Eight weeks of supervised resistance training in 150 sedentary adults revealed that gut microbiome changes correlate directly with strength improvements. Participants achieving 33% or greater strength gains showed significant microbial community shifts, with 27 taxa changing by week 8. Notably, Faecalibacterium and Roseburia hominis—key anti-inflammatory bacteria—increased substantially in high responders. These findings challenge the prevailing assumption that only endurance exercise meaningfully alters gut microbiota. The dose-response relationship between strength gains and microbial changes suggests that training intensity or individual responsiveness, rather than exercise type alone, drives microbiome adaptation. This has profound implications for personalized fitness prescriptions aimed at gut health optimization. The enrichment of Lachnospiraceae family bacteria, known producers of beneficial short-chain fatty acids, potentially links resistance training to improved metabolic health and reduced systemic inflammation. However, the study's 8-week duration leaves questions about long-term sustainability of these changes. For adults seeking microbiome benefits through exercise, these results suggest that progressive overload and measurable strength improvements may be more important than exercise modality itself.