements and used to assess ventilatory patterns.

  5. Pulmonary Function: Peak Expiratory Flow (PEF)

    Time frame: Baseline

    Peak Expiratory Flow (PEF) will be measured using spirometry and reported in liters per second to assess maximal expiratory flow capacity.

  6. Pulmonary Function: Forced Expiratory Flow at 25-75% of FVC (FEF₂₅-₇₅)

    Time frame: Baseline

    Forced Expiratory Flow between 25% and 75% of FVC (FEF₂₅-₇₅) will be assessed using spirometry as an indicator of mid-expiratory airflow and small airway function.

  7. Walking Speed (Timed 25-Foot Walk Test)

    Time frame: Baseline

    Walking speed will be evaluated using the Timed 25-Foot Walk test and examined in relation to respiratory muscle strength and endurance measures.

  8. Perceived Walking Ability (Multiple Sclerosis Walking Scale-12)

    Time frame: Baseline

    Perceived walking ability will be assessed using the Multiple Sclerosis Walking Scale-12 (MSWS-12), a 12-item patient-reported outcome measure of walking impairment in individuals with multiple sclerosis. The total score is transformed to a 0-100 scale, with higher scores indicating greater walking impairment and worse perceived walking ability. MSWS-12 scores will be analyzed as clinical correlates of respiratory muscle strength and endurance.

  9. Fatigue (Modified Fatigue Impact Scale)

    Time frame: Baseline

    Fatigue will be assessed using the Modified Fatigue Impact Scale (MFIS), a 21-item self-report questionnaire evaluating the impact of fatigue on physical, cognitive, and psychosocial functioning in individuals with multiple sclerosis. The total MFIS score ranges from 0 to 84, with higher scores indicating greater fatigue impact and worse fatigue-related outcomes. MFIS scores will be examined in relation to respiratory muscle strength and endurance.

  10. Quality of Life (Multiple Sclerosis International Quality of Life Questionnaire)

    Time frame: Baseline

    Quality of life will be assessed using the Multiple Sclerosis International Quality of Life questionnaire (MusiQoL-31), a 31-item self-administered, multidimensional instrument specifically developed for individuals with multiple sclerosis. MusiQoL scores are linearly transformed to a 0-100 scale, with higher scores indicating better quality of life. MusiQoL-31 scores will be analyzed as clinical correlates of respiratory muscle strength and endurance.

Study contacts

Contact information is provided by the study sponsor or research team.

Mehmet K ALTUNOK, PHD(c) in PT

CONTACT

[email protected]

5558175133 ext. +90

Sponsors and collaborators

Lead sponsor

Selcuk University

Other

Registry information

Official study title

Optimal Cut-off Points of Respiratory Muscle Strength and Endurance to Discriminate Disability Status in Multiple Sclerosis

Important dates

Study start
2026
Primary completion
2026
Study completion
2026
First posted
Jan 28, 2026
Registry last updated
Jan 28, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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