Impact of Training Load on the Gut miCrobiome And Its Relation to exeRcise Performance, mUscle Phenotype, and markerS of Overreaching in Healthy Men

ConditionsExercise Overreaching Butyrate Gut Microbiome Exercise Performance Skeletal Muscle Glucose Tolerance Hormones Vascular Health Muscle Adaptation Physical Fitness Heart Rate Variability (HRV)Anthropometric Measurements Metabolic Health Food Intake

Trial statusRecruiting

Trial phaseNot applicable

Trial typeInterventional

Biological sexMale

Age18-45

SponsorStefan De Smet

About this trial

The goal of this study is to learn how different amounts of supervised indoor cycling training change gut health (gut bacteria, the substances gut bacteria make, and the gut barrier integrity), and how these changes relate to changes in fitness, muscle health, and signs of doing too much training (a state called 'overreaching'). The study includes healthy, recreationally active men aged 18 to 45 years.

The primary questions, for which the study is powered (sufficient participants included), are:

1. Does moderate load training change blood and faecal levels of butyrate (a short-chain fatty acid made by gut bacteria) after eight weeks compared with a control group? 2. Compared to moderate load training, do higher training loads lead to different responses in blood and faecal levels of butyrate?

Researchers will compare:

* A control group that does not complete structured training; * A moderate-load training group that completes eight weeks of supervised cycling (4x/week); * A high-load training group that completes four weeks of moderate-load training followed by four weeks of higher training load (twice the number of training sessions).

Participants will:

* Be randomly assigned to one of the three groups; * Complete 8 weeks of supervised indoor cycling sessions if assigned to a training group; * Complete four study assessment periods (baseline, after week four, after week eight, and after a short taper (rest period); * Provide blood, stool, skeletal muscle, urine, saliva, and breath samples during the assessment periods; * Complete fitness and performance tests and questionnaires during the assessment periods.

Eligibility criteria

This trial accepts healthy volunteers

Qualifiers

Males between 18 and 45 years old.

Recreationally active individuals, with a weekly exercise training volume between one and six hours per week.

Good health status confirmed by a sport medical screening, which includes a sport medical questionnaire and resting electrocardiogram.

Body Mass Index (BMI) between 18.5 and 27.5 kg/m².

Disqualifiers

Engagement in strenuous competitive sports one month prior to or during the study intervention.

Medication and vaccination: Pro- or antibiotic treatment during the past three months, non-steroidal anti-inflammatory drugs (NSAIDs) or cholestyramine during the past month, drugs interfering with intestinal permeability (e.g., prokinetics, laxatives, lubiprostone, loperamide, anti-spasmodics, linaclotide, proton pump inhibitors) during the past month. Vaccinations within one month prior to or during the study intervention.

Blood donations within three months or plasma donation within one month prior to or during the study intervention.

Inflammatory bowel disease (Crohn or colitis ulcerosa) or celiac disease.

Trial design

Design model

Parallel

Treatments tested in this trial

Supplement
Dietary supplement
The nature of the intervention does not allow blinding of study participants. However, to induce an 'expectancy-effect' in the control group, participants allocated to the control group will receive dietary placebo supplementation. Participants will be told (deceived) that this novel 'plant extract' is believed to have the potential to mimic training effects on gut health and exercise performance. The dietary placebo capsule will consist of 1 g sugar. Intake of the dietary placebo capsule will take place after a fasting state of six hours or more, at a fixed timepoint once a week, and under direct supervision of a research investigator (Sofie Engelborghs). The control group does not participate in any study-related training sessions, but will be asked to continue and monitor (Polar Pacer heart rate monitor) their normal physical activities and sports.
Moderate load exercise training
Behavioral
The moderate load training group will enroll in an exercise intervention of 8 weeks. This intervention consists of cycling sessions on an electromagnetically braked ergometer under direct supervision of the investigators at the Exercise and Muscle Physiology Group. Training intensities are prescribed based on the power output associated with the first and second lactate threshold and maximal power output obtained during a maximal incremental step test with capillary lactate measurements. Three types of training sessions will be prescribed: moderate-intensity continuous training (2x/week), high-intensity interval training (1x/week), and sprint interval training (1x/week). The training load will gradually increase over time, by increasing the session duration and/or intervals.
High load exercise training
Behavioral
Participants allocated to the high load training group will conduct a similar intervention as the moderate load training group, but with double the amount of training sessions (8x/week) throughout the last four weeks of the 8-week training program. The four weeks of high load training aims to induce a state of overreaching in some though not all participants allocated to the high load training group.

Treatment groups

45 Participants

are divided into 3 treatment groups

Group A: Control groupPlacebo comparator 1 intervention

Group B: Moderate load training groupExperimental treatment 1 intervention

Group C: High load training groupExperimental treatment 1 intervention

Trial outcomes

Primary outcomes

Serum butyrate concentrations

Diet and in particular fiber intake will be standardized for three days prior to and during the assessment days during which venous blood sample collection will take place. To promote microbial SCFAs production, participants will consume 15 g of oligofructose five hours prior to venous blood sample collection. Serum butyrate concentration will be assessed using gas chromatography-mass spectrometry.

Time frame