Journal Title (Medline/Pubmed accepted abbreviation): Int J Sports Nutr Exerc Metab
Page numbers: 457-465
doi (if applicable): N/A
Background:T estosterone levels are related to many physiologic conditions such as protein synthesis, muscle strength, fat oxidation, and adiposity. Therefore, research into improving exercise performance has focused on supplementation with testosterone precursors or derivatives to increase the levels of free testosterone. However, an alternative approach is to reduce testosterone breakdown by inhibiting the enzymes responsible (aromatase and 5-α-reductase). Evidence from aromatase inhibitor (AI) studies suggest that anabolic benefits may be obtained, although it is uncertain to what extent the testosterone increase is necessary to achieve a performance benefit.
Hypothesis/purpose of study:To determine the effects on strength, body composition, and hormonal profiles of fenugreek (Trigonella foenum-graecum [standardized for Grecunin]), which may inhibit aromatase and 5-α-reductase activity
Subjects:30 resistance-trained (> 1 year of total-body resistance training) males were randomized to placebo (n = 13; age, 21 ± 3 yr; height, 180 ± 6.4 cm; weight, 84 ± 15 kg; body fat, 18.3% ± 6.8%) or fenugreek (n = 17; age, 21 ± 2.8 yr; height, 178 ± 5.8 cm; weight, 85 ± 9.6 kg; body fat, 18.8% ± 4.8%).
Experimental design: Randomized, double-blind, weight-matched, parallel-group study
Treatments and protocol:Participants were divided into 2 groups based on weight; members of each group were randomized to 500 mg of placebo or fenugreek. Participants performed 4 exercise sessions: practice, baseline (T1), and 2 experimental after 4 (T2) and 8 (T3) weeks of supplementation. Each session consisted of a 1-repitition maximum (1RM) upper and lower body exercise preceded by a warm-up and a 10-minute rest. This was followed by a 15-minute rest and a Wingate anaerobic capacity test. A resistance training program for upper and lower body was detailed for each participant during supplementation. Blood samples were drawn at all testing for chemistry and hematology profiles and levels of anabolic hormones. Side effects and health status were determined weekly.
The results showed that fenugreek did not completely block aromatase and 5-α-reductase activity because total and bioavailable testosterone increased without a corresponding increase in its breakdown product dihydrotestosterone. Although fenugreek had no effect on fat-free mass, body fat percentage was significantly reduced. It is unclear why the authors did not report any data on changes in fat mass. There may be a relationship between androgen levels and adiposity; however, this study did not measure lipolysis markers. Total and bioavailable testosterone levels did increase to a very small degree (< 5 ng/mL on a mean basis for each) with fenugreek supplementation, but this did not translate into increased muscle strength. Higher levels of total or bioavailable testosterone than those observed in this study are necessary to increase muscle strength.