Muscle quality (MQ) is increasingly recognized as a vital metric for healthy aging, potentially offering good prognostic value. However, there is a lack of robust longitudinal protocols integrating ultrasound-assessed MQ with functional performance and body composition in older women.
MethodsThis randomized controlled trial will involve community-dwelling women aged 60 and older. Participants will be randomized into an experimental group performing a multicomponent training (MT) program or a control group. The intervention consists of a 32-week supervised program (3 sessions/week, 50 minutes/session) combining aerobic, strength, balance, and coordination exercises. The primary outcome is the modification of muscle architecture (echo intensity and thickness) in the rectus femoris and rectus abdominis muscles, assessed via ultrasound. Secondary outcomes include functional capacity (assessed by SPPB, TUG, and 5-time sit-to-stand tests), handgrip strength, and body composition.
DiscussionWe hypothesize that long-term MT will induce positive architectural adaptations, such as reduced echogenicity (indicating lower intramuscular fat), which will correlate with improved functional independence. This protocol aims to validate ultrasound as a sensitive, non-invasive tool for monitoring skeletal muscle health during aging.
La calidad muscular (CM) es reconocida cada vez más como una métrica vital para el envejecimiento saludable, ofreciendo potencialmente un buen valor pronóstico. Sin embargo, existe una falta de protocolos longitudinales robustos que integren la CM evaluada por ultrasonido con el rendimiento funcional y la composición corporal en mujeres mayores.
MétodosEste ensayo controlado aleatorizado involucrará a mujeres de 60 años o más que viven en la comunidad. Las participantes serán asignadas aleatoriamente a un grupo experimental que realizará un programa de Entrenamiento Multicomponente (EM) o a un grupo de control. La intervención consiste en un programa supervisado de 32 semanas (3 sesiones por semana, 50 minutos por sesión) que combina ejercicios aeróbicos, de fuerza, equilibrio y coordinación. La variable primaria es la modificación de la arquitectura muscular (intensidad de eco y grosor) en los músculos recto femoral y recto abdominal, evaluada mediante ecografía. Las variables secundarias incluyen la capacidad funcional (evaluada mediante las pruebas SPPB, TUG y la prueba de sentarse y levantarse de la silla 5 veces), la fuerza de prensión manual y la composición corporal.
DiscusiónPlanteamos la hipótesis de que el entrenamiento multicomponente a largo plazo inducirá adaptaciones arquitectónicas positivas, como una reducción de la ecogenicidad (lo que indica una menor grasa intramuscular), lo cual se correlacionará con una mejor independencia funcional. Este protocolo tiene como objetivo validar la ecografía como una herramienta sensible y no invasiva para monitorear la salud del músculo esquelético durante el envejecimiento.
Population aging has become the most defining and significant demographic phenomenon in recent years, with a notable increase in life expectancy.1 This is why the term healthy aging is important, defined by five dimensions that include metabolic and physiological health, physical function, cognitive function, psychological well-being, and social well-being.1,2
Traditionally, research focused on muscle mass; however, the term muscle quality (MQ), defined in different ways in scientific literature, is currently gaining importance.3 Despite the lack of consensus, a distinction can be made between muscle-specific strength or functional MQ, defined as the difference between muscle strength and muscle mass, and muscle composition or morphological MQ, often assessed through fat infiltration.4 The Delphi Consensus from the Global Leadership Initiative in Sarcopenia (GLIS) has created the first global conceptual definition of sarcopenia, which includes muscle mass, strength, and muscle-specific strength.3 Consequently, a recent study argues that due to the absence of a universally accepted definition, MQ should be viewed as an umbrella term.5
There is no universal consensus on MQ assessment techniques.6 However, MQ, supported by basic, applied, and epidemiological research data, has been proposed as a specific and sensitive metric for assessing the impact of aging on quality of life and longevity.7 Techniques such as magnetic resonance imaging and computed tomography have been used to assess muscle quality in research settings, with the aim of determining fat infiltration in muscle and using muscle attenuation.6,8 However, ultrasound is a safe diagnostic imaging method that does not expose the patient to radiation, is low cost, portable, and available in most clinical settings.9,10 In addition, it is a promising tool for assessing both muscle quantity and quality.11 It allows the measurement of qualitative muscle parameters such as pennation angle, fascicle length, echo intensity, muscle stiffness, contraction potential, and microcirculation.12,13
The first step towards standardizing muscle assessment using ultrasound was taken by SARCopenia through UltraSound (SARCUS), with a consensus proposal for anatomical reference points accompanied by an instructional video on these measurements. Initially, five main parameters were recorded: muscle thickness, pennation angle, fascicle length, echo intensity, and cross-sectional area.14 Four additional parameters were later introduced: muscle volume, muscle stiffness assessed by elastography, muscle contraction potential by correlating the cross-sectional area at rest with the cross-sectional area at maximum contraction, and muscle microcirculation.13
Although SARCUS defines different muscles and body regions,13,14 the rectus femoris muscle is proposed as a useful location for performing the ultrasound assessment due to its easy access and superficiality, with most measurements being taken in the supine position.15 Furthermore, this muscle is easily identifiable thanks to its central tendon, which appears hyperechoic on ultrasound images.16
Echo intensity plays an important role in assessing MQ. Increased echogenicity may be caused by an alteration in muscle architecture due to increased fat content, fibrosis, or inflammation.16 Some ultrasound machines cannot perform all measurements on screen during the examination.14 However, there are different software programs available for measuring these parameters, notably ImageJ.13,16
Multicomponent training (MT) combines three or more components of physical fitness in a single training session, making it an interesting option for improving physical and functional abilities in older people.17 Implementing an MT program with an average duration of 27 weeks, 2.6 sessions per week, and 45 minutes per session can improve strength, flexibility, functional fitness, and quality of life in older women.18
Specifically, older women face a higher risk of sarcopenia due to hormonal changes that accelerate muscle atrophy compared to men.19
Despite the existence of studies supporting ultrasound, there is a notable gap in scientific literature. Currently, there are no robust longitudinal protocols that holistically integrate the assessment of muscle quality using advanced ultrasound parameters, functional performance, and body composition in older women. Establishing the relationship between different changes in muscle architecture and functional improvements is essential for designing effective strategies for healthy ageing.
To fill this gap, the present study aims to evaluate the effect of a 32-week MT program on the architecture and MQ of the rectus femoris and rectus abdominis using ultrasound in women over 60 years of age. Secondarily, we will analyze concurrent changes in muscle strength, physical performance, and body composition. Our hypothesis is that the MT program will induce significant positive adaptations in muscle architecture (e.g., increased thickness, reduced echo intensity) that will correlate significantly with gains in functional capacity.
MethodsDesign and setting of the studyA prospective, longitudinal, parallel-group, controlled clinical trial lasting 9 months will be conducted. Two experimental groups will be formed: the intervention group, in which subjects will undergo physical training, and the control group, without exercise. The reporting of this clinical trial conforms to the Consolidated Standards for Reporting Trials (CONSORT 2025) statement.20
The study protocol was approved by the Salamanca Health Area Drug Research Ethics Committee (code 1416) and was conducted in adherence to the Declaration of Helsinki.21 The trial was registered on ClinicalTrials.gov (identifier: NCT07359495).
Participants, all of whom belong to the Geriatric Revitalization Program (GRP), will attend their senior centers as usual. The corresponding selection criteria will be applied to determine eligibility.
Participants will be randomly assigned (1:1 ratio) to two groups using R software version 4.2.1 by an external statistician who will not participate in the analysis. The experimental group will perform an MT program. The control group will maintain their usual lifestyle.
A single-blind (outcome assessors/statistician blinded) will be used, in which the evaluators and the statistician will be unaware of the group assignments. An external researcher will manage the randomization and instruct the therapists, who will not participate in data collection. Participants, although aware of the physical nature of the intervention, will be kept blind to the study hypothesis and the comparative assignment of groups. The blinding will not be lifted under any circumstances. See Fig. 1 for the study flow chart.
Study period
The study will be conducted between September 2026 and June 2027. The baseline assessment will take place in September 2026. The intervention will be carried out between October 2026 and May 2027, and the final assessment will be conducted in June 2027.
Study subjects and selection criteriaThe participants will be women over the age of 60, residing in Salamanca and belonging to the GRP. All participants who voluntarily enroll in the PRG must read, understand, and sign the informed consent form. Only participants who meet the selection criteria will be included in the study.
The inclusion criteria will be: being a woman over 60 years of age, residing in the community, and enrolled in the GRP. On the other hand, the exclusion criteria will be having neuromuscular diseases, recent abdominal surgery, metal implants incompatible with measurements, unstable cardiovascular diseases, or previous participation in another exercise program. Exclusion criteria during the intervention will include total attendance of less than 85% and participation in other exercise programs during the intervention period.
Sample sizeA sample size calculation was performed assuming a moderate effect size (Cohen's d≈0.5) to detect differences between groups using a one-way analysis of variance. A statistical power of 80% and a significance level of 0.05 were established. The estimated sample size was approximately 18 participants per group; however, it was increased by 10% to compensate for possible losses during follow-up, resulting in a total of 20 subjects per group (40 participants in total). The calculation was performed using G*Power software (version 3.1).22
Procedures and data collectionEvaluationsData collection will be carried out at the Faculty of Nursing and Physiotherapy of the University of Salamanca at two different times. The baseline assessment will be carried out after recruitment but before randomization, recording sociodemographic variables and primary outcome measures using standardized objective tests. After this phase, participants will be randomly assigned to their respective intervention groups.
The final evaluation will be carried out immediately after the end of the intervention period. To ensure data consistency, all measurements will be taken by the same researcher, who has specific training. Personalized reports on clinical progress will be provided to those participants who expressly request to know their results.
InterventionsAll participants will continue with their usual lifestyle, following their medical treatment guidelines, level of physical activity, and dietary patterns. The exercise sessions will be taught by healthcare professionals, specifically physical therapists, with experience in teaching exercise sessions to older adults. The sessions will be held at senior centres in the city of Salamanca. Adherence to the program will be verified through daily attendance records. A minimum attendance of 85% of the sessions is required to remain in the study. In case of two consecutive unexcused absences, the physical therapists will contact the participant by phone to identify the cause and encourage adherence. Participants who fall below the 85% threshold will be excluded from the final analysis.
There will be three 50-minute sessions per week for 32 weeks. The sessions will be divided into three parts: a warm-up, the main part, and finally a cool-down. The sessions will begin with active mobility and end with muscle stretching. During the main part of the session, moderate-intensity physical activity will be carried out in various forms. The exercises will include aerobic work, muscle strengthening, joint mobility, balance and coordination, along with fun activities involving colours, numbers, letters, memory, etc. The LIFE and SPRINTT studies will be used as a reference, as they have been proven to be safe for older people and effective in preventing disability.23,24
- A.
Intervention group (MT)
Participants in this group will follow the multi-component exercise programme. The load progression will be based on individual perceived exertion. At the beginning of the intervention, participants will be taught how to interpret the modified Borg scale. At the end of each week, each person's perception of exertion will be recorded in relation to the three sessions completed. The aim will be to maintain a constant level of between 5 and 7 on the scale, which corresponds to ‘hard’ and ‘very hard’. If the perceived exertion is greater than 7, it will be reduced, and conversely, if it is less than 5, the intensity will be increased.
The protocol prioritizes functional movements with low technical and material costs, thus facilitating replicability and post-study adherence.
The exercise battery includes lower body work (squats, deadlifts, front and sagittal plane lunges, hip abduction/extension, and plantar flexion) and upper body work (wall flexion–extensions, shoulder raises, and elbow flexion–extensions). In addition to the strength exercises mentioned above, balance exercises such as walking in tandem, standing on one leg, side steps, and weight transfer will also be performed. Aerobic capacity will be worked on by walking at a moderate intensity, and flexibility will be improved through stretching the main muscle groups.
- A.
Control group
Participants in this group will maintain their usual diet and physical activity, without changing their habits during the intervention period. They will not participate in other physical exercise programs, nor will they engage in frequent and systematic physical exercise. To verify that no systematic exercise is performed, participants in the control group will complete a monthly physical activity log, which will be reviewed by the research team via telephone call.
Study variablesAll variables will be measured at the beginning and end to check for change after the different interventions.
- 1.
Sociodemographic variables: personal data, medical history, presence of comorbidities, use of medications will be collected in a personal interview, and finally, blood pressure will be taken.
- 2.
Ultrasound variables (primary). Musculoskeletal ultrasound will be used, in transverse and longitudinal planes, following SARCUS guidelines.13,14
- a.
Muscles: rectus femoris and rectus abdominis on the right side.
- b.
Parameters:
Participants will lie supine on a hydraulic stretcher for 5min to allow for natural fluid redistribution and normalize measurements. The head of the stretcher will not be tilted unless strictly necessary. In this case, a small pillow will be used to tilt the head slightly without interfering with the dorsal or lumbar region. The patient's feet will point toward the ceiling to eliminate hip rotation and perform the ultrasound measurement with neutral hip rotation. The measurement will be performed with the muscles relaxed and on the right side of the participants.
A MyLab25Gold ultrasound scanner will be used in standard B mode. A linear transducer probe with a length of 5cm will be used. The probe will be positioned neutrally, i.e., perpendicular to the skin, with plenty of gel applied to the area to be scanned and minimal pressure between the transducer and the skin. The beam frequency will be 12MHz. The depth will be maintained at 5cm and the gain at 52%. These values will be stable in all ultrasounds, except in situations where the deep aponeurosis of the rectus femoris or rectus abdominis muscles cannot be seen at this depth.
Echo intensity values remain stable between depths of 4 and 6cm, suggesting that changing the image depth may not be problematic, with constant depth being ideal, although small deviations are acceptable. Image gain should be kept constant.26
The rectus femoris muscle will be evaluated using the midpoint between the greater trochanter and the upper pole of the patella as an anatomical reference point. This distance will be measured with a tape measure, in addition to measuring the distance between the greater trochanter and the lateral malleolus. Both cross-sectional and longitudinal images will be taken.
Considering that small variations in ultrasound measurement may occur, three measurements will be taken for each section.
For the evaluation of the rectus abdominis, the subject's position will be the same as for the rectus femoris, using the same ultrasound machine and the same parameters.
The rectus abdominis muscle will be evaluated using a reference point 3cm lateral to the navel, as there is no clear anatomical reference point for this muscle.27 Similarly, both cross-sectional and longitudinal images will be taken. As with the rectus femoris, three measurements will be taken for each section.
- a.
- 3.
Functional variables (secondary): Handgrip strength will be assessed using dynamometry due to its association with various outcomes of aging, being a key component in sarcopenia and frailty.28 Measurements will be taken using the Hydraulic Jamar device with the subject standing and the elbow flexed at 90°. The standardized protocol will be followed, using this instrument due to its excellent psychometric properties, demonstrating high test–retest reproducibility (r>0.80), and near-perfect interobserver reliability (r=0.98).29,30
The Short Physical Performance Battery (SPPB) will be used, a quick and objective three-part physical function test with excellent test–retest reliability, predictive validity, and clinical applicability, mainly used for fall risk stratification.31
The Timed Up and Go (TUG) test will be used as it is a valid tool for detecting balance deficits, which are associated with an increased risk of falls in older adults.32
The 5-time sit-to-stand (5STS) test will be used, a functional test that serves to assess lower limb strength. The participant will be asked to complete five consecutive cycles of standing up and sitting down from a chair without using their arms for support. This variant will be used as it has been shown to be a more sensitive and specific measure than the original test.33
- 4.
Anthropometric variables: body composition will be measured using body mass index (BMI),34 electrical bioimpedance BIA (TANITA BC-418),35 abdominal circumference, and waist-to-hip ratio. Height will also be measured using a height rod.
The main objective of this randomized clinical trial is to evaluate whether a long-term MT program (32-week) can modify muscle architecture and quality, as assessed by echo intensity, in older women. While muscle mass and functionality remain the cornerstone metrics previous studies,36 this protocol proposes investigating MQ as a complementary parameter. Emerging evidence suggest that MQ could potentially offer additional insights into functionality that are not fully captured by strength, mass, or body composition alone in older adults.37
Our central hypothesis is that MT may induce significant positive adaptations in muscle architecture, specifically by increasing muscle thickness and reducing echo intensity. Aging is known to cause intramuscular and connective tissue fat infiltration (myosteatosis), which increases echo reflection and, therefore, echo intensity.38 The mechanical stimulus of MT is expected to reverse this process, improving muscle fiber density and reducing intramuscular lipid content, which should correlate with an improvement in force generation per unit of muscle area (muscle-specific strength).
An innovative aspect of this protocol is the inclusion of the evaluation of the rectus abdominis muscle alongside the rectus femoris muscle. Historically, the assessment of sarcopenia has focused on the lower limbs. However, the concept of ‘Nutritional Ultrasound’ has highlighted the usefulness of the rectus abdominis muscle as an early marker of malnutrition and protein catabolism in hospitalized elderly patients.16 In this study, we transfer this concept to the community population, hypothesizing that the quality of the rectus abdominis is a key biomarker of core stability, essential for balance and fall prevention, and that it could respond positively to global MT.
The 32-week duration is a notable feature of this study design. Shorter interventions (e.g., 8 or 12 weeks) are generally sufficient time to observe neural adaptations, but insufficient to detect significant structural changes in muscle architecture (such as pennation angle or profound changes in echo intensity) in the elderly population. A longitudinal follow-up approaching one year allows for the observation of long-term adherence and the sustainability of physiological adaptations. In addition to the broader literature, recent randomized clinical trials conducted within our research framework and the context of the GRP have shown that long-term resistance-based and MT interventions can improve strength, physical performance, and body composition in older women, and that baseline nutritional intake may modulate training responsiveness.39–41 The present protocol is aligned with this emerging evidence and extends it by incorporating ultrasound-derived outcomes to characterize training-related changes in muscle architecture.
The study has limitations inherent to its design. Firstly, as it is an exercise intervention, it is not possible to blind the participants, which could induce a placebo effect in the functional tests, although the ultrasound variables remain objective. Furthermore, ultrasound assessment is intrinsically operator-dependent and susceptible to variations such as probe pressure. To mitigate this technical variability, we strictly adhered to the SARCUS protocol, using a single blinded evaluator and standardised equipment settings. Beyond technical factors, biological variability, such as hydration status and muscle glycogen levels, can cause small fluctuations in muscle thickness and echo intensity; although we attempt to control for time of day, this remains an unavoidable limitation. Finally, in some older adults, skin laxity or subcutaneous fat thickness may compromise image resolution, which could affect the accuracy of architectural measurements.
If the results support our hypotheses, this protocol will provide solid evidence to recommend MT not only to increase muscle mass, but also as a therapeutic tool capable of improving internal muscle architecture (“quality”). This would further validate the use of ultrasound as an accessible and non-invasive clinical monitoring tool in healthy aging.
Ethics approval and consent to participateThe study protocol was reviewed and approved by the Salamanca Health Area Drug Research Ethics Committee (approval code: 1416) and is conducted in accordance with the principles of the Declaration of Helsinki. The trial has been registered at ClinicalTrials.gov (identifier: NCT07359495). All participants will be required to provide written informed consent prior to enrolment in the study.
FundingThis study is supported by a research contract under Article 60 of the Spanish Organic Law of the University System (LOSU) between the City Council of Salamanca and the University of Salamanca (Project Code: 18L1VH). The funding body had no role in the study design; data collection, analysis, or interpretation; manuscript preparation; or the decision to submit the manuscript for publication.
Declaration of competing interestsThe authors declare that they have no competing interests.
The authors gratefully acknowledge the institutional support of the University of Salamanca and the City Council of Salamanca.
