Tribulus is Good for Something: 1.25 g/day Modulate IGF-1 Availability and Alleviate Muscle Damage While Promoting Anaerobic Performance of Intensely Trained Male Boxers

Tribulus terrestris extracts - While the boxing gloved protect a boxers fists from damage, the TT extracts may protect his muscle. Recent study yields surprising results and insights into the performance enhancing effects of TT and why it may have failed to work in previous studies.
Yes, it's (a) not a rodent study, (b) published in a peer-reviewed journal, (c) not sponsored by a supplement company (but the Chinese government), and was (d) conducted not just with untrained and mostly sedentary or "recreational trained" human beings, but even with fifteen highly trained male boxers (national second-level athletes, 2–3 years of training) who were recruited from the boxing team of Shanghai University of Sport Affiliated School of Sports in China. This alone makes the latest study from the Shanghai University of Sport newsworthy. The fact that the scientists actually observed significant and practically effects when they 'fed' their subjects 1.25g of a standardized tribulus terrestis (TT) extract (bought on the free market from Pronova Biocare, Sweden) with a saponin content of >40% per day, however, makes the study even more interesting.
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In contrast to previous studies that focused exclusively on testosterone and (sometimes) DHT, when it comes to identifying mechanisms for potential performance increases, the study at hand was designed to investigate the effects of Tribulus terrestris (TT) extracts on muscle mass, muscle damage, and anaerobic performances of trained male boxers and whether those may be brought about by androgen, IGF-1, and/or changes in IGF-1 or the concentration of its binding protein (IGFBP-3). To this ends, the previously mentioned fifteen male boxers were divided into an exercise group (E, n = 7) and an exercise plus TT group (E + TT, n = 8). The two groups both undertook 3-weeks of high intensity and 3-weeks of high volume training. The latter were separated by a 4-week rest period.
Table 1: Training protocol of the boxers with high intensity and high volume training (Ma. 2015) | Abbreviations: HR, heart rate; RM, repetition maximum.
"All athletes received similar 3-week high intensity training and 3-week high volume training separated by a 4-week rest. Besides special technical training, the main part of the high intensity training was strength training including maximum strength training (twice a week, on Tuesday and Friday) and speed strength training (twice a week, on Monday and Thurs day). For high volume training [see Table 1], the boxers undertook endurance training (10,000 m race every day and low to moderate intensity rope skipping twice a week, on Tuesday and Friday), and special technical training and speed strength training similar to high intensity training" (Ma. 2015).
The supplement, the aforementioned TT extracts (1,250 mg/day), was orally administered only in the E + TT group, obviously. Before the pills were handed out to the subjects, their exact compositions had been analyzed and their saponin content had been confirmed by UHPLC–Q-TOF/MS.
Not all TT extracts are created equal! If you've previously taken tribulus supplements and have seen no results, the reason could well be that they did not contain the right amount or type of saponins. As Ma et al highlight, the content of 25(R)-Spirostan-3,6,12-trione/25(R)-Spirostan-4-ene-3,12-dione and TT saponin A varies "depending on geographical region, climate23 and part of herb, which may partly explain the divergent results of TT extracts from different studies" (Ma. 2015).
The results of the pre- and post assessments of muscle mass, anaerobic performance, and blood indicators revealed no inter-group differences for testosterone, DHT, muscle mass or total IGF-1. Creatine kinase (CK), the IGF binding protein IGFBP-3 and the subjects' absolute and relative muscle power, on the other hand, increased significantly more in the supplement (E + TT) vs. control (E) group (Figure 1 shows the relative difference of the change from baseline, i.e. ΔE+TT - ΔE).
Figure 1: Differences in relative changes of IGF-BP3, the ratio of IGF/IGF-BP3, mean power, relative mean power and creatine kinase (CK) - higher values denote significant increases compared to control (E), lower values decreases in (E+TT) vs. (E) (all p < 0.05) | data calculated based on Ma. 2015
Against that background it is only logical that the scientists speculate that the performance increase and reduction in muscle damage they observed could be a result of the increased availability of IGF-1 (the total IGF-1 to IGF1BP-3 ratio is an indicator of the amount of insulin growth factor 1 that's actually floating around unbound in the blood).
Figure 2: Overview of the general role of IGF-1; focus on what is missing when it declines as we age (Berryman. 2013).
If you look at the far-reaching effects of IGF-1 on muscle (Frystyk. 2010) and its general effects on human metabolism as depicted in Figure 2 from Berryman, et al (2013), it certainly appears reasonable to assume that the significant increase in IGF-1 availability could explain the decreased muscle damage in the study at hand as well as similar results from a human study by Milasius, et al (2009) and studies in overtrained and intensely trained rodents by Zhang, et al (2010), Wang et al (2010) and Yin et al (2013), respectively.
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What's the verdict, then? In view of the large influence the exact ratio and concentration of saponins will probably have on the effect of a given TT extract and its variability according to region, harvest and the part(s) of the plant that was/were used to prepare the extract (see red box) it is not impossible that previous studies by Antonio et al (2000) and Rogerson et al (2007) simply didn't find performance benefits in resistance-trained men and rugby players, because they used the 'wrong' extracts (or the training was not intense enough, some of the benefits in the study at hand were after all blunted performance decreases during intense training).

While it is hard to determine whether or not this hypothesis is true, there's no reason to debate the conclusion Ma et al draw based on their more recent results in trained boxers - a conclusion that reads: "Taking 1,250 mg capsules containing TT [...] alleviated muscle damage and promoted anaerobic performance of trained male boxers, which may be related to the decrease of plasma IGFBP-3 rather than androgen in plasma" (Ma. 2015) | Comment on Facebook!
  • Antonio, et al. "The effects of Tribulus terrestris on body composition and exercise performance in resistance-trained males." International Journal of Sport Nutrition and Exercise Metabolism, 10 (2000): 208–215.
  • Berryman, Darlene E., et al. "The GH/IGF-1 axis in obesity: pathophysiology and therapeutic considerations." Nature Reviews Endocrinology 9.6 (2013): 346-356.
  • Frystyk, Jan. "Exercise and the growth hormone-insulin-like growth factor axis." Medicine and science in sports and exercise 42.1 (2010): 58-66.
  • Ma, Yiming, Zhicheng Guo, and Xiaohui Wang. "Tribulus Terrestris extracts alleviate muscle damage and promote anaerobic performance of trained male boxers and its mechanisms: Roles of androgen, IGF-1 and IGF binding protein-3." Journal of Sport and Health Science (2015).
  • Milasius, K., R. Dadeliene, and Ju Skernevicius. "The influence of the Tribulus terrestris extract on the parameters of the functional preparedness and athletes’ organism homeostasis." Fiziol Zh 55.5 (2009): 89-96.
  • Rogerson, Shane, et al. "The effect of five weeks of Tribulus terrestris supplementation on muscle strength and body composition during preseason training in elite rugby league players." The Journal of Strength & Conditioning Research 21.2 (2007): 348-353.
  • Wang et al. "Effects of Tribulus terrestris on exercise ability, endocrine and immune functions of over-trained rats." Journal of Shanghai University of Sport 46 (2010).
  • Yin, Liang, et al. "The Effects of Tribulus Terrestris on the Time of Exhaustion in Rats with High Intensity Training and Its Mechanism." Journal of Shanghai University of Sport 5 (2013).
  • Zhang, Shuang, et al. "[Effect of gross saponins of Tribulus terrestris on cardiocytes impaired by adriamycin]." Yao xue xue bao= Acta pharmaceutica Sinica 45.1 (2010): 31-36.
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