Dynamic Stability of Gut Microbiota in Elite Volleyball Athletes: Microbial Adaptations during Training, Competition and Recovery

Junior Carlone^1,2,3,4*Saverio Giampaoli²Eugenio Alladio⁵Gioele Rosellini²Filippo Barni⁶Elena Salata⁶Attilio Parisi²Alessio Fasano^3,4,7Antonio Tessitore²

• ¹University of Verona, Verona, Italy
• ²Universita degli Studi di Roma Foro Italico, Rome, Italy
• ³Mass General Hospital for Children Pediatric Group Practice, Boston, United States
• ⁴Harvard Medical School, Boston, United States
• ⁵Universita degli Studi di Torino, Turin, Italy
• ⁶Raggruppamento Carabinieri Investigazioni Scientifiche, Rome, Italy
• ⁷Fondazione EBRIS, Salerno, Italy

Introduction To examine how different weekly training and competition schedules influence gut microbiota composition in elite volleyball players, investigating the relationship between training and competition demands, recovery periods and microbial dynamics to identify potential biomarkers for training load and recovery status assessment. Methods Seven elite athletes from the Italian Men's SuperLega Championship (age: 26.5±4.5 years; weight: 96±11 kg; height: 200±0.1 cm; BMI: 24±1.9) were monitored at four timepoints over eight weeks Regular Season periods (T0, T1), Rest Period (T2) and International Tournament Period (T3). Faecal samples underwent 16S rRNA sequencing analysis, with concurrent Mediterranean Diet adherence and Stool Consistency assessments. Repeated measures ANOVA and oneway ANOVA were performed to evaluate microbial abundance changes. Results 16S rRNA sequencing revealed Firmicutes predominance (41.22-76.03%), followed by Actinobacteria (9.66-54.45%) and Bacteroidetes (0.73-26.56%). The Firmicutes/Bacteroidetes ratio fluctuated in response to training intensity and competition 6:1 during T0 and T1, decreasing to 3:1 during T2 and returning to 5:1 during T3. Dominant bacterial families included Ruminococcaceae (26.97-28.3%), and Lachnospiraceae (9.66-12.61%). Significant enrichment of Rikenellaceae abundance occurred during Rest Periods (p<0.05). Alpha diversity remained stable despite individual variation. Mediterranean diet adherence declined during Regular Season Periods (T0: 6.3±1.5, T1: 5.5±0.8), while stool consistency gradually improved. Discussion Despite overall stability, elite athletes gut microbiota adapted to volleyball varying training demands primarily via Firmicutes/Bacteroidetes ratio modulations and Rikenellaceae enrichment during Recovery Periods. These microbial alterations represent potential biomarkers for assessing training load and recovery status. Additional investigation is necessary to elucidate how these microbial dynamics influence athletic performance outcomes.