In 1972, Nautilus inventor Arthur Jones published an article asking weight-trainees to focus on a concept that few of us had previously considered. This concept was specified as “negative training,” accentuating the lowering part (resistance) of an exercise. Arthur Jones cracked open a new era in progressive strength training – an era brimming with possibilities, anticipation and great expectations of muscular strength and related muscular size.  However it also proved to be an era clouded by confusion, question marks and, ultimately, misunderstanding.

In retrospect, when Arthur Jones spoke, many of us listened. In plain English, he explained that we all possess three levels of strength: concentric (lifting), static (holding) and negative (lowering). Negative strength is approximately 40% greater than positive strength, and static strength is midway between positive and negative.

A scientific study presented in a 2009 article (Roig, British Journal of Sports/Medicine) stated,  “Eccentric (negative) training performed at high intensities was shown to be more effective in promoting increases in muscle mass measured in muscle girth. Eccentric training showed a trend towards increased muscle cross-sectional area measured with MRI.  The superiority of eccentric training to increase muscle strength and mass appears to be related to the higher loads developed during negative contractions.” According to Ellington Darden, Ph.D., “When the strain on the muscle is focused and intense from multiple repetitions with controlled negatives, the movement mechanisms at the microscopic cellular level (actin protein filaments and myosin movement molecules) pull apart and tear slightly. ALL GROWTH from strength training MUST be stimulated by preparing and slightly tearing at least some of the involved actin and myosin tissues. That slight tearing is the catalyst for repair and overcompensation.” Science seems to indicate that negative work is possibly the most significant phase of the repetition. The question thus presents itself as “What is the practical application of such information into the workout itself?” After all, with a barbell or a conventional machine, even by “accentuating the negative,” you can only lower what you can lift!

Since Arthur Jones raised our awareness of the importance of negative training nearly 40 years ago, many trainees have experimented, attempting to capture the potential value of “negatives.” Through trial and error, much was learned, though in more than a few instances at a great orthopedic price.

One aspect of negative work was evident immediately. From workout #1, regardless of the equipment or the paradigm of sets and reps, the degree of delayed onset muscular soreness (DOMS) generated by negative work was unprecedented. The day after the workout, the resultant muscular soreness was brutal; the day after was even worse. Since most trainees sincerely equate soreness with results, it was inevitable that many participants quickly concluded that if some negative work was good, more would certainly be better. This thinking, however, did not take into consideration that due to the heavier work inherent in “negatives,” the greater is the resulting muscular fatigue and the resultant “inroad” – the depletion of momentary strength, repetition by repetition during the set of an intense exercise. It didn’t take us long for realization to be forced upon us; negative work greatly stimulated muscular response, however, the intensity of effort and the resultant inroad necessitated a much longer systemic recovery. And there were more covert problems and valuable lessons to be learned.

  1. Utilizing a barbell necessitated the use of “spotters” who would have to coordinate the hand-off of the heavier resistance to the trainee who would then lower the weight slowly. An inherent problem was the necessity of a smooth hand-off. Uneven hand-offs often overloaded one side of the body and facilitated the chance of injury.
  2. Chin-ups and dips proved to be two of the most popular exercises to perform “negatives.” Placing a stool beneath a chinning bar or parallel bars enabled the trainee to climb up and slowly lower his or her bodyweight plus added resistance in the form of a weighted belt or dumbbell. Problems arose when the heavy resistance plus rapid breathing permitted extended rest between reps, enabling the set to degenerate into a series of single reps, allowing sufficient time for the muscles to partially recover instead of efficiently fatiguing. This gave the illusion of stimulating strength, but in reality invited injury.

The most practical way to utilize “negatives” proved to be “negative accentuated” training. Performed best (only) on machines, the trainee would lift the resistance with both limbs then lower slowly with one limb, then lift again with both limbs and lower slowly with the other limb. This enabled the trainee to train without spotters and feel more in control of the entire rep. Alas, again, problems were prevalent. There was still the necessity of allowing one limb to rest and recover while the other limb was lowering the resistance. Secondly, there was again the problem of overloading one side of the body, especially during heavy legwork or overhead pressing.

Due to the aforementioned problems, plus a myriad of others, the concept of negative training and its promise of   unprecedented value was lost – UNTIL NOW! Forty years after Arthur Jones initiated the conversation of eccentric exercise, Mats Thulin of Sweden and his X-Force team of engineers have taken a giant step towards refining and perfecting the “negative accentuated” training system by solving the previous problems that had caused its premature demise.


According to Ellington Darden, PH.D., who is currently conducting research of X-Force equipment at the Gainesville Health and Fitness Center in Gainesville, Fla.: “The approach that Thulin applies so effectively involves a tilting weight stack powered by an electric servo motor (note: the trainee does ALL of the work). As the user begins the positive stroke, the weight stack tilts to a 45-degree angle –instantly reducing the selected resistance by approximately 29%. At the apex of the positive stroke, the tilted weight stack returns to vertical. The user then lowers 100% of the selected resistance. For example, on the X-Force Pec Seated  Press machine, you select 140 pounds. As you start the positive phase (lifting the resistance), you are moving 100 pounds. (Note: 100 is 29% less than 140 pounds, and 140 pounds is 40% more than 100 pounds.) QUICKLY, in 0.5 of a second, the weight stack goes back to the vertical position as you do a controlled negative rep with 140 pounds. Ideally, the set is completed in 5-8 repetitions.”

Bjorn Alber, M.D. sums up the above: “In conventional training, the trainee is expected to complete 8-12 repetitions before reaching muscular failure. In X-Force training, thanks to a high inroad (capacity to exhaust muscles), the trainee can be expected to reach failure in 5-8 repetitions! In order to ensure the involvement of all three phases of muscular action (concentric, static and eccentric), X-Force recommends a 3-1-5 cadence approach – three seconds of concentric work followed by one second of static work, and then five seconds of eccentric work.”

And what of the practical application of X-Force training?

On January 5, 2012, Main Line Health and Fitness in Bryn Mawr, Pa., became the first training center in the USA to purchase X-Force. (The equipment is now also available at the Gainesville Health and Fitness Center under the direction of industry leader Joe Cirulli. As mentioned earlier, large-scale research is currently being conducted in Gainesville under the direction of Ellington Darden, Ph.D.

Briefly, as background relevant to my own opinions and critique: I have contributed to Iron Man magazine on a semi-regular basis for 40-plus years. I was one of, if not the first, strength and conditioning coaches on a collegiate level in the mid-1960s. I competed successfully on a collegiate level in Olympic lifting (240-220-275) and power lifting (365-415-535) as a 180 1/4 pound competitor (note: which activities produced major degenerative change throughout my entire spine). The resulting injuries initiated a change of thinking towards the direction of high-intensity training on Nautilus equipment. I subsequently served as head professional judge of the International Federation of Body Builders.  Thus, I believe that I have adequately “walked the walk,” which allows me the benefit of having an experienced, informed opinion. As this article is being written, I have personally trained on X-Force equipment for 3 months, once a week, a total of 14 workouts. To unequivocally state that these workouts at age 67 have been the most productive workouts of my life is an understatement. At an age where most trainees are simply trying to “maintain” their current levels of strength, I have stimulated lean muscular gains as fast or faster, and certainly more efficiently, than any previous type of training. After the first six weeks of training, I had increased my bodyweight six pounds (body fat 7.3% at start, 7.7%, six weeks later). This is a “game-changer,” and is not supposed to occur at my age. I have found that one workout a week on X-Force equipment is all that I need or want. I expect to see similar results (or better) being stimulated by younger intense trainees working out in the same manner. Metabolic training-building muscle and burning fat. Hyperbole? Hardly. THE X-FORCE EQUIPMENT IS THAT GOOD!

Since Main Line Health and Fitness has had the most experience with X-Force in the USA, I will share what we have learned:

  1. The equipment is smooth. This is an important feature. Since the trainee is lifting the resistance, holding the resistance statically at the “turnaround,” experiencing the total negative phase, and smoothly lowering the 40% heavier resistance, he or she is completely in control of the entire repetition. The intensity of the repetitions now possible with X-Force has to be experienced to be appreciated. It is a completely new and exciting RESULT-STIMULATING way to train. Nothing before it can remotely compare.
  2. The initial response felt by EVERY trainee is “WOW, I have NEVER felt anything like this!” There is an immediate physiological and psychological realization that “THIS really works.”
  3. The 0.5-second turnaround of the weight stack from tilt to vertical is so smooth and so easily controlled by the focus of the trainee, that after using X-Force for several sessions, the 40% heavier negative feels perfectly normal, “just right,” as if THIS is the way that a complete repetition SHOULD feel.
  4. For the first time there is no “respite” during a full repetition, no “looking forward” to lowering the resistance. The positive reps, rep by rep, feel harder AND the negative reps, rep by rep, feel harder. This is a whole new mind-set. After THIS experience, there is no allure to “going back” to conventional training.


  1. Ellington Darden indicates in his own workouts that X- Force repetitions were, in several instances, 50% more demanding per repetition than on conventional equipment, thus each set required 30% less time, reaching failure, indicating a far more efficient “inroad.” It is his strong opinion that growth stimulation is closely linked to this inroad. (


  1. The excitement generated by X-Force equipment is equivalent to the introduction of Nautilus and the principles of Arthur Jones in 1970. Yet, while Nautilus had the tremendous potential to stimulate muscular gains and revolutionize an industry, that great potential, in this opinion, was never fully realized. How can X-Force, with its even greater potential for RESULTS, realize that potential? I believe that the answer lies with understanding, teaching, supervision, focus and determination. Much of the great value of Nautilus was lost due to a fundamental misunderstanding and a TOTAL MISUSE of the equipment.


  1. I experienced the misunderstanding of Nautilus equipment firsthand. As head judge of the IFBB in the early 1980s, and by this time an experienced advocate of the Nautilus principles and machines, I had the opportunity to train along with a lineup of IFBB professionals at a local training center in Atlantic City, N.J., before an IFBB contest that was being held that evening. The facility was equipped with mostly free weights and a single line of vintage Nautilus machines. Every pro opted for the free weights. I, alone, began the Nautilus circuit. Being the current head judge and having gained total respect from the competitors, I had no trouble having the pros, one at a time, “try” the Nautilus machines. Without a single exception, not one pro had any idea how to correctly use the machines. And yet, EVERY pro, once properly instructed, respected the equipment and quickly realized its value. To several pros, Nautilus was a revelation. And this was 10 years AFTER Nautilus had become commercially available. Whether any pro continued to train on Nautilus is irrelevant. They all learned something that day, and so did I.

In retrospect, it was approximately at this time when the lunacy of “only free weights build mass,” was beginning to take hold. This distortion was, in my opinion, the beginning of the end of common sense in the field of athletic training. Currently, strength and conditioning coaches AT EVERY LEVEL “teach” athletes the “value” of “explosive” lifting, from which the ONLY “explosion” likely to occur, either immediately or eventually, is in the major joints of the athlete’s body.


X-Force training has the great opportunity to usher in a new era of higher-intensity exercise, stimulating deeper inroads and greatly reduced training time.

With 3 months of experience, most of our trainees are training once every seven days, approximately 10 HARD sets per workout. Each set is comprised of 5-8 reps to failure (45-72 seconds per set).

X-FORCE MACHINES STAND ALONE!  They are in a league of their own.

Thus far, at Main Line Health and Fitness, EVERY set has been supervised. Why? Because I am personally determined that X-Force succeeds in realizing its unmatched potential to stimulate muscular results at our facility. X-Force WILL be taught correctly, results already have been stimulated.

I am available to answer any questions regarding our X-Force experience. I am happy to share any information. It is merely a matter of integrity.