title: The effect of five weeks of Tribulus terrestris supplementation on muscle strength and body composition during preseason training in elite rugby league players.
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.
authors.affiliation: School of Exercise Science and Sport Management, Southern Cross University Lismore, New South Wales, Australia. srogerson10@bigpond.com
authors.forename: Shane
authors.initials: S
authors.lastname: Rogerson
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Riches
authors.forename: Carl
authors.initials: C
authors.lastname: Jennings
authors.forename: Robert P
authors.initials: RP
authors.lastname: Weatherby
authors.forename: Rudi A
authors.initials: RA
authors.lastname: Meir
authors.forename: Sonya M
authors.initials: SM
authors.lastname: Marshall-Gradisnik
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001823:Body Composition / Q000187:drug effects*; D015992:Body Mass Index; D019587:Dietary Supplements; D004311:Double-Blind Method; D005538:Football / Q000502:physiology*; D006801:Humans; D008297:Male; D053580:Muscle Strength / Q000187:drug effects*; D010806:Physical Education and Training / Q000379:methods*; D008517:Phytotherapy / Q000379:methods*; D016896:Treatment Outcome; D032444:Tribulus