Baseline Oral Microbiota Richness Is Associated with Training-Induced Improvements in Relative Handgrip Strength in Older Adults

Background: Considerable inter-individual variability exists in exercise-induced adaptations among older adults. Although microbial ecosystems have been linked to muscle function and physical performance, the role of the oral microbiota in exercise responsiveness remains unclear. Objective: To explore whether baseline oral microbiota characteristics are associated with training-induced changes in relative handgrip strength (rHGS) in older adults. Methods: This preliminary exploratory longitudinal study included 18 community-dwelling older adults who completed a 16-week supervised exercise intervention. Oral microbiota composition was assessed at baseline using 16S rRNA gene sequencing. Participants were classified as responders when ΔrHGS was >0 and as non-responders when ΔrHGS was ≤0; this operational threshold did not account for measurement error or clinically meaningful change. Associations between baseline microbiota variables and ΔrHGS were examined using group comparisons, Spearman correlations, FDR correction, and exploratory linear regression models. Results: Responders showed higher baseline bacterial genus richness than non-responders at the nominal level (86.15 ± 8.90 vs. 71.60 ± 13.32; p = 0.023), although this difference did not remain significant after FDR correction (pFDR = 0.069). Baseline richness was positively associated with ΔrHGS (ρ = 0.578, p = 0.012, pFDR = 0.036) and remained associated with ΔrHGS in exploratory sensitivity models. Genus-level findings did not remain significant after FDR correction and were interpreted as exploratory candidate signals. Conclusions: In this preliminary cohort, greater baseline oral microbiota richness was associated with larger improvements in rHGS after exercise training. These hypothesis-generating findings require confirmation in larger studies with functional microbiome assessment before causal or predictive interpretations can be made.