Ultrasound Muscle Biomarkers as Predictors of Isometric Quadriceps Muscle Strength and Handgrip in Healthy Adults: an Observational Study (MUSCLE-US)

This observational study aims to determine whether ultrasound-derived muscle biomarkers can predict isometric quadriceps muscle strength and handgrip in healthy adults aged 18-89 years.

The main questions it aims to answer are:

• Which ultrasound muscle characteristics are associated with isometric quadriceps muscle strength and handgrip?
• Can ultrasound-derived biomarkers be used to develop predictive models of muscle strength in healthy adults?

Participants will undergo:

• Ultrasound assessment of the quadriceps and forearm flexor muscles;
• Measurement of isometric quadriceps muscle strength and handgrip using standardized dynamometry protocols;
• Assessment of functional capacity, mobility and balance;
• Completion of questionnaires related to health status, physical activity, nutrition, fatigue and health-related quality of life.

The study will also assess the reliability of ultrasound measurements and explore the relationship between ultrasound variables, muscle strength, physical function and health-related factors.

Study Overview

• Status: Not yet recruiting
• Conditions: Muscle Strength; Healthy Adult; Skeletal Muscle Ultrasound

Detailed Description

Peripheral muscle strength is an important determinant of physical function, independence and health outcomes. Reduced quadriceps muscle strength and handgrip have been associated with functional limitations, frailty, hospitalization and mortality. Although muscle ultrasound is increasingly used to assess muscle morphology and quality, its ability to predict muscle strength remains incompletely understood.

The MUSCLE-US study is a monocentre observational study designed to investigate the relationship between ultrasound-derived muscle biomarkers and isometric quadriceps muscle strength and handgrip in healthy adults. Participants aged 18-89 years will be recruited from community settings and stratified by age and sex.

Ultrasound assessments will be performed on the quadriceps and forearm flexor muscles using standardized acquisition procedures. First-order variables (e.g., muscle thickness, cross-sectional area, pennation angle, fascicle length), second-order texture features and higher-order ultrasound biomarkers will be extracted and analysed.

Isometric quadriceps muscle strength and handgrip will be measured using standardized dynamometry protocols. Additional assessments will include functional capacity tests, mobility and balance measures, physical activity, nutritional status, fatigue, dyspnoea, health-related quality of life, lifestyle factors and comorbidity profiles.

The primary objective is to identify ultrasound biomarkers associated with quadriceps muscle strength and handgrip, and to develop predictive models of muscle strength. Secondary objectives include assessment of ultrasound measurement reliability and exploration of relationships between ultrasound biomarkers, muscle strength, physical function and health-related characteristics.

Recruitment, assessor training, ultrasound standardisation procedures and reliability analyses will be conducted during the initial phase of the project, followed by the main recruitment and data collection phase and subsequent statistical modelling and dissemination activities.

• Study Type: Observational
• Enrollment (Estimated): 300

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: Beatriz Sánchez-Sánchez, PT, Ph.D.; Phone Number: +34 918 85 48 28; Email: beatriz.sanchez@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 aged 18-89 years residing in Spain. Participants will be recruited through community advertisements, institutional dissemination channels, and collaborating centres. The study aims to investigate the relationship between ultrasound-derived muscle biomarkers and isometric quadriceps muscle strength and handgrip in a healthy adult population.

Description

Inclusion Criteria:

• Healthy adults aged 18-89 years.
• Resident in Spain for at least 5 years.
• Living independently in the community and able to complete all study assessments.
• Able to understand and follow verbal instructions in Spanish.
• Able and willing to provide written informed consent prior to study participation.

Exclusion Criteria:

• Neurological, musculoskeletal, or systemic disorders affecting muscle strength or mobility.
• Recent surgery or acute injury affecting the upper or lower limbs.
• Recent use of medications affecting the musculoskeletal system (e.g., systemic corticosteroids for >1 week during the previous 6 months or muscle relaxants during the previous week).
• Cognitive or psychiatric conditions limiting participation.
• Pregnancy.
• Recent postpartum period (≤3 months after delivery).
• Presence of clinically relevant pain, fatigue, physical deconditioning, or functional limitations that may interfere with study procedures or measurement validity.
• Acute illness at the time of assessment.
• Uncontrolled hypertension (≥140/90 mmHg).
• Resting peripheral oxygen saturation ≤90%.
• Moderate-to-severe pain (Numeric Rating Scale ≥4/10).
• Any medical condition considered by the investigator to contraindicate study participation.

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort
Healthy adults; Healthy/community-dwelling adults aged 18-89 years participating in an observational study evaluating ultrasound-derived muscle biomarkers and their relationship with isometric quadriceps muscle strength and handgrip.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Isometric quadriceps muscle strength	Quadricpes maximal voluntary contraction measured using a handheld dynamometer according to a standardized testing protocol. Peak force will be recorded in kilograms-force (kgf).	Day 1
Handgrip	Maximal voluntary handgrip measured using a hydraulic hand dynamometer according to the American Society of Hand Therapists protocol. Peak force will be recorded in kilograms-force (kgf).	Day 1
Ultrasound-derived muscle biomarkers	Muscle ultrasound biomarkers obtained from standardized B-mode ultrasound images of selected quadriceps and forearm muscles. Candidate variables include muscle morphology, architecture, grayscale characteristics and texture-based parameters. The final set of ultrasound-derived biomarkers will be defined following assessor training, protocol standardization and pilot reliability analyses.	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
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
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
• Investigators: Principal Investigator: Nicola S. Diciolla, PT, Ph.D., University of Alcalá

Study record dates

Study Major Dates

• Study Start (Estimated): June 1, 2026
• Primary Completion (Estimated): June 1, 2028
• Study Completion (Estimated): June 1, 2029

Study Registration Dates

• First Submitted: June 9, 2026
• First Submitted That Met QC Criteria: June 9, 2026
• First Posted (Actual): June 15, 2026

Study Record Updates

• Last Update Posted (Actual): June 15, 2026
• Last Update Submitted That Met QC Criteria: June 9, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: Handgrip; Muscle quality; Muscle ultrasound; Muscle thickness; Predictive models; Skeletal muscle ultrasonography; Muscle biomarkers; Isometric quadriceps muscle strength; Echo intensity
• Other Study ID Numbers: CEIP/2026/2/39

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Individual participant data (IPD) that underlie the results reported in publications, after de-identification, will be made available. Shared data may include demographic characteristics, anthropometric variables, isometric quadriceps muscle strength, handgrip, ultrasound-derived muscle variables, functional capacity measures, and patient-reported outcomes/questionnaire data collected as part of the study. Direct identifiers will be removed before data sharing. Data sharing will comply with applicable ethical approvals, informed consent provisions, and data protection regulations.
• IPD Sharing Time Frame: De-identified individual participant data and supporting documents will become available beginning 12 months after publication of the primary study results and will remain available for at least 5 years thereafter.
• IPD Sharing Access Criteria: Researchers who provide a methodologically sound proposal for secondary analyses or validation studies may request access to the de-identified dataset. Requests will be reviewed by the study investigators. Data will be provided following approval of the proposal and execution of a data-sharing agreement, when required, in accordance with ethical and legal requirements. Supporting documents, including the study protocol, statistical analysis plan, informed consent form template, and analytic code, will be made available upon reasonable request.
• 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