Physiological implications of preparing for a natural male bodybuilding competition

Abstract

This study aimed to describe the body composition and physiological changes which take place during the in-season and recovery periods of a group of natural bodybuilders. Natural male bodybuilders (n = 9) were assessed 16 (PRE16), 8 (PRE8), and 1 (PRE1) week(s) before, and 4 (POST4) weeks after a bodybuilding competition. Assessments included body composition, resting metabolic rate (RMR), serum hormones, and 7-day weighed food and training diaries. Change in parameters was assessed using repeated-measures analysis of variance. Dietary protein intake remained high throughout the study period (2.8–3.1 g kg⁻¹ d⁻¹). Fat mass (FM) was significantly reduced from PRE16 to PRE1 (8.8 ± 3.1 vs. 5.3 ± 2.4 kg, P < .01). There was a small decrease in lean mass (LM) from PRE8 to PRE1 (71.8 ± 9.1 vs. 70.9 ± 9.1 kg, P < .05). No changes in RMR were observed (P > .05). Large reductions in total and free testosterone (16.4 ± 4.4 vs. 10.1 ± 3.6 nmol L⁻¹, P < .05; 229.3 ± 72.4 vs. 116.8 ± 76.9 pmol L⁻¹, P < .05), and insulin-like growth factor-1 (IGF-1) (27.0 ± 7.7 vs. 19.9 ± 7.6 nmol L⁻¹, P < .05) occurred between PRE16 and PRE1. LM and IGF-1 increased from PRE1 to POST4 (70.9 ± 9.1 vs. 72.5 ± 8.5 kg, P < .05; 19.9 ± 7.6 vs. 25.4 ± 9.3 nmol L⁻¹, P < .05). Despite substantial reductions in FM, participants maintained almost all of their LM. The reduction in anabolic hormone concentration is likely attributable to the prolonged negative energy balance, despite a high dietary protein intake.

Keywords:

• Lean mass
• fat mass
• resting metabolic rate
• protein
• hormones
• body composition

ORCID

Lachlan Mitchell http://orcid.org/0000-0003-1316-3688

Additional information

Funding

This work was supported by Sports Dietitians Australia. Helen O’Connor and Gary Slater receive payment from Sports Dietitians Australia for professional presentations delivered in a continuing education course for Sports Dietitians. This work was also supported by the Collaborative Research Network for Advancing Exercise & Sports Science (CRN-AESS) Capacity Building Seeding Grant Scheme, Australia, awarded to Daniel Hackett.