The Effect of Probiotic Supplementation on the Exercise Performance of Long-distance Runners. (PreludiumKP)

The Impact of the Gut Microbiome on Intestinal Mucosal Function and Exercise Performance in Marathon Runners.

The study is designed as a randomized double-blind placebo-controlled clinical trial with a 4-week probiotics intervention period. The study will be conducted between January 2022 and March 2025 at the Medical University of Gdańsk, Department of Bioenergetics and Physiology of Exercise (Gdańsk, Poland). A total of 40 endurance-trained adult men, specifically long-distance runners with previous experience in marathon races, will be enrolled. Only participants who meet all inclusion criteria and do not meet any exclusion criteria will be included in the study. Participants will be randomly assigned to the probiotic (PRO) or placebo (PL) group in a 1:1 ratio. Athletes will supplement 4 capsules of the study product (probiotic mixture) daily.

To eliminate the effect of diet on the gut microbiome, all athletes will receive an individually balanced box diet designed to provide 100% of energy requirements, protein intake of 1.6 g/kg/day, and at least 8 g/kg/day of carbohydrates. Participants will continue their training programs and perform at least 5 endurance workouts per week. To assess training loads, athletes will report average pulse range, subjective fatigue, and duration of training sessions.

The investigators will examine whether 4 weeks of probiotic supplementation in conjunction with a personalized diet may have a direct or indirect influence on sport performance. This will be assessed through evaluation of aerobic fitness capacity using treadmill tests. The cardiopulmonary exercise test (CPET) will determine maximum oxygen uptake, minute lung ventilation, and heart rate. Body composition analysis and assessments of blood and fecal samples will also be performed. Blood samples will be analyzed for serum pro-inflammatory cytokines (IL-6 and TNF-α). Collected fecal samples will be subjected to quantitative and qualitative analysis of the intestinal microbiota using next-generation sequencing. The analysis will include intestinal permeability markers (calprotectin, zonulin, IFABP) and bacterial metabolism products such as short-chain fatty acids (SCFA). All assessments and procedures will be carried out both before and immediately after the supplementation period.

All obtained data will undergo statistical analysis. Descriptive statistics will be used for background information and to examine trends in the analyzed parameters, with mean values and 95% confidence intervals. Depending on the distribution of the data, parametric or non-parametric tests will be applied. Statistical significance will be set at p < 0.05.

To the best of the investigators' knowledge, this will be the first intervention study comprehensively assessing the influence of probiotic supplementation in conjunction with a standardized diet on inflammatory response, intestinal permeability, gut microbiome composition, and aerobic capacity of competitive long-distance runners. The collected data will provide evidence regarding the potential influence of probiotic supplementation on parameters of sport performance.

Study Overview

• Status: Active, not recruiting
• Conditions: Intestinal Microbiome; Probiotic; Runners
• Intervention / Treatment: Dietary supplement: probiotics or placebo; Dietary supplement: Box diet

• Study Type: Interventional
• Enrollment (Actual): 27
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Poland
  • Gdansk, Poland
    • Medical University of Gdansk

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Endurance-trained adult men (aged ≥ 18 years)
• Long-distance runners with experience in at least three marathons or half-marathons
• Average running speed between 10.549 and 14.065 km/h
• At least 3 years of regular endurance training experience
• Completion of 5 or more training sessions per week

Exclusion Criteria:

• Age below 18 years
• Female gender
• Antibiotic therapy within the last 3 months
• Diagnosed inflammatory bowel disease
• Chronic musculoskeletal injuries within the last 6 months
• Heart failure or heart defects

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: A; Participants who supplement probiotics or placebo	Dietary supplement: probiotics or placebo; The study product is a probiotic mixture Sanprobi Active & Sport, containing 2,5 x 109 CFU/g per capsule (≥500 million CFU in one capsule) of five strains of lactic acid bacteria (Bifidobacterium lactis W51, Lactobacillus brevis W63, Lactobacillus acidophilus W22, Bifidobacterium bifidum W23 and Lactococcus lactis W5); maize starch, maltodextrin, plant proteins and hydroxypropyl ethylcellulose tablets' coating. OR PLACEBo identically-looked; Dietary supplement: Box diet; To eliminate the effect of diet on the gut microbiome, all athletes received optimal, individually-balanced box-diet.; Other Names: GroupA
Experimental: B; Participants who supplement probiotics or placebo	Dietary supplement: probiotics or placebo; The study product is a probiotic mixture Sanprobi Active & Sport, containing 2,5 x 109 CFU/g per capsule (≥500 million CFU in one capsule) of five strains of lactic acid bacteria (Bifidobacterium lactis W51, Lactobacillus brevis W63, Lactobacillus acidophilus W22, Bifidobacterium bifidum W23 and Lactococcus lactis W5); maize starch, maltodextrin, plant proteins and hydroxypropyl ethylcellulose tablets' coating. OR PLACEBo identically-looked; Dietary supplement: Box diet; To eliminate the effect of diet on the gut microbiome, all athletes received optimal, individually-balanced box-diet.; Other Names: GroupA

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
The assessment of the impact of probiotic supplementation on maximal oxygen uptake value among athletes.	Aerobic capacity will be assessed using an incremental treadmill test performed to volitional exhaustion. After a brief standing period on the treadmill to ensure stabilization of the measurement equipment, participants will complete a standardized low-intensity warm-up, followed by a stepwise increase in exercise intensity until exhaustion. Heart rate will be continuously monitored (Polar Electro Oy, Kempele, Finland), and respiratory variables (VO₂, VCO₂, VE, and RER) will be measured breath-by-breath using a calibrated metabolic cart (Oxycon Pro, Jaeger, Germany). Peak oxygen uptake (VO₂peak) will be defined as the highest value recorded during the test.	Baseline visit (before supplementation period) and after 4 weeks of supplementation period (post-intervention).
Analysis of gut microbiome	Fecal samples will be collected by participants before and after the 4-week intervention period using standardized containers. Samples will be immediately frozen at -80°C and analyzed by an independent laboratory. The intestinal microbiota will be assessed using next-generation sequencing of selected 16S rRNA gene regions. Microbiome composition will be characterized by alpha diversity (Chao1, ACE, Shannon, inverted Simpson) and beta diversity (Bray-Curtis and weighted UniFrac), and analyzed in relation to intestinal permeability markers (calprotectin, zonulin, IFABP) and bacterial metabolites (short-chain fatty acids, SCFA).	Baseline (pre-intervention) and after 4 weeks of supplementation (post-intervention).

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Assessment of inflammatroy state	The blood samples will be collected during sport test at the two points time: PRE and POST intervention, at the same conditions. Blood samples from the arm vein will be drawn by a specialist nurse into appropriate standardized tubes containing clotting activator. Each time up to 4 ml of blood will be collected. Blood samples will be taken indirectly before the start of exercise tests and 30 minutes after the end of the tests. The blood will then be centrifuged at 3000 x g to separate serum. The material will be placed into separately labeled microcentrifuge tubes and stored at -80 ° C for later determinations. We assess the level of serum pro-inflammatory cytokines (IL-6 and TNF-α) using a commercially available enzyme-linked immunosorbent assay (ELISA) kits.	Baseline (pre-supplementation) and after 4 weeks of supplementation (post-intervention), with blood samples collected immediately before exercise and 30 minutes after the exercise test.

Collaborators and Investigators

• Sponsor: Medical University of Gdansk

Study record dates

Study Major Dates

• Study Start (Actual): December 1, 2023
• Primary Completion (Estimated): March 1, 2026
• Study Completion (Estimated): March 1, 2026

Study Registration Dates

• First Submitted: December 31, 2025
• First Submitted That Met QC Criteria: February 8, 2026
• First Posted (Actual): February 13, 2026

Study Record Updates

• Last Update Posted (Actual): February 13, 2026
• Last Update Submitted That Met QC Criteria: February 8, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: runners; athletes; Probiotisc; intestinal mucosal unction
• Additional Relevant MeSH Terms: Dietary Supplements; Food; Diet, Food, and Nutrition; Physiological Phenomena; Food and Beverages; Probiotics
• Other Study ID Numbers: Runners2023; 2021/41/N/NZ4/02364 (Other Grant/Funding Number: ational Science Centre (Poland))

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No