Table 1 Overview of feasibility outcomes and progression criteria
Feasibility criteria | Assessment | Progression criteria to a subsequent triala |
|---|---|---|
Recruitment and eligibility | Number of eligible athletes | N/A |
Percentage assessed for eligibility; fulfilling inclusion criteria, recruited and included (of total number identified) | >  25% agreed to participate of total eligible population | |
Reasons for ineligibility and non-participation | Information to be descriptively summarized. If necessary inclusion/exclusion criteria are to be reconsidered. | |
Data collection | Percentage of completed assessments/questionnaires | >  75% answering all questions at all assessments |
Numbers of missing items (e.g., laboratory measurements), reasons for missing data collection | < 20% missing information for primary outcomes [30] | |
Adherence to intervention | A rate of adherence to protocol for both intervention and control interventions | > 80% of participants at baseline |
Retention | The number of randomized participants retained/who managed to complete the study protocol Collect the reasons for premature study termination | > 80% of participants at baseline |
Feasibility of procedures and experimental setting | Number of:  1. Fasting blood samples collected  2. Correctly taken stool samples by study participants  3. Successfully analysed microbiome composition | >  75% of analytic procedures successfully completed |
Acceptability of intervention | Evaluated among participants post-trial:  1. Rating (from 0 to 10) of study procedures (intervention, measurements, time burden, personal value)  2. Willingness to participate again  3. Open feedback | Having an average of at least 5 points for each rating > 50% willing to participate again |
Resources needed to complete the study and the intervention | Length of time required for:  1. Study personnel to collect the data the monthly visits  2. Participants to provide data at the monthly visits | < 60 min to complete questionnaires and physical examinations during monthly study visits |
Safety analyses | Number of serious adverse events | No serious adverse events related to the study intervention or other procedures. |