Table 1 Overview of the feasibility and minimum progression criteria and outcomes reached during the pilot trial
Assessment | Minimum achievement for progression to a subsequent trial | Achieved in the pilot trial | ||
|---|---|---|---|---|
Recruitment and eligibility | Invited athletes | N/A | 43 | |
Reasons for non-participation | Descriptive summary | “unknown (no response)” (n = 11), “no time” (n = 9), “not interested” (n = 7), “distance to study center too far” (n = 2) | ||
Athletes willing to participate, fulfilling inclusion criteria and providing informed consent | > 25% agreed to participate | 33% (n = 14) | ✓ | |
Ineligible athletes | Descriptive summary | 0 | ||
Retention | The number of randomized athletes retained/who managed to complete the study protocol | > 80% of athletes at the study start | 100% | ✓ |
Data collection | Completed questionnaires | > 75% completed, collected, or analyzed at each visit | 100% | ✓ |
Completed diaries | 96% | ✓ | ||
Stool samples collected | 98% | ✓ | ||
Successfully analyzed microbiome composition | 100% | ✓ | ||
Fasting blood samples collected | 100% | ✓ | ||
Successfully analyzed blood samples | 100% | ✓ | ||
Reasons for missing data | Descriptive summary | One stool sample and two training diaries missing due to competition and related stress | ||
Adherence to intervention | Adherence to daily intake for both supplements | > 80% of days | 86% for probiotics and 79% for prebiotics | ✓/✖ |
Acceptability | Rating (from 0–10) over six items a | Having an average of at least five points for each item | 8.1 | ✓ |
Overall study rating (0–10) | Having an average of at least five points | 8.0 | ✓ | |
Willingness to participate again | > 50% of athletes willing to participate again | 71% | ✓ | |
Open feedback | Descriptive summary | − : participation costs too much time, inconvenient to visit the study center so often + : interesting subject, participation is beneficial and does not cost much time | ||
Resources needed | Time needed for athletes to collect data before each visit (stool collection, diaries, questionnaires) | < 60 min for each visit | 50 min | ✓ |
Time needed to perform all assessments during each visit | < 60 min for each visit | 25 min | ✓ | |
Safety analyses | Number of serious adverse events | No serious adverse events related to the study intervention or other procedures | No serious events occurred | ✓ |