Jung-Chul Lee, An-Sik Heo
Background/Objectives: Ashwagandha (Withania somnifera) is increasingly marketed as an adjunct that amplifies the strength and muscle-size gains produced by resistance training. Prior meta-analyses pooled trials across mixed exercise contexts rather than trials confined to structured resistance training. We therefore quantified adjunctive ashwagandha effects on muscular strength, chest circumference and body composition within such trials. Methods: We searched twelve bibliographic sources (including PubMed/MEDLINE, Europe PMC, OpenAlex and Cochrane CENTRAL) and two trial registers (ClinicalTrials.gov, WHO ICTRP) without date restriction to 23 August 2026, with reference-list, included-study-list and forward-citation screening, for randomized controlled trials (RCTs) combining a standardized ashwagandha extract (root or root-and-leaf) with structured resistance training in healthy adults (PRISMA 2020). Screening, extraction and risk-of-bias assessment were duplicated independently. Change-from-baseline standardized mean differences (SMDs; Hedges g) were pooled with restricted maximum-likelihood random-effects models, with RoB 2, leave-one-out and Hartung-Knapp-Sidik-Jonkman (HKSJ) sensitivity analyses, and GRADE. Embase, Scopus, Web of Science and CINAHL were unavailable to us, but Embase- and CINAHL-derived records were retrieved indirectly through CENTRAL. Results: Four RCTs were eligible; three (n = 161) provided poolable data, and one preprint was reported narratively because its bench-press values were not interpretable as absolute loads. Ashwagandha was associated with greater gains than placebo in 1-RM bench press (SMD 0.60, 95% CI 0.20-1.01), lower-body 1-RM (0.52, 0.19-0.86) and chest circumference (0.86, 0.41-1.31), but not body fat (-0.32, -0.72-0.08). Heterogeneity was low to moderate (I2 = 7-34%); all three pooled trials raised at least some concerns on RoB 2. Under HKSJ adjustment both strength estimates lost statistical significance and each depended on one influential trial; for chest circumference (k = 2), the HKSJ interval was too imprecise to be informative. GRADE certainty was Low for both strength outcomes and body fat, and Very Low for chest circumference. Conclusions: Current evidence does not establish that adjunctive ashwagandha meaningfully enhances resistance-training adaptations; it indicates possible benefits for maximal strength and, indirectly, upper-body girth, but the evidence base is small, statistically fragile and of low to very low certainty, with no dependable effect on adiposity. Adequately powered, independently funded RCTs using direct measures of hypertrophy are required. This review received no external funding and was not registered.