Introduction: Increasing sedentary lifestyle, microbiota imbalance and exercise-induced muscle fatigue are among the main causes of metabolic stress and performance decline, even in young individuals. The potential effects of functional foods-particularly polyphenol and anthocyanin-rich beverages-on both gut microbiota and muscle performance have attracted attention in recent years. In this context, intervention studies focused on the gut-muscle axis represent a promising and valuable area of research.
Objective: This study aims to investigate the effects of a functional beverage enriched with anthocyanins and polyphenols -extracted from Sambucus nigra L. (black elderberry)- combined with a regular exercise program on muscle performance, muscle morphology, fatigue level, and gut microbiota composition in healthy individuals.
Method: This 12-week double-blind, randomized, placebo-controlled trial will include participants adhering to a berry-free diet. Participants will be randomly assigned to two groups: the intervention group will consume a functional elderberry beverage formulated with high-purity anthocyanins obtained via supercritical CO₂ extraction; the control group will receive a placebo beverage with matched taste and energy content but without active compounds. Both groups will engage in a structured combined exercise program (3 days/week). Pre- and post-intervention assessments will include gut microbiota profiling (16S rRNA sequencing), short-chain fatty acid analysis, systemic biomarkers, muscle morphology (via ultrasound), exercise performance, and body composition. Mediator analyses will be used to explore the role of the gut-muscle axis in the observed effects.
Unique value: This project represents one of the few human-based intervention studies systematically evaluating the interaction between functional beverages, exercise, and microbiota through the lens of muscle fiber-type-specific adaptations. Furthermore, by integrating mediator analyses and multi-level outcome measures, the study aims to elucidate the physiological relevance of the gut-muscle axis in a holistic manner. The development, standardization, and sensory evaluation of the elderberry-based beverage also contribute valuable insights to functional product innovation.
Engaging in regular physical activity at least 2 days per week
Body Mass Index (BMI) between 18.5 and 29.9 kg/m²
No use of antibiotics, probiotics, or prebiotics within the past 3 months
No history of chronic illness or autoimmune disorders
Pregnancy or breastfeeding
Known food allergies
Regular use of medications such as corticosteroids, NSAIDs, or immunosuppressants
Professional-level athletes
Parallel
Elderberry-Based Functional Beverage
Dietary supplementA polyphenol- and anthocyanin-rich beverage derived from Sambucus nigra L., administered once daily for 12 weeks as a dietary supplement.
Placebo Beverage
Dietary supplementA placebo beverage that mimics the elderberry drink in color and flavor but contains no polyphenols or bioactive compounds. Consumed once daily for 12 weeks.
Change in Perceived Muscle Fatigue (VAS Score) After 12 Weeks
Muscle fatigue perception will be assessed using a 10-point visual analog scale (VAS), where 0 indicates no fatigue and 10 indicates extreme fatigue. Unit of Measure: Units on a 10-point scale Interpretation: A lower score indicates improvement.
Change in Time-to-Exhaustion Performance After 12 Weeks
Muscle endurance will be assessed by measuring the time (in seconds) a participant can continue a standardized exercise until exhaustion. Unit of Measure: Seconds Interpretation: A higher time indicates improvement.
Change in Gut Microbiota Composition
Fecal samples will be collected to evaluate taxonomic and functional changes in gut microbiota using 16S rRNA sequencing. Relative abundance of key microbial taxa (e.g., Akkermansia muciniphila, Faecalibacterium prausnitzii) and alpha diversity indexes will be reported. Unit of Measure: Alpha diversity index units (e.g., Shannon index); relative abundance (%) Interpretation: Increased diversity or beneficial taxa indicate improvement
Change in Muscle Architecture Parameters
Muscle architecture will be assessed via ultrasound by measuring muscle thickness (mm) and pennation angle (degrees) separately for each muscle. Each parameter will be reported individually. Unit of Measure: millimeters (mm) and degrees (°) Interpretation: Increases in muscle thickness and pennation angle reflect hypertrophic adaptations.
Change in Exercise Performance (VO₂peak)
Maximal oxygen consumption (VO₂peak) will be measured using a graded treadmill test following standard protocols. Improved values will reflect enhanced aerobic capacity. Unit of Measure: mL/kg/min Interpretation: Higher VO₂peak indicates improved aerobic performance.
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