Eighteen healthy, male basketball players, have been divided into 2 groups, one group was supplemented with 17 g/day of soluble dietary fiber (Nutriose®), over four weeks and the other received placebo. Their morphological characteristics, neuromuscular and cardiovascular endurance, and rating of perceived exertion according to the RPE (Rating of Perceived Exertion) scale were assessed. Measurements were performed before supplementation and after 4 weeks of supplementation. Fecal samples have been taken from all participants immediately before and after the supplementation period, their total DNA extracted and sent for amplicon sequencing. This work emphasizes both the relevance of prebiotics in sports nutrition. Fiber has been a neglected dietary component of sports nutrition and in this study a statistically significant positive impact on perception of fatigue has been demonstrated, which signifies the need for more studies in this direction.Supplementary_ANOVA: The analysis of research data processed by conventional methods of descriptive statistics: arithmetic mean and standard deviation (SD). ANOVA 2x2 was used to analyze the variables between the initial and the final measurements both within each group and between groups of basketball players (9 players in each group). Statistical software Statistica ver. 13.0 (Tulsa, OK, United States) was used for all analyses. Statistical comparisons were performed with commercially available software (GraphPad Prism v. 8.0, GraphPad Software, San Diego, CA, USA) and RPE variables were analyzed using a two-way repeated-measures analysis of variance (ANOVA) to evaluate the differences between trials. Tests of normality and assumptions were conducted, and if a significant violation was found, an appropriate adjustment to the degrees of freedom was made. For the TTE, the last time point was the subjective time to task failure. Two-tailed paired samples t-tests were used to assess the differences between pre-to-post TTE in the neuromuscular assessments. Statistical significance was declared when P<0.05. Data are presented as Means ± SD in-text and tables, and as Means ± SEM in the figures, unless otherwise stated.Supplementary Figure 1 and Supplementary Figure 2: The impact of fiber supplementation on gut microbiome was assessed through monitoring of relative taxonomic abundance in both participant groups at two time points. Time point 1, immediately before starting supplementation intervention and time point 2 immediately after 4 weeks of fiber supplementation period. Supplementary Dataset 1: The distribution of microbial taxa on phylum level.

Eighteen healthy, male basketball players, have been divided into 2 groups, one group was supplemented with 17 g/day of soluble dietary fiber (Nutriose®), over four weeks and the other received placebo. Their morphological characteristics, neuromuscular and cardiovascular endurance, and rating of perceived exertion according to the RPE (Rating of Perceived Exertion) scale were assessed. Measurements were performed before supplementation and after 4 weeks of supplementation. Fecal samples have been taken from all participants immediately before and after the supplementation period, their total DNA extracted and sent for amplicon sequencing. This work emphasizes both the relevance of prebiotics in sports nutrition. Fiber has been a neglected dietary component of sports nutrition and in this study a statistically significant positive impact on perception of fatigue has been demonstrated, which signifies the need for more studies in this direction.Supplementary_ANOVA: The analysis of research data processed by conventional methods of descriptive statistics: arithmetic mean and standard deviation (SD). ANOVA 2x2 was used to analyze the variables between the initial and the final measurements both within each group and between groups of basketball players (9 players in each group). Statistical software Statistica ver. 13.0 (Tulsa, OK, United States) was used for all analyses. Statistical comparisons were performed with commercially available software (GraphPad Prism v. 8.0, GraphPad Software, San Diego, CA, USA) and RPE variables were analyzed using a two-way repeated-measures analysis of variance (ANOVA) to evaluate the differences between trials. Tests of normality and assumptions were conducted, and if a significant violation was found, an appropriate adjustment to the degrees of freedom was made. For the TTE, the last time point was the subjective time to task failure. Two-tailed paired samples t-tests were used to assess the differences between pre-to-post TTE in the neuromuscular assessments. Statistical significance was declared when P<0.05. Data are presented as Means ± SD in-text and tables, and as Means ± SEM in the figures, unless otherwise stated.Supplementary Figure 1 and Supplementary Figure 2: The impact of fiber supplementation on gut microbiome was assessed through monitoring of relative taxonomic abundance in both participant groups at two time points. Time point 1, immediately before starting supplementation intervention and time point 2 immediately after 4 weeks of fiber supplementation period. Supplementary Dataset 1: The distribution of microbial taxa on phylum level.