The effect of five weeks of Tribulus terrestris supplementation on muscle strength and body composition during preseason training in elite rugby league players

J Strength Cond Res. 2007 May;21(2):348-53. doi: 10.1519/R-18395.1.

Abstract

Tribulus terrestris is an herbal nutritional supplement that is promoted to produce large gains in strength and lean muscle mass in 5-28 days (15, 18). Although some manufacturers claim T. terrestris will not lead to a positive drug test, others have suggested that T. terrestris may increase the urinary testosterone/epitestosterone (T/E) ratio, which may place athletes at risk of a positive drug test. The purpose of the study was to determine the effect of T. terrestris on strength, fat free mass, and the urinary T/E ratio during 5 weeks of preseason training in elite rugby league players. Twenty-two Australian elite male rugby league players (mean +/- SD; age = 19.8 +/- 2.9 years; weight = 88.0 +/- 9.5 kg) were match-paired and randomly assigned in a double-blind manner to either a T. terrestris (n = 11) or placebo (n = 11) group. All subjects performed structured heavy resistance training as part of the club's preseason preparations. A T. terrestris extract (450 mg.d(-1)) or placebo capsules were consumed once daily for 5 weeks. Muscular strength, body composition, and the urinary T/E ratio were monitored prior to and after supplementation. After 5 weeks of training, strength and fat free mass increased significantly without any between-group differences. No between-group differences were noted in the urinary T/E ratio. It was concluded that T. terrestris did not produce the large gains in strength or lean muscle mass that many manufacturers claim can be experienced within 5-28 days. Furthermore, T. terrestris did not alter the urinary T/E ratio and would not place an athlete at risk of testing positive based on the World Anti-Doping Agency's urinary T/E ratio limit of 4:1.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Analysis of Variance
  • Body Composition / drug effects*
  • Body Mass Index
  • Dietary Supplements*
  • Double-Blind Method
  • Football / physiology*
  • Humans
  • Male
  • Muscle Strength / drug effects*
  • Physical Education and Training / methods*
  • Phytotherapy / methods*
  • Treatment Outcome
  • Tribulus*