Dr. Casey Butt is one of the most controversial figures in bodybuilding. He is a life long natural lifter, but more then that, Casey Butt is a student of natural bodybuilding. His study on natural bodybuilding potential is the definitive measuring stick for the sport. More information on Casey Butt can be found at www.weightrainer.net.

In Part 1 of our interview with Casey Butt, we explore the topics of natural muscular potential and full body routines.

Muscle and Strength: I want to start off by introducing you to those in the natural bodybuilding community who are unaware of your work and research. Can you please tell us a bit about your personal story, background and your research?

Casey Butt: I've been training for roughly 20 years - a little longer if you count my younger years when I just fooled around with the weights. During that time I've trained and corresponded with national and world caliber bodybuilders, powerlifters and Olympic weightlifters (some drug-using, some not), and been involved in all three sports on a casual basis, although competition has never been my motivation. Academically, I have degrees in physics with an applied math minor, pure math with a biochemistry minor, electrical engineering, Masters in mechanical engineering and a Ph.D. in controls engineering. I've written for MILO and Hardgainer magazines as well as websites and training certification organizations. I no longer personally train "clients" as I simply don't have the time, and never felt entirely comfortable charging people for one-on-one training knowledge anyway. In the late 1990s I started the WeighTrainer website to help spread real training and nutrition knowledge free of bias and without ulterior motives. For a time I published a magazine under the same name.

At this point I'm probably best known for my more recent work regarding muscular potential. That's no doubt because it's turned out to be a very controversial subject - many people don't like to accept the reality of limitations, even though they may never personally achieve anything even close to such a limit. Very early on, I was somewhat of a weight loss "guru" as I was once morbidly obese and lost 170 pounds during my first year of serious training (without drugs or surgery). Some people might also know me for my sometimes blunt style and advocacy of full-body routines, basic exercises and periodization for drug-free trainees.

Muscle and Strength: Regarding your work on natural muscular potential, what are some of the biggest objections you receive when the topic comes up on Internet forums? And what do you make of the numerous claims of posters that they have exceeded projected limits?

Casey Butt: Usually the objections aren't very well thought out. Something like, "My uncle is as big as your equations predict and he doesn't even train and is an alcoholic." Or, "I passed all of those equations" during my first year of training." If people even faintly understood what the equations are and what they're based on they wouldn't make such preposterous claims.

Fundamentally, the muscular body weight equation is based on "improvements" to the Body Mass Index (BMI) and Fat-Free Mass Index (FFMI). The shortcoming of both of those indexes is that they consider only a subject's height and not bone structure itself. It is a rather simple exercise to analyze population data and see that there is a clear correlation between joint structure size (as indicated by wrist and ankle girths for simplicity) and both body weight and lean body mass (LBM). From there, the BMI and FFMI can be modified to take that into consideration.

Here's were it gets interesting: With the form of the equation determined, data from 1947 to 2009 (it's an ongoing process) world, national and regional drug-free bodybuilding competitors shows a strong correlation between height, wrist and ankle girths, and maximum peak LBM. Scaled for height and bone structure size, the largest drug-free bodybuilders of the past 60+ years all top out at essentially the same level. In other words, Reg Park, who was one of the largest elite bodybuilders of the 1950s, carried roughly the same degree of development as a more modern drug-tested champion such as Dave Goodin or Jim Cordova - when scaled accordingly. Even Steve Reeves, who was not known for great muscular size, scales to the same level when his height and bone structure are taken into account. That's not saying that modern bodybuilders don't look more muscular than those of earlier eras because of their extremely low contest body fat levels and aesthetics, but in terms of LBM with body fat percentage factored in, they haven't gotten significantly larger.

The logical conclusion must be that this level of development represents a virtual ceiling as to the amount of muscle a person can develop without steroids. If that were not true then surely top drug-free bodybuilders of the past 60+ years would have surpassed that level - yet they have not.

Physiologically, I don't think any of this should come as a shock. After all, testosterone is needed for muscle development and maintenance, and the human range of natural testosterone production in good health only goes so high. That in itself, just as it is the primary reason as to why males carry more muscle and have more muscle building potential than females, limits how big a person can get without taking exogeneous steroids.

Similarly to the LBM equation, I used data from 60+ years of bodybuilders (some of which I collected myself, some from other trustworthy and verifiable sources) to fit prediction equations for the maximum potential size of individual body parts.

For many people, despite the clear, undeniable correlations, the idea of limitations presents a mental stumbling block and they'll throw up all sorts of arguments such as "Bodybuilders aren't necessarily those with the highest muscular potentials", to "My uncle is an alcoholic and doesn't train and he's already as big as those equations predict."

The rebuttals are fairly simple. The equations will be slanted in the direction of championship physiques because this is what they were based on. Because of that, the equations assume a relatively small waist and hip structure. This can cause less aesthetically gifted individuals to reach the weight predictions without corresponding levels of muscular development because of "extra" weight they carry due to their larger waists and hips. However, we're talking on the order of a few pounds here. Nothing as silly as, "I weigh 20 pounds more than the predictions."

As for bodybuilders not carrying the most lean body mass, that is only true under certain circumstances. One is very thick-waisted and large hipped athletes, and the other case is heavy athletes who allow their body fat levels to climb above 15% to 20%. Lean body mass increases with body fat, and this can cause fatter individuals to carry more lean body mass than the equations predict because the equations were formulated to be accurate in the 8% -12% body fat range. When these people lean out they will not be above the predictions unless, as discussed, they have very thick waist and hip structures. In practically every case, their girth measurements, such as the biceps, chest, thigh, etc, measurements will fall under the predictions.

And therein lies the answer to people who swear they have exceeded the predictions. Over the past several years several people have made that claim to me and in every single case they were carrying well over the 12% body fat up to which the equations were intended to be used. I myself exceed the predictions when I'm 15% body fat or more, but not at 10%, where I'm several percent under the predictions. In fact, a mark of a champion is being able to maintain muscle mass as fat is dropped (presumably influenced by a naturally high testosterone level).

What must be kept in mind is that these equations were formulated on some of history's biggest and greatest bodybuilders. They essentially scale your structure to that level of development. Most people, in fact, will not be able to reach that level because they don't have the naturally high testosterone levels, full muscle bellies, robust joint structures, etc, to allow the development and support of that amount of muscle mass (not everyone can be a champion bodybuilder) - for that reason the e-book contains a range of equations based on populations of varying genetic potentials, not just champions. To claim to exceed the elite-based equations is really quite a claim indeed. If people do honestly believe they're at that level then they should objectively assess their body fat percentages. If they still think so, then they should look in the mirror - a world-class physique, at least with regards to muscle size, not necessarily aesthetics, will be looking back at them.

Muscle and Strength: You mentioned that you carry several other beliefs that are somewhat controversial. I want to ask you about them. Let's talk about full body routines. Why do you believe they are best for naturals? And why have they gone the way of the dinosaur over the last 30-40 years? For the most part on lifting forums, I only see HIT practitioners and 5x5 programs that slant towards being "full body"...

Casey Butt: Year-round, elaborate split routines, in the typical bodybuilding sense, were essentially "born" as a consequence of several occurrences in the early 1960s and have become popular because bodybuilders copied the routines of their drug-using heroes. In the 1950s and early '60s Weider was promoting higher volume, more isolation laden, training routines as more modern and sophisticated than the "old fashioned" lower volume routines that were the staple of the York training courses - and in certain regards it was true. And the magazines naturally focused on bodybuilding champions' pre-contest training, which was higher in volume than the rest of the training year. Several top bodybuilders did, in fact, train on split routines in the 1950s and earlier, but this was typically reserved for sharpening up in the weeks leading up to contests, with full-body routines used for building up during the rest of the year.

By the early 1960s steroids entered the picture as primarily a pre-contest training aid (following the Weightlifters' practice of ramping up steroid use as contests drew near) and this allowed for yet further increases in training volume. Around this point split routines became the norm rather than the exception. Again, pre-contest training was the focus of the magazines as readers wanted to know what Mr. So-and-so did to win the title. What got lost however, was the fact that most of these lifters followed full-body routines to build up during the off-season and when they were not dosing Nilevar or Dianabol.

As bodybuilders realized that steroids could be used to very effectively bulk up in the "off-season" their use spilled over to the entire training year and split routines were adopted as the off-season template followed by top bodybuilders. It's natural that aspiring trainees copied their heroes' routines and practices, but they were generally kept in the dark about steroid use as the major magazines purposefully hid it and promoted aspects of bodybuilding more profitable to them (training courses such as isometrics in the power rack and the supplements of the day - wheat germ oil, desiccated liver, protein powders and pills, etc.). That practice has been part and parcel of the training media since the introduction of steroids, and if anything is even more rampant today.

Steroids change a trainee's tolerance and response to exercise in a number of ways. Most importantly, steroids are an artificial source of testosterone and mimic it's anabolic/androgenic properties. For that reason, steroid users do not have to be concerned with maintaining and manipulating their own natural testosterone levels through training and diet. A natural trainee's progress, however, is inexorably linked to his hormonal response to training. Training of too low a systemic magnitude and there is no response, too much and the body can't keep up and overtraining results.

On the scientific front, several studies over the decades have shown that protein synthesis and hormonal responses to training return to baseline within 36-48 hours of even intense, high-volume weight training. At the same time, routines consisting of compound exercises have been shown to be vastly superior to those consisting predominantly of isolation exercises and machines, with regards to lean body mass and strength gains. Volume wise, 2-4 sets in the 8-12 rep range have been shown to be the most efficient count for hypertrophy and growth hormone release, whereas 4-6 sets of 4-6 reps have been shown to be near optimal for strength building and testosterone release. On top of that are the findings that intense exercise involving larger total muscle masses, such as performing heavy Squats and Deadlifts, results in the most dramatic responses of the body with regards to testosterone and growth hormone levels. The blood cortisol:testosterone ratio begins to climb into unfavorable territory after 45-60 mins of intense training as well.

Put together, the body of credible scientific literature over the past 60+ years points directly to relatively brief (an hour or so) full-body routines as being the superior form of exercise for hypertrophy and strength building purposes, particularly in the absence of exogeneous anabolic steroids. For a bodybuilder trying to build up, there's no advantage to performing many isolation exercises and no need to do more than 2-6 sets of any exercise. Each session should include movements that tax the largest amount of muscle mass as possible so as to elevate testosterone and growth hormone levels. The most logical routine design that fits this prescription best is the full-body routine, centered around basic free-weight exercises.

I find it ironic that the majority of modern science supports not what is considered modern by most, but what is considered old-fashioned and was exactly what Reg Park, Clancy Ross, John Grimek, Steve Reeves, George Eiferman, Jack Delinger, etc, all recommended before the introduction of steroids into bodybuilding. Park and Ross were even particularly careful to caution trainees that split routines are okay before contests to lean out, but not best for building up in the off-season ...and building up is what most natural bodybuilders spend the majority of their time aspiring to do.

I've been deliberately careful to specify here that this is all within the context of building muscle mass. There are times when split routines are an equally or more viable training option, particularly pre-contest when lagging muscle heads begin to become apparent at low body fat levels and must be addressed (though for trainees who never intend to dip much below 10% body fat or so they may never even be aware of such deficiencies). There are also certain groups of trainees who naturally respond well to split routines, even in the off-season. Those are typically people who have naturally high testosterone levels, robust joint structures, and can deliver significant enough training loads to the muscles in a single bout to justify longer breaks between training sessions. Highly experienced trainees who are close to their genetic potentials can also benefit from a split routine that allows them to focus more work on lagging body parts - though this can also usually be done on an advanced full-body routine.

The majority of drug-free trainees, however, who are looking to build more overall body muscle mass, strength, a visually impressive physique, and don't have particularly robust joints, would be far better off focusing on just getting stronger on the basic free-weight movements to the practical exclusion of every other thought - and full-body routines are the near ideal vehicle for that, most of the time. That's how Park did it, he didn't have any glaring weaknesses, and as I mentioned in response to the previous question, no drug-tested bodybuilder yet has surpassed that level of development.