The effects of ingesting a tribulus containing proprietary supplement with combined resistance training on strength, body composition, and hormonal changes in males

Methods Twenty-eight (22±4.48 yrs, 179.22±9.04 cm, 83.41±11.95 kg, 15.90±5.07 %BF) resistance-trained males between the ages of 18 and 30 were randomly assigned by body weight to ingest either a placebo or tribulus blend (tribulus fruit extract-40% saponins) in a double-blind manner. Subjects participated in a supervised 4-day per week periodized resistance training program split into two upper and two lower extremity workout per week. At baseline (T1), 4 weeks (T2), and 8 weeks (T3), body composition (DEXA), muscular strength (1RM), muscular endurance, and anaerobic power measurements (Wingate) were determined. Venous blood samples were obtained using standard procedures at all time points. Blood analyses included serum and whole blood metabolic profile and the serum analysis of free testosterone, cortisol, and insulin were conducted using standard EIA and ELISA assay protocols. Statistical analyses utilized a two-way ANOVA with repeated measures for all dependent variables (p 0.05) indicating that supplementation had no additional benefit. A significant main effect for time was observed for serum insulin (p = 0.01), however there was no significant differences between groups. No significant main effects or interactions (p > 0.05) were noted on measures of anaerobic power, muscular endurance, RHR & BP, nutritional dietary intake, cortisol, free testosterone, or on the markers of the metabolic/CBC panel.