Reference Equations and Normative Data for Isometric Quadriceps and Handgrip Muscles STrength in Southern European Populations - RESTart: a Multicentre Study (RESTart)

This observational study aims to learn about peripheral muscle strength in healthy adults and people with chronic respiratory diseases. The study aims to develop reference data for quadriceps muscle strength and handgrip in adults living in Southern Europe and to assess whether these reference data can be used in people with chronic respiratory diseases.

The main questions it aims to answer are:

• What are the normal values for quadriceps and handgrip muscle strength in healthy adults aged 18-89 years living in Spain, Portugal and Italy?
• Can the reference values developed in healthy adults be applied to people with chronic respiratory diseases?

Participants will attend one study visit. During this visit, researchers will:

• Measure quadriceps muscle strength and handgrip.
• Collect information about age, sex, height, weight and other health characteristics.
• Perform simple functional tests related to mobility and physical performance.
• Ask participants to complete questionnaires about symptoms, physical activity and health-related quality of life.

Study Overview

• Status: Not yet recruiting
• Conditions: Healthy; Muscle Strength; Chronic Respiratory Diseases

Detailed Description

The RESTart study (Reference equations and normative data for isometric quadriceps and handgrip STrength in Southern European populations) is a multicentre observational cross-sectional study conducted in Spain, Portugal and Italy.

Peripheral muscle dysfunction, particularly reduced quadriceps muscle strength and handgrip, is common in people with chronic respiratory diseases and is associated with impaired physical function, hospitalisation and mortality. Accurate interpretation of muscle strength measurements requires population-specific reference equations and normative values. However, currently available reference data may not adequately represent Southern European populations.

The primary objective of the study is to develop reference equations and normative values for isometric quadriceps muscle strength and handgrip in healthy adults aged 18-89 years. A secondary objective is to validate/assess clinical application of these reference data in people with chronic respiratory diseases, including chronic obstructive pulmonary disease, interstitial lung disease, asthma, bronchiectasis and cystic fibrosis.

Healthy participants will be recruited from community settings using proportional stratification according to age, sex and country. Participants with chronic respiratory diseases will be recruited from collaborating clinical centres.

Primary outcomes are isometric quadriceps muscle strength and handgrip assessed using standardised dynamometry protocols. Secondary outcomes include functional capacity, mobility and balance, symptoms, physical activity, health-related quality of life, and anthropometric variables; lung function and laboratory parameters only when available from medical records.

The study is expected to provide robust reference equations and normative values for Southern European populations, supporting improved identification and monitoring of peripheral muscle dysfunction in both clinical practice and research.

• Study Type: Observational
• Enrollment (Estimated): 2815

Contacts and Locations

• Study Contact: Name: Nicola S. Diciolla, PT, Ph.D.; Phone Number: +34 918 85 48 28; Email: nicola.diciolla@uah.es
• Study Contact Backup: Name: Maria Torres-Lacomba, PT, Ph.D.; Phone Number: +34 918 85 48 28; Email: maria.torres@uah.es

Study Locations

• Spain
  • Madrid
    • Alcalá de Henares, Madrid, Spain, 28805
      • University of Alcala
      • Contact: Nicola S. Diciolla, PT, Ph.D.; Phone Number: +34 918 85 48 28; Email: nicola.diciolla@uah.es
      • Contact: Maria Torres-Lacomba, PT, Ph.D.; Phone Number: +34 918 85 48 28; Email: maria.torres@uah.es

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

Community-dwelling healthy adults and adults with chronic respiratory diseases recruited from participating centres in Spain, Portugal and Italy. Healthy participants will be recruited from the general population to develop reference equations and normative values for isometric quadriceps and handgrip strength. Participants with chronic respiratory diseases will be recruited from clinical settings to externally validate the developed reference equations and assess their clinical applicability.

Description

Healthy adults cohort

Inclusion Criteria:

• Age between 18-89 years.
• Spanish, Portuguese or Italian, or permanently resident in one of those countries for at least five years.
• Be community-dwelling (i.e., not hospitalised or institutionalised).
• Be functionally independent and capable of performing study assessments without assistance or limiting pain.
• Be able to follow verbal instructions in the local language (Spanish, Portuguese or Italian, as appropriate).
• Provide written informed consent.

Exclusion Criteria:

• Acute or chronic musculoskeletal conditions affecting strength: recent fractures, severe osteoarthrosis, ligament injury, acute tendinitis in hands/knee areas, among others.
• Recent surgery (e.g., within the past six months) in upper or lower limbs.
• Neuromuscular disorders: Parkinson, multiple sclerosis, stroke, peripheral neuropathies, among others.
• Non-communicable diseases affecting strength or functional status: active cancer, any unstable heart diseases; any CRD; active rheumatological diseases, obesity (BMI≥30kg/m2), uncontrolled metabolic diseases, among others (not included: controlled dyslipidaemia or arterial hypertension).
• Cognitive impairments (e.g., dementia) or psychiatric disorders impairing following instructions.
• Aid devices for walking or compromised functional mobility.
• Moderate-to-severe pain during the assessment (VAS ≥4).
• Systemic corticosteroids use for over one week in the previous six months (i.e., risk of muscle atrophy in type II fibres; or steroid myopathy).
• Muscle relaxants use during the previous week (i.e., risk of not full muscle activation).
• Pregnancy and postpartum (i.e., potential physiological changes which may alter muscle strength).
• Current smoking.

Chronic respiratory disease cohort

Inclusion criteria:

• Aged 18-89 years.
• Clinical diagnosis of a chronic respiratory disease (e.g., COPD, interstitial lung disease, asthma, bronchiectasis, cystic fibrosis), confirmed by spirometry or clinical records.
• Clinically stable (no exacerbation within the past four weeks).
• Capacity to provide informed consent and complete study procedures.

Exclusion criteria:

• Coexisting conditions which meet the exclusion criteria defined for healthy participants, apart from chronic respiratory diseases.
• Current requirement for hospitalisation or acute medical management.
• Severe functional limitation preventing completion of assessments.

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort
Healthy adults cohort; Healthy community-dwelling adults aged 18-89 years recruited in Spain, Portugal and Italy for the development of reference equations and normative data for isometric quadriceps strength and handgrip.
Chronic respiratory disease cohort; Adults with stable chronic respiratory diseases recruited for external validation/clinical application of the developed reference equations and normative values. Eligible conditions include chronic obstructive pulmonary disease, interstitial lung disease, asthma, bronchiectasis and cystic fibrosis.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Isometric quadriceps muscle strength	Quadricpes maximum voluntary contraction measured using a handheld dynamometer according to the standardised RESTart protocol. Strength will be recorded as the highest value obtained during the assessment and expressed in kilograms-force (kgf).	Day 1
Handgrip	Handgrip mMaximum voluntary contraction measured using a hydraulic handgrip dynamometer according to standardised assessment procedures. Strength will be recorded as the highest value obtained during the assessment and expressed in kilograms-force (kgf).	Day 1

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Five-repetition sit-to-stand test	Functional capacity assessed by the time required to complete five sit-to-stand repetitions according to standardised procedures. Results will be expressed in seconds. Lower values indicate better lower-limb functional capacity.	Day 1
One-minute sit-to-stand test	Functional capacity assessed as the number of sit-to-stand repetitions completed in one minute according to standardised procedures. Higher values indicate better functional exercise capacity.	Day 1
Timed Up and Go test	Mobility and dynamic balance assessed using the Timed Up and Go test. Results will be expressed in seconds. Lower values indicate better mobility and dynamic balance.	Day 1
Modified Medical Research Council dyspnoea scale	Dyspnoea severity assessed using the modified Medical Research Council dyspnoea scale. Scores range from 0 to 4, with higher scores indicating greater breathlessness.	Day 1
Modified Borg dyspnoea scale	Perceived breathlessness assessed using the modified Borg dyspnoea scale. Scores range from 0 to 10, with higher scores indicating greater breathlessness.	Day 1
Dyspnoea-12	Dyspnoea assessed using the Dyspnoea-12 questionnaire. The total score ranges from 0 to 36, with higher scores indicating more severe breathlessness.	Day 1
Functional Assessment of Chronic Illness Therapy-Fatigue	Fatigue assessed using the Functional Assessment of Chronic Illness Therapy-Fatigue questionnaire. Scores range from 0 to 52, with higher scores indicating less fatigue.	Day 1
EuroQol 5-Dimension 5-Level	Health-related quality of life assessed using the EuroQol 5-Dimension 5-Level (EQ-5D) questionnaire. The index score will be calculated according to the appropriate national value set. Higher scores indicate better health status. Self-rated health assessed using the EQ-5D Visual Analogue Scale. Scores range from 0 to 100, with higher scores indicating better perceived health.	Day 1
St George's Respiratory Questionnaire	Respiratory-specific health-related quality of life assessed using the St George's Respiratory Questionnaire. Scores range from 0 to 100, with higher scores indicating worse respiratory health-related quality of life.	Day 1
International Physical Activity Questionnaire-short form	Physical activity assessed using the International Physical Activity Questionnaire-short form. Results will be expressed as minutes per week spent in vigorous/moderate/total physical activity, time per week spent walking and hours per day spent in sedentary behaviour (sitting).	Day 1
Mini Nutritional Assessment-short form	Nutritional status assessed using the Mini Nutritional Assessment-short form. Scores range from 0 to 14, with higher scores indicating better nutritional status.	Day 1

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Age	Participant age recorded in completed years.	Day 1
Weight	Participant weight recorded in kilograms.	Day 1
Height	Participant height recorded in metres.	Day 1
Body mass index	Body mass index calculated as weight divided by height squared.	Day 1
Sex	Participant biological sex recorded as female or male.	Day 1
Forced expiratory volume in one second percentage predicted (FEV1%pred)	Lung function measured by spirometry when available from medical records.	Day 1
Forced vital capacity percentage predicted (FVC%pred)	Lung function measured by spirometry when available from medical records.	Day 1
Systemic inflammation markers	CRP, IL-6, eosinophils, fibrinogen, neutrophil elastase, ESR, KL-6, SP-D, FeNO, IgE, calprotectin, if available, from medical records.	Day 1
Charlson Comorbidity Index	Comorbidity burden assessed using the Charlson Comorbidity Index. Higher scores indicate greater comorbidity burden.	Day 1
Anatomical Therapeutic Chemical (ATC) Classification System	Current medication use classified according to the Anatomical Therapeutic Chemical (ATC) Classification System.	Day 1
Smoking Exposure (pack-year index)	Lifetime smoking exposure quantified using the pack-year index, calculated from self-reported smoking history.	Day 1
Alcohol Use Disorders Identification Test-Consumption	Alcohol consumption assessed using the Alcohol Use Disorders Identification Test-Consumption (AUDIT-C). Higher scores indicate greater alcohol consumption and increased risk of hazardous drinking.	Day 1

Collaborators and Investigators

• Sponsor: University of Alcala

Study record dates

Study Major Dates

• Study Start (Estimated): June 1, 2026
• Primary Completion (Estimated): June 1, 2029
• Study Completion (Estimated): June 1, 2030

Study Registration Dates

• First Submitted: May 31, 2026
• First Submitted That Met QC Criteria: May 31, 2026
• First Posted (Actual): June 5, 2026

Study Record Updates

• Last Update Posted (Actual): June 8, 2026
• Last Update Submitted That Met QC Criteria: June 4, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: Asthma; COPD; Pulmonary rehabilitation; Cystic fibrosis; Bronchiectasis; Interstitial lung disease; Muscle strength; Healthy adults; Reference equations; Handgrip; Reference values; Quadriceps strength; Chronic respiratory diseases; Normative data; Dynamometrry; Peripheral muscle dysfunction; Southern Europe
• Additional Relevant MeSH Terms: Pathologic Processes; Chronic Disease; Disease Attributes; Genetic Diseases, Inborn; Immune System Diseases; Respiratory Tract Diseases; Digestive System Diseases; Lung Diseases; Infant, Newborn, Diseases; Bronchial Diseases; Lung Diseases, Obstructive; Respiratory Hypersensitivity; Hypersensitivity, Immediate; Hypersensitivity; Pancreatic Diseases; Congenital, Hereditary, and Neonatal Diseases and Abnormalities; Pathological Conditions, Signs and Symptoms; Pulmonary Disease, Chronic Obstructive; Asthma; Lung Diseases, Interstitial; Cystic Fibrosis; Bronchiectasis
• Other Study ID Numbers: CEIP/2025/6/174

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: De-identified individual participant data underlying the results reported in publications arising from this study, including demographic characteristics, anthropometric measurements, peripheral muscle strength assessments, functional capacity outcomes, patient-reported outcomes/questionnaire scores, and other variables collected according to the study protocol, upon reasonable request to the principal investigator.
• IPD Sharing Time Frame: Beginning 12 months following publication of the primary study results and ending 5 years after publication.
• IPD Sharing Access Criteria: Researchers who provide a methodologically sound proposal for secondary analyses consistent with the aims of the study (e.g., individual participant data meta-analyses, validation studies, methodological research, and other scientifically justified secondary analyses).
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF; ANALYTIC_CODE

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No