(27) HORMONAL ADAPTATIONS TO COMPETITION PREPARATION IN MALE AND FEMALE PHYSIQUE ATHLETES

Physique competitors use severe caloric restriction to reduce body fat before the competition. We previously showed decreased body fat, resting energy expenditure, and serum leptin and T3 concentrations during competition preparation among physique athletes (Isola et al. 2023). Low energy availability during preparation for the competition may also induce other extensive changes in endocrine function. This study examined the effects of competition preparation on several hormones in male and female physique competitors.

Forty-five physique athletes (29±5 years, 6±2 training years) volunteered for the study and were allocated to the competitor (COMP, male n=13, female n=10) and control group (CONT, male n=10, female n=12) who did not compete. COMP prepared for the national championships using 20±4 weeks caloric restriction. Measurements were at 23 and 2 weeks before the competition. DXA measured body fat and fat-free mass, and ultrasound for the vastus lateralis cross-sectional area (VL CSA). Energy availability (EA) was calculated by subtracting exercise energy expenditure (assessed by training logs) from total daily energy intake (assessed by food diaries) and dividing it by fat-free mass. Maximal isometric knee extension torque (ISOM) was determined using a dynamometer. Fasted serum total (T) and free testosterone (FT), sex hormone binding globulin (SHBG), oestradiol, follicle-stimulating hormone (FSH), insulin growth factor-I (IGF-I), IGF binding protein-3 (IGFBP-3), adrenocorticotropic hormone (ACTH), cortisol, and insulin concentrations were measured.

In COMP, body fat% decreased from 16±5 to 6±2 % in males and from 25±5 to 12±5 % in females (p< 0.001). Compared to CONT groups, fat and fat-free mass, EA, and VL CSA decreased (p< 0.05-0.001) in both COMP males and females. ISOM decreased in COMP females (p< 0.001), and ISOM per VL CSA in COMP males (p< 0.05) compared to CONT groups. Changes in ISOM were associated with changes in FM in COMP groups (r = 0.642, p< 0.001, n=23). In COMP males, serum T, FT, IGFBP-3, and insulin decreased (p< 0.05-0.001), and SHBG, oestradiol, and cortisol increased (p< 0.05-0.001) compared to CONT males. In COMP females, IGF-1 and IGFBP-3 decreased (p< 0.01-0.001) compared to CONT females.

The weight loss in COMP led to expected drastic decreases in fat mass and energy availability. At the same time, fat-free mass and muscle size of knee extensors decreased somewhat (Isola et al. 2023). In this study, a decrease in fat mass was associated with muscle strength decrements in competitors. Thus, a negative energy balance, rather than muscle atrophy, may be an essential factor in impaired muscle strength output during weight loss in physique competitors. In the present study, physique athletes preparing for competition, the changes in endocrine function due to low energy availability were like those recently reviewed (Areta et al. 2021). In males, sex hormones, insulin, IGFBP-3, and cortisol responded to the caloric restriction, while in females, only IGF-I and IGFBP-3 showed downregulation. More extensive endocrine changes observed in male competitors could be due to more demanding weight loss as their body fat% was reduced to very low levels. Overall, adaptive changes in present hormones to weight loss appeared not extensive and were unrelated to the changes in body composition or energy availability.

Isola et al. (2023). Appl Physiol Nutr Metab. In press.

Areta et al. (2021) Eur J Appl Physiol. 121(1):1-21

Acknowledgements: The authors would like to thank the research assistants and participants for their time and effort in completing this study and the Renaissance Periodization^TM, Finnish Fitness Sports Association, Support Foundation of the Finnish Defence Forces, and Finnish Sports Research Foundation for their financial support.