Purpose:

This clinical trial aims to evaluate the efficacy and safety of Lactiplantibacillus plantarum LM1001 in improving muscle strength in older adults. The study is designed to investigate its potential effects on muscle strength based on the gut-muscle axis.

Methodology:

This study is a randomized, double-blind, placebo-controlled, single-center clinical trial. A total of 100 participants will be enrolled and randomly assigned to either the test group (n=50) or the placebo group (n=50). Participants in the test group will receive 500 mg of Lactiplantibacillus plantarum LM1001 (1.0 × 10¹⁰ CFU/day) once daily for 12 weeks, while those in the placebo group will receive a matching placebo.

Key Outcome Measures:

To evaluate the effects on muscle strength, the following parameters will be assessed at baseline and after the 12-week intervention period:

- Primary Outcome Measures: Changes in isokinetic knee extension and flexion strength.

- Secondary Outcome Measures: Changes in muscle strength-related parameters, including muscle power, skeletal muscle mass (SMM), and skeletal muscle mass index (SMI), as well as physical performance measures such as handgrip strength, Short Physical Performance Battery (SPPB) score, Timed Up and Go (TUG) test, and health-related quality of life assessed by EQ-5D-5L.

- Safety Assessments: Safety will be evaluated based on the incidence of adverse events, serum biochemical parameters, and clinical laboratory test results.

Inclusion Criteria:

• Adults aged 50 to 84 years (male or female)
• Body mass index (BMI) between 18.5 and 30.0 kg/m²
• Reduced skeletal muscle mass (≤110% of standard value by BIA)
• Decreased handgrip strength according to age- and sex-specific criteria
• Short Physical Performance Battery (SPPB) score over 9
• Able to perform normal physical activity and provide written informed consent

Exclusion Criteria:

• Clinically significant acute or chronic diseases requiring treatment
• Conditions affecting muscle function or physical performance (e.g., severe musculoskeletal, neurological, or cognitive disorders, including sarcopenia)
• Significant gastrointestinal disorders or history of major gastrointestinal surgery
• Severe psychiatric disorders or recent use of antipsychotic medications
• Respiratory diseases affecting lung function
• Excessive alcohol intake, substance abuse, or heavy smoking
• Known hypersensitivity to the investigational product or its components
• Recent use of medications or supplements affecting muscle function or gut microbiota (e.g., antibiotics, probiotics, steroids)
• Regular high-intensity or resistance exercise
• Clinically significant abnormal laboratory findings or uncontrolled medical conditions
• Recent fractures within the past year
• Participation in another clinical trial within 3 months prior to screening
• Pregnant or breastfeeding women
• Individuals unable to communicate or ambulate
• Any other condition deemed unsuitable by the investigator

Participants, care provider, investigators, and outcome assessors are blinded to the group allocation. The investigational product and placebo are identical in appearance, taste, and packaging.