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Putting Tribex-500 to the Test
Part 2 - Elite Endurance Athletes

By Dr. John M Berardi, Ph.D.
First published at www.t-mag.com, Aug 4 2000.

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Tribex-500 has received more attention lately than Britney Spears's perpetually exposed midriff. The Biotest product was the subject of two scientific investigations presented at the American College of Sports Medicine's national meeting. The two studies were very different in nature with one looking at power athletes and one looking at endurance athletes. However, the goal of both projects was to see if Tribex could produce measurable increases in athletic performance, recovery, strength and size.
If you read Part 1 of my report, which covered Dr. Jose Antonio's study of power athletes, you know that Tribex tended to increase lean body mass in the football players and bodybuilders involved in the study. Although I had a few criticisms of the study, it was still an intriguing look at some preliminary data on the effectiveness of the product. This week, due to your overwhelming feedback and questions, I'm back with the second report.

Getting to the Source

The second study was headed by hardcore researcher Steve McGregor. I say "hardcore" because of his background in molecular microbiology and chemistry. This guy didn't cruise through college taking nothing but activity classes! Currently Steve is an exercise physiology PhD student at the University of Toledo. With a successful research background and interests in muscle growth, muscle recovery, and nutritional supplementation. Steve's work has gotten a lot of attention both within the research world as well as within the athletic community.

This fall Steve will be taking his considerable talents to Eastern Michigan University, former home to well-known prohormone researcher Dr. Tim Ziegenfuss (and, come to think of it, Testosterone editor-in-chief, TC). If you're smart, you'll be keeping your eye on this guy for more cutting edge research in the near future. Today, we'll be discussing his most recent work with Tribex-500.

JB: Before we begin talking about this particular study, I wanted to mention that it's not often that researchers venture out of their labs to share their data and opinions with "lay" publications. Why do you think that is?

SM: There are probably a few reasons why this doesn't happen a great deal. First of all, there's the interest/communication gap. A lot of basic research just wouldn't be terribly interesting to the lay public. Secondly, some researchers might have difficulty communicating abstract concepts to the so-called "uninitiated."

Science, by its nature, primarily attracts individuals who are introverted. I think there'll always only be a select few researchers who are able to bridge the science gap and successfully interact with the lay public. Finally, there's always the concern about the perception of commercialism on the part of the researcher, which might result in the investigator's objectivity being called into question.

JB: I'd like to start with a quick synopsis of your background so that the readers can get a feel for who you are and what makes you tick. You know, the man behind the myth.

SM: Well, I have a BS in biology/chemistry and an MS in biology (molecular microbiology). I've been working on a PhD in exercise physiology at the University of Toledo for the past four years and I'll start as an assistant professor of exercise science at Eastern Michigan University in the fall.

JB: Tell us about your research.

SM: As far as research goes, I have two primary areas of interest. The more esoteric aspect focuses on responses to muscle injury. Using techniques such as electron microscopy, biochemistry, and cell and molecular biology, we look at the physiological, cellular and genetic responses to muscle injury. By examining this area, I hope to get at the mechanisms of muscle genesis and regeneration at the most fundamental levels.

The other area relates to nutraceutical supplementation. I've completed various studies examining prohormone and herbal supplementation and the resulting effects on biochemistry and performance. I'm interested in the potential physiological benefits of various supplements, not only with regard to performance, but also improved health and longevity.

Like most readers of your magazine, I'm in search of supplements that will make individuals feel better, and build or maintain strength as they get older. Ultimately, I think these two areas of interest will merge. As we learn more about the basic nature of muscle regeneration and nutraceuticals become more sophisticated and well developed, it'll be possible to enhance muscular development quite effectively using commercially available supplements.

JB: Why did you get involved in this field in the first place?

SM: My research interests really stem from my interests in athletics and performance enhancement. While an undergrad, I played intercollegiate soccer and raced bicycles to stay in shape. The bicycle racing continued as I worked on the MS and after graduation I raced at the elite domestic level for a couple of years. I was always interested in the science of performance and supplements.

So when I realized bicycle racing wasn't my path to immortality, I began a PhD in exercise physiology.

For several years I've been coaching and training competitive cyclists and triathletes. Aside from the endurance sports, I've always lifted weights in an effort to improve performance, so I remain interested in that area as well.

JB: Let's delve into the main attraction here, the Tribex-500 study that made some waves at the ACSM national conference in Indianapolis this year. From your presentation, I know that you gave Tribex to elite endurance cyclists over the course of a competitive season.

Most people typically think of Tribex as a bodybuilding and weight lifting supplement. Quite frankly, I'm sure that many T-mag readers are wondering why the heck they should care about what Tribex can do for the endurance athlete. What was your motivation for trying it out on endurance athletes and what did you expect to find?

SM: Well, you're right, most people don't draw the connection between what a supplement like Tribex is intended to do and endurance performance. It really should be quite obvious though. In essence, what do bodybuilders and strength athletes want to accomplish through supplementation? They want enhanced recovery and improved strength, right? These two factors then lead to muscle growth and improved body composition. Endurance athletes are looking for the same basic responses, but for slightly different reasons.

Before I address Tribex specifically though, I'd like to back up a bit in an effort to make the rationale for the study more clear. It's been well demonstrated that highly trained endurance athletes have chronically suppressed androgen (Testosterone) levels. The mechanism for this has yet to be discovered, but it's clear that endurance training in excess of 8-10 hours per week will result in lower Testosterone levels.

This is really a catch-22, because in order to be successful at the elite levels of endurance sport, it's essential to train at high volumes. In fact, most bicycle racers probably train more than twice the threshold level of eight hours. So, you need to train or race a lot, but this training will result in lower T levels. To be able to train and race at a high level, though, you need to recover, and Testosterone is a potent stimulator of recovery. This is why some high level athletes might use Testosterone and anabolic steroids.

So, when over-the-counter androgens (i.e. androstenedione) became available I was intensely interested in their effectiveness. After having done one of the early studies and being aware of some of the other results that most everyone is familiar with now, I realized that "andro" supplements (specifically androstenedione) were probably not going to cut it as performance enhancers. For that reason I became intrigued with tribulus as a potential candidate for androgen elevation.

I hope I haven't belabored the point too much, but this gets to the gist of the study. From personal experience, I know that during a racing season, cyclists walk a thin line between peak performance and overtraining. This is exemplified during multi-day stage races where the cyclist races intensely for several days in succession.

A stage race is analogous to a weight lifter doing a five-set leg workout of forced reps every day for eleven days in a row. You're performing maximal intensity, glycogen depleting, neuromuscular fatiguing workouts everyday. In this scenario many individuals just break down, while the successful individuals simply don't break down as much. Because Tribex was purported to elevate Testosterone levels (and possess anabolic characteristics, due to the inclusion of ipriflavone) we wanted to see if it could improve recovery and result in enhanced performance during peak training and intensified racing.

JB: Eleven consecutive days of forced-rep squats, huh? Ouch! I guess I can see why these athletes might need something to boost recovery. I had a few criticisms of the study by Dr. Antonio. The first was the fact that there was no placebo control group and therefore it was difficult to determine whether or not it was the training or the supplement that caused the favorable changes. The second was that although the athletes seemed to be in great shape, we couldn't be sure if the subjects improved so much because they had taken some time off before the study or if Tribex really took them through a plateau. The third was that there was no examination of the mechanism by which Tribex exerted its actions. Briefly, how did you address these concerns in your study?

SM: I'd agree with most of your criticisms. These are all points that need to be addressed in any performance-enhancement study. First, we included both a treatment and control group. The groups were balanced with five subjects in each.

As far as training status of the subjects, we went to great lengths to ensure that both groups were highly trained and were equal in ability. All subjects had been racing for at least three years and were considered elite or expert racers. They'd all trained for at least 12 hours per week for the previous four months. The idea here was that the training potential of each subject had already been maximized (i.e. they were at their peak.)

Further, all of the subjects were pushing the limits of training and recovery leading up to a stage race. Therefore, small changes in performance might be more evident and easier to see. Finally, with regard to potential mechanisms of action of the supplement, we measured resting hormone levels on three different occasions. During the performance trials we also measured respiratory gasses in order to see what was happening metabolically.

JB: So when all was said and done, you knew the differences between peak condition cyclists following their regular routine both with and without Tribex. It looks like you designed a well-controlled study here. You mentioned the measurement of hormone levels and metabolism. What hormones did you measure?

SM: We measured total Testosterone, free Testosterone, cortisol, and estradiol. In addition, we examined the Testosterone-to-cortisol ratios and the free-Testosterone-to-cortisol ratios.

Sports scientists have been searching for biochemical and hormonal indicators of overtraining in highly trained athletes for years. Since high volume training suppresses T levels, and training stress can increase cortisol levels, both of these hormones are of interest. Unfortunately, neither of these hormones alone are good indicators of overtraining.

By examining the free-Testosterone-to-cortisol ratio though, we have a more sensitive measure of hormonal change. Of course, because tribulus was purported to elevate Testosterone levels, we wanted to measure T.

The free-Testosterone-to-cortisol ratio has been applied most extensively to endurance athletes. Some investigators argue that the ratio isn't as useful in strength athletes. Most of the studies that have been done in strength athletes, though, have been relatively short in duration. Further, many bodybuilders train at a much higher volume than pure strength athletes. It's probably not uncommon for some bodybuilders to train at least eight hours per week. This would put them at a higher risk of hormonal alterations.

JB: So basically since bodybuilders often use large volumes of training, like endurance athletes, they might suffer from decreased T and increased cortisol. In addition, they might benefit from knowing their T-to-cortisol and free-T-to-cortisol ratios in order to assess whether they have an optimal hormonal environment for recovery. Any recommendations for an optimal T:C ratio or FT:C ratios?

SM: The T:C ratio is of little value. The really sensitive indicator is the FT:C ratio. And as an absolute threshold level, this ratio is of little value due to individual differences in hormone levels as well as variations in results between laboratories. The best approach would be for an individual to have hormone levels tested over an extended period at the same lab. A 20% reduction in the FT:C ratio from the mean would then indicate a state of overtraining.

JB: So, as in body comp measurement, one should be more interested in the change rather than the actual value. You also measured performance, correct? Since I know very little about elite cycling, tell me what tests you chose and how these tests apply to real-world cycling.

SM: For the performance test, we had the subjects complete a 16 km (10 mile) laboratory time trial on a computerized ergometer (a high tech stationary bike). There are several reasons that we chose this test. First of all, the trials were performed at 110% of individual anaerobic threshold (IAT). Not to get too technical here, but the IAT is where lactate (a metabolic byproduct of intense anaerobic exercise) begins to accumulate in the blood plasma. Breathing also becomes labored in response to acidosis (the build up of acidic molecules in the blood).

Most recreationally active people can maintain this effort for two to four minutes before succumbing to the pain. A highly trained competitive cyclist must maintain this level of intensity for extended periods and in this case, the trial lasted approximately 25 minutes. Therefore, this test would measure anaerobic power production as opposed to pure aerobic endurance. In addition, this test can be useful in the diagnosis of overtraining.

We hypothesized that the time trial performed after the stage race would be slower than the one performed before. This would be due to glycogen depletion, muscular fatigue or general lethargy. If Tribex were indeed anabolic, then the group on Tribex would have enhanced recovery and improved performance versus the group on the placebo.

JB: So these cyclists can sustain work at the IAT for 8 to 12 times longer than even active individuals? That's intensity, man! Can you summarize your findings for us?

SM: Here's a table describing the results:

I should note that the difference in FT was not statistically significant (p = 0.08), but may have been with more subjects. Differences in C and FT:C were statistically significant though. For performance, all of these results were statistically significant.

JB: Well, the numbers certainly all seem to be in the right direction. Practically speaking, just how big are these differences and what do they mean? I mean, we're just talking about small percentage increases in performance which might only amount to a few seconds, right?

SM: As an example, in the 2000 Tour de France, Lance Armstrong won the final time trial with a 0.6% margin over second place. In the first time trial, which was similar in nature to our performance test, the winner completed it in 19 minutes 3 seconds, twentieth place was approximately 5% slower. So the difference between the Tribex groups 2.14% improvement and the 2.15% decrease in performance in the placebo group could mean the difference between 1st and 20th place!

JB: Wow! The percent changes in the hormone values also look impressive, but what do they mean?

SM: Well, as far as the hormonal changes, over the course of the study, the placebo FT:C ratio declined to the point where they would be diagnosed as overtrained. At the same time, the FT:C ratio in the Tribex group improved more than 50%.

JB: I guess the results are pretty impressive! Can you give me any insight as to what you think the potential mechanisms of action were for the favorable changes in the endocrine and performance profiles of the cyclists taking Tribex?

SM: First, performance. At this point it is merely speculation, but I think there are two likely possibilities. In studies performed some years ago, it was demonstrated that ipriflavone, one of the ingredients in Tribex, improved endurance in untrained individuals. Also, under conditions of ischemia (low blood flow and oxygen delivery) ipriflavone protected heart muscle from damage in animals.

I won't go into too much detail here, but I think that ipriflavone enables the muscle to contract more forcefully due to its effect on cellular calcium flux. The muscle may also be protected from contraction-induced injury due to the same mechanism. In other studies, one of the components in tribulus was shown to increase the force of contraction of the heart muscle.

In our study, it may be that the combination of ipriflavone and Tribulus enabled the athletes to produce more forceful contractions. For technical reasons I won't belabor, I don't think the cardiovascular effects were responsible for the performance improvements. If the supplement does enable skeletal muscle to contract more forcefully, this would be of value to strength athletes as well.

As far as the endocrine responses, that's a bit complex. Simply put though, since cortisol is a stress-response hormone, the athletes on Tribex perceived less stress. That is, they produced more force per contraction with less stress and potentially, less damage. This enabled them to go faster and have an easier time doing it.

JB: So basically Tribex may increase the ability of a muscle (both heart and skeletal muscle) to contract more forcefully, may protect the muscle from the damage that accompanies such forceful contractions, and may create a better systemic hormonal profile for training. I know I'm pretty excited about such results. As a scientist, how impressed were you with the results?

SM: I'm very reluctant to talk about personal impressions with regard to scientific studies. I understand that many readers place great trust in the opinions of experts, so it would probably be less than ethical for me to evaluate results of my own study for your readers. I will say this, though: it's unusual to find statistically significant improvements like this in supplement studies. I think we can let the results speak for themselves.

Conclusion

While letting the results speak for themselves, I think it would be remiss if I didn't point out one very interesting perspective. Often we think aerobic/endurance training is diametrically opposed to anaerobic/bodybuilding training. As McGregor pointed out, bodybuilders who volume train may be subject to the same physiological responses as endurance athletes. Therefore, although this study looked at Tribex in endurance athletes, it isn't too far of a stretch to assume that Tribex may also benefit other types of athletes as well. The next step, of course, would be to investigate the use of Tribex in bodybuilders. Until that's done, however, we have these intriguing results to think about.