Arthur Jones and the Colorado Experiment

Resistance training wouldn’t be what it is today, in many ways, without Arthur Jones. He pioneered the weight resistance machine with the Nautilus line, which made him extremely wealthy. Those machines, especially the ones built in the 1970s, are still being used today and are like tanks.  

Arthur Jones got his line of machines into rehab facilities, gyms, and fitness centers. Their unique design targeted muscles in ways standard free weight lifting could not replicate. One of the most notable of the Nautilus line is the pullover machine. It’s considered the Holy Grail by many because of its design and effectiveness and was a key machine for Olympian winner Dorian Yates.  

arthur jones and the colorado experiment

The Incredible Results from HIT 

Arthur had many people run through his gauntlet of HIT (High Intensity Training). The results were nothing short of incredible. His theories on weight lifting were likewise, ahead of their time. At a time when bodybuilding was reaching peak popularity with Arnold Schwarzenegger at the center, the Nautilus line and HIT training were sweeping the fitness world throughout.  

Instead of training for hours a day every day at the gym with multiple sets, you could perform an entire workout in as little as 20-30 minutes, a few days a week. And in doing so, you would gain muscle – a lot of muscle. Through pushing each body part to absolute failure with good, quality form, you are properly stimulating the muscles in the right manner.  

The training styles and methods that Arthur Jones was implementing didn’t go without controversy either. That will be discussed later. One thing was certain though. The program worked. The machines worked, and the time saved through the program design were very desirable to many people.  

arthur jones and the colorado experiment

Jones felt that a rapid rate of growth could be established from HIT. “[F]rom my own personal experience, and from the experiences of many other people, I was aware that a very rapid rate of muscular growth was at least possible. Why, then, I was forced to ask myself, couldn’t such a rate of growth be maintained right up to the point of individual potential1?” 

Selling a Solution 

How should Jones go about showing people that it was possible to gain high rates of growth in a short time period? If they maxed out their efforts, it was possible he hypothesized. The solution came in the form of a “study”, which in many ways was marketing for both the machines and his HIT methods.  

Jones would take a subject and train them solely Nautilus equipment and place them under constant supervision to refute any drug or competitive advantage claims. The participant would train under the HIT method for one month and Jones would track the results.  

Jones already had a high level training facility in Florida, but knew that he had to go to a neutral site. By staying in Florida, “we realized that doing so would leave us open to charges of misrepresentation after the fact. So, instead, the experiment was conducted in Fort Collins, Colorado, under the supervision of Dr. Elliot Plese in the Colorado State University’s Department of Physical Education Laboratory.1 

arthur jones and the colorado experiment

Thus, the Colorado Experiment is born. Jones would take his subject and work them as hard and as quickly as humanly possible. If the subject was honest and performed at peak, Jones felt that the results would be not only convincing, but in his words, “dramatic”.  

Casey Viator Selected for the Colorado Experiment 

Arthur Jones recruited Casey Viator as his test subject. At age 19, Casey was the youngest person to ever win the Mr. America title. After that win, Casey suffered a major setback, which applies some controversy to the study itself. Dr. Ellington Darden, who spent 20 years with Nautilus and worked closely with both Arthur Jones and Casey Viator, describes what happened to Casey. 

After winning the contest, Viator took some time off from training and returned in December of 1972, weighing 200.5 pounds. In early January of 1973, Viator was involved in a serious accident involving a wire-extrusion machine and lost most of the little finger on his right hand. Then, he almost died from an allergic reaction to an anti-tetanus injection. 

arthur jones and the colorado experiment

As a result, from January through April of 1973, Viator did no training. In fact, most of the time he was depressed, and he had little appetite. His muscles atrophied, and he lost 33.63 pounds, with 18.75 of the pounds being attributed to the near-fatal injection. Some, perhaps most, of Viator's success from the Colorado Experiment was that he was rebuilding muscle that he had already built two years earlier.2 

With the extreme loss in weight, it provided an excellent opportunity for Casey to regain so much of what was lost during that time period.  

The Goal of the Colorado Experiment 

Arthur Jones knew that if he was to properly market his equipment, he would need to take a drastic approach. In order to make that happen, he would need to demonstrate how much muscle an individual could gain using his machines, and the HIT method. “The Colorado Experiment was conducted for the purpose of clearly demonstrating that rapid large-scale increases in both muscular mass and strength can be produced from a very brief program of exercise”3 

Because the expectation of large muscular increase, Jones knew he would be accused of giving Viator steroids or other performance enhancing drugs. In fact, Jones was very much against drugs of any kinds. He felt that the large-scale transformation was worth the risk of drug accusations. “[W]e also realized that it had to be dramatic in order to attract the attention that we feel it deserves.  

The results of the Colorado Experiment will probably be a controversial subject for years to come, but in the end the facts will be clearly established and accepted by almost everybody; so perhaps controversy is a necessary evil, required to bring the truth into the open1”. 

arthur jones and the colorado experiment

Another goal was to demonstrate the shorter workout duration. Less than an hour, usually between 30-40 minutes of grueling, intense work to the point of failure, 3-4 days a week was all that was needed. Additionally, the HIT training from each machine will keep the cardiovascular system at an advantageous rate, of at least 150 BPM.  

The Colorado Experiment 

Arriving at the Department of Physical Education at Colorado State University, Arthur Jones personally trained Casey Viator during the month of May 1973. Casey trained every other day, completing exactly 14 workouts from May 1 to May 29 under the supervision of Dr. Elliot Plese, Director of Exercise Physiology Lab.  

Even with the loss of weight and muscle that occurred with Casey Viator, Dr. Plese was still impressed with his strength. Using a universal machine for both pre and post testing, Casey’s initial test numbers were as follows: 

  • Leg press: 32 reps @ 400 lbs 
  • Standing press: 8 reps @ 160 lbs 
  • Supinated grip chinning: 7 reps @ 50 lbs 
  • Parallel dipping: 12 reps @ 50 lbs 

Casey’s bodyfat was measured at 13.8%, which was already very lean for an individual. As they prepared for the coming work, Arthur jones had six assertions regarding the success of his machines and high intensity training: 

  • The growth of human muscular tissue is related to the intensity of exercise; increases in strength and muscle mass are rapidly produced by very brief and infrequent training if the intensity of exercise is high enough 
  • Increasing the amount of training is neither necessary nor desirable; a large amount of high intensity training will reduce the production of strength 
  • “Negative work” is one of the most important factors involved in exercise performance for the purpose of increasing strength and muscle mass 
  • No special diet is required; well-balanced diet is sufficient 
  • Steroids are neither necessary nor desirable 
  • The maximum possible increases in strength and muscle mass can be produced only by the use of full-range, direct resistance3 

The Importance of Performing Negative Work 

Using all Nautilus machines, Arthur trained Casey in a variety of “negative” training, forcing the contraction of the muscles for the longest period of time. What’s great about machine training is the ability to train in a negative fashion, and do it safely.  

Jones has a strong point in his rationale behind negative training versus positive training. “Your muscles have distinct “strength levels”…your POSITIVE strength level is the weakest…your HOLDING strength level is considerably stronger…and your NEGATIVE strength level is the highest. This simply means that you can “hold” more weight than you can “raise”…and that you can “lower” more weight than you can “hold”1”. 

A combination of the positive and negative work pushing the body to limit, both in cardiovascular work (by changing machines after each exercise) and in performing the maximum amount of work the body can handle. This all contributed in the massive growth that was seen in Casey.  

The Results 

The results in may have produced more questions than it answered. It did, however, show incredible, almost unreal results. The amount of strength, muscle, and weight gain was nothing short of spectacular. In exactly 14 sessions with roughly 7 hours (33.6 minutes per session on average) total of training, Casey Viator gained 45.28 pounds in muscle with a loss of 17.93 pounds of body fat. This resulted in a total increase of 63.21 pounds of muscular gain.  

arthur jones and the colorado experiment

How is that possible? 

To start, results like this aren’t exactly typical, as this is stated clearly in the study. Both the rate of muscular growth and reduction of fat were quite incredible, but not alarmingly noticeable as the study went on.  

“Neither subject produced sudden spurts of growth that might have indicated dehydration prior to the start of the experiment; on the contrary, the actual gains and the rate of gains displayed by both subjects remained remarkably steady throughout the experiment. 

“But remarkable as they were, the bodyweight gains do not indicate the actual results; because both subjects reduced their starting level of bodyfat during the experiment, indicating that they were rapidly adding bodyweight while reducing bodyfat at the same time, a result that I previously considered impossible1 

Casey gained weight every day. In the first week alone, he gained 27.25 pounds of muscle. That alone is absolutely incredible. Looking closer it was 20.25 pounds of muscle, with 7 pounds of fat lost. His daily average from there resulted in a daily average of 1.05 pounds of muscle per day for the remaining three weeks. 

How did Casey’s strength compare after the experiment was over? 

  • Leg press: 32 reps @ 400 lbs --> 45 reps @ 840 lbs 
  • Standing press: 8 reps @ 160 lbs --> 11 reps @ 200 lbs 
  • Supinated grip chinning: 7 reps @ 50 lbs --> 11 reps @ 75 lbs 
  • Parallel dipping: 12 reps @ 50 lbs --> 16 reps 100 lbs 

Clearly, the system in which Casey trained was met with outstanding success. As Arthur Jones predicted, it didn’t come without criticism and controversy. 

Controversy Surrounding the Experiment 

Anytime that an individual packs on 45 pounds of muscle, loses 17 pounds of fat, for a total gain of 63 pounds of lean muscle, questions will be raised. Dr. Darden discussed some of the criticisms and accusations that occurred after the Colorado Experiment.  

Casey was Using Steroids. 
That is one of the most obvious accusations. However, Arthur Jones was greatly motivated against drug use Jones knew that the results would raise eyebrows, so he hired an independent individual named Tom Wood, who shadowed during the entire study. “I’ve spoken with Tim several times about his participation in the Colorado Experiment and he confirms Casey did not take anabolic steroids during the 28-day study.2”. 

What was Casey Eating? 
Bodybuilders naturally eat large amounts of food. So, in the reports that Casey ate a balanced diet are not necessarily surprising. He is said to have consumed 4,000 to 5,000 calories a day. To the average person that is an enormous amount of food. For bodybuilders, it is not. Keep in mind the amount of work Casey was subjected to in a short period of time. There were glycogen stores he needed to replenish.” Arthur did not believe in force feeding or in ‘bulking’ diets. A daily food diary was kept for Casey and everything he consumed was meticulously recorded. [M]ost days were closer to 4,000 (calories), which is minimal considering the brutal workouts he was going through.”1 

This Could Never be Duplicated… 
While duplicating the results are incredibly difficult as Casey possessed unreal genetics. However, Dr. Darden did explain that in Casey’s example, he was “mostly rebuilding muscle he had previously built.”1 That being said, there were eight subjects that were put through programs similar to that of the Colorado Experiment that experienced similar results. These individuals all gained over 10 lbs of muscle in a span of 4-6.  

Final Thoughts 

While the Colorado Experiment wasn’t a scientific study, the results are definitely worth noting and it is quite a story. It’s an experiment that feels part mythology, part Pumping Iron, and part awesome. If nothing else, it was a genius marketing strategy because people still discuss it 47 years later.  

Arthur Jones was ahead of his time in many respects. He also didn’t give a damn about what others thought, which one can give much respect to. He followed what he thought was right, and in many respects it paid off for him and for many others who followed and trained under him. For that matter, Nautilus is still a name many recognize today.




  1. Baye, D. (2013, September 05). The Colorado Experiment. Retrieved September 17, 2020, from
  2. Ellington Darden PhD, T. (2016, June 13). The Colorado Experiment: Fact or Fiction. Retrieved September 17, 2020, from
  3. 3. Nautilus & Athletic Journal Articles [PDF]. (n.d.).

Leave a comment

Please note, comments must be approved before they are published

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

You may also like

View all
Example blog post
Example blog post
Example blog post