Rydzik, LukaszIlbak, IsmailDuz, SerkanAmbrozy, TadeuszPalka, TomaszKopanska, MartaNiewczas, Marta2026-04-042026-04-0420252077-0383https://doi.org/10.3390/jcm14207203https://hdl.handle.net/11616/108550Background: Evidence on acute endocrine responses to K-1 kickboxing is limited. This pilot study assessed pre-to-post changes in GH, IGF-1 and insulin after a single K-1 bout and explored relationships with training experience (TE), final heart rate (HRFINAL) and perceived exertion (RPE). Methods: Elite male K-1 athletes (n = 10) completed an interclub, referee-supervised three-round bout (3 x 2 min). Venous blood was sampled pre-fight and +2 min. GH, IGF-1 and insulin were assayed (ELISA). Paired t-tests and Pearson's r quantified changes and associations. Results: GH rose from 1.20 +/- 2.05 to 11.27 +/- 8.82 ng/mL (p = 0.007; d = 1.85), and insulin from 5.95 +/- 1.56 to 12.95 +/- 5.95 mu U/mL (p = 0.002; d = 1.86); IGF-1 showed no change (200.90 +/- 55.89 to 203.00 +/- 54.10 ng/mL; p = 0.497). Delta GH and Delta insulin correlated positively with HRFINAL (rp = 0.89 and 0.88, both p < 0.001) and RPE (rp = 0.70 and 0.68; p = 0.024 and 0.031), and negatively with TE (rp = -0.72 and -0.68; p = 0.019 and 0.031). Conclusions: A single K-1 fight elicited large acute increases in GH and insulin but not IGF-1 at +2 min. HRFINAL and RPE tracked response magnitude, while more experienced athletes showed smaller deltas. Findings are preliminary and limited by a small sample, elite-only cohort, in an interclub setting, with immediate sampling and absence of a control group.eninfo:eu-repo/semantics/openAccesscombat sportssports confrontationgrowth hormoneinsulin-like growth factor 1insulinArticle14204115607410.3390/jcm142072032-s2.0-105020291492Q1WOS:001603765400001Q10000-0002-0131-15940000-0001-7611-48380000-0002-3364-09900000-0002-7392-52290000-0001-7361-94780000-0002-9535-173X0000-0001-5225-9397