Effects of Caffeine and Rhodiola rosea, Alone and Combined, on DanceSport-Specific Jive Performance: A Randomized, Blinded, Placebo-Controlled Trial

Background/Objectives: Evidence on caffeine (CAF), Rhodiola rosea, and their combined use in DanceSport remains limited. This randomized, blinded, placebo-controlled trial, retrospectively registered at ClinicalTrials.gov (NCT07690085), evaluated Jive-specific performance after a four-week standardized intervention. Methods: Forty-eight male collegiate DanceSport athletes were randomly allocated by drawing lots to placebo control (CTR), CAF, RHO (Rhodiola rosea), or RHO + CAF (n = 12/group). RHO was administered using Tongrentang Brand Rhodiola Capsule (0.4 g/capsule; three capsules twice daily; 2.4 g·day−1) for four weeks, and CAF was administered at 3 mg·kg−1 body mass 30 min before Post testing. The registry lists four primary outcomes: kick-extension angle, post-kick leg-retraction angle, trunk anteroposterior sway, and 30 s valid-kick success rate. Post values were analyzed by ANCOVA using the corresponding Pre value as covariate, with Holm correction across the primary-outcome family. Results: Training attendance was 100%. All four primary-outcome tests remained significant after Holm correction (adjusted p = 0.000768–0.006182; partial η2 = 0.248–0.386). Adjusted success rates were 84.66% (CTR), 90.69% (CAF), 84.43% (RHO), and 92.31% (RHO + CAF); CAF and RHO + CAF were higher than CTR and RHO. The CAF × RHO interaction was not significant. Conclusions: Group differences were outcome-specific. The combined condition showed the highest adjusted success rate, but the data did not establish a synergistic interaction. The findings apply to the Rhodiola rosea intervention used in this study.