Isola, VHulmi, JJMbay, TKyröläinen, HHäkkinen, KAhola, VHelms, ERAhtiainen, JP2025-06-302025-06-302024-09-11European Journal of Applied Physiology, ISSN: 1439-6319 (Print); 1439-6327 (Online), Springer Science and Business Media LLC, 125(2), 393-408. doi: 10.1007/s00421-024-05606-z1439-63191439-6327http://hdl.handle.net/10292/19440Purpose: Physique athletes engage in rigorous competition preparation involving intense energy restriction and physical training to enhance muscle definition. This study investigates hormonal changes and their physiological and performance impacts during such preparation. Methods: Participants included female (10 competing (COMP) and 10 non-dieting controls (CTRL)) and male (13 COMP and 10 CTRL) physique athletes. COMP participants were tested 23 weeks before (PRE), one week before (MID), and 23 weeks after the competition (POST). Non-dieting CTRL participants were tested at similar intervals. Measurements included body composition (DXA), muscle cross-sectional area (ultrasound), energy availability (EA) derived by subtracting exercise energy expenditure (EEE) from energy intake (EI) and dividing by fat-free mass (FFM), muscle strength, and various serum hormone concentrations (ACTH, cortisol, estradiol, FSH, IGF-1, IGFBP-3, insulin, and free and total testosterone and SHBG). Results: During the diet, EA (p < 0.001), IGF-1 (p < 0.001), IGFBP-3 (p < 0.01), and absolute muscle strength (p < 0.01–0.001) decreased significantly in both sexes in COMP. Decreases in IGF-1 were also associated with higher loss in FFM. In males, testosterone (p < 0.01) and free testosterone (p < 0.05) decreased, while SHBG (p < 0.001) and cortisol (p < 0.05) increased. Insulin decreased significantly only in males (p < 0.001). Mood disturbances, particularly increased fatigue in males (p < 0.05), highlighted the psychological strain of competition preparation. All these changes were restored by increased EA during the post-competition recovery period. Conclusion: Significant reductions in IGF-1 and IGFBP-3 during competition preparation may serve as biomarkers for monitoring physiological stress. This study offers valuable insights into hormonal changes, muscle strength, and mood state during energy-restricted intense training.Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.http://creativecommons.org/licenses/by/4.0/BodybuildingEnergy availabilityIGF-1POMSREDsWeight loss32 Biomedical and Clinical Sciences42 Health Sciences4207 Sports Science and ExerciseClinical ResearchPreventionNutrition1106 Human Movement and Sports SciencesSport Sciences3202 Clinical sciences3208 Medical physiology4207 Sports science and exerciseHumansMaleFemaleMuscle StrengthAthletesInsulin-Like Growth Factor IAdultYoung AdultEnergy MetabolismInsulin-Like Growth Factor Binding Protein 3HormonesBody CompositionTestosteroneMuscle, SkeletalAthletic PerformanceCompetitive BehaviorMuscle, SkeletalHumansTestosteroneHormonesInsulin-Like Growth Factor IInsulin-Like Growth Factor Binding Protein 3Competitive BehaviorBody CompositionEnergy MetabolismAdultFemaleMaleMuscle StrengthAthletic PerformanceYoung AdultAthletesHumansMaleFemaleMuscle StrengthAthletesInsulin-Like Growth Factor IAdultYoung AdultEnergy MetabolismInsulin-Like Growth Factor Binding Protein 3HormonesBody CompositionTestosteroneMuscle, SkeletalAthletic PerformanceCompetitive BehaviorJournal ArticleOpenAccess10.1007/s00421-024-05606-z