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Abstract

The study of ergogenic aids and their influence results in many uncertainties that have yet to be answered or explained. There is speculation about the effectiveness of Tribulus terrestris (TT) as an ergogenic aid and its effectiveness for increasing power and strength. Little research has been completed to monitor its effects on cholesterol and blood pressure. The purpose of this study was to evaluate the effect of TT on muscular strength, blood pressure, and cholesterol in a sedentary population. Eighteen males (18 - 24 yrs,) were randomly assigned using a double-blind protocol into either TT group (n=9) or placebo (n=9), while subjects participated in an 8-week resistance training program. Each group either ingested a 650mg TT pill or a wheat grass equivalent pill with no change in diet. Strength outcomes were measured by having participants perform a 10-rep max strength test. Body fat outcomes were analyzed by including 7-site skinfold measurements and upper and lower body circumferences. Blood lipids and glucose were measured using the Cholestech LDX machine. The training protocol consisted of Smith machine bench press, Smith machine squat, Hammer Strength lat-pulldown, and Hammer Strength seated bicep curl with a ten percent progressive overload rate each week. Baseline body composition, cardiovascular health including cholesterol, and strength were not significantly different. Two-by-two repeated measures ANOVA was used to analyze differences between the control and TT groups for all dependent measures. There was a 100% adherence rate as all subjects completed the training protocol for the entire eight weeks. Although changes did exist such as decrease in body fat percentage (TT- 14.4 ± 6.0 to 11.9 ± 6.1; Control-14.0 ± 5.4 to 11.3 ± 4.7) and total cholesterol (TT- 173.4 ± 30.8 to 167.2 ± 28.2; Control- 171.6 ± 30.4; TT- 155.6 ± 24.8), there were no significant differences after 8 weeks between the two groups. There was however, a significant decrease in overall cholesterol for the TT group after training (167.2 ± 28.2) (F = 10.24; P = .006). Individual variables of cholesterol such as LDL, HDL, triglycerides and blood pressure were not significantly different between groups. The results indicated no significant interaction due to TT use for all measurements in a sedentary population while under an 8-week resistance training program. Suggestions for future studies should focus on long term intervention such as a twelve to fifteen week study.

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