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.
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.
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.