Tribulus terrestris failed to improve exercise performance and body composition following a detraining period

Purpose: Detraining can result in a decrease in exercise performance and negative changes in body composition. Tribulus terrestris L. is a herb that has been suggested to raise testosterone levels and thus, theoretically, may have positive effects on exercise performance and body composition The main purpose of this study was to determine the potential ergogenic effects of Tribulus Terrestris L. in preventing the loss of muscle mass and strength, and its effects on aerobic performance following a period of detraining in collegiate-level athletes. Methods: Thirteen university-student athletes (age: 23.9 ± 2.1 y) volunteered to participate in this randomized, double-blind, crossover study. Participants received either a daily oral supplement of Tribulus terrestris L. (20 mg·kg⁻¹ × 3 times·day⁻¹) for 4 weeks or a placebo with a 2-week wash-out period between trial periods. Before and after each intervention period, participants’ body composition, isometric torque, VO₂max, and time-trial exercise test to exhaustion, were assessed. Blood samples were collected before and after exercise (2 and 24 h) to determine total serum testosterone levels. Blood lactate was measured before and after each exercise test. Results: The results demonstrated that total serum testosterone of the placebo group decreased at rest (following the detraining period baseline 20.1 ± 4.7 nmol L⁻¹ vs. detraining 14.8 ± 5.6 nmol L⁻¹; p < 0.001, 0.001), but supplementation with Tribulus terrestris L. maintained the resting values of testosterone after detraining (baseline 19.2 ± 6.4 nmol L⁻¹ vs. detraining 18.5 ± 5.8 nmol L⁻¹, p = 0.343). At 2-h post-exercise, the level of the hormone was significantly greater for the Tribulus terrestris L. group compared with the placebo group (23.8 ± 9.1 vs. 16.8 ± 5.4 nmol L⁻¹, p = 0.04). Tribulus terrestris L supplementation did not have any effect on body composition, aerobic performance, or muscle strength. Conclusion: Four weeks of Tribulus terrestris L. supplementation failed to improve exercise performance and body composition following a detraining period.