Respiratory Muscle Strength and Endurance Cut-Offs in Multiple Sclerosis

January 23, 2026 updated by: Mehmet Kaan ALTUNOK, Selcuk University

Optimal Cut-off Points of Respiratory Muscle Strength and Endurance to Discriminate Disability Status 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.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Study Type

Observational

Enrollment (Estimated)

40

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Locations

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

Adults aged 18 years and older diagnosed with multiple sclerosis who are clinically stable, able to communicate effectively, and eligible for respiratory muscle strength and endurance assessments.

Description

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.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Individuals with Multiple Sclerosis
Individuals diagnosed with multiple sclerosis undergoing assessment of respiratory muscle strength, respiratory muscle endurance, pulmonary function, walking performance, fatigue, and quality of life to determine optimal cut-off values for discriminating disability status.
Other: Respiratory Muscle Strength and Endurance Assessment
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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
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.
Baseline
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.
Baseline

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
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.
Baseline
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.
Baseline
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.
Baseline
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.
Baseline
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.
Baseline
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.
Baseline
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.
Baseline
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.
Baseline
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.
Baseline
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.
Baseline

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Selcuk University

Investigators

  • Study Chair: Haluk GÜMÜŞ, Prof. Dr., Selçuk University, Faculty of Medicine, Department of Neurology, Konya, Türkiye
  • Study Chair: Gülşah ÖZSOY, Assist. Prof. Dr., Selcuk University, Faculty of Health Sciences, Department of Physiotherapy and Rehabilitation, Konya, Türkiye
  • Study Chair: Zehra KORKUT, Assist. Prof. Dr., Selcuk University, Faculty of Health Sciences, Department of Physiotherapy and Rehabilitation, Konya, Türkiye
  • Study Chair: İsmail ÖZSOY, Assoc. Prof. Dr., Selcuk University, Faculty of Health Sciences, Department of Physiotherapy and Rehabilitation, Konya, Türkiye
  • Study Chair: Yasemin GEDİKLİ ERTÜRK, MSc. in PT, Selcuk University, Faculty of Health Sciences, Department of Physiotherapy and Rehabilitation, Konya, Türkiye
  • Study Chair: Tuğbanur BAYTOK, Dr., Selçuk University, Faculty of Medicine, Department of Neurology, Konya, Türkiye
  • Study Chair: Selen GÜR ÖZMEN, Assoc. Prof. Dr., Bahçeşehir University, Faculty of Health Sciences, Department of Physiotherapy and Rehabilitation, Istanbul, Türkiye
  • Study Chair: Cahit AYAN, Dr., Selçuk University, Faculty of Medicine, Department of Neurology, Konya, Türkiye

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

February 2, 2026

Primary Completion (Estimated)

June 30, 2026

Study Completion (Estimated)

July 30, 2026

Study Registration Dates

First Submitted

January 15, 2026

First Submitted That Met QC Criteria

January 23, 2026

First Posted (Actual)

January 28, 2026

Study Record Updates

Last Update Posted (Actual)

January 28, 2026

Last Update Submitted That Met QC Criteria

January 23, 2026

Last Verified

January 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • SelcukU_PT_MS_RESP_ENDURANCE_1

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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