Effects of Probiotic Supplementation on Performance Retention During Detraining and Recovery After Simulated Return-to-Training Stress in College Volleyball Players: An Exploratory Randomized, Single-Blind, Placebo-Controlled Trial.
Eight weeks of multi-strain probiotic supplementation was associated with selected differences in performance and recovery during a training transition, but after accounting for multiple comparisons, evidence was limited to lower muscle soreness and a smaller reduction in non-dominant knee extension maximum work at 24 h.
Key Findings
Results
After correcting for multiple comparisons, probiotic supplementation was associated with lower muscle soreness following a simulated return-to-training stressor.
Twenty-eight national-level university volleyball players were randomized to probiotic or placebo groups (n = 14 per group)
The simulated return-to-training stressor consisted of 200 weighted vertical jumps
Recovery was monitored for 48 hours post-stressor
Lower muscle soreness remained statistically significant after accounting for multiple comparisons
Before multiple comparison correction, the probiotic group also showed lower creatine kinase responses
Results
After correcting for multiple comparisons, the probiotic group showed a smaller reduction in non-dominant knee extension maximum work at 180°/s at 24 hours post-stressor.
This was one of only two outcomes that remained significant after multiple comparison correction
The measure assessed was non-dominant knee extension maximum work at an isokinetic speed of 180°/s
The significant difference was observed at the 24-hour recovery time point
Before multiple comparison correction, the probiotic group also showed smaller reductions in selected strength-recovery and rate-of-force-development measures more broadly
Results
Before accounting for multiple comparisons, the probiotic group showed smaller declines in shuttle-test performance and vertical jump height across the 8-week intervention period.
The 8-week intervention comprised regular training, tapering and competition, and reduced training phases
Smaller declines were observed in both standing and approach vertical jump height in the probiotic group
No significant between-group differences were found in maximal-strength or Wingate outcomes
These performance differences did not survive multiple comparison correction
Results
Gut microbiota alpha diversity, specifically Chao1 richness, decreased more in the probiotic group than in the placebo group over the intervention.
Chao1 richness, a measure of species richness, showed a greater decrease in the probiotic group
Changes in Simpson diversity did not differ significantly between groups
Relative abundances of Firmicutes, Lachnospiraceae, and Bifidobacteriaceae did not differ between groups
Gut microbiota were assessed before and after the 8-week supplementation period
Conclusions
The study was an exploratory trial with a small sample size, and its authors concluded that findings require confirmation in larger, prospectively registered trials with prespecified outcomes.
The trial was randomized, single-blind, and placebo-controlled
Sample size was 28 participants total (14 per group)
The trial was described as 'exploratory' by the authors
The authors noted uncertainty about the effects of probiotic supplementation on performance and recovery during training transitions prior to the study
The authors explicitly called for 'larger, prospectively registered trials with prespecified outcomes' to confirm findings
What This Means
This research suggests that taking a multi-strain probiotic supplement for 8 weeks may offer some benefits to competitive volleyball players during periods when their training load changes significantly, such as tapering before competition and then returning to heavier training. The study tested 28 national-level university volleyball players, half of whom took probiotics and half a placebo, over an 8-week period that included different training phases. After the main intervention, researchers had players perform 200 weighted vertical jumps to simulate the stress of returning to intense training, then tracked their recovery for 48 hours.
The most notable findings were that players taking probiotics reported less muscle soreness after the simulated high-intensity training session, and they showed better maintenance of one measure of knee strength (specifically, the work capacity of the non-dominant leg at a fast movement speed) at 24 hours post-exercise. There were also some early signs that probiotics might help players maintain their shuttle-run and jumping performance during the training transition period, though these differences were no longer statistically convincing once researchers applied corrections for testing many outcomes simultaneously. Interestingly, the probiotic group showed a greater decrease in one measure of gut bacterial diversity (Chao1 richness), while other gut microbiota measures did not differ between groups.
This research suggests that probiotic supplementation could be a useful strategy for athletes managing muscle soreness and recovery during demanding periods involving training load changes, but the evidence is still preliminary. The study was small and exploratory, and the authors themselves emphasize that these findings need to be confirmed in larger, more rigorously designed studies before strong conclusions can be drawn. The results provide a useful foundation for future research rather than definitive guidance for athletic practice.
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Liu J, Zhao K, Liu C, Liu Z, Jiang W. (2026). Effects of Probiotic Supplementation on Performance Retention During Detraining and Recovery After Simulated Return-to-Training Stress in College Volleyball Players: An Exploratory Randomized, Single-Blind, Placebo-Controlled Trial.. Nutrients. https://doi.org/10.3390/nu18193203